阅读说明：本技术 氨的分离方法及沸石 (Process for separating ammonia and zeolite ) 是由 田中学 松尾武士 青岛敬之 于 2018-06-15 设计创作，主要内容包括：提供一种氨气的分离方法,其使用高温下分离稳定性优异的沸石膜,该沸石膜可从由包含氨气且包含氢气和氮气的多种成分构成的混合气体中,高选择性、且高透过度地将氨气分离至透过侧；以及一种氨分离方法,其为使用沸石膜,从至少含有氨气、氢气和氮气的混合气体中使氨气选择性透过而分离氨的方法,所述混合气体中的氨气浓度为1.0体积％以上。(Disclosed are methods for separating ammonia gas, which are capable of separating ammonia gas from a mixed gas containing ammonia gas and a plurality of components including hydrogen gas and nitrogen gas with high selectivity and high permeability, and methods for separating ammonia, which are methods for separating ammonia by selectively permeating ammonia gas from a mixed gas containing at least ammonia gas, hydrogen gas and nitrogen gas, wherein the ammonia gas concentration in the mixed gas is 1.0 vol% or more, using a zeolite membrane, and which have excellent separation stability at high temperatures.)

1, Ammonia separation method, which is from at least containing ammonia, hydrogen and nitrogen gas mixture gas, using zeolite membrane ammonia selective permeation and separation of ammonia method,

the ammonia gas concentration in the mixed gas is 1.0 vol% or more.

2. The method for separating ammonia according to claim 1, wherein a volume ratio of hydrogen gas/nitrogen gas in the mixed gas is 0.2 or more and 3 or less.

3. The method for separating ammonia according to claim 1 or 2, wherein the temperature at which ammonia gas is separated is higher than 50 ℃ and lower than 500 ℃.

4. The ammonia separation method according to , wherein the zeolite constituting the zeolite membrane is RHO-type zeolite or MFI-type zeolite.

5, A method for separating ammonia, comprising a step of producing ammonia from hydrogen and nitrogen, wherein ammonia is separated from a mixed gas containing ammonia gas obtained in the production step by the method for separating ammonia according to any of claims 1 to 4.

6/ kinds of zeolite membranes each containing a zeolite, wherein a molar ratio of nitrogen to Al as determined by X-ray photoelectron spectroscopy is 0.01 to 4.

7, kinds of zeolite membranes, which are zeolite membranes containing zeolite and are characterized in that the molar ratio of an Si element to an Al element as determined by X-ray photoelectron spectroscopy is 2.0 to 10 inclusive.

8/ kinds of zeolite membranes each comprising a zeolite, wherein a molar ratio of an alkali metal element to an Al element determined by X-ray photoelectron spectroscopy is 0.01 to 0.070.

9, zeolite membrane composites for ammonia separation, which comprises a porous support and a zeolite membrane comprising a zeolite on the surface thereof, wherein the zeolite has a thermal expansion coefficient at 300 ℃ within + -0.25% of the thermal expansion coefficient at 30 ℃, and has a thermal expansion coefficient at 400 ℃ within + -0.35% of the thermal expansion coefficient at 30 ℃.

10. The zeolite membrane composite for ammonia separation according to claim 9, wherein the ratio of the rate of change of the thermal expansion coefficient at 400 ℃ to the rate of change of the thermal expansion coefficient at 30 ℃ to the rate of change of the thermal expansion coefficient at 300 ℃ to the rate of change of the thermal expansion coefficient at 30 ℃ of the zeolite is within ± 120%.

Technical Field

The present invention relates to methods for separating ammonia by selectively permeating ammonia gas through a zeolite membrane from a mixed gas composed of a plurality of components including ammonia gas and hydrogen gas and/or nitrogen gas, and further relates to zeolite membranes capable of efficiently separating ammonia from a mixed gas composed of a plurality of components including ammonia gas and hydrogen gas and/or nitrogen gas even under high-temperature conditions.

Background

In recent years, as a method for separating a gas (gas) mixture, a membrane separation and concentration method using a membrane such as a polymer membrane or a zeolite membrane has been proposed.

The polymer membrane has excellent processability, for example, as a flat membrane or a hollow fiber membrane, but has a problem of being easily swollen and having low heat resistance, and also has a problem of being low in resistance to reactive chemicals and easily causing deterioration due to adsorptive components such as sulfide, and is a problem that the polymer membrane is easily deformed by pressure to lower the separation performance, and therefore, it is not practical particularly in ammonia separation under high temperature conditions of , which is a problem of the present invention.

In view of the above, in recent years, various inorganic membranes having excellent chemical resistance, oxidation resistance, heat stability and pressure resistance have been proposed, in which a zeolite membrane has sub-nanometer order ordered pores and functions as a molecular sieve, and therefore, not only can selectively permeate a specific molecule, but also it is expected to be used as a highly durable separation membrane capable of separating and concentrating at a temperature of ℃ higher than that of the molecular membrane.

as zeolite membranes for gas separation, zeolite membranes such as a-type membranes, FAU membranes, MFI membranes, SAPO-34 membranes, and DDR membranes are known, and a zeolite membrane composite for gas separation which exhibits high throughput and separation performance and is suitable for separation of gases discharged from thermal power stations, petrochemical industries, and the like, for example, separation of carbon dioxide from nitrogen, carbon dioxide from methane, hydrogen from hydrocarbons, hydrogen from oxygen, hydrogen from carbon dioxide, nitrogen from oxygen, and paraffins from olefins has been proposed (for example, patent document 4).

In addition, , the present invention is also applicable to the separation of ammonia gas from hydrogen gas and nitrogen gas, and the membrane separation is applied, for example, to the membrane separation in the ammonia production process of the haber-bosch process using , which is an industrially important process, and as a process characteristic of the haber-bosch process, there is a point that the ammonia production reaction is an equilibrium reaction, and it is thermodynamically preferable to perform the reaction under high pressure and low temperature conditions, but in order to secure the catalytic reaction rate, the production conditions of high pressure and high temperature are always forcibly employed, and further, in the step of recovering ammonia gas as a product from the produced mixed gas because unreacted hydrogen gas, nitrogen gas and ammonia gas coexist in the produced mixed gas, it is necessary to cool the mixed gas to about-20 ℃ to-5 ℃ to perform condensation separation of ammonia (non-patent documents 1 and 2), and particularly, the latter is concerned, because the concentration contained in the produced mixed gas is always low due to the restriction of the reaction equilibrium of the above reaction, and therefore, the cooling separation process of ammonia gas by cooling the ammonia gas to consume a large amount of energy, and the mixed gas is necessary to recycle the temperature to the temperature of the mixed gas, and the temperature is also necessary to be regulated.

In order to avoid such a high energy consumption process, a process has been proposed in which a cooling condensation separation method in a purification step is replaced with a separation method using an inorganic membrane to efficiently recover high-concentration ammonia gas (patent documents 7 and 8).

Examples of a method for separating a mixed gas containing a high concentration of ammonia gas from a mixed gas of hydrogen gas, nitrogen gas, and ammonia gas include: 1) a method of selectively permeating hydrogen and/or nitrogen from the mixed gas using a separation membrane, and 2) a method of selectively permeating ammonia from the mixed gas using a separation membrane.

As the former method of selectively permeating hydrogen and/or nitrogen, there are proposed a method of using a polycrystalline layer of various kinds of zeolites (patent document 5), a method of using a molecular sieve membrane (patent document 6), and further, in patent document 7, there is described a method of selectively permeating hydrogen and/or nitrogen and a method of selectively permeating ammonia, and there is proposed a separation method of separating at least components of hydrogen, nitrogen and ammonia from a mixture of hydrogen, nitrogen and ammonia, which are produced gases, using a separation membrane in which a silica-containing layer is laminated on a ceramic substrate, and specifically, in patent document 7, as a brief flow chart in which a separation membrane is applied to ammonia production, since hydrogen selectively permeates a silica membrane under a high temperature condition, two separation membrane stages are provided, hydrogen is separated to a permeation side with the separation membrane of the 1 st stage, and ammonia which has not permeated through the separation membrane of the 1 st stage are separated to a permeation side with the separation membrane of the 2 nd stage, and further , it is shown that as a mixed gas of hydrogen and ammonia, the mixed gas must be mixed gas at a low temperature of more than 50 ℃.

, as the latter method for selectively permeating ammonia gas, there is proposed, in addition to patent document 7, an efficient ammonia separation method for separating ammonia gas from a mixed gas of ammonia gas and hydrogen gas and/or nitrogen gas by using a specific zeolite having an oxygen 8-membered ring (patent document 8). here, a method for separating ammonia gas by molecular sieve action of zeolite pore diameter is proposed, and , in general, ammonia can be used as a probe molecule adsorbed to an acid site in a temperature-rising desorption method for measuring the acid amount of zeolite, and the peak top temperature thereof can be about 480 ℃.

On the other hand, , an epoch-making production process has been developed in recent years in the ammonia synthesis method, and specifically a production process using an electronic salt (electrode) catalyst supporting ruthenium metal and showing extremely high catalytic activity even at low temperatures (340 to 400 ℃) has been reported (patent document 9).

[ Prior art documents ]

[ patent document ]

[ patent document 1] Japanese patent application laid-open No. 2011-

[ patent document 2] Japanese patent application laid-open No. 2011-

[ patent document 3] Japanese patent application laid-open No. 2011-121854

[ patent document 4] Japanese patent laid-open No. 2012 and 066242

[ patent document 5] Japanese Kohyo publication Hei 10-506363

[ patent document 6] Japanese patent application laid-open No. 2000-507909

[ patent document 7] Japanese patent laid-open No. 2008-247654

[ patent document 8] Japanese patent laid-open No. 2014-058433

[ patent document 9] International publication No. 2015/129471

[ non-patent literature ]

[ non-patent document 1] compiled by the society of chemistry of Japan, edited by the 6 th edition of chemistry for the use of the laboratory of chemistry, Tanshan corporation (2003), p581

[ Nonpatent document 2] society of corporate law, chemical engineering society, integration of chemical Processes (Process) 1 st edition, Tokyo Chemicals, p153

[ Nonpatent document 3] Tantita, Danyugan, Zeolite Vol.21No.2, Zeolite Association (2004), p45-52

Disclosure of Invention

[ problem to be solved by the invention ]

However, in the method of selectively permeating hydrogen and/or nitrogen gas from a mixed gas containing hydrogen, nitrogen and ammonia, the hydrogen and/or nitrogen gas is recovered through a separation membrane, and the essential problem of the present method is that points are adopted as a method of separating hydrogen and/or nitrogen gas from the mixed gas containing ammonia gas at a relatively high concentration, that is, there is a problem that a large amount of ammonia gas permeates along with the permeated hydrogen and/or nitrogen gas in the step of separating hydrogen and/or nitrogen gas, and therefore an economical process cannot be achieved unless a large amount of ammonia permeating therethrough is recovered.

Further , there is a problem that energy for increasing the pressure of hydrogen is required in the process for recycling hydrogen from the membrane separation of the 1 st stage to the permeation side under high temperature conditions proposed in patent document 7, and there is a fear that the membrane area is increased due to insufficient permeability of ammonia in the separation of nitrogen and ammonia in the membrane separation of the 2 nd stage, , in the method of patent document 7 for separating hydrogen as a raw material gas from a mixed gas of hydrogen, nitrogen and ammonia under high temperature conditions, for example, when ammonia synthesis is performed by directly mounting a separation membrane as an embodiment of in an ammonia synthesis reactor, permeation of the raw material gas occurs, and therefore, the reaction is not favorable due to the above-mentioned limitation of reaction balance, and ammonia gas with high concentration cannot be generated, and from the above viewpoint, such a separation membrane is used, and it is difficult to introduce the separation membrane into the production process for ammonia with special superiority.

However, in the method for separating ammonia gas using a separation membrane in which a silica-containing layer is laminated as proposed in the known document 7, it is described that a mixed gas having an ammonia gas concentration of more than 60 mol% is used, and in order to exhibit a blocking effect (blocking effect) due to ammonia, the mixed gas must be cooled to 50 ℃, and the ammonia gas separation is performed to such an extent that the ammonia gas is more or less permeable than the hydrogen gas.

On the other hand, in , the method of separating ammonia gas from a mixed gas of ammonia gas and hydrogen gas and/or nitrogen gas using a specific zeolite having an oxygen 8-membered ring proposed in patent document 8 is a method of permeating ammonia gas, and is not limited as described above, and can be realized as an effective method suitable for industrial processes, however, in the method of separating ammonia by molecular sieve action using zeolite pore diameters proposed in patent document 8, the permeation flux ratio (ideal separation coefficient) of ammonia gas and nitrogen gas is only about 14 at the highest, and the permeation performance is not sufficient, and in patent document 8, the permeation flux ratio of hydrogen gas and ammonia gas with respect to nitrogen gas is determined separately, and by comparing these ratios, although it is proposed that ammonia gas is substantially selectively permeated from a mixed gas of hydrogen gas, nitrogen gas and ammonia gas, particularly from the permeation flux ratio of ammonia gas with respect to hydrogen gas, the permeation performance is not sufficient, and the effectiveness of ammonia gas separation by molecular sieve action using the above-pore diameters is limited, , in patent document 8, it is not necessary to perform separation from a mixed gas of ammonia gas at 140 ℃, but there is a problem that ammonia gas and ammonia gas is permeated from a mixed gas at a low temperature, and also it is not necessary to cause a problem that ammonia gas is adsorbed by zeolite membrane , and zeolite membranes, and thus there are not essential for separation of ammonia gas.

On the other hand, , among ammonia production processes, as described in patent document 9, a catalytic process for producing ammonia which is highly active even under low temperature and low pressure conditions has been recently reported, and this process is expected as a process for reducing energy consumed during production, however, with only this innovative production process, as described above, because the ammonia-producing reaction is an equilibrium reaction, a mixed gas containing a high concentration of ammonia gas greater than the equilibrium composition cannot be produced due to the limitation of the reaction equilibrium, and the problem of reducing the energy consumption during production including the steps of recovering the produced ammonia and recycling the raw material gas cannot be essentially solved, .

The present invention has been made in view of the above-described conventional circumstances, and an object thereof is to provide kinds of ammonia separation methods which can separate ammonia by allowing ammonia gas to permeate through a zeolite membrane with high selectivity and high permeability from a mixed gas composed of a plurality of components including ammonia gas and hydrogen gas and/or nitrogen gas, and which are excellent in high-temperature separation stability and long-term operation stability.

Means for solving the problems

The present inventors have conducted studies on ammonia separation using a zeolite membrane to solve the above problems, and have found that when the ammonia concentration in a mixed gas of hydrogen, nitrogen and ammonia is not less than a predetermined amount, the permeation selectivity of ammonia permeating through the zeolite membrane is significantly improved, and that when systems of the present invention are used, ammonia separation performance can be stably maintained even under a temperature condition of more than 200 ℃.

Embodiment (invention a) of the present invention is achieved based on the above findings, and provides the following inventions.

[A1] method for separating ammonia by selectively permeating ammonia gas through a zeolite membrane from a mixed gas containing at least ammonia gas, hydrogen gas and nitrogen gas, wherein the ammonia gas concentration in the mixed gas is 1.0 vol% or more.

[A2] The method for separating ammonia according to [ A1], wherein the volume ratio of hydrogen gas/nitrogen gas in the mixed gas is 0.2 to 3.

[A3] The method for separating ammonia according to [ A1] or [ A2], wherein the temperature at which ammonia is separated is higher than 50 ℃ and lower than 500 ℃.

[A4] The ammonia separation method according to any of [ A1] to [ A3], wherein the zeolite constituting the zeolite membrane is an RHO-type zeolite or an MFI-type zeolite.

[A5] an ammonia separation method comprising a step of producing ammonia from hydrogen and nitrogen, wherein the ammonia is separated from the mixed gas containing ammonia gas obtained in the production step by the separation method described in any of [ A1] to [ A4] of item .

Further, the present inventors have made studies on ammonia gas separation using zeolite membranes to solve the above-mentioned problems, and as a result, they have found that ammonia gas can be separated with high selectivity and efficiency as compared with the conventional silica membranes, but the ammonia gas and nitrogen gas having separation performance have a permeation flux ratio (ideal separation coefficient) of only about 14 at the highest, and that, in contrast, ammonia gas separation performance can be significantly improved when a zeolite membrane having a surface in which the molar ratio of nitrogen atoms to Al atoms is within a predetermined range as determined by X-ray photoelectron spectroscopy (XPS) is used.

[B1] zeolite membranes are characterized in that the molar ratio of nitrogen atoms to Al atoms is 0.01 to 4, and the molar ratio is determined by X-ray photoelectron spectroscopy under the following measurement conditions.

(measurement conditions)

The X-ray source for measurement is a monochromatized Al-K α ray with power of 16kV-34W

Method for determining background in quantitative calculation: shirley method

[B2] The zeolite membrane according to [ B1], wherein the zeolite membrane is a zeolite membrane treated with an ammonium salt.

[B3] The zeolite membrane of [ B2], wherein the zeolite membrane is steps of zeolite membrane treated with aluminum nitrate.

[B4] The zeolite membrane of any of of [ B1] to [ B3], the zeolite being a zeolite of the RHO type.

[B5] The zeolite membrane according to any of [ B1] to [ B4], wherein the zeolite membrane is for separating ammonia gas.

[B6] method for separating ammonia, which comprises separating ammonia by permeating ammonia through a zeolite membrane described in any one of [ B1] to [ B5] from a mixed gas containing at least ammonia and hydrogen and/or nitrogen.

[B7] Ammonia separation method, which is composed of hydrogen and nitrogen gas ammonia production process in the separation method of [ B6] separation method.

In addition, the present inventors have made an -step study on the separation of ammonia gas using a zeolite membrane to solve the above-mentioned problems, and have found that although the conventional zeolite membrane for ammonia gas separation can separate ammonia gas with high selectivity and efficiency, the separation performance of the zeolite membrane is only about 14 at the maximum in the permeation flux ratio (ideal separation coefficient) of ammonia gas to nitrogen gas, and that the durability of the zeolite membrane is lost even under a low temperature condition of ℃ which is 140 ℃, and on the other hand, if a zeolite membrane having a surface in which the molar ratio of Si atoms to Al atoms determined by X-ray photoelectron spectroscopy (XPS) is in a predetermined range is used, it is possible to exhibit a remarkable ammonia gas separation performance and improve the separation stability under a high temperature condition.

[C1] zeolite membranes are characterized in that the molar ratio of Si atoms to Al atoms is 2.0-10, which is determined by X-ray photoelectron spectroscopy under the following measurement conditions.

(measurement conditions)

The X-ray source for measurement is a monochromatized Al-K α ray with the output power of 16kV-34W

Method for determining background in quantitative calculation: shirley method

[C2] The zeolite membrane according to [ C1], wherein the molar ratio of nitrogen atoms to Al atoms in the zeolite membrane is 0.01 or more and 4 or less, and the molar ratio is determined by X-ray photoelectron spectroscopy under the following measurement conditions.

(measurement conditions)

The X-ray source for measurement is a monochromatized Al-K α ray with the output power of 16kV-34W

Method for determining background in quantitative calculation: shirley method

[C3] The zeolite membrane according to [ C1] or [ C2], characterized in that the zeolite membrane is a zeolite membrane treated with an aluminum salt.

[C4] The zeolite membrane according to any of [ C1] to [ C3], wherein the zeolite membrane is a zeolite membrane treated with an ammonium salt.

[C5] The zeolite membrane according to any of [ C1] to [ C4], wherein the zeolite membrane is a zeolite membrane treated with an ammonium salt and then with an aluminum salt.

[C6] The zeolite membrane of any of of [ C1] to [ C5], the zeolite being a zeolite of the RHO type.

[C7] The zeolite membrane according to any of [ C1] to [ C6], wherein the zeolite membrane is for separating ammonia.

[C8] method for separating ammonia, which comprises separating ammonia by permeating ammonia through a zeolite membrane described in any one of [ C1] to [ C7] from a mixed gas containing at least ammonia and hydrogen and/or nitrogen.

[C9] Ammonia separation method, which is composed of hydrogen and nitrogen gas ammonia production process in the separation method [ C8] to separate the ammonia.

Further, the present inventors have made studies on the separation of ammonia gas using a zeolite membrane in order to solve the above problems and found that when a zeolite membrane having a surface with a molar ratio of alkali metal atoms to Al atoms determined by X-ray photoelectron spectroscopy (XPS) being within a predetermined range is used, the permeability can be improved while maintaining high ammonia gas separation selectivity.

[D1] zeolite membranes are characterized in that the molar ratio of alkali metal atoms to Al atoms is 0.01 to 0.070, which is determined by X-ray photoelectron spectroscopy under the following measurement conditions.

(measurement conditions)

The X-ray source for measurement is a monochromatized Al-K α ray with the output power of 16kV-34W

Method for determining background in quantitative calculation: shirley method

[D2] The zeolite membrane according to [ D1], wherein the zeolite membrane has a molar ratio of nitrogen atoms to Al atoms of 0.01 to 4, and the molar ratio is determined by X-ray photoelectron spectroscopy under the following measurement conditions.

(measurement conditions)

The X-ray source for measurement is a monochromatized Al-K α ray with the output power of 16kV-34W

Method for determining background in quantitative calculation: shirley method

[D3] The zeolite membrane according to [ D1] or [ D2], characterized in that the zeolite membrane is a zeolite membrane treated with an alkali metal salt.

[D4] The zeolite membrane according to any of [ D1] to [ D3], wherein the zeolite membrane is a zeolite membrane treated with an ammonium salt.

[D5] The zeolite membrane according to any of [ D1] to [ D4], wherein the zeolite membrane is a zeolite membrane treated with an ammonium salt and then treated with an alkali metal salt.

[D6] The zeolite membrane of any of [ D1] to [ D5], the zeolite being a zeolite of the RHO type.

[D7] The zeolite membrane according to any of [ D1] to [ D6], wherein the zeolite membrane is for separating ammonia gas.

[D8] method for separating ammonia, which comprises separating ammonia by permeating ammonia through a zeolite membrane described in any one of items [ D1] to [ D7] from a mixed gas containing at least ammonia and hydrogen and/or nitrogen.

[D9] Ammonia separation method, which is composed of hydrogen and nitrogen gas ammonia production process obtained in the separation method [ D8] to separate.

In addition, the present inventors have made studies on ammonia gas separation using a zeolite membrane composite in order to solve the above-mentioned problems, and have found that ammonia gas can be separated with high selectivity and efficiency as compared with the conventional silica membrane, but when a zeolite membrane composite obtained by forming a CHA-type zeolite membrane as proposed in patent document 8, in which the rates of change of thermal shrinkage rates of 200 ℃ and 300 ℃ with respect to 30 ℃ are monotonous changes of 0.13% and 0.30% (c-axis direction), is used as described in reference example E1, the ammonia gas separation performance is reduced and improved particularly in a temperature range of more than 200 ℃, and it is presumed that cracks are generated at the zeolite grain boundaries due to thermal shrinkage of the zeolite and gas permeates through the cracks, and on the other hand, when the RHO-type zeolite as described in example E of the present invention is changed at a high thermal shrinkage rate of 1.55% with respect to heat at 200 ℃ with respect to 30 ℃, the RHO-type zeolite exhibiting high linear shrinkage behavior, and the high thermal expansion rate of ammonia gas can be increased by about 0.02% under the condition of high thermal expansion and high thermal expansion rate.

That is, to solve the above-mentioned problems, is an object of the present invention, namely, to separate ammonia gas with high selectivity and high permeability from a gas mixture comprising a plurality of components including ammonia gas and hydrogen gas and/or nitrogen gas under high temperature conditions, and it is necessary to apply a zeolite membrane composite obtained by forming a film of zeolite exhibiting a thermal expansion change rate in a predetermined temperature range among various zeolite membrane composites, and to achieve the present invention.

[E1] zeolite membrane composites for ammonia separation, which are zeolite membrane composites for ammonia separation comprising a zeolite, wherein the rate of change of the thermal expansion coefficient at 300 ℃ with respect to the thermal expansion coefficient at 30 ℃ is within. + -. 0.25%, and the rate of change of the thermal expansion coefficient at 400 ℃ with respect to the thermal expansion coefficient at 30 ℃ is within. + -. 0.35%.

[E2] The zeolite membrane composite for ammonia separation described in [ E1], wherein the ratio of the rate of change in the thermal expansion coefficient at 400 ℃ relative to the thermal expansion coefficient at 30 ℃ to the rate of change in the thermal expansion coefficient at 300 ℃ relative to the thermal expansion coefficient at 30 ℃ of the zeolite is within. + -. 120%.

[E3] The zeolite membrane composite for ammonia separation described in [ E1] or [ E2], wherein the zeolite is a RHO-type zeolite or an MFI-type zeolite.

[E4]According to [ E1]～[E3]A zeolite membrane composite for ammonia separation as claimed in any one of items , wherein SiO of the zeolite is₂/Al₂O₃The molar ratio is 6 to 500.

[E5] method for separating ammonia, which comprises separating ammonia from a gas mixture containing at least ammonia and hydrogen and/or nitrogen by using the zeolite membrane complex for ammonia gas separation described in any of [ E1] to [ E4 ].

[E6] Ammonia separation method, which is composed of hydrogen and nitrogen gas ammonia production process in the steps of ammonia separation method by [ E5] separation method.

In particular, the second to fifth embodiments are techniques relating to an ammonia gas separation membrane that contributes to completion of an energy-saving ammonia production process, and are also techniques expected to be applied to a reaction separation type ammonia production process of , which is an embodiment of the present invention.

[ Effect of the invention ]

According to embodiment of the present invention, ammonia gas can be continuously separated to the permeation side with high selectivity and high efficiency from a mixed gas composed of a plurality of components including ammonia gas and hydrogen gas and nitrogen gas, and further, according to the present invention, ammonia gas can be stably used even under high temperature conditions of more than 50 ℃ and steps of more than 200 ℃, so that the permeation rate of ammonia gas is high, and as a result, the membrane area necessary for separation can be reduced, making it possible to separate ammonia at low cost with a small scale of equipment.

As a specific example of the zeolite membrane of the present invention, in the ammonia production process represented by the haber-bosch process or the like, when ammonia is recovered from a mixed gas composed of a plurality of components including ammonia gas and hydrogen gas and nitrogen gas recovered from a reactor, ammonia separation can be performed more efficiently than in the conventional cooling condensation separation method, and the cooling energy for ammonia condensation can be reduced.

In addition, as another aspect, the zeolite membrane of the present invention can stably separate ammonia gas from a mixed gas composed of a plurality of components including ammonia gas and hydrogen gas and nitrogen gas at a high permeability and with high efficiency even under high temperature conditions, and therefore, a reaction separation type ammonia production process can be devised, in which the zeolite membrane of the present invention is installed in a reactor, and the ammonia gas is produced and the produced ammonia gas is recovered.

According to the second to fifth embodiments of the present invention, ammonia gas can be continuously separated to the permeate side with high selectivity and high efficiency stably even under high temperature conditions from a mixed gas composed of a plurality of components including ammonia gas and including hydrogen and/or nitrogen. Further, the zeolite membrane of the present invention can be stably used even under higher temperature conditions, and therefore the permeability of ammonia gas is high, and as a result, the membrane area necessary for separation can be reduced, making it possible to separate ammonia gas at low cost with a small-scale apparatus.

As a specific example of the zeolite membrane of the present invention, in the ammonia production process represented by the haber-bosch process or the like, when ammonia is recovered from a mixed gas composed of a plurality of components including ammonia gas and hydrogen gas and/or nitrogen gas recovered from a reactor, the ammonia can be separated more efficiently than in the conventional cooling condensation separation method, and therefore the cooling energy for ammonia condensation can be reduced.

In addition, as another aspect, the zeolite membrane of the present invention can stably separate ammonia gas from a mixed gas composed of a plurality of components including ammonia gas and hydrogen gas and/or nitrogen gas at a high permeability and with high efficiency even under high temperature conditions, and therefore, a reaction separation type ammonia production process can be devised, in which the zeolite membrane of the present invention is installed in a reactor, and the ammonia gas is produced and the produced ammonia gas is recovered.

In particular, the application of the th to the fifth embodiment to the reaction separation type ammonia production process is expected to reduce the reaction pressure in the ammonia production process, and also to significantly increase the conversion rate of the raw material gas into ammonia gas and reduce the amount of recycle of the recovered gas to the reactor in the production process.

[ description of the drawings ]

Fig. 1 is a schematic diagram showing the structure of the apparatus for ammonia gas separation test in the example.

Fig. 2 shows the results of measuring the thermal expansion coefficient of the zeolite according to example E4 according to the temperature.

[ notation ] to show

1 Zeolite Membrane Complex

2 pressure-resistant container

3 sealing part at front end of support body

4 Joint part of zeolite membrane composite and permeation gas recovery tube

5 pressure gauge

6 back pressure valve

7 supply gas (sample gas)

8 permeation of gas

9 purge gas

10 impermeable gas

11 permeate gas recovery tube

12 purge gas supply pipe

Detailed Description

In addition, in the present specification, a porous support-zeolite membrane composite "formed by a zeolite membrane on a porous support may be referred to as a" zeolite membrane composite "or a" membrane composite ", and the" porous support "may be simply referred to as a" support ", and the" aluminosilicate zeolite "may be referred to as a" zeolite ".

Embodiment (invention a) of the ammonia separation method of the present invention is a method for separating ammonia from a mixed gas composed of a plurality of components including at least ammonia, hydrogen, and nitrogen, stably and continuously to the permeation side with high permeability and high selectivity by using a zeolite membrane, and is characterized in that ammonia is selectively permeated from a mixed gas of hydrogen and nitrogen containing ammonia in a predetermined amount or more and is separated.

In another embodiment of the ammonia separation method according to the present invention, a mixed gas containing ammonia and a plurality of components including hydrogen and/or nitrogen is brought into contact with a predetermined zeolite membrane, and ammonia is selectively permeated and separated from the mixed gas.

Hereinafter, the details are explained.

< method for producing ammonia >

The ammonia separation method according to the present embodiment is effective in combination with an ammonia production method for obtaining a mixed gas containing at least ammonia, hydrogen and nitrogen, since it can be used effectively when ammonia is efficiently separated from the mixed gas containing at least ammonia, hydrogen and nitrogen, that is, in addition to the ammonia production method for separating ammonia obtained in the second step from ammonia obtained in the step, which includes the th step for producing ammonia from hydrogen and nitrogen and the second step for separating ammonia obtained in the step by the ammonia separation method described later, the method for producing ammonia in which the th step and the second step are performed in reactors is also which is a preferable embodiment of the present invention, and the execution of the th step and the second step in reactors means that the th step and the second step are performed simultaneously, that is, in the embodiments of the present invention, ammonia can be produced from hydrogen and nitrogen in a vessel, and ammonia can be efficiently produced while ammonia is separated from the mixed gas containing ammonia.

The industrial process for producing ammonia is not particularly limited, and includes a haber-bosch process, in which ammonia is produced by reacting nitrogen and hydrogen over a catalyst at a high temperature and a high pressure of 300 to 500 ℃ and 10 to 40MPa using iron oxide as a catalyst, the produced ammonia contained in the gas at the outlet of a reactor is cooled and condensed to be separated, and the product is recovered, and unreacted nitrogen and hydrogen are separated and recycled as a raw material gas, and further, as a method for improving the haber-bosch process, a Ru-based supported catalyst capable of producing ammonia under a lower pressure condition was developed in 1980, and the process combined with the haber-bosch process is also industrially realized, but the basic production process is not changed over 100 years, and thus is roughly classified into an iron-based catalyst and a Ru-based catalyst, the molar ratio of the raw material gas used in the production of ammonia is preferably hydrogen/nitrogen ratio which is the theoretical ratio, but the molar ratio of the produced industrial catalyst is easily changed over 100 years, and the preferred ammonia production process is preferably reduced by using a combination of the hydrogen/hydrogen-based catalyst, and the conditions for producing ammonia are preferably lower than the conditions for producing ammonia.

< Ammonia separation method >

An th embodiment of the method for separating ammonia of the present invention is characterized in that a zeolite membrane is used, a mixed gas composed of a plurality of components including ammonia and hydrogen and nitrogen is brought into contact with the zeolite membrane, and ammonia is selectively permeated from the mixed gas and separated.

The ammonia separation method of the present invention is characterized in that a mixed gas containing ammonia and a plurality of components including hydrogen and/or nitrogen is brought into contact with a predetermined zeolite membrane, and ammonia is selectively permeated from the mixed gas to be separated.

As described above, according to the present invention, ammonia gas is produced from hydrogen gas and nitrogen gas in a reactor, and ammonia can be efficiently produced and recovered in the reactor while allowing the produced ammonia gas to permeate through a zeolite membrane.

The ammonia separation by the zeolite membrane in the present invention is mainly separation by a hopping mechanism (hoppingmechanism) of ammonia in zeolite pores, but separation as a molecular sieve is also utilized by pore size control by the zeolite membrane adsorbing ammonia, ammonium ions, and the like. By the former action, ammonia having high affinity for the zeolite membrane can be caused to permeate the zeolite membrane with high selectivity; further, by the latter action, gas molecules having a size not smaller than the effective pore size of the zeolite membrane adsorbing ammonia can be efficiently separated from gas molecules having a size not smaller than the effective pore size of the zeolite membrane, and thus ammonia can be more efficiently separated.

However, in the zeolite membrane as such, the pore diameter in the zeolite membrane is narrowed by adsorption of ammonia and ammonium ions contained in the zeolite, and the permeation rate of hydrogen gas having a particularly small molecular size can be particularly reduced, and in the case of using a zeolite having a pore diameter larger than the molecular size of hydrogen gas, nitrogen gas, or ammonia gas, this action also narrows the pores of the zeolite membrane, and thus inhibits permeation of nitrogen gas or hydrogen gas, and shows that the adsorption of ammonia and ammonium ions in the zeolite pores causes a jump movement due to adsorption/desorption of ammonia in the pores, and this action shows selective separation of ammonia gas.

In the embodiment (invention a) of the present invention, as described above, the ammonia separation by the jump mechanism of ammonia in zeolite pores is characterized by utilizing ammonia adsorption on zeolite, and therefore, it is necessary to control the ammonia gas concentration in a feed gas containing hydrogen, nitrogen and ammonia to be a predetermined amount or more, as the concentration of ammonia in the feed gas is 1.0% by volume or more, this is important because the ammonia adsorbed on zeolite and the ammonia in a gas phase have an adsorption equilibrium relationship, and the adsorption ability of ammonia on zeolite depends greatly on the ammonia gas concentration in the feed gas, as shown in the comparative example of the present invention, a slight ammonia permeation selectivity can be exhibited even in an ammonia gas concentration of less than 1.0% by volume, but this effect is not significant, and therefore, in the present invention, a feed gas using an ammonia concentration of 1.0% by volume or more is important, and when such a gas is brought into contact with a zeolite membrane under pressurized conditions, the ammonia separation selectivity from ammonia in the feed gas is improved, and the ammonia concentration of ammonia is preferably equal to or more than 0.0% by volume, and when the ammonia is brought into contact with a zeolite membrane under other known conditions, the ammonia separation process, the ammonia is considered to be a high, and the ammonia concentration of ammonia is equal to be equal to or more favorable, and when the ammonia is taken from the ammonia concentration of ammonia, the ammonia is taken from the ammonia feed gas, the ammonia concentration of ammonia, and the ammonia concentration of ammonia is taken from the ammonia, and the ammonia is taken from the ammonia feed gas is taken from the ammonia feed process under the same, and the concentration of ammonia is taken from the case of the process of the case of the ammonia is taken from the case of the process of the case of the process is taken from the case of the process of the case of the process of the case of the process of the case of the process of the case of.

As described above, the reason why the transmission selectivity of ammonia that permeates the zeolite membrane is significantly improved when the ammonia gas concentration in the mixed gas of hydrogen, nitrogen and ammonia is a predetermined amount or more is not known in detail, but when the ammonia gas concentration in the mixed gas is increased, the zeolite membrane in which ammonia is adsorbed in the pores is first formed because adsorption balance between the ammonia gas and the zeolite is likely to occur, and the zeolite membrane in which ammonia is adsorbed in the pores is formed, the pore diameter in the zeolite membrane is narrowed, and the transmission rate of hydrogen having a small molecular size is reduced, and when a zeolite having a pore diameter larger than the molecular size of hydrogen, nitrogen and ammonia is used, the effect is similarly narrowed in the pores of the zeolite membrane, and thus the inhibition of hydrogen gas transmission is significantly exhibited, and further , the ammonia adsorbed in the zeolite pores can cause a jump movement due to adsorption/desorption of ammonia in the pores by a pressure difference between the inside and outside of the membrane, and selective separation of ammonia is exhibited by this behavior.

That is, the present invention is techniques of actively adsorbing ammonia on zeolite to control the pore size of zeolite membrane and improve the selectivity of ammonia separation, and techniques of selectively permeating ammonia by using the jump movement caused by ammonia adsorption/desorption in the pores, whereas patent document 8 proposes a technique of separating ammonia by using a molecular sieve having a pore size of zeolite without producing such adsorption because such an ammonia adsorption zeolite membrane causes clogging in ammonia permeation, and techniques of hardly producing ammonia adsorption and having low thermal stability even if ammonia is adsorbed as in the silica membrane proposed in patent document 7.

In addition , in the present invention, where ammonia separation is performed mainly by the mechanism of in-pore hopping accompanying adsorption/desorption of ammonia on zeolite, the temperature at the time of ammonia separation has a great influence on the long-term durability of the zeolite membrane used, the ammonia separation performance of the zeolite membrane, and the manufacturing energy balance of the whole process when combined with an ammonia production facility, and thus is an important design factor . from these points of view, in the present invention, in the case of separating the generated gas in ammonia synthesis, the temperature at the time of ammonia separation is usually the same as or lower than the synthesis temperature of ammonia, the temperature at the time of ammonia separation is the temperature in the separator performing ammonia separation, that is, the temperature supplied to the mixed gas to be separated, and the temperature of the ammonia gas to be separated, the temperature of ammonia gas to be separated may be considered to be substantially the same as the temperature in the separator.

In the method for separating ammonia by the intra-pore hopping movement according to the present invention, the velocity is controlled by controlling the molar ratio of the alkali metal atoms to the Al atoms in the zeolite pores to be less than the saturation amount ratio, and therefore, the control of the molar ratio is important, and there is a case where the method is preferably combined with the method of controlling the molar ratio to be 0.01 to 0.070 as in the fourth embodiment of the present invention.

The other gas composition in the supply gas (mixed gas) is not particularly limited, and the volume ratio of hydrogen gas/nitrogen gas contained in the supply gas is usually 3 or less, more preferably 2 or less, and by adjusting this volume ratio, the permeation amount of hydrogen at the time of ammonia separation can be reduced, and the ammonia separation selectivity is improved, for the reason as described above, in the case of obtaining the supply gas of the ammonia separation process of the present invention from the ammonia production process, it is not particularly limited, but it is preferably combined with a Ru-based ammonia production catalytic process that reduces the volume ratio of hydrogen gas/nitrogen gas in the raw material gas, and in addition , the lower limit thereof is effective within the range of effective numbers, that is, the upper limit 3 or less means 2.5 or less and 3.5 or more, and in addition , 0.2 or more means 0.15 or more and less than 0.25, and 1.0 or more means 0.95 or less and less than 1.05, because the ammonia separation selectivity is improved, and thus, the lower limit is not particularly limited.

In the present invention, the higher the pressure of the supplied gas (mixed gas), the higher the separation performance of the zeolite membrane, and the smaller the area of the zeolite membrane to be used, and therefore, the preferred embodiment is that the pressure is not particularly limited as long as the pressure is equal to or higher than atmospheric pressure, and the pressure can be appropriately reduced and adjusted to a desired pressure. When the gas to be separated is lower than the pressure used for separation, it can be used by pressurizing with a compressor or the like.

The pressure of the supplied gas is usually atmospheric pressure or higher, preferably 0.1MPa or higher, and more preferably 0.2MPa or higher. The upper limit is usually 20MPa or less, preferably 10MPa or less, more preferably 5MPa or less, and may be 3MPa or less.

The pressure on the permeation side is not particularly limited as long as it is lower than the pressure of the gas on the supply side, and is usually 10MPa or less, preferably 5MPa or less, more preferably 1MPa or less, and further steps are preferably 0.5MPa or less, and may be a pressure reduced to atmospheric pressure or less depending on the case.

The pressure difference between the gas on the supply side and the gas on the permeation side is not particularly limited, and is usually 20MPa or less, preferably 10MPa or less, more preferably 5MPa or less, and further steps are preferably 1MPa or less, and further, is usually 0.001MPa or more, preferably 0.01MPa or more, more preferably 0.02MPa or more.

Here, the differential pressure is a difference between the partial pressure on the supply side and the partial pressure on the permeation side of the gas. The pressure [ Pa ] is not particularly limited, and means an absolute pressure.

The flow rate of the supplied gas may be a flow rate to compensate for the decrease in the permeated gas, or a flow rate at which the supplied gas is mixed as much as possible by adjusting the concentration of the gas having low permeability in the supplied gas in the vicinity of the membrane to in the whole gas, and may be related to the tube diameter of the zeolite membrane composite and the separation performance of the membrane, but is usually 0.001mm/sec or more, preferably 0.01mm/sec or more, more preferably 0.1mm/sec or more, particularly preferably 0.5mm/sec or more, more preferably 1mm/sec or more, and the upper limit is not particularly limited, and is usually 1m/sec or less, preferably 0.5m/sec or less, in terms of the linear velocity.

The purge gas used in the method of the present invention is, for example, a gas 9 supplied from a line 12 shown in fig. 1, and the pressure of the purge gas is usually atmospheric pressure, but is not particularly limited to atmospheric pressure, preferably 20MPa or less, more preferably 10MPa or less, and further steps are preferably 1MPa or less, and the lower limit is preferably 0.09MPa or more, more preferably 0.1MPa or more, and in some cases, it may be used by reducing the pressure.

The flow rate of the purge gas is not particularly limited, but is usually 0.5mm/sec or more, preferably 1mm/sec or more in terms of linear velocity, and the upper limit is not particularly limited, and is usually 1m/sec or less, preferably 0.5m/sec or less.

The gas separation apparatus is not particularly limited, and a zeolite membrane composite is usually used as a membrane module (hereinafter, "separation apparatus using a zeolite membrane composite and/or a zeolite membrane composite" may be simply referred to as "membrane module"). The membrane module may be, for example, a device as schematically shown in fig. 1, or a membrane module exemplified by "gas separation and purification technology" (published by 2007, the center of eastern research, ltd.) on page 22, etc. may be used.

The operation of separating the mixed gas in the apparatus of FIG. 1 is described in example .

In this case, the gas to be separated is supplied to the membrane module of stage 1, the gas that has not permeated through the membrane may be supplied steps to the membrane module of stage 2, or the gas that has permeated may be supplied to the membrane module of stage 2.

In the case of separation using a membrane module provided in multiple stages, when gas is supplied to the membrane module in the post stage, the pressure of the supplied gas may be adjusted by a booster or the like as necessary.

Generally, as the performance of the membrane, the separation performance of the membrane having high permeability tends to be low, and the permeation performance of the membrane having high separation performance tends to be low at , whereby the membrane having high permeability is reduced when the gas component to be separated or concentrated is treated to a predetermined concentration, whereas the membrane having high permeability is likely to permeate to the permeation side at , whereby the concentration of the component having high permeability in the gas on the permeation side tends to be reduced, whereas the membrane having high separation performance is less likely to permeate to the permeation side, whereby the concentration of the component having high permeability in the gas on the permeation side is higher, but the necessary membrane area tends to be larger, whereas the relationship between the necessary membrane area and the concentration or the permeation/non-permeation amount of the target gas is difficult to control in the separation by 1 membrane, and the control becomes easy by using the membranes having different performances, and the overall permeation/non-permeation yield of the target gas can be maximized by optimizing the relationship between the necessary membrane area and the permeation/non-permeation amount of the target gas.

For example, when ammonia cannot be separated sufficiently by the membrane separation in stage 1, the gas on the non-permeation side can be separated by steps using a multistage membrane, and when ammonia and hydrogen are contained in the permeation side together with ammonia, the gas can be separated by a membrane having high separation performance between ammonia and hydrogen.

The zeolite membrane used in the present invention has excellent chemical resistance, oxidation resistance, heat stability, and pressure resistance, and also has excellent durability, while exhibiting high ammonia permeability and separation performance.

Here, the high permeability means that a sufficient treatment amount is exhibited, for example, a permeation flux (Permean) of a gas component permeating a membrane [ mol/(m)²·s·Pa)]For example, when ammonia is permeated at a temperature of 200 ℃ and a differential pressure of 0.3MPa, it is usually 1X 10^-9Above, preferably 5 × 10^-9Above, more preferably 1 × 10^-8The above step is preferably 2X 10^-8Above, particularly preferably 5X 10^-8Above, 1X 10 is particularly preferable^-7Above, most preferably 2X 10^-7The above. The upper limit is not particularly limited, and is usually 3X 10^-4The following.

In addition, the permeation flux [ mol/(m) of the zeolite membrane composite used in the present invention²·s·Pa)]For example, when nitrogen is permeated under the same conditions, it is usually 5X 10^-8Hereinafter, 3 × 10 is preferable^-8Hereinafter, more preferably 1 × 10^-8Hereinafter, particularly preferably 5 × 10^-9Hereinafter, the most preferable is 1X 10^-9Below, it is desirable that the permeation flux be 0 to trueSometimes 1X 10 is required for use^-10～1×10^-14Left and right.

Here, the permeation flux (also referred to as "permeability") is a value obtained by dividing the amount of a permeation substance by the product of the membrane area, time, and partial pressure difference between the supply side and the permeation side of the permeation substance, and has a unit of [ mol/(m)/²·s·Pa)]This is the value calculated by the method described in example .

The ideal separation coefficient and the separation coefficient are indices indicating selectivity generally used in membrane separation, the ideal separation coefficient is a value calculated by the method described in example , and the separation coefficient is a value calculated as follows.

When the separation coefficient α is obtained, it is calculated by the following equation.

α＝(Q’1/Q’2)/(P’1/P’2)

[ in the above formula, Q '1 and Q' 2 represent the respective transmission amounts [ mol/(m) of a gas having high permeability and a gas having low permeability²·s·Pa)]And P '1 and P' 2 represent partial pressures [ Pa ] of a gas having a high permeability and a gas having a low permeability in the supplied gas, respectively]。〕

The separation coefficient α may be determined as follows.

α＝(C’1/C’2)/(C1/C2)

In the above formula, C '1 and C' 2 represent the concentrations of a gas having high permeability and a gas having low permeability in a permeated gas [ volume% ], and C1 and C2 represent the concentrations of a gas having high permeability and a gas having low permeability in a supplied gas [ volume% ], respectively. Angle (c)

The ideal separation coefficient is, for example, generally 15 or more, preferably 20 or more, more preferably 25 or more, and most preferably 30 or more when ammonia and nitrogen are permeated at a temperature of 200 ℃ and a differential pressure of 0.3MPa, and is generally 2 or more, preferably 3 or more, more preferably 5 or more, and further steps are preferably 7 or more, particularly preferably 8 or more, particularly preferably 10 or more, and most preferably 15 or more when ammonia and hydrogen are permeated at a temperature of 200 ℃ and a differential pressure of 0.3 MPa.

The separation coefficient of the zeolite membrane used in the present invention is determined, for example, by adjusting the volume ratio of ammonia to nitrogen to 1: 1, it is usually 2 or more, preferably 3 or more, more preferably 4 or more, and still more preferably 5 or more. The upper limit of the separation coefficient is a case where only ammonia is completely permeated, and in this case, the separation coefficient is infinite, and in practice, the separation coefficient may be about 10 ten thousand or less.

The zeolite membrane used in the present invention is excellent in chemical resistance, oxidation resistance, heat stability and pressure resistance, exhibits high permeability and separation performance, and is excellent in durability as described above, and the ammonia separation method of the present invention using such a zeolite membrane can be suitably used for ammonia separation from a product of ammonia synthesis. In the ammonia separation method of the present invention, a zeolite membrane may be installed in an ammonia synthesis reactor, ammonia may be selectively permeated and separated in the reactor, and the equilibrium between hydrogen gas and nitrogen gas in the reactor and ammonia gas may be shifted to be utilized as a membrane reactor for synthesizing ammonia with high conversion efficiency.

(Zeolite)

In the present invention, the zeolite constituting the zeolite membrane is aluminosilicate. The aluminosilicate contains oxides of Si and Al as main components, and may contain elements other than these without impairing the effects of the present invention. As the cation species contained in the zeolite of the present invention, a cation species which is easily coordinated to the ion exchange sites of the zeolite is preferable, and for example, a cation species selected from the group consisting of elements in columns 1, 2, 8, 9, 10, 11 and 12 of the periodic table, NH₄ ⁺And two or more kinds of cationic species among them, more preferably a cationic species selected from the group consisting of elements in columns 1 and 2 of the periodic table, NH₄ ⁺And two or more kinds of cationic species among them.

The zeolite used in the present invention is an aluminosilicate. SiO of aluminosilicate₂/Al₂O₃The molar ratio is not particularly limited, but is usually 6 or more, preferably 7 or more, and more preferably 8 or moreIn addition, in respect of , it is usually 500 or less, preferably 100 or less, more preferably 80 or less, further steps are preferably 50 or less, particularly preferably 45 or less, further steps are preferably 30 or less, most preferably 25 or less₂/Al₂O₃The zeolite having a molar ratio is preferable because the compactness of the zeolite membrane, the chemical resistance, the heat resistance, and other durability can be improved. In addition, from the viewpoint of the separation performance of permeating ammonia from a mixed gas composed of a plurality of components including ammonia and hydrogen and nitrogen, it is preferable to use zeolite containing a large amount of Al because the acid site of the Al element serves as an adsorption site of ammonia, and to use SiO showing the above-mentioned property₂/Al₂O₃The zeolite has high permeability and high selectivity for separating ammonia.

SiO of zeolite₂/Al₂O₃The molar ratio can be adjusted by the reaction conditions of hydrothermal synthesis described later.

In addition, in this specification, SiO₂/Al₂O₃The molar ratio is a value determined by scanning electron microscopy-energy dispersive X-ray spectrometry (SEM-EDX). In this case, in order to obtain information on a film having a thickness of only several micrometers, the acceleration voltage of X-rays is generally 10kV and the measurement is performed.

The structure of the zeolite used in the present invention is represented by a code defined by the International Zeolite Association (IZA), and examples thereof include ABW, ACO, AEI, AEN, AFI, AFT, AFX, ANA, ATN, ATT, ATV, AWO, AWW, BIK, CHA, DDR, DFT, EAB, EPI, ERI, ESV, GIS, GOO, ITE, JBW, KFI, LEV, LTA, MER, MON, MTF, OWE, PAU, PHI, RHO, RTE, RWR, SAS, SAT, SAV, SIV, TSC, UFI, VNI, YUG, AEL, AFO, AHT, DAC, FER, HEU, IMF, ITH, MEL, MFS, MWW, RRO, SFG, STI, SZR, TER, TON, TUN, moni, pami, MFI, fafu, etc.

Wherein the preferred skeleton density is 18.0T/nm³The following zeolites are more preferably AEI, AFX, CHA, DDR, ERI, LEV, RHO, MOR, MFI, FAU, and are more preferably AEI, CHA, DDR, RHO,MOR, MFI, FAU, particularly preferably CHA, RHO or MFI, most preferably RHO or MFI. By using zeolite having a low framework density, when a permeated component other than ammonia is present in the mixed gas containing ammonia, resistance at the time of permeation of the permeated component can be reduced, and the amount of ammonia permeation can be easily increased.

In the fifth embodiment of the present invention (zeolite membrane composite E), the skeleton density is preferably 18.0T/nm³The following zeolites are more preferably AFX, DDR, ERI, LEV, RHO, MOR, MFI, and FAU, and the further steps are preferably DDR, RHO, MOR, MFI, and FAU, and most preferably RHO and MFI.

Here, the skeleton density (unit: T/nm)³) Means the unit volume (1 nm) of the zeolite³) The number of T atoms (atoms other than oxygen among the atoms constituting the framework of the zeolite) present in (A) is determined by the structure of the zeolite. In addition, the relationship between the FRAMEWORK density and the structure OF ZEOLITE is shown in "ATLAS OF ZEOLITE FRAMEWORK TYPES (ATLAS OF ZEOLITE FRAMEWORK TYPES)" (6 th revised edition, 2007 eisweieer press).

The membrane separation of ammonia from hydrogen and nitrogen according to the present invention is characterized by ammonia separation based on a hopping mechanism of ammonia in zeolite pores by adsorption of ammonia on zeolite, but is not particularly limited, and among these, a zeolite having pores with a diameter close to the molecular diameter of ammonia is sometimes preferable because the selectivity of ammonia separation is improved, and from this viewpoint, a zeolite having oxygen 8-membered ring pores is preferable as the zeolite structure₂/Al₂O₃In the case of zeolite having a molar ratio, the pore diameter of the zeolite membrane can be controlled by ammonia adsorbed to Al sites, and thus ammonia can be separated with high permeability and high selectivity.

Therefore, the effective pore diameter of zeolite used for membrane separation is , which is an important design factor because it has a great influence on the pore diameter of the zeolite membrane adsorbing ammonia.

For example, the pore size of zeolite is slightly affected by the atomic diameter of the metal species introduced into the zeolite framework. When a metal having an atomic diameter smaller than that of silicon, specifically, for example, boron (B) or the like is introduced, the pore diameter becomes small; when a metal having an atomic diameter larger than that of silicon, specifically, tin (Sn) or the like is introduced, the pore diameter becomes large. In addition, there are cases where the pore size can be affected by desorbing the metal introduced into the zeolite framework by treatment with an acid.

When ions in zeolite are ion-exchanged by 1-valent ions having a large ion radius by ion exchange, the effective pore diameter is reduced, and when ion-exchanged by 1-valent ions having a small ion radius, the effective pore diameter is a value close to the pore diameter of the zeolite structure, .

For example, by silylating the terminal silanols of the outer surface of the zeolite membrane, steps further, by laminating silylated layers, the effective pore size of the pores toward the outer surface of the zeolite is reduced.

The separation function of the zeolite membrane composite used in the present invention is not particularly limited, and can be embodied by controlling the surface physical properties of zeolite, and by controlling the affinity and adsorption of gas molecules to the zeolite membrane. That is, the adsorption of ammonia on zeolite is controlled by controlling the polarity of zeolite, and the ammonia is easily permeated.

For example, as in the second embodiment of the present invention, the polarity of zeolite is controlled by the presence of nitrogen atoms, whereby the affinity of ammonia for zeolite can be controlled and the ammonia can be easily permeated.

Further, by substituting Al atoms for Si atoms in the zeolite framework, the polarity can be increased, and thus, gas molecules having a large polarity, such as ammonia, can be actively adsorbed and permeated in the zeolite pores. Further, other atom sources than Al atom sources such as Ga, Fe, B, Ti, Zr, Sn, Zn, etc. may be added to the hydrothermally synthesized aqueous reaction mixture to control the polarity of the resulting zeolite.

In addition, ion exchange can control not only the pore size of zeolite but also the adsorption performance of molecules, and thus the permeation rate.

(Zeolite Membrane)

The zeolite membrane in the present invention is a membrane-like material composed of zeolite, and is preferably formed by crystallizing zeolite on the surface of a porous support. The film-forming component may contain, in addition to zeolite, an inorganic binder such as silica or alumina, an organic substance such as a polymer, or a silylation agent for modifying the surface of zeolite, if necessary.

As described above, the zeolite contained in the zeolite membrane used in the present invention may be 1 kind of zeolite, or may contain a plurality of kinds of zeolites. In addition, zeolites such as ANA, GIS, MER, which are liable to form a mixed phase, may contain amorphous components in addition to crystals.

(zeolite film B) according to another aspect of the present invention is a zeolite film containing zeolite, characterized in that the molar ratio of nitrogen element to Al element determined by X-ray photoelectron spectroscopy is 0.01 or more and 4 or less, and zeolite film B is particularly preferably used in the ammonia separation method according to embodiment .

The zeolite membrane B is preferably a zeolite membrane having a surface on which a molar ratio of nitrogen atoms to Al atoms specified by X-ray photoelectron spectroscopy (XPS) is within a predetermined range, and the surface of the zeolite membrane in this specification means a surface on the side to which a mixed gas containing ammonia and a plurality of components including hydrogen and/or nitrogen is supplied for separating ammonia, and when the zeolite membrane composite is used in a form in which the zeolite membrane composite is formed into a membrane on a porous support, it means a surface which does not come into contact with the porous support.

(measurement conditions)

The X-ray source for measurement is a monochromatized Al-K α ray with the output power of 16kV-34W

Method for determining background in quantitative calculation: shirley method

In the second embodiment of the present invention, the content of nitrogen atoms contained in the zeolite membrane surface determined by the XPS measurement is usually 0.01 or more, preferably 0.05 or more, more preferably 0.10 or more, and further steps are preferably 0.20 or more, particularly preferably 0.30 or more, and particularly preferably 0.50 or more in terms of a molar ratio to Al atoms on the zeolite membrane surface, and the upper limit thereof is not particularly limited, but is usually 4 or less, preferably 3 or less, and more preferably 1 or less, depending on the structure of a nitrogen atom-containing cation species in the zeolite contained in the zeolite membrane and the amount of nitrate ions remaining when the nitrate treatment of the zeolite membrane is performed as necessary.

The nitrogen atom contained in the zeolite membrane in the second embodiment of the present invention includes ammonium ion (NH) contained in zeolite described later₄ ⁺) Nitrogen atoms derived from a cationic species obtained by protonating an organic amine having 1 to 20 carbon atoms such as methylamine, dimethylamine, trimethylamine, ethylamine, diethylamine, triethylamine, ethylenediamine, dimethylethylenediamine, tetramethylethylenediamine, diethylenetriamine, triethylenetetramine, aniline, methylaniline, benzylamine, methylbenzylamine, hexamethylenediamine, N-diisopropylethylamine, N-trimethyl-1-adamantanamine, pyridine, piperidine, or the like, nitrogen atoms derived from an organic template (structure-directing agent) when a nitrogen atom-containing organic template is used in the production of a zeolite membrane, and nitrogen atoms derived from a nitrate ion remaining in the nitrate treatment of a zeolite membrane, which is performed as necessary, described later.

The present embodiment is not particularly limited, but is characterized in that ammonia is adsorbed on zeolite to control the effective pore size of zeolite for membrane separation and to separate ammonia by the mechanism of ammonia hopping in zeolite pores, as described below. In the present invention in which ammonia is separated by mainly utilizing the mechanism of pore hopping accompanying adsorption/desorption of ammonia on zeolite as described above, it is an important design factor how the adsorption affinity of ammonia on the zeolite membrane surface in the supply mixed gas containing ammonia is higher than that of other gases such as hydrogen and nitrogen contained in the mixed gas. From this viewpoint, when nitrogen atoms in the above-described form are present on the zeolite membrane surface, the affinity of adsorption of ammonia on the zeolite membrane is improved by interaction with ammonia in the supplied gas such as hydrogen bonding, and thus the ammonia separation performance tends to be improved.

(zeolite film C) according to another embodiment of the present invention is a zeolite film containing zeolite, and is characterized in that the molar ratio of Si element to Al element determined by X-ray photoelectron spectroscopy is 2.0 or more and 10 or less, and the zeolite film C is preferably used in the ammonia separation method according to embodiment .

The zeolite film C used in the present invention is characterized by having a surface with a molar ratio of Si atoms to Al atoms in a predetermined range as determined by X-ray photoelectron spectroscopy (XPS). In the present specification, the molar ratio of Si atoms to Al atoms contained in the zeolite membrane is a value determined by X-ray photoelectron spectroscopy (XPS) under the following measurement conditions.

(measurement conditions)

The X-ray source for measurement is a monochromatized Al-K α ray with the output power of 16kV-34W

Method for determining background in quantitative calculation: shirley method

In the present embodiment, the content of Si atoms contained in the zeolite membrane surface determined by the XPS measurement is 2.0 or more, preferably 2.5 or more, and more preferably 3.0 or more in terms of a molar ratio to Al atoms on the zeolite membrane surface, and the upper limit thereof is usually 10 or less, preferably 8.0 or less, more preferably 7.0 or less, and particularly preferably 6.7 or less. In the present invention, the molar ratio of Si atoms to Al atoms in the zeolite membrane can be controlled by controlling the zeolite SiO in the zeolite membrane as described below₂/Al₂O₃The method of the ratio, the method of treating the zeolite membrane with an aluminum salt, and the like. By using the thus defined Si atom/Al atom molar ratioIn the case of separating ammonia from a mixed gas containing ammonia and a plurality of components including hydrogen and/or nitrogen, as is apparent from the present example, the zeolite membrane can exhibit high permeation selectivity and high permeability while improving the density and durability such as chemical resistance and heat resistance of the zeolite membrane, and can improve the thermal stability of separation at high temperatures.

In the present embodiment, when the content of nitrogen atoms contained in the zeolite membrane surface determined by XPS measurement is controlled to a predetermined range as needed while controlling the content of Si atoms on the zeolite membrane surface, it is preferable to allow nitrogen atoms to coexist on the zeolite membrane surface and to appropriately control the content of nitrogen atoms, because separation selectivity in separating ammonia from a mixed gas composed of a plurality of components contained in the zeolite membrane surface tends to be significantly improved, and thus when nitrogen atoms are present on the zeolite membrane surface as needed, the content of nitrogen atoms is usually 0.01 or more, preferably 0.05 or more, more preferably 0.10 or more, further steps are preferably 0.20 or more, particularly preferably 0.30 or more, particularly preferably 0.50 or more, in terms of molar ratio with respect to Al atoms on the zeolite membrane surface, the upper limit thereof is related to the amount of nitrate ions remaining when nitrate treatment of a cationic species containing nitrogen atoms in the zeolite contained in the zeolite membrane is performed, and thus the upper limit is not particularly limited to 4 or more, preferably 3 or less, further preferably 1 or more, and when nitrate treatment of a mixed gas containing nitrogen atoms is performed, thus the effective separation efficiency of ammonia from a mixed gas containing nitrogen atoms is more than 0.005, and the upper limit is preferably from the high ammonia is expressed in terms of a high ammonia-3-5-3, and/5-3, and-3, and/4-3, more-3, and-3, more-3-.

In the present embodiment, the nitrogen atom in the case where the zeolite membrane contains a nitrogen atom may be an ammonium ion (NH) contained in zeolite described later₄ ⁺) The component is selected from methylamine, dimethylamine, trimethylamine, ethylamine, diethylamine, triethylamine, ethylenediamine and dimethylmethaneNitrogen atoms of cationic species obtained by protonating organic amines having 1 to 20 carbon atoms such as ethylenediamine, tetramethylethylenediamine, diethylenetriamine, triethylenetetramine, aniline, methylaniline, benzylamine, methylbenzylamine, hexamethylenediamine, N-diisopropylethylamine, N-trimethyl-1-adamantanamine, pyridine, and piperidine, nitrogen atoms derived from an organic template (structure-directing agent) used when an organic template containing nitrogen atoms is used for producing a zeolite membrane, and nitrogen atoms derived from nitrate ions remaining at the time of nitrate treatment of a zeolite membrane, which is performed as needed, which will be described later.

In the present embodiment, steps further, when the content of alkali metal atoms contained in the zeolite membrane surface determined by XPS measurement is controlled to a predetermined range, the ammonia permeability tends to increase when ammonia is separated from a mixed gas composed of a plurality of components containing ammonia and hydrogen and/or nitrogen, therefore, it is preferable to control the content thereof as needed . as alkali metal atoms when alkali metal atoms are present on the zeolite membrane surface as needed, Li, Na, K, Rb, Cs and two or more kinds of metal atoms thereof are exemplified, Li, Na, Cs are preferable, Na is more preferable for the reason that alkali metal atoms are excellent in ammonia separation performance and widely used as , Na is further preferable, these alkali metal atoms are present in the form of cations as ion pairs of Al sites in the zeolite constituting the zeolite membrane, and usually, as described below, they are introduced into the zeolite membrane by ion exchange treatment of the synthesized zeolite membrane, when alkali metal atoms are present on the zeolite membrane surface, the content of alkali metal atoms is adjusted as needed, preferably 0.06equivalent to 0.05, more preferably 0.05, and particularly, when the content of alkali metal atoms is more preferably 0.05, and more preferably 0.05, more preferably.

The present embodiment is not particularly limited, but is characterized in that ammonia is adsorbed on zeolite to control the effective pore size of zeolite for membrane separation and to separate ammonia by the mechanism of ammonia hopping in zeolite pores, as described below. In the present invention in which ammonia is separated mainly by the mechanism of pore hopping accompanying adsorption/desorption of ammonia on zeolite as described above, it is an important design factor to make the adsorption affinity of ammonia on the zeolite membrane surface higher in the supply mixed gas containing ammonia than in other gases such as hydrogen and nitrogen contained in the mixed gas. From this viewpoint, when a large number of Al atoms are present on the zeolite membrane surface, the polarity of the zeolite membrane surface changes, and the adsorption affinity with ammonia in the supply gas improves, thereby improving the ammonia separation performance. In the present embodiment, the Al atom content on the zeolite membrane surface can be determined by SiO of the zeolite constituting the zeolite membrane₂/Al₂O₃The control of the ratio and the aluminum salt treatment after the zeolite membrane formation, particularly the latter aluminum salt treatment, has an effect of sealing fine defects existing on the zeolite membrane surface, and contributes to the improvement of separation thermal stability at high temperature of the zeolite membrane, which is an object of the present invention, while improving the denseness, chemical resistance, heat resistance and other durability of the zeolite membrane.

(zeolite film D) according to another embodiment of the present invention is a zeolite film containing zeolite, and is characterized in that the molar ratio of an alkali metal element to Al element determined by X-ray photoelectron spectroscopy is 0.01 or more and 0.070 or less, and zeolite film D is particularly preferably used in the ammonia separation method according to embodiment .

The zeolite film D used in the fourth embodiment of the present invention is preferably a zeolite film having a surface with a molar ratio of alkali metal atoms to Al atoms determined by X-ray photoelectron spectroscopy (XPS) within a predetermined range. In the present specification, the molar ratio of the alkali metal atoms to the Al atoms contained in the zeolite membrane is a value determined by X-ray photoelectron spectroscopy (XPS) under the following measurement conditions.

(measurement conditions)

The X-ray source for measurement is a monochromatized Al-K α ray with the output power of 16kV-34W

Method for determining background in quantitative calculation: shirley method

In the present embodiment, as the alkali metal atoms contained in the zeolite membrane surface identified by the XPS measurement, Li, Na, K, Rb, Cs, and two or more kinds of metal atoms among them are preferable, and Na is more preferable because of the excellent ammonia separation performance and the wide use of as the alkali metal.

In the present embodiment, it is important to control the content of the alkali metal atom contained in the zeolite membrane surface determined by the XPS measurement, and the content is 0.01 or more, preferably 0.02 or more, more preferably 0.03 or more, further is preferably 0.04 or more, and particularly preferably 0.05 or more in terms of a molar ratio to the Al atom on the zeolite membrane surface, and the upper limit thereof is usually 0.10 molar equivalent or less, preferably 0.070 molar equivalent or less, more preferably 0.065 molar equivalent or less, further is preferably 0.060 molar equivalent or less, and particularly preferably 055 molar equivalent or less.

In the present embodiment, the molar ratio of the alkali metal atoms to the Al atoms in the zeolite membrane can be controlled by adjusting the amount of ion exchange in the ion exchange treatment of the zeolite, as described below. By using a zeolite membrane having such a predetermined alkali metal atom/Al atomic ratio, when ammonia is separated from a mixed gas containing ammonia and a plurality of components including hydrogen and/or nitrogen, high transmission selectivity is exhibited, and the ammonia permeability can be improved as compared with a zeolite membrane containing no alkali metal atom.

In the present embodiment, when the content of the alkali metal atoms on the zeolite membrane surface is controlled and the content of the nitrogen atoms contained in the zeolite membrane surface determined by XPS measurement is controlled to be within a predetermined range as needed, since separation selectivity in separating ammonia from a mixed gas composed of a plurality of components including ammonia and hydrogen and/or nitrogen tends to be significantly improved, it is preferable that the alkali metal atoms and the nitrogen atoms coexist on the zeolite membrane surface and the content thereof is appropriately controlled, when the nitrogen atoms are present on the zeolite membrane surface as needed, the content of the nitrogen atoms is usually 0.01 or more, preferably 0.05 or more, more preferably 0.10 or more, and further is preferably 0.20 or more, particularly preferably 0.30 or more, particularly preferably 0.50 or more in terms of molar ratio with respect to the Al atom on the zeolite membrane surface, the amount of the nitrate ion remaining when the nitrate treatment of the zeolite membrane is performed as needed, and therefore, there is no particular limitation, and it is usually 4 or less, preferably 0.50 or more, and the upper limit thereof is preferably equal to the lower limit of the nitrogen atoms contained in terms of chemical composition, and the effective separation resistance of ammonia is preferably equal to or less than 0.005, and the lower limit of hydrogen atoms is preferably equal to or less than 0.5.

In the present embodiment, the nitrogen atom in the case where the zeolite membrane contains a nitrogen atom may be an ammonium ion (NH 4) contained in zeolite described later⁺) And nitrogen atoms derived from cationic species obtained by protonating organic amines having 1 to 20 carbon atoms such as methylamine, dimethylamine, trimethylamine, ethylamine, diethylamine, triethylamine, ethylenediamine, dimethylethylenediamine, tetramethylethylenediamine, diethylenetriamine, triethylenetetramine, aniline, methylaniline, benzylamine, methylbenzylamine, hexamethylenediamine, N, N-diisopropylethylamine, N, N, N-trimethyl-1-adamantanamine, pyridine, and piperidine, and from the production of zeoliteNitrogen atoms of the organic template when an organic template containing nitrogen atoms (structure directing agent) is used for the membrane, nitrogen atoms derived from nitrate ions remaining at the time of nitrate treatment of the zeolite membrane, which will be described later as necessary, and the like.

In the present invention which separates ammonia mainly by the pore hopping mechanism accompanying adsorption/desorption of ammonia on zeolite as described above, although selectivity of ammonia separation from a mixed gas composed of a plurality of components including ammonia and containing hydrogen and/or nitrogen is improved by the blocking effect caused by adsorption of ammonia on Al sites in zeolite pores, in addition , since ammonia is highly adsorbed on Al sites, permeation performance (permeation amount) tends to be impaired, on the other hand, when the alkali metal atoms in the zeolite constituting the zeolite membrane of the present invention are present in the form of cations as ion pairs of Al sites, the adsorption amount of ammonia on Al sites can be controlled, in addition , the adsorption selectivity of ammonia separation can be maintained by the size of alkali metal cations, and in these mechanisms, the selectivity of ammonia separation can be improved while maintaining the ammonia separation performance, namely, when the adsorption amount of ammonia on Al sites is lowered by the size of Al atoms, which is less than 630.01, and when the adsorption amount of ammonia on the zeolite is less than , the adsorption amount of ammonia is considered to be more important than 0.01.

(zeolite membrane composite E) according to another aspect of the present invention is a zeolite membrane composite for ammonia separation comprising a porous support and a zeolite membrane containing zeolite on the surface thereof, wherein the rate of change of the thermal expansion coefficient of zeolite at 300 ℃ and 400 ℃ with respect to the thermal expansion coefficient at 30 ℃ is within a predetermined range, and the zeolite membrane composite E is preferably used in the ammonia separation method according to embodiment .

Specifically, the zeolite has a coefficient of thermal expansion at 300 ℃ within. + -. 0.25% of that at 30 ℃ and a coefficient of thermal expansion at 400 ℃ within. + -. 0.35% of that at 30 ℃.

The thermal expansion coefficient defined by the zeolite of the present embodiment is a value calculated under the following conditions. In the present specification, a positive thermal expansion coefficient indicates that the zeolite expands, and a negative thermal expansion coefficient indicates that the zeolite contracts.

(method of measuring the rate of change of thermal expansion)

In the present invention, the rate of change of the thermal expansion coefficient of zeolite at a predetermined temperature with respect to the thermal expansion coefficient at 30 ℃ can be determined by the following formula (1) by obtaining the lattice constants measured at 30 ℃ and at a predetermined temperature by the temperature-rising XRD measurement under the following conditions.

(specification of temperature-elevating XRD measuring apparatus)

[ TABLE 1]

TABLE 1

(measurement conditions)

[ TABLE 2]

TABLE 2

Measuring the atmosphere: atmosphere (es)

Temperature rising conditions are as follows: 20 ℃/min

The determination method comprises the following steps: XRD measurement was carried out after keeping at the measurement temperature for 5 minutes.

The measurement data was corrected for a fixed slit using a variable slit.

Rate of change in thermal expansion (lattice constant measured at predetermined temperature) ÷ (lattice constant measured at 30 ℃) -1 … (1)

The zeolite of the present invention has a rate of change in thermal expansion coefficient at 300 ℃ relative to that at 30 ℃ of 0.25% or less, preferably 0.20% or less, more preferably 0.15% or less, particularly preferably 0.10% or less, and most preferably 0.05% or less in absolute terms. That is, the rate of change of the thermal expansion coefficient of zeolite at 300 ℃ to the thermal expansion coefficient at 30 ℃ is within. + -. 0.25%, preferably within. + -. 0.20%, more preferably within. + -. 0.15%, particularly preferably within. + -. 0.10%, most preferably within. + -. 0.05%.

, the coefficient of change of the thermal expansion coefficient of zeolite at 400 ℃ to the thermal expansion coefficient of 30 ℃ is 0.35% or less, preferably 0.30% or less, more preferably 0.25% or less, particularly preferably 0.20% or less, particularly preferably 0.15% or less, most preferably 0.10% or less in absolute terms, that is, the coefficient of change of the thermal expansion coefficient of zeolite at 400 ℃ to the thermal expansion coefficient of 30 ℃ is within ± 0.35%, preferably within ± 0.30%, more preferably within ± 0.25%, particularly preferably within ± 0.20%, particularly preferably within ± 0.15%, most preferably within ± 0.10%, when a zeolite membrane composite is formed by forming a membrane of a zeolite exhibiting a low coefficient of change of thermal expansion on a porous surface, a zeolite membrane composite is formed by passing ammonia through a gas mixture comprising a plurality of components including ammonia and/or nitrogen, and when the zeolite composite is passed through a porous surface, the zeolite membrane is heated to a temperature condition of more than 200 ℃, particularly a temperature condition of more than 250 ℃, a temperature condition of more than 300 ℃ including hydrogen and a temperature of the zeolite and/or a hydrogen and/or a temperature of a gas mixture including a component including ammonia and a high thermal expansion coefficient of a zeolite, and a thermal expansion coefficient of a thermal expansion, and a thermal expansion of a thermal expansion coefficient of a thermal expansion of a thermal contraction of a zeolite membrane, and a thermal contraction of.

This is not known in detail, but is not particularly limited, and it is considered that the formation of a dense zeolite membrane composite allows the zeolite to move on the support appropriately even if the zeolite thermally contracts and thermally expands during the temperature rise, and thus the high separation performance is exhibited in high temperature conditions without generating cracks. Therefore, when ammonia is stably separated under high temperature conditions, a zeolite exhibiting nonlinear thermal expansion/contraction behavior during temperature rise can also be used. The zeolite used in the present invention is not particularly limited, and RHO (D.R.Corbin.etaL.J.Am.chem.Soc,112,4821-4830), MFI, AFI, DDR (Parks.H.etaL.Stud.Surf.Sci.Catal.1997,105,1989-1994) and the like are known, for example.

In addition, the zeolite of the present embodiment has a ratio of the rate of change in the thermal expansion coefficient at 400 ℃ to the thermal expansion coefficient at 30 ℃ to the rate of change in the thermal expansion coefficient at 300 ℃ to the thermal expansion coefficient at 30 ℃ of usually 120% or less, preferably 115% or less, more preferably 110% or less, particularly preferably 105% or less, and most preferably 103% or less in absolute terms. In the zeolite membrane composite formed by forming a membrane on a porous support using zeolite exhibiting such a predetermined ratio of change rate of thermal expansion coefficient between predetermined temperatures, even when uneven heat generation occurs in the reactor at the initial stage of the reaction at the start of ammonia production, for example, the occurrence of grain boundary cracks due to local thermal expansion (contraction) of zeolite can be suppressed, and thus ammonia can be stably separated to the transmission side with high transmittance and high efficiency.

In the zeolite membrane composite of the present embodiment, when the zeolite having a coefficient of thermal expansion within a predetermined range is prepared through a step of adhering zeolite as seed crystals to a porous support at the time of membrane synthesis, ammonia can be separated stably with high selectivity even under high temperature conditions in many cases, and in the preparation of the zeolite membrane composite as described above, the coefficient of thermal expansion of the zeolite used as the seed crystals is 0.25% or less, preferably 0.20% or less, more preferably 0.15% or less, particularly preferably 0.10% or less, and most preferably 0.05% or less, in terms of the absolute value of the coefficient of thermal expansion at 300 ℃ relative to the coefficient of thermal expansion at 30 ℃, and , the coefficient of thermal expansion at 400 ℃ relative to the coefficient of thermal expansion at 30 ℃ is usually 0.30% or less, preferably 0.25% or less, more preferably 0.20% or less, particularly preferably 0.15% or less, and most preferably 0.10% or less, in terms of the absolute value.

For example, regarding the relationship between the cation species of the RHO type zeolite and the thermal expansion coefficient, as described in Chemical communication (Communications), 2000,2221-2222, it is known that the thermal expansion coefficient changes due to the cation species contained in the zeolite, and therefore, in order to obtain the zeolite membrane composite of the present embodiment which can stably separate ammonia with high selectivity even under high temperature conditions, it is particularly important to select a predetermined cation species among the RHO type zeolites, and in addition, in , the thermal expansion coefficient of the MFI zeolite according to the example of the present embodiment is such that a zeolite membrane composite exhibiting the characteristics of the present embodiment can be produced by selecting an appropriate cation species among the zeolites, as in the case of the RHO type zeolite.

The cation species contained in the zeolite of the present embodiment is preferably a cation species which is easily coordinated to the ion exchange sites of the zeolite, and is, for example, a cation species selected from the group consisting of elements in columns 1, 2, 8, 9, 10, 11 and 12 of the periodic table, NH₄ ⁺And two or more kinds of cationic species among them, more preferably a cationic species selected from the group consisting of elements in columns 1 and 2 of the periodic table, NH₄ ⁺And two or more kinds of cationic species among them.

The zeolite used in the present embodiment is aluminosilicate. SiO of aluminosilicate₂/Al₂O₃The molar ratio is not particularly limited, but is usually 6 or more, preferably 7 or more, more preferably 8 or more, and further steps are preferably 10 or more, particularly preferably 11 or more, particularly preferably 12 or more, and most preferably 13 or more₂/Al₂O₃The molar ratio is usually 500 or less, preferably 100 or less, more preferably 90 or less, and the amount in the step is preferably 80 or less, particularly preferablyIt is preferably 70 or less, more preferably 50 or less, and most preferably 30 or less. By using SiO in a predetermined range as described above₂/Al₂O₃The zeolite with a molar ratio can improve the compactness of the zeolite membrane, the chemical reaction resistance, the heat resistance and other durability. In addition, from the viewpoint of the separation performance of permeating ammonia from a gas mixture composed of a plurality of components including ammonia and hydrogen and/or nitrogen, it is preferable to use zeolite containing a predetermined amount of Al because the acid sites of Al element become ammonia adsorption sites as described above, and to use SiO showing the above-described adsorption sites by using zeolite containing Al in a predetermined amount₂/Al₂O₃The zeolite has high permeability and high selectivity for separating ammonia. SiO of zeolite₂/Al₂O₃The molar ratio can be adjusted by the reaction conditions of hydrothermal synthesis described later.

The thickness of the zeolite membrane used in the present invention is not particularly limited, but is usually 0.1 μm or more, preferably 0.3 μm or more, more preferably 0.5 μm or more, further is preferably 0.7 μm or more, further is preferably 1.0 μm or more, and particularly preferably 1.5 μm or more, further is usually 100 μm or less, preferably 60 μm or less, more preferably 20 μm or less, further is preferably 15 μm or less, further is preferably 10 μm or less, and particularly preferably 5 μm or less, and when the thickness of the zeolite membrane is not less than the above-described lower limit, defects tend to be less generated and separation performance is improved, and when the thickness of the zeolite membrane is not more than the above-described upper limit, the permeation performance tends to be improved, and further steps tend to suppress the occurrence of cracks in the zeolite membrane due to temperature rise in a high temperature region, and thus the decrease in permeation selectivity at high temperature tends to be suppressed.

The average -fold particle size of the zeolite forming the zeolite membrane is not particularly limited, but is usually 30nm or more, preferably 50nm or more, more preferably 100nm or more, and the upper limit thereof is not more than the thickness of the membrane, and when the average -fold particle size of the zeolite is not less than the lower limit, the grain boundary of the zeolite can be reduced, and therefore, good permeation selectivity can be obtained.

In the present invention, the average -th particle size is determined by measuring -th particle sizes of arbitrarily selected 30 or more particles in the observation of the surface or fracture surface of the zeolite membrane composite of the present invention with a scanning electron microscope, and taking the average value as the average value.

The shape of the zeolite membrane is not particularly limited, and any shape such as a tubular shape, a hollow fiber shape, a monolithic (monoliths) type, a honeycomb type, and the like can be used. The size of the zeolite membrane is not particularly limited, and for example, the zeolite membrane can be formed as a zeolite membrane composite formed on a porous support having a size described later.

(porous support)

In the present invention, the zeolite membrane is preferably formed on the surface of the porous support or the like. Preferably, the zeolite is crystallized in the form of a membrane on a porous support.

The porous support used in the present invention preferably has chemical stability capable of crystallizing zeolite into a film shape on its surface, and examples of suitable porous supports include gas-permeable porous polymers such as polysulfone, cellulose acetate, aramid, vinylidene fluoride, polyethersulfone, polyacrylonitrile, polyethylene, polypropylene, polytetrafluoroethylene, and polyimide, ceramic sintered bodies such as silica, α -alumina, γ -alumina, mullite, zirconia, titania, yttria, silicon nitride, and silicon carbide, sintered metals such as iron, bronze, and stainless steel, net-like molded bodies, and inorganic porous bodies such as glass and carbon molded bodies.

As described above, preferred ceramic sintered bodies include α -alumina, γ -alumina, silica, mullite, zirconia, titania, yttria, silicon nitride, silicon carbide and the like, which may be single sintered bodies or a mixture of a plurality of sintered bodies, and these ceramic sintered bodies have parts of the surfaces thereof converted to zeolites during zeolite membrane synthesis, thereby improving the adhesion between the porous support and the zeolite membrane and improving the durability of the zeolite membrane composite.

In particular, an inorganic porous support containing at least kinds of alumina, silica, and mullite is more preferable because partial zeolitization of the inorganic porous support is likely to occur, and thus the combination of the inorganic porous support and zeolite becomes strong, and a dense zeolite membrane having high separation performance is likely to be formed.

The porous support used in the present invention preferably has an effect of crystallizing zeolite formed on the porous support on its surface (hereinafter also referred to as "porous support surface").

The average pore diameter of the porous support in the vicinity of the surface of the porous support is usually 0.02 μm or more, preferably 0.05 μm or more, more preferably 0.1 μm or more, further steps are preferably 0.15 μm or more, further steps are preferably 0.5 μm or more, particularly preferably 0.7 μm or more, most preferably 1.0 μm or more, usually 20 μm or less, preferably 10 μm or less, more preferably 5 μm or less, particularly preferably 2 μm or less.

The surface of the porous support is preferably smooth and may be polished by polishing the surface or the like as necessary.

The pore diameter of the porous support used in the present invention is not limited and need not be particularly controlled except for the vicinity of the surface of the porous support, but the porosity of the other portion is usually 20% or more, more preferably 30% or more, usually 60% or less, and preferably 50% or less. The porosity of the portion other than the vicinity of the surface of the porous support affects the permeation flow rate when separating gas and liquid, and when the porosity is not less than the lower limit, the permeate tends to be easily diffused, and when the porosity is not more than the upper limit, the strength of the porous support tends to be easily prevented from being lowered. In addition, as a method for controlling the permeation flow rate, a porous support in which porous bodies having different porosities are combined in a layered form can be used.

The shape of the porous support used in the present invention is not particularly limited as long as it is a shape capable of effectively separating a mixed gas and a liquid mixture, and specific examples thereof include a flat plate shape, a tubular shape, a cylindrical shape, a honeycomb-shaped support having a large number of through holes, and a monolith shape. The size and the like of the porous support are arbitrary, and may be appropriately selected and adjusted so as to obtain a desired zeolite membrane composite. Among them, the shape of the porous support may be preferably tubular.

The length of the tubular porous support is not particularly limited, and is usually 2cm or more, preferably 4cm or more, more preferably 5cm or more, particularly preferably 10cm or more, particularly preferably 40cm or more, and most preferably 50cm or more, and is usually 200cm or less, preferably 150cm or less, and more preferably 100cm or less.

The inner diameter of the tubular porous support is usually 0.1cm or more, preferably 0.2cm or more, more preferably 0.3cm or more, particularly preferably 0.4cm or more, usually 2cm or less, preferably 1.5cm or less, more preferably 1.2cm or less, particularly preferably 1.0cm or less, the outer diameter is usually 0.2cm or more, preferably 0.3cm or more, more preferably 0.6cm or more, particularly preferably 1.0cm or more, usually 2.5cm or less, preferably 1.7cm or less, more preferably 1.3cm or less, the wall thickness of the tubular porous support is usually 0.1mm or more, preferably 0.3mm or more, more preferably 0.5mm or more, further steps are preferably 0.7mm or more, more preferably 1.0mm or more, particularly preferably 1.2mm or more, usually 4mm or less, preferably 3mm or less, more preferably 2mm or less, the inner diameter, the outer diameter and the wall thickness of the tubular porous support are each of equal to or more of the above-mentioned lower limit values in terms of economical point, the breaking strength of the support can be increased, and the upper limit of the tubular porous support can be increased, and the performance tends to be increased, and the lower limit of the upper limit of the tubular porous support can be increased.

The change rate of the thermal expansion coefficient of the porous support used in the fifth embodiment at 300 ℃ to the thermal expansion coefficient at 30 ℃ is 0.25% or less, preferably 0.20% or less, more preferably 0.15% or less, particularly preferably 0.10% or less, most preferably 0.05% or less in absolute terms, that is, the change rate of the thermal expansion coefficient at 300 ℃ to the thermal expansion coefficient at 30 ℃ of the porous support of zeolite membrane composite E is ± 0.25% or less, preferably ± 0.20% or less, more preferably ± 0.15% or less, particularly preferably ± 0.10% or less, most preferably ± 0.05% or less, and is a change rate of the thermal expansion coefficient at 400 ℃ of the porous support of zeolite membrane composite E to the thermal expansion coefficient at 30 ℃ is usually 0.30% or less, preferably 0.25% or less, more preferably 0.20% or less, particularly preferably 0.15% or less, most preferably 0.10% or less, even if the change rate of the thermal expansion coefficient at 400 ℃ to the thermal expansion coefficient at 30 ℃ is more than 0.30 ℃ and more preferably 0.84%, even if the thermal expansion coefficient of the porous support is more than 0.25% or more than 0.84, the thermal expansion coefficient, and more preferably the thermal expansion coefficient of ammonia is within 0.25% or more preferably within 0.0.84% and more than 0.0% and more preferably, even if the temperature of the porous support is increased, and the temperature of the ammonia is increased, and the temperature of the ammonia is more preferably increased, and the porous support is more preferably increased.

The ratio of the rate of change in the thermal expansion coefficient of the porous support used in the fifth embodiment, which is 400 ℃ relative to the thermal expansion coefficient of 30 ℃, to the rate of change in the thermal expansion coefficient of the porous support used in the fifth embodiment, which is 300 ℃ relative to the thermal expansion coefficient of 30 ℃, is usually 120% or less, preferably 115% or less, more preferably 110% or less, particularly preferably 105% or less, and most preferably 103% or less in absolute terms. In the zeolite membrane composite formed by forming the membrane on the porous support exhibiting the predetermined thermal expansion ratio between the predetermined temperatures, for example, even when uneven heat generation occurs in the reactor during ammonia production, the generation of cracks in the zeolite membrane due to local thermal expansion (contraction) of the porous support can be suppressed, and therefore, ammonia can be stably separated into the permeation side with high permeability and high efficiency even under high temperature conditions.

(Zeolite Membrane Complex)

In the present invention, the zeolite membrane is preferably used as a zeolite membrane composite comprising at least a zeolite and a support.

In the present invention, the zeolite membrane composite is a state in which the zeolite is fixed in a membrane form, preferably crystallized and fixed, on the surface of the porous support or the like, and in some cases, is preferably fixed in part inside the support.

As the zeolite membrane composite, for example, zeolite is preferably crystallized into a membrane shape by hydrothermal synthesis on the surface of a porous support or the like.

The position of the zeolite membrane on the porous support is not particularly limited, and when a tubular support is used, the zeolite membrane may be formed on the outer surface or the inner surface, and further steps may be formed on both surfaces depending on the system to be applied.

The zeolite and the support constituting the zeolite membrane composite are not particularly limited, and the zeolite and the support are preferably used in combination arbitrarily, but among them, particularly preferred combinations of zeolite and porous support include MFI-type zeolite-porous alumina support, RHO-type zeolite-porous alumina support, DDR-type zeolite-porous alumina support, AFI-type zeolite-porous alumina support, CHA-type zeolite-porous alumina support, and AEI-type zeolite-porous alumina support, preferably CHA-type zeolite-porous alumina support, MFI-type zeolite-porous alumina support, and RHO-type zeolite-porous alumina support, more preferably MFI-type zeolite-porous alumina support, and RHO-type zeolite-porous alumina support.

In the embodiments (zeolite membranes B to E) of the present invention, the MFI type zeolite-porous alumina support and the RHO type zeolite-porous alumina support are preferable, and the RHO type zeolite-porous alumina support is more preferable.

< method for producing zeolite membrane composite >

In the present invention, the method for forming the zeolite membrane composite is not particularly limited as long as the above-described zeolite membrane can be formed on the porous support, and the zeolite membrane composite can be produced by a known method. For example, any of the following methods can be used: (1) a method of crystallizing zeolite into a film form on a support, (2) a method of fixing zeolite to a support with an inorganic binder, an organic binder or the like, (3) a method of fixing a polymer in which zeolite is dispersed to a support, and (4) a method of fixing zeolite to a support by immersing a zeolite slurry in a support and optionally performing suction.

Among these, a method of crystallizing zeolite into a film shape on a porous support is particularly preferable. The method of crystallization is not particularly limited, but a method of directly crystallizing zeolite on the surface of a support or the like by hydrothermal synthesis by putting the support into a reaction mixture for hydrothermal synthesis used for zeolite production (hereinafter, this may be referred to as "aqueous reaction mixture") is preferable.

In this case, for example, the zeolite membrane composite can be produced by charging the aqueous reaction mixture having the adjusted composition homogenized into a heat-resistant pressure-resistant container such as an autoclave having a porous support therein, sealing and heating for hours.

The aqueous reaction mixture contains a source of Si atoms, a source of Al atoms, a source of alkalinity, and water, and further contains an organic template (structure directing agent) as needed.

In order to further understand the method for producing the zeolite membrane composite, the following description will be made in detail with respect to the RHO type zeolite membrane composite and the MFI type zeolite membrane composite as representative examples, but the zeolite membrane and the method for producing the same of the present invention are not limited to these descriptions.

(RHO type zeolite film)

The RHO type zeolite used in the present invention is a zeolite having a RHO structure according to a code specifying the zeolite structure defined by the International Zeolite Association (IZA). The RHO type zeolite is structurally characterized by having a diameter of

The oxygen 8-membered ring of (a) is a three-dimensional pore.

The RHO-type zeolite used in the present invention has a framework density of

The framework density is defined as per unit of zeolite

The number of atoms constituting the framework other than oxygen in (b) is determined by the structure of the zeolite. The relationship between the framework density and the structure of zeolite is shown in "atlas of framework types of zeolite" (revised 5 th edition, 2007 eisweier press).

(MFI type zeolite Membrane)

The MFI-type zeolite used in the present invention is a zeolite having an MFI structure according to a code specifying the zeolite structure defined by International Zeolite Association (IZA). The MFI-type zeolite is characterized by having a structure represented by

Or

Three-dimensional pores formed by oxygen 10-membered rings of diameter, the structure of which can be characterized by X-ray diffraction data.

The MFI-type zeolite used in the present invention has a framework density of

The framework density is defined as per unit of zeoliteThe number of atoms constituting the framework other than oxygen in (b) is determined by the structure of the zeolite. The relationship between the framework density and the structure of zeolite is shown in "atlas of framework types of zeolite" (revised 5 th edition, 2007 eisweier press).

< method for producing RHO type zeolite membrane >

(silicon atom source)

The silicon (Si) atom source used in the aqueous reaction mixture is not particularly limited, and examples thereof include aluminosilicate zeolite, fumed silica, colloidal silica, amorphous silica, sodium silicate, silicon alkoxides (silicon alkoxides) such as methyl silicate, ethyl silicate, and trimethylethoxysilane, tetraethylorthosilicate, and aluminosilicate gel, and preferably aluminosilicate zeolite, fumed silica, colloidal silica, amorphous silica, sodium silicate, methyl silicate, ethyl silicate, silicon alkoxides, and aluminosilicate gel, and kinds thereof may be used alone, or two or more kinds thereof may be used in combination.

The Si atom source is used so that the amount of other raw materials used relative to the Si atom source is within the appropriate range described above or below.

(aluminum atom source)

The aluminum (Al) atom source used for producing the porous support-RHO type zeolite membrane composite is not particularly limited, and examples thereof include aluminosilicate zeolite, amorphous aluminum hydroxide, aluminum hydroxide of gibbsite structure, aluminum hydroxide of bayerite structure, aluminum nitrate, aluminum sulfate, alumina, sodium aluminate, boehmite, pseudoboehmite, aluminum alkoxide, and aluminosilicate gel, and aluminosilicate zeolite, amorphous aluminum hydroxide, sodium aluminate, boehmite, pseudoboehmite, aluminum alkoxide, and aluminosilicate gel are preferable, and aluminosilicate zeolite, amorphous aluminum hydroxide, sodium aluminate, and aluminosilicate gel are particularly preferable, and kinds thereof may be used alone, or two or more kinds thereof may be used in combination.

When aluminosilicate zeolite is used as the Al atom source, it is preferable that 50% by mass or more, particularly 70 to 100% by mass, and particularly 90 to 100% by mass of the total Al atom source is the aluminosilicate zeolite, and when aluminosilicate zeolite is used as the Si atom source, it is preferable that 50% by mass or more, particularly 70 to 100% by mass, and particularly 90 to 100% by mass of the total Si atom source is the aluminosilicate zeolite, and when the proportion of aluminosilicate zeolite is in this range, the Si atom/Al atom molar ratio of the RHO type zeolite film is increased, and a zeolite film having excellent acid resistance, water resistance, and an application range of can be obtained.

The preferred range of the amount of Al atom source (including the above-mentioned aluminosilicate zeolite and other Al atom source) contained in the raw material mixture other than the seed crystal to be used relative to silicon (Si atom) (Al atom/Si atom ratio) is usually 0.01 or more, preferably 0.02 or more, more preferably 0.04 or more, further steps are preferably 0.06 or more, usually 1.0 or less, preferably 0.5 or less, more preferably 0.2 or less, further steps are preferably 0.1 or less.

In the embodiments (for example, inventions B to E) of the present invention, when the Al atom/Si atomic ratio is more than 1.0, the water resistance and acid resistance of the obtained RHO type zeolite film are lowered, and the use as a zeolite film is limited, and when the Al atom/Si atomic ratio is less than 0.01, it is difficult to obtain a RHO type zeolite film.

The aqueous reaction mixture may contain an atom source other than the silicon atom source and the aluminum atom source, for example, an atom source such as gallium (Ga), iron (Fe), boron (B), titanium (Ti), zirconium (Zr), tin (Sn), or zinc (Zn).

The type of the base used as the alkali source is not particularly limited, and an alkali metal hydroxide or an alkaline earth metal hydroxide can be used.

The metal species of these metal hydroxides are usually sodium (Na), potassium (K), lithium (Li), rubidium (Rb), cesium (Cs), calcium (Ca), magnesium (Mg), strontium (Sr), and barium (Ba), preferably Na, K, and Cs, and more preferably Na and Cs. Further, two or more kinds of metal species of the metal oxide may be used in combination, specifically, Na and Cs are preferably used in combination.

As the metal hydroxide, specifically, for example, alkali metal hydroxides such as sodium hydroxide, potassium hydroxide, lithium hydroxide, rubidium hydroxide, and cesium hydroxide; and alkaline earth metal hydroxides such as calcium hydroxide, magnesium hydroxide, strontium hydroxide, and barium hydroxide.

Further, as the alkali source for the aqueous reaction mixture, hydroxide ions of counter anions of the organic template described below may be used.

In the crystallization of the zeolite according to the present invention, an organic template (structure directing agent) is not essential, but the use of an organic template of a type corresponding to each structure is preferable because the ratio of silicon atoms to aluminum atoms in the crystallized zeolite is increased to improve crystallinity.

Any template may be used as the organic template, regardless of the type, as long as the desired zeolite membrane can be formed, and types of templates may be used, or two or more types may be used in combination.

The kind of the organic template suitable for the reaction differs depending on the zeolite structure to be synthesized, and any organic template may be used as long as it can obtain a desired zeolite structure. Specifically, for example, in the case of the RHO structure, 18-crown-6-ether or the like can be used.

When the organic template is cationic, it may be accompanied by anions which do not impair zeolite formation. As the ion representing such an anion, Cl may be contained^-、Br^-、I^-Plasma, hydroxide, acetate, sulfate, and carboxylate. Among them, hydroxide ions are particularly preferably used, and the hydroxide ions function as the alkali source.

The ratio of Si atom source to organic template in the aqueous reaction mixture, as organic template to SiO₂Molar ratio of (organic template/SiO)₂Ratio) of usually not less than 0.005, preferably not less than 0.01, more preferably not less than 0.02, further steps of preferably not less than 0.05, particularly preferably not less than 0.08, most preferably not less than 0.1, usually not more than 1, preferably not more than 0.5, more preferably not more than 0.4, further steps of preferably not more than 0.35, particularly preferably not more than 0.30, most preferably not more than 0.25₂When the ratio is within this range, a zeolite having excellent acid resistance and less tendency to desorb Al atoms can be obtained, while forming a dense zeolite film. In addition, under these conditions, zeolite which can form a dense RHO type aluminosilicate excellent in acid resistance is particularly preferable.

The molar ratio (R/Si atom) of silicon (Si atom) contained in the raw material mixture for hydrothermal synthesis other than the alkali metal atom source (R) and the seed crystal is usually 0.1 or more, preferably 0.15 or more, more preferably 0.20 or more, further steps are preferably 0.25 or more, particularly preferably 0.30 or more, particularly preferably 0.35 or more, usually 2.0 or less, preferably 1.5 or less, more preferably 1.0 or less, further steps are preferably 0.8 or less, particularly preferably 0.6 or less, and most preferably 0.5 or less.

When the molar ratio of the alkali metal atom source to silicon (R/Si atoms) is greater than the above upper limit, the resulting zeolite is likely to be dissolved, and the zeolite cannot be obtained or the yield may be significantly reduced. When the ratio R/Si atom is less than the lower limit, the Al atom source and the Si atom source of the raw material may not be sufficiently dissolved, and a uniform raw material mixture for hydrothermal synthesis may not be obtained, and it may be difficult to form RHO type zeolite.

(amount of Water)

The molar ratio of the amount of water in the raw material mixture for hydrothermal synthesis to silicon (Si atoms) contained in the raw material mixture other than the seed crystal is usually 10 or more, preferably 20 or more, more preferably 30 or more, further steps are preferably 40 or more, particularly preferably 50 or more, usually 200 moles or less, preferably 150 or less, more preferably 100 or less, further steps are preferably 80 or less, and particularly preferably 60 or less, above the upper limit, the reaction mixture is too dilute and it becomes difficult to form a defect-free dense film, and when less than 10, the reaction mixture is concentrated and therefore spontaneous nuclei are likely to be formed, inhibiting the growth of RHO-type zeolite from the support, and it becomes difficult to form a dense film.

(seed crystal)

In the present invention, seed crystals can be used as which is a component of the raw material (raw material compound) for producing "zeolite".

In the hydrothermal synthesis, the presence of the seed crystal is not essential in the reaction system, but the presence of the seed crystal can promote crystallization of the zeolite on the porous support. The method for allowing the seed crystal to exist in the reaction system is not particularly limited, and a method of adding the seed crystal to the aqueous reaction mixture, a method of attaching the seed crystal to a support, and the like in the case of synthesizing the powdery zeolite can be used. By adhering the seed crystal to the support in advance, a zeolite membrane having high separation performance and being dense can be easily formed.

The seed crystal used is a zeolite capable of promoting crystallization, and the crystal form of the seed crystal is preferably the same as that of the zeolite film to be formed, regardless of the type of the zeolite. For example, when a zeolite membrane of RHO type aluminosilicate is formed, it is preferable to use a seed crystal of RHO type zeolite.

The seed crystal has a particle diameter of usually 20nm or more, preferably 50nm or more, more preferably 100nm or more, and further steps are preferably 0.15 μm or more, particularly preferably 0.5 μm or more, and most preferably 0.7 μm or more, and usually 5 μm or less, preferably 3 μm or less, more preferably 2 μm or less, and particularly preferably 1.5 μm or less.

Depending on the pore diameter of the support, the smaller the particle size of the seed crystal, the more preferable the particle size is, and the seed crystal can be pulverized and used as necessary. The seed crystal has a particle diameter of usually 5nm or more, preferably 10nm or more, more preferably 20nm or more, usually 5 μm or less, preferably 3 μm or less, more preferably 2 μm or less.

The method for adhering the seed crystal to the support is not particularly limited, and for example, a dip coating method in which the seed crystal is dispersed in a solvent such as water, the support is immersed in the dispersion, and the seed crystal is adhered to the surface, a suction method in which the seed crystal is dispersed in a solvent such as water, ends are sealed in the dispersion, and then the support is sucked from the other end of the support, and the seed crystal is firmly adhered to the surface of the support, a method in which a substance obtained by mixing the seed crystal with a solvent such as water into a slurry is applied to the support, and a dip coating method and a suction method are preferable for producing a zeolite film with good reproducibility in order to control the amount of adhering the seed crystal, and a method in which the slurry-like seed crystal is applied and a suction method are preferable for the purpose of adhering the seed crystal to the support and/or for removing the excess seed crystal, and the support to which the seed crystal is adhered may be wiped with a finger or the like wearing a glove after the dip coating method and the suction method.

The alkali concentration of the alkaline aqueous solution is not particularly limited, and is usually 0.0001 mol% or more, preferably 0.0002 mol% or more, more preferably 0.001 mol% or more, further preferably 0.002 mol% or more in the step , and is usually 1 mol% or less, preferably 0.8 mol% or less, more preferably 0.5 mol% or less, further preferably 0.2 mol% or less in the step .

The amount of the seed crystal dispersed is not particularly limited, but is usually 0.05% by mass or more, preferably 0.1% by mass or more, more preferably 0.5% by mass or more, further steps of preferably 1% by mass or more, particularly preferably 2% by mass or more, and most preferably 3.0% by mass or more, and further usually 20% by mass or less, preferably 10% by mass or less, more preferably 5% by mass or less, further steps of preferably 4% by mass or less.

Further, , when the amount of the seed crystal in the dispersion is more than a certain degree, the amount of the seed crystal attached to the porous support by, for example, dip coating is nearly constant, and when the amount of the seed crystal in the dispersion is too large, the waste of the seed crystal increases, which is disadvantageous in terms of cost.

After the seed crystal is attached to the support by a dip coating method, a suction method, or application of slurry, it is desirable to perform zeolite membrane formation after drying. The drying temperature is usually 50 ℃ or higher, preferably 80 ℃ or higher, more preferably 100 ℃ or higher, usually 200 ℃ or lower, preferably 180 ℃ or lower, more preferably 150 ℃ or lower. The drying time is not problematic if sufficient drying is possible, and is usually 10 minutes or more, preferably 30 minutes or more, and the upper limit is not particularly limited, but is usually 5 hours or less from an economical point of view.

The support to which the seed crystal is attached after drying may be wiped and pushed with a finger or the like wearing a latex glove for the purpose of adhering the seed crystal to the support and/or removing the excess seed crystal.

The amount of the seed crystal previously attached to the porous support is not particularly limited, and is in an amount of 1m per porous support²The mass of the film-forming surface is usually 0.1g or more, preferably 0.3g or more, more preferably 0.5g or more, further steps are preferably 0.80g or more, most preferably 1.0g or more, usually 100g or less, preferably 50g or less, more preferably 10g or less, further steps are preferably 8g or less, most preferably 5g or less.

When the amount of the seed crystal is less than the lower limit, it tends to be difficult to form a crystal, the growth of the film becomes insufficient, and the growth of the film becomes uneven, further, when the amount of the seed crystal is more than the upper limit, there is a case where unevenness of the surface grows due to the seed crystal, or spontaneous nuclei easily grow due to the seed crystal falling from the support, and the growth of the film on the support is hindered.

When the zeolite membrane is formed on the porous support by hydrothermal synthesis, the method for immobilizing the support is not particularly limited, and any form such as vertical and horizontal may be used. In this case, the zeolite membrane may be formed by a standing method, or may be formed under stirring of the aqueous reaction mixture.

The hydrothermal synthesis is carried out by charging the support having the seed crystal supported thereon and the prepared mixture for hydrothermal synthesis or an aqueous gel obtained by aging the mixture into a pressure-resistant vessel, and maintaining the mixture at a predetermined temperature under a self-generated pressure or under a gas pressure not inhibiting the degree of crystallization while stirring, rotating or shaking the vessel, or in a static state. The hydrothermal synthesis in a static state is desirable in terms of not inhibiting the crystal growth from the seed crystal on the support.

The reaction temperature when forming a zeolite membrane by hydrothermal synthesis is not particularly limited as long as it is a suitable temperature for obtaining a membrane having a target zeolite structure, and is usually 100 ℃ or higher, preferably 110 ℃ or higher, more preferably 120 ℃ or higher, particularly preferably 130 ℃ or higher, particularly preferably 140 ℃ or higher, most preferably 150 ℃ or higher, usually 200 ℃ or lower, preferably 190 ℃ or lower, more preferably 180 ℃ or lower, and further ℃ or lower, and when the reaction temperature is too low, the zeolite is difficult to crystallize.

The heating (reaction) time in forming the zeolite membrane by hydrothermal synthesis is not particularly limited as long as it is a suitable time for obtaining a membrane having a target zeolite structure, and is usually 3 hours or more, preferably 8 hours or more, more preferably 12 hours or more, particularly preferably 15 hours or more, usually 10 days or less, preferably 5 days or less, more preferably 3 days or less, and further steps are preferably 2 days or less, particularly preferably 1.5 days or less.

The pressure in the hydrothermal synthesis is not particularly limited, and the autogenous pressure generated when the aqueous reaction mixture charged into the sealed vessel is heated to the above-mentioned temperature range may be sufficient, and an inert gas such as nitrogen may be added as needed in the step .

The zeolite membrane composite obtained after the 1 st hydrothermal synthesis is not necessarily washed and dried, but the composition of the aqueous reaction mixture can be ensured to be the target composition by washing and drying, the synthesis times in the multiple synthesis are usually more than 2 times, usually less than 10 times, preferably less than 5 times, and more preferably less than 3 times, and the washing with water can be times, and can also be repeated several times.

The zeolite membrane composite obtained by hydrothermal synthesis is washed with water, and then subjected to heat treatment to be dried. Here, the heat treatment means heating to dry the zeolite membrane composite, and when an organic template is used, it means removing the organic template by firing.

The temperature of the heat treatment is usually 50 ℃ or higher, preferably 80 ℃ or higher, more preferably 100 ℃ or higher, usually 200 ℃ or lower, and preferably 150 ℃ or lower for the purpose of drying, and the temperature of the heat treatment is usually 250 ℃ or higher, preferably 300 ℃ or higher, more preferably 350 ℃ or higher, further is preferably 400 ℃ or higher, usually 800 ℃ or lower, preferably 600 ℃ or lower, more preferably 550 ℃ or lower, and particularly preferably 500 ℃ or lower for the purpose of removing the organic template by firing.

When the temperature of the heat treatment is too low for the purpose of removing the organic template by firing, the residual ratio of the organic template tends to increase, and the pores of the zeolite decrease, so that the permeation amount for ammonia separation may decrease. If the heat treatment temperature is too high, the difference in thermal expansion coefficient between the support and the zeolite increases, and the zeolite membrane is likely to crack, whereby the zeolite membrane loses its denseness, and the separation performance is lowered.

The time of the heat treatment is not particularly limited as long as the zeolite membrane is sufficiently dried or the organic template can be removed by firing, but is preferably 0.5 hour or more, more preferably 1 hour or more for the purpose of drying, and is changed depending on the temperature rising rate and the temperature lowering rate, preferably 1 hour or more, more preferably 5 hours or more for the purpose of removing the organic template by firing. The upper limit of the heating time is not particularly limited, but is usually 200 hours or less, preferably 150 hours or less, and more preferably 100 hours or less.

The heating treatment for firing the template may be performed in an air atmosphere, or may be performed in an atmosphere containing an inert gas such as nitrogen or an added oxygen.

In the hydrothermal synthesis in the presence of an organic template, the zeolite membrane composite obtained is washed with water, and then, the organic template is removed by, for example, heat treatment, extraction, or the like, preferably by the heat treatment, i.e., firing.

The temperature increase rate in the heat treatment for removing the organic template by firing is desirably as slow as possible in order to prevent cracks from being formed in the zeolite membrane due to the difference in thermal expansion coefficient between the porous support and the zeolite, and is usually 5 ℃/min or less, preferably 2 ℃/min or less, more preferably 1 ℃/min or less, and further steps are preferably 0.5 ℃/min or less, particularly preferably 0.3 ℃/min or less, and the lower limit of the temperature increase rate is usually 0.1 ℃/min or more in view of handling properties.

In addition, in the heating treatment for removing the organic template by firing, it is necessary to control the temperature reduction rate after the heating treatment so as to avoid the occurrence of cracks in the zeolite film, and it is desirable that the temperature reduction rate is as slow as possible, similarly to the temperature increase rate. The cooling rate is usually 5 ℃/min or less, preferably 2 ℃/min or less, more preferably 1 ℃/min or less, still more preferably 0.5 ℃/min or less, and particularly preferably 0.3 ℃/min or less. The lower limit of the cooling rate is usually 0.1 ℃/min or more in view of workability.

Method for producing < MFI type zeolite membrane >

(silicon atom source)

The silicon (Si) atom source used in the aqueous reaction mixture is not particularly limited, and there may be used, for example, aluminosilicate zeolite, fumed silica, colloidal silica, amorphous silica, sodium silicate, silicon alkoxides such as methyl silicate, ethyl silicate, trimethylethoxysilane, tetraethyl orthosilicate, aluminosilicate gel, etc., preferably fumed silica, colloidal silica, amorphous silica, sodium silicate, methyl silicate, ethyl silicate, silicon alkoxides, aluminosilicate gel, kinds of them may be used alone, or two or more kinds may be mixed and used.

The Si atom source is used so that the amount of other raw materials used relative to the Si atom source is within the appropriate range described above or below.

(aluminum atom source)

The aluminum (Al) atom source used for producing the porous support-MFI type zeolite membrane composite is not particularly limited, and examples thereof include aluminosilicate zeolite, amorphous aluminum hydroxide, aluminum hydroxide of gibbsite structure, aluminum hydroxide of bayerite structure, aluminum nitrate, aluminum sulfate, alumina, sodium aluminate, boehmite, pseudo boehmite, aluminum alkoxide, and aluminosilicate gel, and amorphous aluminum hydroxide, sodium aluminate, boehmite, pseudo boehmite, aluminum alkoxide, and aluminosilicate gel are preferable, and amorphous aluminum hydroxide, sodium aluminate, and aluminosilicate gel are particularly preferable, and kinds thereof may be used alone, or two or more kinds thereof may be mixed and used.

The preferred range of the amount of Al atom source (including the above-mentioned aluminosilicate zeolite and other Al atom source) contained in the raw material mixture other than the seed crystal to be used relative to silicon (Si atom) (Al atom/Si atom ratio) is usually 0.001 or more, preferably 0.002 or more, more preferably 0.003 or more, further step is preferably 0.004 or more, usually 1.0 or less, preferably 0.5 or less, more preferably 0.2 or less, and further step is preferably 0.1 or less in terms of molar ratio.

The aqueous reaction mixture may contain other atom sources than the Si atom source and the Al atom source, for example, atom sources such as Ga, Fe, B, Ti, Zr, Sn, and Zn.

The type of the base used as the alkali source is not particularly limited, and an alkali metal hydroxide or an alkaline earth metal hydroxide can be used.

As the metal hydroxide, specifically, for example, alkali metal hydroxides such as sodium hydroxide, potassium hydroxide, lithium hydroxide, rubidium hydroxide, cesium hydroxide and the like; and alkaline earth metal hydroxides such as calcium hydroxide, magnesium hydroxide, strontium hydroxide, and barium hydroxide.

Further, as the alkali source for the aqueous reaction mixture, hydroxide ions of counter anions of the organic template described below may be used.

In the crystallization of the zeolite according to the present invention, an organic template is not essential, but the use of an organic template (structure directing agent) of a type corresponding to each structure is preferable because the ratio of silicon atoms to aluminum atoms in the crystallized zeolite is increased to improve crystallinity.

Any template may be used as the organic template, regardless of the type, as long as the desired zeolite membrane can be formed, and types of templates may be used, or two or more types may be used in combination.

The kind of the organic template suitable for the reaction may vary depending on the zeolite structure to be synthesized, and the organic template may be one that can obtain a desired zeolite structure. Specifically, for example, in the case of the MFI structure, tetrapropylammonium hydroxide or the like can be used.

When the organic template is cationic, it may be accompanied by anions which do not impair zeolite formation. As the ion representing such an anion, Cl may be contained^-、Br^-、I^-Plasma, hydroxide, acetate, sulfate, and carboxylate. Among them, hydroxide ions are particularly preferably used, and the hydroxide ions function as the alkali source.

The ratio of Si atom source to organic template in the aqueous reaction mixture, as organic template to SiO₂Molar ratio of (organic template/SiO)₂Ratio) of usually 0.005 or more, preferably 0.01 or more, more preferably 0.02 or more, particularly preferably 0.05 or more, particularly preferably 0.1 or more, usually 1 or less, preferably 0.5 or less, more preferably 0.3 or lessParticularly preferably 0.25 or less, and particularly preferably 0.2 or less. Organic template/SiO of aqueous reaction mixture₂When the ratio is within this range, a zeolite having excellent acid resistance and less tendency to desorb Al atoms can be obtained, while forming a dense zeolite film. In addition, under these conditions, in particular, zeolite which is dense and has excellent acid resistance is formed from an MFI-type aluminosilicate.

The molar ratio (R/Si atom) of silicon (Si atom) contained in the raw material mixture for hydrothermal synthesis other than the alkali metal atom source (R) and the seed crystal is usually 0.01 or more, preferably 0.02 or more, more preferably 0.03 or more, further steps are preferably 0.04 or more, particularly preferably 0.05 or more, usually 1.0 or less, preferably 0.6 or less, more preferably 0.4 or less, further steps are preferably 0.2 or less, and particularly preferably 0.1 or less.

When the molar ratio of the alkali metal atom source to silicon (R/Si atoms) is greater than the above upper limit, the resulting zeolite is likely to be dissolved, and the zeolite cannot be obtained or the yield may be significantly reduced. When the ratio R/Si atom is less than the lower limit, the Al atom source and the Si atom source of the raw materials may not be sufficiently dissolved, and a uniform raw material mixture for hydrothermal synthesis may not be obtained, and it may be difficult to form MFI-type zeolite.

(amount of Water)

The molar ratio of the amount of water in the raw material mixture for hydrothermal synthesis to silicon (Si atoms) contained in the raw material mixture other than the seed crystal is usually 10 or more, preferably 15 or more, more preferably 20 or more, further steps are preferably 25 or more, particularly preferably 30 or more, usually 500 moles or less, preferably 300 or less, more preferably 200 or less, further steps are preferably 150 or less, and particularly preferably 100 or less, and above the upper limit, the reaction mixture is too dilute and it becomes difficult to form a defect-free dense film, and below 10, the reaction mixture is concentrated and therefore spontaneous nuclei are easily formed, and growth of MFI type zeolite from the support is inhibited, and it becomes difficult to form a dense film.

(seed crystal)

In the present invention, seed crystals can be used as which is a component of the raw material (raw material compound) for producing "zeolite".

In the hydrothermal synthesis, the presence of the seed crystal is not essential in the reaction system, but the presence of the seed crystal can promote crystallization of the zeolite on the porous support. The method for allowing the seed crystal to exist in the reaction system is not particularly limited, and a method of adding the seed crystal to the aqueous reaction mixture, a method of attaching the seed crystal to a support, and the like in the case of synthesizing the powdery zeolite can be used. By adhering the seed crystal to the support in advance, a zeolite membrane having high separation performance and being dense can be easily formed.

The seed crystal used is a zeolite capable of promoting crystallization, and the crystal form of the seed crystal is preferably the same as that of the zeolite film to be formed, regardless of the type of the zeolite. For example, when a zeolite membrane of MFI-type aluminosilicate is formed, it is preferable to use a seed crystal of MFI-type zeolite.

The seed crystal has a particle diameter of usually 1nm or more, preferably 10nm or more, more preferably 50nm or more, and further steps are preferably 0.1 μm or more, particularly preferably 0.5 μm or more, particularly preferably 0.7 μm or more, most preferably 1 μm or more, usually 5 μm or less, preferably 3 μm or less, more preferably 2 μm or less, most preferably 1.5 μm or less, and particularly preferably 1.2 μm or less.

Depending on the pore diameter of the support, the smaller the particle size of the seed crystal, the more preferable the particle size is, and the seed crystal can be pulverized and used as necessary. The seed crystal has a particle diameter of usually 0.5nm or more, preferably 1nm or more, more preferably 2nm or more, and usually 5 μm or less, preferably 3 μm or less, more preferably 2 μm or less.

The method for adhering the seed crystal to the support is not particularly limited, and for example, a dip coating method in which the seed crystal is dispersed in a solvent such as water, the support is immersed in the dispersion, and the seed crystal is adhered to the surface, a suction method in which the seed crystal is dispersed in a solvent such as water, ends are sealed in the dispersion, and then the support is sucked from the other ends, thereby firmly adhering the seed crystal to the surface of the support, a method in which the seed crystal is mixed with a solvent such as water to form a slurry, and the like are applied to the support.

The alkali concentration of the alkaline aqueous solution is not particularly limited, and is usually 0.0001 mol% or more, preferably 0.0002 mol% or more, more preferably 0.001 mol% or more, further preferably 0.002 mol% or more in the step, and is usually 1 mol% or less, preferably 0.8 mol% or less, more preferably 0.5 mol% or less, further preferably 0.2 mol% or less in the step.

The amount of the seed crystal dispersed is not particularly limited, but is usually 0.05% by mass or more, preferably 0.1% by mass or more, more preferably 0.5% by mass or more, further steps of preferably 1% by mass or more, particularly preferably 2% by mass or more, and most preferably 3% by mass or more, and furthermore, is usually 20% by mass or less, preferably 10% by mass or less, more preferably 5% by mass or less, further steps of preferably 4% by mass or less.

Further, , when the amount of the seed crystals in the dispersion is more than or equal to a certain , the amount of the seed crystals attached to the porous support by, for example, a dip coating method is nearly constant, and when the amount of the seed crystals in the dispersion is too large, the waste of the seed crystals increases, which is disadvantageous in terms of cost.

After the seed crystal is attached to the support by a dip coating method, a suction method, or application of slurry, it is desirable to perform zeolite membrane formation after drying. The drying temperature is usually 50 ℃ or higher, preferably 80 ℃ or higher, more preferably 100 ℃ or higher, usually 200 ℃ or lower, preferably 180 ℃ or lower, more preferably 150 ℃ or lower. The drying time is not problematic if sufficient drying is possible, and is usually 10 minutes or more, preferably 30 minutes or more, and the upper limit is not particularly limited, but is usually 5 hours or less from an economical point of view.

The support to which the seed crystal is attached after drying may be wiped and pushed with a finger or the like wearing a latex glove for the purpose of adhering the seed crystal to the support and/or removing the excess seed crystal.

The amount of the seed crystal previously attached to the porous support is not particularly limited, and is in an amount of 1m per porous support²The mass of the film-forming surface is usually 0.1g or more, preferably 0.3g or more, more preferably 0.5g or more, further steps are preferably 0.80g or more, most preferably 1.0g or more, usually 100g or less, preferably 50g or less, more preferably 10g or less, further steps are preferably 8g or less, most preferably 5g or less.

When the amount of the seed crystal is less than the lower limit, it tends to be difficult to form a crystal, the growth of the film becomes insufficient, and the growth of the film becomes uneven, and further, when the amount of the seed crystal is more than the upper limit, there is a case where the unevenness of the surface grows due to the seed crystal, spontaneous nuclei easily grow due to the seed crystal falling from the support, and the growth of the film on the support is inhibited.

When the zeolite membrane is formed on the porous support by hydrothermal synthesis, the method for immobilizing the support is not particularly limited, and any form such as vertical and horizontal may be used. In this case, the zeolite membrane may be formed by a standing method, or may be formed under stirring of the aqueous reaction mixture.

The hydrothermal synthesis is carried out by charging the support having the seed crystal supported thereon and the prepared mixture for hydrothermal synthesis or an aqueous gel obtained by aging the mixture into a pressure-resistant vessel, and maintaining the mixture at a predetermined temperature under self-generated pressure or under pressure of a gas not inhibiting crystallization while stirring or rotating or shaking the vessel, or in a static state. The hydrothermal synthesis in a static state is desirable in terms of not inhibiting the crystal growth from the seed crystal on the support.

The reaction temperature in forming the zeolite membrane by hydrothermal synthesis is not particularly limited as long as it is an appropriate temperature for obtaining a membrane having a target zeolite structure, and is usually 100 ℃ or higher, preferably 120 ℃ or higher, more preferably 130 ℃ or higher, particularly preferably 140 ℃ or higher, particularly preferably 150 ℃ or higher, most preferably 160 ℃ or higher, usually 200 ℃ or lower, preferably 190 ℃ or lower, more preferably 180 ℃ or lower, and particularly preferably 170 ℃ or lower. When the reaction temperature is too low, the zeolite becomes difficult to crystallize. In addition, when the reaction temperature is too high, a zeolite different from the target zeolite is easily produced.

The heating (reaction) time in forming the zeolite membrane by hydrothermal synthesis is not particularly limited as long as it is an appropriate time for obtaining a membrane having a target zeolite structure, and is usually 1 hour or more, preferably 5 hours or more, more preferably 10 hours or more, usually 10 days or less, preferably 5 days or less, more preferably 3 days or less, and steps are preferably 2 days or less, particularly preferably 1 day or less.

The pressure in the hydrothermal synthesis is not particularly limited, and the autogenous pressure generated when the aqueous reaction mixture charged into the sealed vessel is heated to the above-mentioned temperature range may be sufficient, and an inert gas such as nitrogen may be added as needed in the step .

The zeolite membrane composite obtained after the 1 st hydrothermal synthesis is not necessarily washed and dried, but the composition of the aqueous reaction mixture can be ensured to be the target composition by washing and drying, the synthesis times in the case of carrying out the synthesis for a plurality of times are usually more than 2 times, usually less than 10 times, preferably less than 5 times, and more preferably less than 3 times, and the washing with water can be carried out times, and can also be repeated for a plurality of times.

The zeolite membrane composite obtained by hydrothermal synthesis is washed with water, and then subjected to heat treatment to be dried. Here, the heat treatment means heating to dry the zeolite membrane composite, and when an organic template is used, it means removing the organic template by firing.

The temperature of the heat treatment is usually 50 ℃ or higher, preferably 80 ℃ or higher, more preferably 100 ℃ or higher, usually 200 ℃ or lower, and preferably 150 ℃ or lower for the purpose of drying, and the temperature of the heat treatment is usually 350 ℃ or higher, preferably 400 ℃ or higher, more preferably 450 ℃ or higher, further steps are preferably 500 ℃ or higher, usually 900 ℃ or lower, preferably 800 ℃ or lower, more preferably 700 ℃ or lower, and particularly preferably 600 ℃ or lower for the purpose of removing the organic template by firing.

When the temperature of the heat treatment is too low for the purpose of removing the organic template by firing, the residual ratio of the organic template tends to increase, and the pores of the zeolite decrease, so that the permeation amount for ammonia separation may decrease. If the heat treatment temperature is too high, the difference in thermal expansion coefficient between the support and the zeolite increases, and therefore the zeolite membrane is likely to be cracked, whereby the zeolite membrane loses its denseness, and the separation performance is lowered. When tetrapropylammonium hydroxide is used as the organic template, the content of nitrogen atoms in the zeolite can be controlled by adjusting the heat treatment temperature.

The time of the heat treatment is not particularly limited as long as the zeolite membrane is sufficiently dried or the organic template can be removed by firing, but is preferably 0.5 hour or more, more preferably 1 hour or more for the purpose of drying, and is changed depending on the temperature rising rate and the temperature lowering rate, preferably 1 hour or more, more preferably 5 hours or more for the purpose of removing the organic template by firing. The upper limit of the heating time is not particularly limited, but is usually 200 hours or less, preferably 150 hours or less, and more preferably 100 hours or less.

The heating treatment for firing the template may be performed in an air atmosphere, or may be performed in an atmosphere containing an inert gas such as nitrogen or an added oxygen.

In the hydrothermal synthesis in the presence of an organic template, the zeolite membrane composite obtained is washed with water, and then, the organic template is removed by, for example, heat treatment, extraction, or the like, preferably by the heat treatment, i.e., firing.

The rate of temperature increase during the heat treatment for removing the organic template by firing is preferably as slow as possible in order to prevent cracks from being formed in the zeolite membrane due to a difference in thermal expansion coefficient between the porous support and the zeolite. The temperature rise rate is usually 5 ℃/min or less, preferably 2 ℃/min or less, more preferably 1 ℃/min or less, particularly preferably 0.5 ℃/min or less, and most preferably 0.3 ℃/min or less. The lower limit of the temperature increase rate is usually 0.1 ℃/min or more in view of workability.

In addition, in the heating treatment for removing the organic template by firing, it is necessary to control the temperature reduction rate after the heating treatment so as to avoid the occurrence of cracks in the zeolite film, and it is desirable that the temperature reduction rate is as slow as possible, similarly to the temperature increase rate. The cooling rate is usually 5 ℃/min or less, preferably 2 ℃/min or less, more preferably 1 ℃/min or less, particularly preferably 0.5 ℃/min or less, and most preferably 0.3 ℃/min or less. The lower limit of the cooling rate is usually 0.1 ℃/min or more in view of workability.

(ion exchange)

In particular, in a certain embodiment of the present invention (for example, the zeolite membrane of invention B, C, D, E), the zeolite membrane synthesized is subjected to an ion exchange treatment, the thermal expansion characteristics and thermal stability of ammonia separation of the zeolite, which is a feature of the present invention, are greatly affected by the cation species in the zeolite, and therefore the present ion exchange is an important control method.

(ion exchange)

Ion exchange when synthesizing a zeolite membrane using an organic template, it is usually performed after removing the organic template. As the ion to be ion exchanged, in the present invention, NH is preferable for increasing the nitrogen content on the surface of the zeolite membrane₄ ⁺Any th item of a cationic species obtained by protonating a C1-20 organic amine such as methylamine, dimethylamine, trimethylamine, ethylamine, diethylamine, triethylamine, ethylenediamine, dimethylethylenediamine, tetramethylethylenediamine, diethylenetriamine, triethylenetetramine, aniline, methylaniline, benzylamine, methylbenzylamine, hexamethylenediamine, N, N-diisopropylethylamine, N, N, N-trimethyl-1-adamantanamine, pyridine, or piperidine, or a cation species obtained by protonating a C1-20 organic amine such as a proton, Na, or the like⁺、K⁺、Li⁺、Rb⁺、Cs⁺Alkali metal ions are subjected to plasma treatment; ca²⁺、Mg²⁺、Sr²⁺、Ba²⁺Alkaline earth metal ions; and transition metal ions such as Fe, Cu, Zn, Ga, La, etc. Among them, proton and NH are preferable₄ ⁺、Na⁺、Li⁺、Cs⁺Fe ion, Ga ion, and La ion. These ions may be mixed in a plurality of kinds in the zeolite, and when the thermal expansion characteristics and the ammonia permeability of the zeolite are balanced, a method of mixing the ions is preferably employed. By controlling the cation species and their amounts in the ion exchange manner, the ammonia affinity of the zeolite and the effective pore diameter in the zeolite pores can be controlled, and the ammonia permeation selectivity and the ammonia permeation rate can be improved. Among these, NH is preferable as an ion species that improves the ammonia permeability selectivity₄ ⁺A cationic species obtained by protonating an organic amine having 1 to 20 carbon atoms such as methylamine, dimethylamine, trimethylamine, ethylamine, diethylamine, triethylamine, ethylenediamine, dimethylethylenediamine, tetramethylethylenediamine, diethylenetriamine, triethylenetetramine, aniline, methylaniline, benzylamine, methylbenzylamine, hexamethylenediamine, N, N-diisopropylethylamine, N, N, N-trimethyl-1-adamantanamine, pyridine, or piperidine,NH₄ ⁺the cationic species obtained by protonating an amine having a small molecular size, such as an organic amine having 1 to 6 carbon atoms, is more preferable for the above reasons, and among them, NH is particularly preferable₄ ⁺, it is preferable that protons and Na coexist as the ion species for increasing the ammonia permeation rate⁺、Li⁺、Cs⁺Fe ion, Ga ion, and La ion, and Na is particularly preferable⁺、Li⁺、Cs⁺Ions, most preferably Na⁺Ions. In the present invention, the molar ratio of nitrogen atoms to Al atoms in the zeolite membrane can be controlled by adjusting the amount of ion exchange necessary for the ion species containing nitrogen atoms in this manner.

In addition, the zeolite of the present invention contains Na⁺In the case of the ion, the content thereof is usually 0.01 or more, preferably 0.02 or more, more preferably 0.03 or more, in steps, preferably 0.04 or more, particularly preferably 0.05 or more in terms of a molar ratio to Al atoms in the zeolite, and the upper limit thereof is not particularly limited, but is usually 0.10 molar equivalent or less, preferably 0.070 molar equivalent or less, more preferably 0.065 molar equivalent or less, in steps, preferably 0.060 molar equivalent or less, particularly preferably 055 molar equivalent or less⁺The zeolite having an Al/Al atomic ratio can separate ammonia at a high permeability from a mixed gas composed of a plurality of components including ammonia and hydrogen and/or nitrogen.

The ion exchange may be carried out by a method in which the zeolite membrane after firing (in the case of using an organic template, etc.) is treated with a nitrate, a sulfate, a phosphate, an organic acid salt, a hydroxide of the cation described above, and a halogen salt of Cl, Br, and optionally an acid such as hydrochloric acid at a temperature of usually room temperature to 100 ℃ for ion exchange, and then washed with water or with hot water at 40 ℃ to 100 ℃.

(nitrate treatment)

In a certain embodiment of the invention (for example, the zeolite membrane of invention B, C, D, E), the nitrate treatment is described below because it is preferable to use the nitrate treatment in combination as a method for adjusting the content of nitrogen atoms in the zeolite membrane.

In the present invention, the zeolite membrane to be synthesized may be subjected to a nitrate treatment as needed, and the nitrate treatment may be performed after removing the organic template by firing in a state including the organic template, and the nitrate treatment is performed by immersing the zeolite membrane composite in, for example, a solution containing a nitrate, whereby the effect of blocking fine defects existing on the membrane surface by the nitrate is obtained, and the effect of increasing the affinity of the zeolite membrane with ammonia is obtained when the nitrate is present in the zeolite pores, and the method of increasing the ammonia permeability is suitably employed.

The concentration of the nitrate is usually 10mol/L or less, and the lower limit is 0.1mol/L or more, preferably 0.5mol/L or more, and more preferably 1mol/L or more. The treatment temperature is usually from room temperature to 150 ℃ or lower, and the treatment may be carried out for about 10 minutes to 48 hours, and these treatment conditions may be set as appropriate depending on the kind of nitrate and solvent used. The zeolite membrane after the nitrate treatment may be washed with water, and the nitrogen atom content of the zeolite membrane can be adjusted to a preferred range by repeating the washing with water.

(aluminum salt treatment)

In the present invention, the zeolite membrane to be synthesized may be subjected to aluminum salt treatment as needed, and the aluminum salt treatment may be carried out after the organic template is removed by firing in a state where the zeolite membrane composite is included, for example, in a solution containing an aluminum salt, whereby fine defects existing on the membrane surface are blocked by the aluminum salt, and thus, it is preferable to carry out the aluminum salt treatment in steps, where the presence of the aluminum salt in zeolite pores has an effect of attracting ammonia, and the solvent used in the aluminum salt treatment is suitably used as a means for improving the permeability of ammonia, and the salt may be water or an organic solvent if soluble, and the aluminum salt to be used is not particularly limited, and kinds of them may be used alone, or two or more kinds of them may be used in combination.

The concentration of the aluminum salt is usually 10mol/L or less, and the lower limit is 0.1mol/L or more, preferably 0.5mol/L or more, and more preferably 1mol/L or more, the treatment temperature is usually from room temperature to 150 ℃ or less, and the treatment may be carried out for about 10 minutes to 48 hours, and these treatment conditions may be set as appropriate depending on the kind of the aluminum salt and the solvent used, the zeolite membrane after the aluminum salt treatment may be washed with water, and the Al atom content of the zeolite membrane may be adjusted by repeating the washing with water, and in order to increase the Si atom/Al atom ratio of the present invention, it is preferable to decrease the concentration and the treatment amount of the aluminum salt to be treated, or to increase the number of washing times after the aluminum salt treatment, and in addition , it is preferable to decrease the ratio, increase the concentration and the treatment amount of the aluminum salt to be treated, or to.

(silylation treatment)

In the present invention, the zeolite membrane to be synthesized can be subjected to silylation treatment if necessary, which is performed by immersing the zeolite membrane composite in a solution containing, for example, an Si compound, whereby the zeolite membrane surface is modified with the Si compound to obtain a zeolite membrane having predetermined physicochemical properties, for example, by forming a layer containing a large amount of Si — OH on the zeolite membrane surface by cutting and compacting, the polarity of the membrane surface can be improved to improve the separation performance of polar molecules, and furthermore, by modifying the zeolite membrane surface with the Si compound, an effect of blocking fine defects present on the membrane surface can be obtained in some cases, and steps can be performed to control the pore diameter of the zeolite by silylation treatment, and a method of improving the ammonia permeation selectivity by performing the treatment can be appropriately employed.

The solvent used in the silylation treatment may be water or an organic solvent. In addition, the solution may be acidic or basic, in which case the silylation reaction is catalyzed by acid or base. The silylation agent to be used is not particularly limited, and an alkoxysilane is preferable. The treatment temperature is usually from room temperature to 150 ℃ or lower, and the treatment may be carried out for about 10 minutes to 30 hours, and these treatment conditions may be set as appropriate depending on the type of silylation agent and solvent used.

In the present invention, the content of nitrogen atoms contained in the zeolite membrane surface of the present invention can be controlled by the following methods and suitable combinations of these methods, as described above: a method of selecting a cation species containing a nitrogen atom in the zeolite contained in the zeolite membrane to adjust the Al atom/Si atom ratio of the zeolite; a method of adjusting the amount of ion exchange in the ion exchange method to adjust the content of nitrogen atoms; a method of using an organic template (structure directing agent) containing nitrogen atoms when producing a zeolite membrane, if necessary, and adjusting the amount of the organic template added, the heating temperature and the heating time when firing to remove the organic template; a method of treating a zeolite membrane with nitrate; and a method for adjusting the washing frequency of the zeolite membrane after the nitric acid treatment in washing.

In the present invention, the content of Al atoms contained in the zeolite membrane surface of the present invention can be controlled by the following methods and suitable combinations of these methods, as described above: a method for adjusting the Al atom/Si atom ratio in zeolite contained in the zeolite membrane; a method of treating a zeolite membrane with an aluminum salt; and a method for adjusting the number of times of washing with water when the zeolite membrane treated with an aluminum salt is washed with water.

In the present invention, the content of the alkali metal element contained in the zeolite membrane surface of the present invention can be controlled by the following methods and suitable combinations of these methods, as described above: a method for adjusting the Al atom/Si atom ratio in zeolite contained in the zeolite membrane; a method of adjusting the amount of ion exchange in the ion exchange method to adjust the content of alkali metal atoms; and a method for adjusting the number of times of washing with water when the zeolite membrane is washed with water.

The zeolite membrane composite thus produced has excellent characteristics and can be suitably used as a membrane separation means for separating ammonia from a mixed gas in the present invention.