阅读说明：本技术 一种提高抗硫抗水性能的In/H-β催化剂制备方法 (Preparation method of In/H-beta catalyst for improving sulfur resistance and water resistance ) 是由 朱荣淑 洪梅 赵玖虎 董磊 朱满玉 于 2021-09-28 设计创作，主要内容包括：本发明公开了一种提高抗硫抗水的In-H/β催化剂的制备方法。该制备方法包括以下步骤：取包括氨基酸、硅源、铝源、M源、有机胺模板剂、水的原料混合反应,得到反应凝胶；将反应凝胶晶化,得到M-β分子筛；继续与铵盐溶液混合,离子交换,得到H-β分子筛；步骤4：将H-β分子筛与铟盐溶液混合,离子交换后,得到In/H-β分子筛。氨基酸作为导引剂在制备过程中会促进结晶,并使得最终制得的In/H-β催化剂能够获得较强的酸活性中心,从而能够在SO-(2)和H-(2)O干扰下,表现出最佳的CH-(4)-SCR催化活性和循环性能。(The invention discloses a preparation method of an In-H/beta catalyst for improving sulfur resistance and water resistance. The preparation method comprises the following steps: mixing and reacting raw materials including amino acid, a silicon source, an aluminum source, an M source, an organic amine template and water to obtain reaction gel; crystallizing the reaction gel to obtain an M-beta molecular sieve; continuously mixing with an ammonium salt solution, and carrying out ion exchange to obtain the H-beta molecular sieve; and 4, step 4: and mixing the H-beta molecular sieve with an indium salt solution, and performing ion exchange to obtain the In/H-beta molecular sieve. The amino acid as a guiding agent can promote crystallization In the preparation process, and the finally prepared In/H-beta catalyst can obtain stronger Acid active center, thereby being capable of being in SO 2 And H 2 Shows the best CH under the interference of O 4 SCR catalytic activity and cycle performance.)

A method for preparing an In/H-beta catalyst, comprising the steps of:

step 1: mixing and reacting raw materials including amino acid, a silicon source, an aluminum source, an M source, an organic amine template and water to obtain reaction gel;

step 2: crystallizing the reaction gel, cooling, washing, drying and roasting to obtain the M-beta molecular sieve;

and step 3: mixing the M-beta molecular sieve with an ammonium salt solution for reaction, washing, drying and roasting after ion exchange is finished to obtain the H-beta molecular sieve;

and 4, step 4: mixing and reacting the H-beta molecular sieve with an indium salt solution, and washing, drying and roasting after ion exchange to obtain an In/H-beta molecular sieve;

wherein M is at least one of alkali metal and alkaline earth metal.

2. The method according to claim 1, wherein the molar ratio of amino acid/silica in the reaction gel is 0.1-0.5, based on silica as the silicon source.

3. The method according to claim 2, wherein the aluminum source and the M source are calculated by oxide, the organic amine template is calculated by quaternary ammonium ion, the molar ratio of silica to alumina is 5 to 200, the molar ratio of M oxide to silica is 0.01 to 0.4, and the molar ratio of quaternary ammonium ion to silica is 0.1 to 0.8.

4. The method according to claim 1, wherein the amino acid is at least one selected from the group consisting of proline, alanine, glutamic acid, histidine, serine, and arginine.

5. The method according to any one of claims 1 to 3, wherein the calcination temperature in the step 2 to 4 is 400 to 600 ℃ and the calcination time is 1 to 6 hours.

6. An In/H-beta catalyst prepared by the preparation method according to any one of claims 1 to 5.

An In/H-beta catalyst characterized In that,the concentration of acid sites is 50. mu. mol/g or more.

8. The In/H-beta catalyst according to claim 7,the concentration ratio of acid site/Lewis acid site is more than 0.55.

9. The denitration method is characterized in that the selective catalytic reduction method is adopted to treat the waste gas, and CH is used₄As the reducing agent, the catalyst is the In/H-beta catalyst as described In any one of claims 6 to 8.

10. A purification treatment apparatus comprising an SCR reactor containing the In/H-beta catalyst according to any one of claims 6 to 8.

Technical Field

The application relates to the technical field of selective catalytic reduction denitration, In particular to a preparation method of an In-H/beta catalyst for improving sulfur resistance and water resistance.

Background

Nitrogen Oxides (NO) emitted by combustion of fossil fuels_x) Not only can cause damage to the human respiratory system, but also photochemical smog, acid rain and other serious environmental problems. In this regard, researchers have proposed a series of solutions, and Selective Catalytic Reduction (SCR) denitration is currently considered to convert NO to NO_xConversion to N₂Thereby solving NO_xOptimum method of emission, wherein CH₄Is the main component of natural gas, has rich reserves, is completely civil and has low price, and is NO_xThe most promising of the technologies is eliminated.

Development of high-efficiency catalyst for CH₄The commercialization of the SCR technology is of great interest. Zeolite-based catalysts are receiving increasing attention due to their high internal surface area, uniform microporous system, considerable ion exchange capacity and high thermal stability. The beta molecular sieve has three-dimensional 12-membered ring channels with pore diameters of 0.55 x 0.55nm and 0.76 x 0.64nm, is one of the most important zeolite frameworks in SCR applications, and can be used as an effective catalyst carrier. Metals or metal oxides are often incorporated into the zeolite framework to further enhance its catalytic performance. Pan et al found that In/H-beta catalyst prepared by indium salt impregnation In CH₄Higher catalytic performance in SCR systems. And the subject group further optimizes the preparation conditions, and can also prepare the In/H-beta catalyst with higher activity.

However, in industrial applications, SO needs to be considered in addition to the catalytic performance of the catalyst itself₂And high concentrations of moisture, factors that interfere with the SCR process. In the experimental process, the current results showThe In/H-beta catalyst's tolerance to sulfur dioxide and water vapor remains to be improved. In the absence of SO₂And H₂In the case of O, NO_xThe removal efficiency can reach more than 90 percent, but 100ppm SO is added into the raw material steam₂And 5 vol.% H₂After O, NO_xThe removal efficiency drops drastically (only about 10%). Therefore, there is a need to improve the In/H-beta catalyst In SO by improving the preparation method₂And H₂Catalytic performance in the presence of O.

Disclosure of Invention

The present application is directed to solving at least one of the problems in the prior art. To this end, the present application proposes a method of treating SO₂And H₂Still has good CH in the presence of O₄A preparation method of an In/H-beta catalyst with SCR catalytic performance.

In a first aspect of the present application, there is provided a process for the preparation of an In/H-beta catalyst, the process comprising the steps of:

step 1: mixing and reacting raw materials including amino acid, a silicon source, an aluminum source, an M source, an organic amine template and water to obtain reaction gel;

step 2: crystallizing the reaction gel, cooling, washing, drying and roasting to obtain the M-beta molecular sieve;

and step 3: mixing the M-beta molecular sieve with an ammonium salt solution for reaction, washing, drying and roasting after ion exchange is finished to obtain the H-beta molecular sieve;

and 4, step 4: mixing and reacting the H-beta molecular sieve with an indium salt solution, and washing, drying and roasting after ion exchange to obtain an In/H-beta molecular sieve;

wherein M is at least one of alkali metal and alkaline earth metal.

According to the preparation method of the embodiment of the application, at least the following beneficial effects are achieved:

the amino acid as a guiding agent can promote crystallization In the preparation process, and the finally prepared In/H-beta catalyst can obtain strongerAcid active center, thereby being capable of being in SO₂And H₂Shows the best CH under the interference of O₄SCR catalytic activity and cycle performance.

In some embodiments of the present application, the silicon source is silica, and the molar ratio of amino acid/silica is 0.1 to 0.5. Further, the molar ratio of proline/silica is preferably 0.15 to 0.45, more preferably 0.2 to 0.4, and even more preferably 0.3.

In some embodiments of the present disclosure, the aluminum source, the M source are calculated by oxide, the organic amine templating agent is calculated by quaternary ammonium ion, the silica/alumina molar ratio is 5 to 200, the oxidation M/silica molar ratio is 0.01 to 0.4, and the quaternary ammonium ion/silica molar ratio is 0.1 to 0.8.

In some embodiments of the present application, the water/silica molar ratio is from 5 to 50.

In some embodiments of the present application, the amino acid is selected from at least one of proline, alanine, glutamic acid, histidine, serine, arginine.

In some embodiments of the present application, the amino acid is proline.

Amino acid as a guiding agent can promote crystallization in the preparation process, and simultaneously generate a certain number of mesopores in the beta molecular sieve, and the existence of the mesopores can promote the diffusion of reactants and products so as to improve the catalytic performance. However, the inventor finds out In the further experimental process that the tolerance of the In/H-beta catalyst to sulfur dioxide and water vapor is not only limited by the factor of mesoporous, but also related to other physicochemical properties. Compared with other amino acids, the unique cyclic side chain of proline enables the finally prepared In/H-beta catalyst to obtain strongerAcid active center, thereby being capable of being in SO₂And H₂Shows the best CH under the interference of O₄SCR catalytic activity and cycle performance.

In some embodiments herein, the silicon source is selected from at least one of white carbon, water glass, ethyl orthosilicate, silica sol, silica gel, and solid silica gel.

In some embodiments herein, the aluminum source is selected from at least one of aluminum salts, aluminates, meta-aluminates, aluminum hydroxides, pseudoboehmite, aluminum sec-butoxide, aluminum isopropoxide.

In some embodiments of the present application, M is selected from at least one of lithium, sodium, potassium, cesium, strontium, calcium, barium.

In some embodiments herein, the source of M is selected from at least one of a base, a salt of M, including but not limited to sodium hydroxide, potassium hydroxide, sodium chloride, potassium chloride, and the like.

In some embodiments of the present application, the organic amine templating agent is selected from at least one of diethylamine, triethylamine, morpholine, tetraethylammonium hydroxide, tetraethylammonium chloride, tetraethylammonium bromide, tetraethylammonium iodide, and the like.

In some embodiments of the present application, the concentration of indium ions in the indium salt solution is 0.01 to 0.1 mol/L.

In some embodiments of the present disclosure, the crystallization temperature of the reaction gel in step 2 is 100 to 220 ℃, and the crystallization time is 5 to 200 hours.

In some embodiments of the present application, the reaction temperature of the ion exchange reaction in steps 3 to 4 is 70 to 100 ℃, and the reaction time is 20min to 12 h.

In some embodiments of the present application, the ion exchange reaction, washing, and drying in step 3 are repeated 1 to 3 times and then baked.

In some embodiments of the present application, the calcination temperature in the steps 2 to 4 is 400 to 600 ℃, and the calcination time is 1 to 6 hours.

In some embodiments of the present application, the drying temperature in the steps 2 to 4 is 60 to 150 ℃ and the drying time is 1 to 24 hours.

In a second aspect of the present application, there is provided an In/H- β catalyst prepared by the foregoing preparation method.

In a third aspect of the present application, there is provided an In/H-beta catalyst, the In/H-beta catalystThe concentration of acid sites is 50. mu. mol/g or more. Preferably, the first and second liquid crystal materials are,the concentration of acid sites is 60. mu. mol/g or more, 70. mu. mol/g or more, 80. mu. mol/g or more, 90. mu. mol/g or more, 100. mu. mol/g or more, 110. mu. mol/g or more, 120. mu. mol/g or more.The concentration of acid sites was calculated from the Integrated Molar Extinction Coefficient (IMEC).

In some embodiments of the present application,the concentration ratio of acid site/Lewis acid site is more than 0.55. Preferably, the first and second liquid crystal materials are,the ratio of acid/Lewis acid is more than 0.6, more than 0.65, more than 0.7 and more than 0.72. The concentration of Lewis acid sites was also calculated from the Integrated Molar Extinction Coefficient (IMEC).

In some embodiments of the present application, the concentration of Lewis acid sites is 140. mu. mol/g or more. Preferably, the concentration of Lewis acid sites is 145. mu. mol/g or more, 150. mu. mol/g or more, 155. mu. mol/g or more, 160. mu. mol/g or more, or 165. mu. mol/g or more.

In some embodiments of the present application, the In/H-beta catalyst has a methane selectivity of 80% or more (detection conditions: feed gas contains 400ppm NO, 400ppm CH)₄、10vol.％O₂、100ppm SO₂、5vol.％H₂O and the balance of Ar are used as balance gas, the flow rate is 100mL/min, and the space velocity is 23600h^-1The temperature programming rate is 4 ℃/min (100 ℃ C. and 650 ℃ C.), and the catalyst dosage is 100 mg). Further, the selectivity of methane is more than 85%, more than 90%, more than 95%, more than 98% and more than 99%.

In some embodiments of the present application, the In/H-beta catalyst contains 400ppm NO, 400ppm CH In the feed gas₄、10vol.％O₂、100ppm SO₂、5vol.％H₂O and the balance of Ar are used as balance gas, the flow rate is 100mL/min, and the space velocity is 23600h^-1The programmed heating rate is 4 ℃/min (100-. And after three cycles, the nitrogen oxide removal rate is still more than 30%, more than 35%, more than 36% and more than 37% at 650 ℃.

In some embodiments of the present application, an In/H-beta catalyst comprises an H-beta molecular sieve support and indium supported on the H-beta molecular sieve support. More specifically, indium is uniformly distributed on the surface and inside of the H-beta molecular sieve carrier.

In some embodiments of the present application, the indium content of the In/H-beta catalyst is 2 to 8 wt% of the total mass of the In/H-beta catalyst. Preferably, the indium content is 3 wt% or more, 3.5 wt% or more, 4 wt% or more, 4.5 wt% or more, or 5 wt% or more. Preferably, the indium content is 7.5 wt% or less, 7.4 wt% or less, 7.3 wt% or less, 7.2 wt% or less, and 7.1 wt% or less.

In some embodiments of the present application, the Si/Al molar ratio In the In/H-beta catalyst is 25 or greater.

In some embodiments of the present application, the In/H-beta catalyst has an In/Al molar ratio of 0.7 or greater. Preferably 0.71 or more, 0.72 or more, 0.73 or more, 0.74 or more, 0.75 or more, 0.76 or more, 0.77 or more, 0.78 or more, 0.79 or more, 0.8 or more.

In a fourth aspect of the present application, a denitration method is provided, wherein the denitration method adopts a selective catalytic reduction method to treat exhaust gas with CH₄As a reducing agent, the catalyst is the In/H-beta catalyst.

In a fifth aspect of the present application, there is provided a purification treatment apparatus comprising an SCR reactor In which the above-described In/H- β catalyst is installed.

Additional aspects and advantages of the present application will be set forth in part in the description which follows and, in part, will be obvious from the description, or may be learned by practice of the present application.

Drawings

Fig. 1 is the results of a comparative denitration activity test of the present application. Wherein, (a) is the change situation of the nitrogen oxide removal rate of the molecular sieve catalyst prepared by different amino acid mediation with temperature, (b) is the change situation of the methane conversion rate of the molecular sieve catalyst prepared by different amino acid mediation with temperature, (c) is the change situation of the methane selectivity of the molecular sieve catalyst prepared by different amino acid mediation with temperature, and (d) is the change situation of the nitrogen oxide removal rate of the In/H-beta-P molecular sieve catalyst In multiple TPSR cycles.

FIG. 2 is a result of an X-ray diffraction (XRD) pattern of In/H-beta-P, In/H-beta-H, In/H-beta-R, In/H-beta-S and In/H-beta-B molecular sieve catalysts of the present application.

FIG. 3 is a graph of Electron Paramagnetic Resonance (EPR) spectra of In/H-. beta. -P and In/H-. beta. -B molecular sieve catalysts of the present application.

FIG. 4 is the imaging results of electron microscopy and combined energy dispersive X-ray (EDX) spectroscopy of In/H-. beta. -P samples of the present application. Wherein a is the result of a scanning electron microscope, and the scale in the figure is 1 μm; b-f are the results of electron microscope combined with EDX spectrum analysis, the scale In the figure is 100nm, and c-f respectively reflect the element distribution of Al, Si, O and In.

FIG. 5 is the results of Transmission Electron Microscopy (TEM) and High Resolution Transmission Electron Microscopy (HRTEM) imaging of In/H-. beta. -P samples of the present application. Wherein the scale in a is 100nm, the scale in b is 50nm, and the lower left corner in b is the lattice fringe of 10 nm.

FIG. 6 shows magic angle spinning solid-state nuclear magnetic resonance (MAS NMR) measurements of In/H-. beta. -P samples of the present application. Wherein a is²⁹As a result of Si, b is²⁷Results for Al.

FIG. 7 is an XPS measurement spectrum of In/H- β -P, In/H- β -H, In/H- β -R and In/H- β -S molecular sieve catalysts of the present application. Wherein a is In 3d_5/2As a result of the spectrum, b is the result of O1s spectrum.

FIG. 8 is a graph of In/H-beta-P, In/H-beta-H, In/H-beta-R and In/H-beta-S molecular sieve catalysts of the present application reduced at hydrogen temperature programmed (H/H-beta-S)₂-TPR) reduction of In.

FIG. 9 is NH for In/H-beta-P, In/H-beta-H, In/H-beta-R and In/H-beta-S molecular sieve catalysts of the present application₃-TPD curve.

FIG. 10 is an infrared spectrum (Py-IR) of adsorbed pyridine for In/H- β -P, In/H- β -H, In/H- β -R and In/H- β -S molecular sieve catalysts of the present application.

Detailed Description

The conception and the resulting technical effects of the present application will be clearly and completely described below in conjunction with the embodiments to fully understand the objects, features and effects of the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, and not all embodiments, and other embodiments obtained by those skilled in the art without inventive efforts based on the embodiments of the present application belong to the protection scope of the present application.

The following detailed description of embodiments of the present application is provided for the purpose of illustration only and is not intended to be construed as a limitation of the application.

In the description of the present application, the meaning of a plurality is one or more, the meaning of a plurality is two or more, and the above, below, exceeding, etc. are understood as excluding the present number, and the above, below, within, etc. are understood as including the present number. If the first and second are described for the purpose of distinguishing technical features, they are not to be understood as indicating or implying relative importance or implicitly indicating the number of technical features indicated or implicitly indicating the precedence of the technical features indicated.

In the description of the present application, reference to the description of the terms "one embodiment," "some embodiments," "an illustrative embodiment," "an example," "a specific example," or "some examples," etc., means that a particular feature, structure, material, or characteristic described in connection with the embodiment or example is included in at least one embodiment or example of the present application. In this specification, the schematic representations of the terms used above do not necessarily refer to the same embodiment or example. Furthermore, the particular features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments or examples.

Example 1

This example provides an In/H-beta catalyst, which is prepared by the following steps:

step 1: 0.16g NaAlO₂And 0.05g NaOH were dissolved in 12.5g tetraethylammonium hydroxide (TEAOH, 25%) and 2.6mL deionized water, and proline (P) was added under ultrasonic conditions to stir well to give a mixture. 2g of fumed silica were dissolved in the mixture and shaken to give a reaction gel. Subsequently, the resulting reaction gel was aged in a magnetic stirrer at room temperature for 4h so that the composition in the reaction gel was 0.3 proline in terms of molar ratio: 1.0SiO₂：0.023Al₂O₃：0.048Na₂O：0.636TEAOH：20H₂O。

Step 2: the aged reaction gel was spin-crystallized in a homogeneous reactor at 140 ℃ at a constant rate of 10rpm for 48 hours. After cooling to room temperature, the dispersion was filtered off, washed with deionized water to pH 7 and then dried at 80 ℃ for 12 hours. And finally, roasting the powder for 3 hours in the air atmosphere at the temperature of 500 ℃, and removing the template agent to obtain the Na-beta molecular sieve.

And step 3: mixing Na-beta molecular sieve with 1M (NH)₄)₂SO₄The solution was prepared as follows 1: a solid-liquid mass ratio of 20 was subjected to ion exchange at 85 ℃ for 4 hours, and then the solid was separated by filtration, washed with distilled water, and dried at 110 ℃. This ion exchange procedure was repeated twice to ensure complete cation exchange. And then roasting for 3 hours in the air atmosphere at 500 ℃ to obtain the H-beta molecular sieve.

And 4, step 4: molecular sieve 3g H-beta was dissolved in 100ml of 0.033M indium nitrate solution and ion exchanged at 85 ℃ for 8h, then the solid was isolated by filtration, washed with distilled water until pH 7 and dried at 80 ℃ for 12 h. And then roasting for 3 hours at 500 ℃ In an air atmosphere to obtain the In/H-beta molecular sieve.

Comparative examples 1 to 7 provide In/H-beta molecular sieves, which are prepared by a method different from that of example 1, using different amino acids, specifically alanine (a), glutamic acid (E), histidine (H), serine (S), threonine (T), arginine (R), and aspartic acid (D), respectively. To distinguish example 1 from comparative examples 1-7, the final molecular sieve product was then added with the corresponding amino acid abbreviation X, denoted as In/H- β -P as In example 1, and the products of comparative examples 1-7 were denoted as In/H- β -A, In/H- β -E, In/H- β -H, In/H- β -S, In/H- β -T, In/H- β -R and In/H- β -D, respectively.

Comparative example 8, an In/H-beta molecular sieve was provided, which was prepared In a manner different from that of example 1 In that no amino acid was added In step 1.In addition, the crystallization time in step 2 was extended to 6 days due to the absence of amino acids. The molecular sieve is designated as In/H-beta-B.

₄Comparative CH-SCR performance test

NO for In/H-beta-X catalyst using continuous flow fixed bed reactor_xThe selective catalytic reduction was evaluated by the following specific procedure:

(1) the molecular sieve catalysts prepared in example 1 and comparative examples 1-8 are granulated under 20MPa, then ground, and samples with the grain size of 40-60 meshes (0.250-0.425 mm) are screened for further reaction.

(2) 100mg of catalyst sample was weighed into the center of a fixed bed continuous flow reactor. The feed gas contains 400ppm NO and 400ppm CH₄、10vol.％O₂、100ppm SO₂、5vol.％H₂O and Ar as balance gas. The flow rate of the raw gas is 100mL/min, and the space velocity (GHSV) is 23600h^-1. The reactor temperature was increased between 100 ℃ and 650 ℃ with a temperature gradient of 4 ℃/min.

Catalyst activity was monitored using Temperature Programmed Surface Reaction (TPSR) technology. The NO concentration was continuously measured by a nitrogen oxide analyzer (ThermoScientific, 42 i). CH was measured using an on-line gas chromatograph (GC-2014C, Shimadzu, Japan)₄Concentration, the gas chromatograph was equipped with a Porapak-Q column and a Flame Ionization Detector (FID). Analysis of N formed during SCR reaction Using Agilent 7890B GC fitted with 5A molecular sieves₂And (4) the content of O.

In CH₄During the SCR reaction, the reaction formula under ideal conditions is: CH (CH)₄+2NO+O₂＝CO₂+N₂+2H₂O, CH in the presence of oxygen₄Reduction of NO_xNitrogen, water and carbon dioxide are generated. The nitrogen oxide removal rate (eta), the methane conversion rate (gamma), the methane selectivity (alpha) and the nitrogen selectivity (S) are adopted_N2) Four indexes were used to evaluate the denitration activity of the catalyst.

In the formula, c (NO)_x)_inIs NO before reaction_xInitial concentration (ppm);

c(NO_x)_outis NO after reaction_xConcentration (ppm);

c(CH₄)_inis CH before reaction₄Initial concentration (ppm);

c(CH₄)_outis a post-reaction CH₄Concentration (ppm);

c(N₂o) is N formed₂O concentration (ppm).

The results of detecting the denitration activity of example 1 and comparative examples 1 to 8 are shown in fig. 1, wherein a represents the result of removing the nitrogen oxide. As can be seen from a, the removal rate of nitrogen oxides by In/H-beta molecular sieves prepared by different amino acid mediation is also obviously different, when proline-mediated In/H-beta-P is used, In SO₂And H₂Under the condition of O interference, the removal rate of nitrogen oxide is the highest and can reach 40 percent, and the comparison result isThe test results of examples 1 to 7 were all less than 30%. Comparative example 8 does not use amino acid to participate in the reaction, and the nitrogen oxide removal rate under the same conditions is only 10% at most. In addition, it can be seen that the removal rate of nitrogen oxides is almost 0 at In/H-. beta. -D and In/H-. beta. -T temperatures below 600 ℃ and is only 3% or less even at 650 ℃. In/H-beta-B prepared without adding amino acid has the nitrogen oxide removal rate similar to the former two at the temperature of 600 ℃, but the nitrogen oxide removal rate is obviously higher than the former two at the temperature of 650 ℃.

The molecular sieve with the nitrogen oxide removal rate of more than 20 percent is ranked from high to low according to the nitrogen oxide removal rate and is In/H-beta-P (40 percent) > In/H-beta-A (29 percent) > In/H-beta-H (28.7 percent) > In/H-beta-R (25.9 percent) > In/H-beta-S (24.3 percent) > In/H-beta-E (20.4 percent). In the method, because the removal rate of the nitrogen oxides of In/H-beta-A under the low-temperature condition is low, the In/H-beta-P, In/H-beta-H, In/H-beta-R, In/H-beta-S is not further characterized, but only further research is carried out.

As can be seen from b of FIG. 1, the four molecular sieves all exhibit higher CH as the temperature increases₄Conversion, no significant difference between the four catalysts, indicates that methane is the key reductant, in all CH₄The consumption in the SCR reaction is approximately the same. As can be seen in c of FIG. 1, the CH of the four molecular sieves₄The selectivity is a trend of increasing first and then decreasing, and the optimal methane selectivity is achieved at the temperature of about 500 ℃. The methane selectivity is positively correlated with the catalytic performance, particularly In the low-temperature region, the methane selectivity of In/H-beta-P is the highest at 500 ℃, and reaches 100%. Thus, In/H-. beta. -P can realize CH at an optimum reaction temperature₄And NO_xIn CH₄-the desired stoichiometric reaction in SCR. As the temperature continues to rise, CH due to competition for methane side reactions₄The selectivity decreases.

In addition, In/H-beta-P catalysts In SO₂And H₂The excellent durability was still exhibited in the repeated tests under the O-interference condition, and the results were shown as d in FIG. 1, which is the removal rate of nitrogen oxides during the first cycle (1st), the second cycle (2nd), and the third cycle (3rd), respectively, from top to bottomThe result of (1). As can be seen from the figure, even at SO₂And H₂In the case of O interference, the nox removal rate remained almost the same after three temperature cycles up to 650 ℃, especially in the high temperature region, and still up to 37.9% nox removal rate at 650 ℃ after three cycles.

Compositional and structural characterization

The ICP method measured the indium content and Si/Al ratio of In/H- β -P, In/H- β -H, In/H- β -R, In/H- β -S and In/H- β -B, and the results are shown In Table 1.

TABLE 1 comparison of the elemental content in molecular sieves

As can be seen from the table, the Si/Al ratio of the catalyst is approximately around 25, which is also close to the ratio of the starting reaction gel. Previous studies have shown that In/H-beta molecular sieves with about 7 wt% indium content prepared by ion exchange of H-beta molecular sieves with 0.033M indium solution have the best NO removal efficiency. The indium content of the molecular sieve prepared by the method is In the range of 5.7-7.1 wt%, and the indium content is In/H-beta-S from the lowest to the highest<In/H-β-P<In/H-β-H<In/H-β-R<In/H-beta-B. This trend is associated with NO in CH₄Inconsistent order of catalytic activity in SCR, indicating that indium loading may not be a key factor leading to high denitration efficiency. On the other hand, the best denitration catalyst of In/H-. beta. -P has the highest In/Al ratio of 0.8, indicating that it has the highest degree of ion exchange.

FIG. 2 shows the X-ray diffraction (XRD) patterns of In/H-beta-P, In/H-beta-H, In/H-beta-R, In/H-beta-S and In/H-beta-B molecular sieve catalysts. In/H-beta-P, In/H-beta-H, In/H-beta-R and In/H-beta-S, 7.8 °, 13.5 °, 21.5 °, 22.5 °, 25.2 °, 27 ° corresponding to H-beta molecular sieves were observedCharacteristic reflections of 1 °, 29.7 °, 33.4 ° and 43.7 °. Thus, under the action of the amino acid, the pure crystalline beta phase, free of impurities, can be completely crystallized within 2 days. Meanwhile, In was not detected therein₂O₃Indicating that the indium has been successfully exchanged as extra-framework cations and is in a highly dispersed state with negligible amounts of indium oxide detected by X-ray diffraction. Whereas the In/H- β -B sample showed a broad peak only at a position around 32 °, indicating that an amorphous phase still exists therein even if the crystallization time was extended by 3 times to 6 days.

From the above results, it is presumed that the addition of the amino acid promotes the crystallization of the β -molecular sieve, and further the verification test is as follows: 5, 5-dimethylpyrroline-N-oxide (DMPO) was added to the initially synthesized reaction gel. In situ EPR spectra of Na-. beta. -P gel synthesized from proline and Na-. beta. -B gel synthesized without amino acid were compared, and the results are shown in FIG. 3. It can be seen from the figure that there is a clear difference between the two. Due to the resonance transition of DMPO-. OH, Na-. beta. -P is present in a ratio of 1: 2: 2: the ratio of 1 shows a quadruple mode, split to 1.5mT, while Na-. beta. -B is completely free of this mode of Na-. beta. -P. Thus, the crystallization promoting effect of amino acids may be caused by the induction of free radicals.

The structural properties of the molecular sieve were analyzed and the results are shown in table 2. Wherein S is_BETThe BET surface area is measured by a nitrogen adsorption method when the relative air pressure range is 0.05-0.3; v_totalTotal pore volume, from P/P₀Calculating the amount of nitrogen adsorbed when the nitrogen content is 0.98; v_mesoThe mesopore volume was calculated by the t-plot method (t-plot); d_mesoThe mesopore diameter was calculated by the BJH method.

TABLE 2 results of molecular sieve structural analysis

Slave watchAs can be seen In (A), In/H-. beta. -P showed a maximum mesopore volume of 0.27cm³In g, the maximum total pore volume is 0.42cm³(ii)/g; followed by In/H-. beta. -S and In/H-. beta. -R. The possible reasons for the highest mesopore volume and total pore volume of In/H- β -P are its better compatibility with molecular sieve synthesis, and the particular stability of the unique cyclic side chain of the proline molecule. However, it can be seen that the mesoporous size of the molecular sieve is not completely consistent with the removal rate of nitrogen oxides and methane selectivity.

The In/H-. beta. -P samples were analyzed for nanoscale morphology and composition using a Scanning Electron Microscope (SEM) In combination with an energy dispersive X-ray (EDX) spectrum, and the results are shown In FIG. 4, where a is the result of the SEM and b-f are the results of quantitative analysis of the EDX spectrum, from which it is clear that uniform nanoparticles having an average grain size of-150 nm, In which Al, Si and O elements are uniformly distributed In the molecular sieve, and In which is also more uniformly distributed throughout the molecular sieve but slightly aggregated at the surface, were observed. According to the results of EDX analysis, the weight concentration of indium was about 6%, which was consistent with the results of ICP analysis, confirming uniform distribution of indium on the surface and inside of the crystal.

The results of Transmission Electron Microscope (TEM) imaging of the In/H- β -P sample are shown In fig. 5a, which shows that the mosaic structure of the In/H- β -P molecular sieve, In which a large number of crystallites of 10-20nm In size co-grow as medium crystals, form distinct nano-mesopores with well-defined edges. Further examination by high resolution tem (hrtem) showed that the particles were completely crystalline as shown in b of fig. 5, as evidenced by the large number of lattice fringes throughout the sample (b lower left panel). The presence of these mesopores allows easy transport of reactants and products while preventing side reactions. Thus, modulation of proline results In/H- β -P showing more exposed active catalytic sites. These active catalytic sites may enhance hydrothermal stability and resistance to poisoning.

Magic angle spinning solid-state nuclear magnetic resonance (MAS NMR) detection of the coordination structure of the In/H-beta-P sample shows that the result is shown In FIG. 6, wherein a is²⁹As a result of Si, b is²⁷Results for Al. As can be seen from a, it is shown that,²⁹si MAS NMR showed one main peak at-110.8 ppm and-102A shoulder at 6ppm, the former being characteristic of the unique silicon tetrahedral structure in the H-beta lattice and the latter corresponding to Si-OH-Al (Si) due to hydrolysis of the Si-O-Al (Si) bonds. The peak width around-110.8 ppm may be due to different Si sites in the β framework. While Si-OH-Al (Si) is generally considered to be the source of acid sites on the In/H-beta catalyst. As can be seen from b, it is,²⁷al MAS NMR showed two main peaks at 54.8 and 57.6ppm, corresponding to tetrahedral coordination in the beta zeolite at the framework aluminum positions T1-T2 and T3-T9, respectively. These tetrahedrally coordinated Al sites, which are 3+ In charge, produce a negatively charged framework that is compensated by exchangeable cations (e.g., In-containing cations). Whereas a weak peak near 0ppm indicates negligible octahedral aluminum content In/H-. beta. -P.

Chemical state and redox experiments

Photoelectron Spectroscopy (XPS) results of In/H-beta-P, In/H-beta-H, In/H-beta-R, In/H-beta-S and In/H-beta-B are shown In FIG. 7, In which a is In 3d_5/2Spectral measurements, from which it can be seen that three indium chemical states correspond to In of about 445eV₂O₃InO of about 446eV⁺In (OH) at about 447eV_3-z ^z+. Table 3 compares the curve fit contents of these indium states and shows that the proportions of the three indium in the four catalysts are almost the same. Switched InO⁺And in (OH)_3-z ^z+Is the main type of indium, whereas exchanged InO⁺Species is CH₄-active site of SCR reaction. On the other hand, the Binding Energy (BE) value of the In/H-. beta. -X catalyst differs among different catalysts. The BE values for the three types of indium were highest for In/H- β -P, indicating that indium interacts more strongly with the proline-modulated zeolite beta framework.

b is a measurement of the O1s spectrum, and it can be seen from the figure that deconvolution into two main peaks at 532.7eV and 533.6eV, corresponding to different forms of oxygen on the surface: o is_βSurface oxygen and O_γOxygen in the hydroxyl group of (a). Due to its high mobility, O_βCan participate in the oxidation process, which plays a key role in the SCR of NO. O in the sample was obtained by deconvolution and curve fitting_β/(O_β+O_γ) The ratio, results, referring to table 3, did not differ significantly within the narrow range between 0.57 and 0.59. Thus, different amino acids mediate no change in the chemical valence of the oxygen element at the surface of the catalyst.

TABLE 3 elemental chemical states on the surface of molecular sieve catalysts

Hydrogen temperature programmed reduction (H)₂TPR) were studied to determine the reduction of In different molecular sieve samples, and the results are shown In FIG. 8. As can be seen from the graph, all samples exhibited broad reduction signals between 200 ℃ and 500 ℃ with peaks centered at 300 ℃ and 400 ℃, indicating that there was no bulk In requiring higher reduction temperatures₂O₃In doped is illustrated from the side³⁺In a highly dispersed state. The reduction peak of In/H- β -P occurs at the highest temperature centered at-365 ℃, indicating a higher reduction temperature requirement, which may indicate a stronger electron interaction of indium with the zeolite framework, thereby retarding the reduction of indium oxide.

Surface acidity test

Previous results indicate that adjusting the Si/Al ratio in H-beta molecular sieve catalysts changes the number of acid centers in the composite in the metal oxide/beta catalyst. However, in this case, the Si/Al ratio was kept around-25 for all H-. beta. -X samples. XPS Spectroscopy and H₂TPR results also demonstrate that their surface indium and oxygen species are similar. The stronger interaction of the indium species with the In/H- β -P framework revealed by the high binding energy suggests that proline may improve the zeolite properties. Therefore, the surface acidity thereof was further investigated.

NH of In/H-beta-P, In/H-beta-H, In/H-beta-R and In/H-beta-S catalysts₃The TPD curve is shown in FIG. 9. These NH groups₃The TPD curve can be decomposed into peaks I below 200 ℃ corresponding to weak acid sites; a peak II located between 200 ℃ and 350 ℃ corresponding to the middle acid site; peak III, located between 350 ℃ and 650 ℃, corresponds to a strong acid site. Table 4 is NH₃The result of fitting the TPD curve, from which it can be seen that In/H-. beta. -P has the highest number of acid sites, especially strong acid sites. The order of acid positions is In/H- β -P, In/H- β -H, In/H- β -R and In/H- β -S, with CH reflected In FIG. 1₄SCR performances are closely related, and the important effect of acid sites on denitration catalysis is proved.

TABLE 4 number and distribution of acid sites on the surface of molecular sieve catalysts

a: the peak corresponds to temperature (. degree. C.).

b: peak area (a.u.).

c: the calculation method comprises the following steps: integrated Molar Extinction Coefficient (IMEC).

Pyridine (Py) vs. NH₃Has higher selectivity and stability, and can be easily distinguished by FTIR spectrumsted and Lewis acid sites. The infrared spectrum (Py-IR) of the adsorbed pyridine of the four catalysts is shown in FIG. 10. 1540cm^-1And 1450cm^-1The left and right bands correspond to pyridine adsorption respectivelyPyridinium ions (PyH +) formed at the acid site and pyridine interacting with the Lewis acid site. 1490cm^-1The band of (b) is formed by the interaction of PyH + with pyridine coordinated to the Lewis acid site. According to 1540cm^-1And 1450cm^-1Spectral band estimation ofThe amounts of acid, Lewis acid and B/L, the results are shown in Table 4. And NH₃The TPD results are consistent,the amount of acid and the B/L ratio are In the order In/H-beta-P>In/H-β-H>In/H-β-R>In/H-beta-S, with catalysisThe activity is positively correlated. Thus, In CH using In/H-beta catalyst₄In SCR, the number of strong acid sites andthe density of the acid centers plays a crucial role. In addition, as can be seen from the data in table 2, the mediation of the amino acids is to adjust the catalytic activity of the molecular sieve without affecting the framework silica-alumina ratio.

Bound NH₃As a result of-TPD and Py-IR, the In/H-. beta. -P catalyst showed the best CH₄The reason for the SCR activity is that it is strongerThe acid active center, therefore, contributes to a stronger interaction with the indium oxide and indium hydroxy species. In addition, comparing the FT-IR spectra of In/H- β -P and proline, no characteristic FT-IR peak of proline is found In/H- β -P, therefore proline only interacts with the β -zeolite framework during the synthesis phase, which has been completely removed by subsequent washing and calcination steps. That is, the proline is added only to adjust the acidity of the resulting catalyst, and is not added to the finally formed catalyst.

Example 2

This example provides a method for preparing an In/H-beta catalyst, which is different from example 1 In that the crystallization temperature is 220 ℃ and the crystallization time is 48 hours. The In/H-beta catalyst prepared by the method is found to be SO under the same detection conditions₂And H₂Under the interference of O, the higher nitrogen oxide removal rate and methane selectivity are also maintained.

Examples 3 to 6

Examples 3 to 6 respectively provide a method for preparing an In/H- β catalyst, which is different from example 1 In that the amount of proline is adjusted so that the molar ratio of proline to silica In the reaction gel after aging is 0.1, 0.2, 0.4, 0.5. Detection was carried out by reference to the above-mentioned method and found in SO₂And H₂O interference, compared to preparation under the same conditions with or without other amino acidsThe molecular sieve catalyst prepared in the embodiment 3-6 also maintains higher nitrogen oxide removal rate and methane selectivity.

Examples 7 to 9

Examples 7 to 9 respectively provide a method for preparing an In/H- β catalyst, which is different from example 1 In that the concentrations of indium nitrate solutions are adjusted to 0.01M, 0.06M and 0.1M, respectively. The In/H-beta catalysts prepared by the methods are found In SO by adopting the same detection conditions₂And H₂Under the interference of O, the higher nitrogen oxide removal rate and methane selectivity are also maintained.

Example 10

The embodiment provides an exhaust gas treatment device, which comprises at least one SCR reactor, wherein one end of the SCR reactor is connected with an input flow system, and the input flow system comprises a plurality of inlets which are respectively used for introducing methane and exhaust gas into the SCR reactor. An In/H-beta catalyst prepared by any one of the methods In the embodiments 1 to 9 is also preset In the SCR reactor.

The present application has been described in detail with reference to the embodiments, but the present application is not limited to the embodiments described above, and various changes can be made within the knowledge of those skilled in the art without departing from the gist of the present application. Furthermore, the embodiments and features of the embodiments of the present application may be combined with each other without conflict.