阅读说明：本技术 一种花状丝光沸石及其制备方法和应用 (Flower-shaped mordenite and preparation method and application thereof ) 是由 黄守莹 李媖 贺培 吕静 王悦 李茂帅 马新宾 于 2020-05-25 设计创作，主要内容包括：本发明公开了一种花状丝光沸石,其为纳米棒状晶体聚集形成的花状簇形貌,所述纳米棒状晶体的直径为100-300nm、长度1-3μm。本发明还公开了所述花状丝光沸石的制备方法和其作为二甲醚羰基化反应催化剂的应用,本发明先将原料混合后形成的凝胶混合物在室温下陈化,然后将陈化后的母液再进行水热晶化,且凝胶混合物中添加晶种,这两个操作对丝光沸石分子筛的晶化过程具有明显影响。本发明成功制得纳米棒状晶体聚集形成的花状簇形貌的花状丝光沸石,且相对于不经陈化、不添加晶种、以及不添加生长改性剂制得的样品,用于二甲醚羰基化制乙酸甲酯反应时,本发明花状丝光沸石具有更优的催化活性。(The invention discloses flower-shaped mordenite which is in a flower-shaped cluster shape formed by gathering nano rod-shaped crystals, wherein the diameter of the nano rod-shaped crystals is 100-300nm, and the length of the nano rod-shaped crystals is 1-3 mu m. The invention also discloses a preparation method of the flower-shaped mordenite and application of the flower-shaped mordenite as a dimethyl ether carbonylation reaction catalyst. The method successfully prepares the flower-shaped mordenite with the flower-shaped cluster morphology formed by the aggregation of the nano rod-shaped crystals, and has better catalytic activity when used for the reaction of preparing methyl acetate by dimethyl ether carbonylation compared with the samples prepared without aging, seed crystal addition and growth modifier addition.)

1. The flower-shaped mordenite is characterized in that the flower-shaped mordenite is in a flower-shaped cluster shape formed by aggregation of nano rod-shaped crystals, and the diameter of the nano rod-shaped crystals is 100-300nm, and the length of the nano rod-shaped crystals is 1-3 mu m.

2. A process for the preparation of the flower-like mordenite zeolite of claim 1, which comprises the steps of:

(1) taking an aluminum source, a silicon source, an alkali source, a template agent, a growth modifier, water and seed crystals, and stirring and mixing to obtain a gel mixture; the template agent is a nitrogen-containing compound capable of inducing the generation of a mordenite molecular sieve structure; the growth modifier is a cationic surfactant.

(2) Aging the gel mixture obtained in the step (1) at room temperature to obtain a hydrothermal reaction mother liquor;

(3) carrying out hydrothermal treatment on the hydrothermal reaction mother liquor, and washing, drying and roasting the obtained solid after the hydrothermal treatment to obtain Na-type mordenite;

(4) and (4) converting the sodium mordenite obtained in the step (3) into hydrogen mordenite.

3. The preparation method according to claim 2, wherein the silicon source in step (1) is selected from one or more of silica sol, sodium silicate, fumed silica, and ethyl orthosilicate; the aluminum source is selected from one or more of aluminum sulfate, sodium metaaluminate and aluminum nitrate; the alkali source is sodium hydroxide; the template agent is selected from one or more of tetraethylammonium hydroxide, tetraethylammonium bromide, cycloheximide, homopiperazine, cyclohexylamine and 4-methylpiperidine; the growth modifier is selected from one or more of cetyl trimethyl ammonium bromide, cetyl trimethyl ammonium hydroxide, tetradecyl trimethyl ammonium bromide and octadecyl trimethyl ammonium bromide; the seed crystal is a silicon-aluminum molecular sieve containing eight-membered rings and is selected from mordenite.

4. The method according to claim 2, wherein the molar ratio of the silicon source, the aluminum source, the alkali source, the templating agent, the growth modifier, and the water in step (1) is 1: (0.025-0.06): (0.3-0.5): (0.1-0.4): (0.02-0.09): (20-50); the adding amount of the seed crystal is 2-10% of the mass of the silicon dioxide in the silicon source.

5. The method according to claim 2, wherein in the step (1), the water, the alkali source, the templating agent, the aluminum source, and the growth modifier are stirred and mixed to obtain a first mixture, and then the silicon source and the seed crystal are added to the first mixture and stirred and mixed to obtain the gel mixture.

6. The preparation method according to claim 2, wherein the gel mixture obtained in the step (1) is aged for 2-24 h in the step (2) to obtain a hydrothermal reaction mother liquor.

7. The preparation method according to claim 2, characterized in that in the step (3), the hydrothermal reaction mother liquor is filled into a hydrothermal reaction kettle, the kettle is sealed, hydrothermal treatment is carried out for 24-96 h at 150-190 ℃, the obtained solid is washed until the pH is less than 9, the solid is dried, and then the solid is roasted for 2-8 h at 500-600 ℃ in the air atmosphere, so as to obtain the sodium mordenite.

8. The preparation method according to claim 2, characterized in that in the step (3), the sodium mordenite is mixed with the aqueous solution of ammonium ions, and the mixture is stirred for 2-8 hours at 30-100 ℃; and after filtering and drying, roasting for 2-8 h at 400-600 ℃ in an air atmosphere to obtain the hydrogen mordenite.

9. Use of the flower-shaped mordenite of claim 1, as a catalyst in the carbonylation of dimethyl ether to produce methyl acetate, for increasing the conversion of dimethyl ether as a starting material.

10. The application of claim 9, wherein the reaction temperature of the reaction for synthesizing methyl acetate by carbonylation of dimethyl ether is 160-250 ℃, the reaction pressure is 1.0-4.5 MPa, the molar ratio of dimethyl ether and carbon monoxide serving as raw materials is 1: 10-1: 50, and the total reaction space velocity is 3000-12000 h^-1。

Technical Field

The invention belongs to the technical field of chemical catalysis, and particularly relates to flower-shaped mordenite, a preparation method thereof and application thereof as a dimethyl ether carbonylation reaction catalyst.

Background

Methyl acetate is an important chemical intermediate and can be used for producing acetic anhydride, cellulose acetate and the like. Methyl acetate is also an excellent solvent with low toxicity, and can replace acetone, cyclopentane, ethyl acetate and the like to be applied to the production of resin, paint, leather and the like. In addition, the hydrogenation product ethanol of methyl acetate is not only an important chemical raw material, but also a clean fuel. The ethanol is used as a fuel additive, so that the gasoline consumption can be reduced, the oil combustion efficiency can be improved, and the emission of atmospheric pollutants such as hydrocarbons, CO and the like in automobile exhaust can be reduced.

The production process of methyl acetate mainly comprises an esterification method, a methanol carbonylation method, a methanol dehydrogenation method and a methanol/dimethyl ether carbonylation method. The carbonylation reaction catalyzed by the molecular sieve has the advantages of high atom economy, mild reaction conditions and the like, and is widely concerned by academia and industry. Mordenite has a methyl acetate selectivity of more than 99% to dimethyl ether carbonylation reaction, and the high catalytic specificity is benefited by the domain-limiting effect and shape-selective performance brought by the special microporous structure of mordenite. However, the very small pore size also causes severe diffusion limitation problems, which adversely affect the catalytic performance. Therefore, the method for enhancing the diffusion performance of the mordenite by synthesizing the mordenite with a special morphology is a key means for improving the conversion rate of the dimethyl ether as the raw material and the yield of the methyl acetate as the product.

The present invention is directed to solving the above problems.

Disclosure of Invention

The invention provides flower-shaped mordenite which is in a flower-shaped cluster morphology formed by aggregation of nano rod-shaped crystals, wherein the diameter of the nano rod-shaped crystals is 100-300nm, and the length of the nano rod-shaped crystals is 1-3 mu m.

The second aspect of the invention provides a preparation method of the flower-shaped mordenite, and the synthesis method has simple process and is easy to realize large-scale production.

The preparation method of the flower-shaped mordenite comprises the following steps:

(1) taking an aluminum source, a silicon source, an alkali source, a template agent, a growth modifier, water and seed crystals, stirring and mixing uniformly to obtain a gel mixture, wherein the template agent is a nitrogen-containing compound capable of inducing generation of a mordenite molecular sieve structure; the growth modifier is a cationic surfactant.

(2) Aging the gel mixture obtained in the step (1) at room temperature to obtain a hydrothermal reaction mother liquor;

(3) carrying out hydrothermal treatment on the hydrothermal reaction mother liquor, and washing, drying and roasting the obtained solid after the hydrothermal treatment to obtain sodium mordenite;

(4) and (4) converting the sodium mordenite (Na-type mordenite) obtained in the step (3) into hydrogen mordenite (H-type mordenite).

Wherein, the room temperature refers to 25 ℃ +/-5 ℃.

Preferably, the silicon source in step (1) is selected from one or more of silica sol, sodium silicate, fumed silica and ethyl orthosilicate; the aluminum source is selected from one or more of aluminum sulfate, sodium metaaluminate and aluminum nitrate; the alkali source is sodium hydroxide; the seed crystal is a silicon-aluminum molecular sieve containing eight-membered rings and is selected from mordenite. More preferably, the silicon source is selected from silica sol; the aluminum source is selected from sodium metaaluminate; the alkali source is sodium hydroxide; the crystal seed is mordenite.

Preferably, the template agent in step (1) is selected from one or more of tetraethylammonium hydroxide, tetraethylammonium bromide, cyclohexylimine, homopiperazine, cyclohexylamine, and 4-methylpiperidine.

Preferably, the growth modifier in step (1) is selected from one or more of cetyltrimethylammonium bromide, cetyltrimethylammonium hydroxide, tetradecyltrimethylammonium bromide, octadecyltrimethylammonium bromide.

Preferably, the molar ratio of the silicon source, the aluminum source, the alkali source, the template agent, the growth modifier and the water in the step (1) is 1: (0.025-0.06): (0.3-0.5): (0.1-0.4): (0.02-0.09): (20-50); the adding amount of the seed crystal is 2-10% of the mass of the silicon dioxide in the silicon source. In the hydrothermal reaction mother liquor, the mole number of the silicon source is SiO₂The number of moles of the silicon element is equal to that of the silicon element in the hydrothermal reaction mother liquor; the mole number of the aluminum source is Al₂O₃1/2 which is equal to the mole number of aluminum element in the mother liquor of the hydrothermal reaction; the number of moles of the alkali source is determined by the OH in the alkali source^-In moles of (a).

Preferably, in the step (1), the water, the alkali source, the template agent, the aluminum source and the growth modifier are stirred and mixed uniformly, and then the silicon source and the seed crystal are added into the mixture and stirred and mixed to obtain a uniform gel mixture.

Preferably, the gel mixture obtained in the step (1) is aged for 2-24 h in the step (2) to obtain a hydrothermal reaction mother liquor.

Preferably, in the step (3), the hydrothermal reaction mother liquor is filled into a high-pressure hydrothermal reaction kettle, the kettle is sealed, hydrothermal treatment is carried out for 24-96 h at the temperature of 150-190 ℃, the obtained solid is washed until the pH value is less than 9, the solid is dried, and then the solid is roasted for 2-8 h at the temperature of 500-600 ℃ in the air atmosphere, so that the Na-type mordenite is obtained.

Preferably, in the step (3), the Na-type mordenite is mixed with an ammonium ion aqueous solution (such as an ammonium nitrate aqueous solution), and the mixture is stirred for 2 to 8 hours at the temperature of 30 to 100 ℃; and after filtering and drying, roasting for 2-8H at 400-600 ℃ in an air atmosphere to obtain the H-type mordenite. Similarly, the Na-type mordenite can be converted to H-type mordenite by mixing the Na-type mordenite with an aqueous solution of sulfuric acid or hydrochloric acid.

The second aspect of the invention provides the application of the flower-shaped mordenite, which is used as a catalyst for the reaction of synthesizing methyl acetate by carbonylation of dimethyl ether, and is used for improving the conversion rate of dimethyl ether as a raw material.

Preferably, the reaction temperature of the reaction for synthesizing methyl acetate by carbonylation of dimethyl ether is 160-250 ℃, the reaction pressure is 1.0-4.5 MPa, the molar ratio of the dimethyl ether and carbon monoxide as raw materials is 1: 10-1: 50, and the total space velocity of the reaction is 3000-12000 h^-1。

Compared with the prior art, the invention has the following beneficial effects:

1. the mordenite molecular sieve prepared by the invention is in a flower-like cluster shape formed by gathering nano rod-shaped crystals, and the nano rod-shaped crystals have the diameter of 100-300nm and the length of 1-3 mu m. The flower-shaped mordenite has a special shape and smaller grain size, has better diffusion performance due to the special flower-shaped cluster shape, and has important application value in the fields of adsorption, diffusion and the like.

2. According to the preparation method, firstly, a gel mixture formed by mixing the raw materials is aged at room temperature, then, the aged mother liquor is subjected to a hydrothermal crystallization process, and crystal seeds are added into the gel mixture, so that the two operations have obvious influence on the crystallization process of the mordenite molecular sieve. The preparation method successfully prepares the flower-shaped mordenite with the flower-shaped cluster morphology formed by gathering the nano rod-shaped crystals, and the flower-shaped mordenite has good catalytic activity.

3. The mordenite molecular sieve catalyst prepared by the invention shows better activity in the reaction of synthesizing methyl acetate by dimethyl ether carbonylation. The reaction performance of the flower-shaped mordenite (example 1) prepared by the invention on methyl acetate prepared by carbonylation of dimethyl ether is superior to that of a comparison sample 1 (the prepared gel is directly subjected to hydrothermal crystallization without aging and has a rod-shaped bundle shape), a comparison sample 2 (seed crystal is not added and the shape is a pseudo-spherical particle) and a comparison sample 3 (a growth modifier is not added in the preparation process and the shape is not flower-shaped). Under the same reaction conditions, the conversion rate of dimethyl ether of comparative example 1 was 48.2%, the conversion rate of dimethyl ether of comparative example 2 was 53.3%, and the conversion rate of dimethyl ether of comparative example 3 was 49.2%, whereas the conversion rate of dimethyl ether of example 1 was 67.0%, and the conversion rates were increased by 39.0%, 25.7%, and 36.2% respectively, compared to comparative example 1, comparative example 2, and comparative example 3. In addition, the patent of application No. 201510117242.3 also uses microporous template agent (such as tetraethylammonium hydroxide, hexamethylimine, etc.) and mesoporous template agent (such as hexadecyltrimethylammonium bromide, octadecyltrimethylammonium bromide, etc.) to prepare MOR molecular sieve and use it in DME carbonylation reaction, after correcting the reaction conditions (the partial pressure of CO is first order and the partial pressure of CO is uniformly corrected to 1MPa), the time-space yield of methyl acetate of the patent is 226 g/(kg.h) respectively, while the present invention is 306 g/(kg.h), the present invention also has advantages in reaction performance.

4. The mordenite provided by the invention has the advantages of simple preparation process, wide raw material source and relatively low price, and is beneficial to large-scale industrial production.

Drawings

FIG. 1 is an X-ray diffraction pattern of the sample in example 1.

FIG. 2 is a graph of the catalytic performance of the samples in example 1.

FIG. 3 is a scanning electron microscope photograph of the sample in example 1.

Fig. 4 is a scanning electron microscope photograph of the sample in comparative example 1.

Fig. 5 is a scanning electron microscope photograph of the sample in comparative example 2.

Fig. 6 is a scanning electron microscope photograph of the sample in comparative example 3.

FIG. 7 is a scanning electron microscope photograph of the sample in example 7.

FIG. 8 is a scanning electron microscope photograph of a sample in example 8.

Fig. 9 is a scanning electron microscope photograph of the sample in comparative example 4.

Fig. 10 is a scanning electron microscope photograph of the sample in comparative example 5.

Detailed Description

The present invention will be described in further detail with reference to the following detailed description of the preferred embodiments in conjunction with the accompanying drawings. It should be noted that: the following examples are illustrative and not intended to be limiting, and are not intended to limit the scope of the invention. The starting materials required in the following examples and comparative examples are all commercially available.

In this embodiment, the elemental composition of the mordenite was measured using a Vista-MPX inductively coupled plasma emission spectrometer (ICP-OES) from Varian, USA.

In this embodiment, the crystalline phase structure of mordenite was analyzed by a powder X-ray diffractometer model D/max-2500 from (Japan) Physics, Inc., with the source of diffraction being CuK αThe working voltage and the working current are respectively 40kV and 200mA, the scanning range is 5-50 degrees, and the scanning speed is 8 degrees/min. The relative crystallinity of the product was calculated from the sum of the XRD diffraction peak areas of the (200), (330), (150), (202), and (350) crystal planes, and the relative crystallinity was obtained from the other samples, taking the crystallinity of the sample in example 1 as 100%.

In this embodiment, the mordenite morphology was analyzed using Hitachi' S S-4800 scanning electron microscope.

[ example 1 ]

0.96g of sodium hydroxide, 5.80g of tetraethylammonium hydroxide, 0.327g of sodium metaaluminate and 1.20g of hexadecyltrimethylammonium bromide (molar ratio to silicon source: 0.055) are dissolved in this order in 20.19g of water and mixed uniformly with stirring. Then 12g of silica sol (30 wt.% silica mass) was added dropwise to the above mixture under vigorous stirring, followed by 0.18g of seed crystals and mixed with stirring (5 wt.% silica mass) to give a homogeneous gel.

The above gel was aged for 4h at room temperature (27 ℃ C.) with stirring. Then placing the mixture into a kettle, heating and crystallizing the mixture in an oven, wherein the crystallization temperature is 170 ℃, and the crystallization duration is 72 hours. And after crystallization is finished, filtering and recovering a solid product, washing with water until the pH value is less than 9, drying, and roasting at 550 ℃ for 5 hours in an air atmosphere to obtain the Na-type mordenite. Mixing Na-type mordenite with an ammonium ion aqueous solution (such as an ammonium nitrate aqueous solution), and stirring at 80 ℃ for 6 h; filtering, drying, and calcining at 500 deg.C for 4H in air atmosphere to obtain H-type mordenite.

The XRD spectrum of the prepared sample is shown in figure 1, and the sample is a pure-phase mordenite molecular sieve, has good crystallization and has no other impurity phases. The appearance of the sample is shown in figure 3 and is in the shape of flower-like clusters formed by aggregation of the nano rod-shaped crystals.

Taking 0.5g of a catalyst sample (40-60 meshes) after tabletting and screening, at the temperature of 200 ℃, under the conditions of 1.5MPa, 1:49 of raw material molar ratio DME/CO and 6000h of total gas space velocity^-1The reaction was carried out in a fixed bed reactor. Before the reaction, the catalyst is purged for 4 hours by high-purity nitrogen in situ. And (4) keeping the temperature of the reaction tail gas, and performing gas phase on-line chromatographic analysis on the reaction tail gas.

The test results of the activity and the selectivity of the prepared sample for catalyzing the carbonylation of dimethyl ether to synthesize methyl acetate are shown in the attached figure 2.

[ examples 2 to 3 ]

Under the same conditions as those of example 1, only the aging times were changed to 2 hours (example 2) and 24 hours (example 3).

Comparative example 1

The sample in comparative example 1 was a sample obtained by directly subjecting the gel prepared in example 1 to hydrothermal crystallization without aging.

As can be seen from the morphology, the sample prepared in comparative example 1 without aging treatment (FIG. 4) has a rod-like bundle morphology formed by close aggregation of nanorods.

The Si/Al, the relative degree and the performance results of dimethyl ether carbonylation catalysis reaction of the H-type mordenite synthesized in different aging times are shown in Table 1.

TABLE 1 Si/Al, relativity and dimethyl ether carbonylation catalytic performance of H-type mordenite synthesized at different aging times

As can be seen from the activity, the aging treatment contributes to an increase in the activity of the resulting catalyst. The aging time is shortened, and the activity of the prepared catalyst is reduced. When the aging time exceeds 4 hours, further extension of the aging time does not significantly affect the catalyst activity.

[ examples 4 to 5 ]

Under the same conditions as in example 1 except for the above, the amount of the seed crystal to be charged was changed so that the mass percentage of the seed crystal to the silica was 2% (example 4) and 8% (example 5).

Comparative example 2

The sample in comparative example 2 was the sample prepared in example 1 without adding a seed crystal.

From the XRD analysis results, it can be seen that the sample prepared without seeding had significantly lower crystallinity than the seeded sample. See table 2 for relative crystallinity values.

As can be seen from the morphology, the sample is obviously different from the sample prepared by adding the MOR seed crystal, and the sample without adding the seed crystal (figure 5) is a pseudo-spherical particle with the diameter of about 2-3 μm, so the seed crystal has obvious influence on the morphology of the sample.

The Si/Al, the relative degree and the dimethyl ether carbonylation catalysis reaction performance of the H-type mordenite synthesized by different crystal seed addition amounts are shown in Table 2.

TABLE 2 Si/Al, relativity and dimethyl ether carbonylation catalytic performance of H-type mordenite synthesized with different crystal seed addition amounts

From the activity, it can be seen that the sample prepared with the mordenite seed crystals had better activity than the sample prepared without the seed crystals.

It can be seen from the above examples 1-5 and comparative examples 1-2 that the room temperature aging operation before hydrothermal crystallization and the addition of mordenite seed crystal have a significant effect on the crystallization process of the mordenite molecular sieve. It can affect the crystallization kinetics of molecular sieve and promote nucleation, thus obviously affecting the morphology of crystallized product. Therefore, room temperature aging is carried out for a certain time before hydrothermal crystallization, and a proper amount of mordenite seed crystal is added, so that the method has a vital effect on obtaining flower-shaped appearance and good catalytic activity.

[ examples 6 to 9 ]

Otherwise, in the same manner as in example 1, cetyltrimethylammonium bromide was changed to cetyltrimethylammonium hydroxide (example 6), tetradecyltrimethylammonium bromide (example 7), octadecyltrimethylammonium bromide (example 8).

[ COMPARATIVE EXAMPLES 3 to 5 ]

The sample in comparative example 3 was the sample prepared in example 1 without adding a growth modifier. Comparative examples 4 and 5 were conducted under the same conditions as in example 1 except that the amount of cetyltrimethylammonium bromide added was changed from 0.055 in molar ratio to the silicon source to 0.009 (comparative example 4) and 0.15 (comparative example 5), respectively.

The Si/Al, the relative degree and the dimethyl ether carbonylation catalysis reaction performance of the H-type mordenite synthesized by different growth modifiers are shown in the table 3.

From the morphology it can be seen that the sample made without the addition of growth modifier (FIG. 6) is a pseudo-spherical particle with a particle size of about 1 μm. The morphology of the sample prepared by using hexadecyl trimethyl ammonium hydroxide, tetradecyl trimethyl ammonium bromide (figure 7) or octadecyl trimethyl ammonium bromide (figure 8) as the growth modifier has no obvious difference with the sample prepared by using hexadecyl trimethyl ammonium bromide as the growth modifier. If the addition amount of the hexadecyl trimethyl ammonium bromide is less than (shown in figure 9) or more than (shown in figure 10) the range limited by the patent (the molar ratio of the growth modifier to the silicon source is 0.02-0.09), the flower-shaped morphology and the catalytic performance cannot be formed.

TABLE 3 Si/Al, relativity and dimethyl ether carbonylation catalysis performance of different growth modifiers for synthesizing H-type mordenite

[ examples 9 to 10 ] to provide a toner

In the case of otherwise identical experimental conditions to those of example 1, the reaction temperature was changed only to 190 ℃ (example 9), 210 ℃ (example 10). Through activity tests, the temperature has great influence on the activity of the reaction, the high temperature is favorable for the conversion of dimethyl ether into methyl acetate, but on the other hand, the high temperature also leads the inactivation speed of the catalyst to be obviously accelerated.

TABLE 4 reaction Performance of carbonylation of dimethyl ether to methyl acetate by H-type mordenite at different reaction temperatures

[ examples 11 to 13 ] of the present invention

Under otherwise identical experimental conditions as in example 1, the molar ratio of dimethyl ether to CO in the reaction gas was changed to 1:39 (example 11), 1:29 (example 12) and 1:19 (example 13). As can be seen from the activity test, higher CO concentration is beneficial to improving the conversion rate of the dimethyl ether.

TABLE 5 reaction performance of H-type mordenite in catalyzing carbonylation of dimethyl ether to synthesize methyl acetate under different raw material gas compositions

[ examples 14 to 16 ] of the present invention

In the case where the other experimental conditions were exactly the same as in example 1, only the reaction pressure was changed to 1.0MPa (example 16), 2.0MPa (example 17), and 2.5MPa (example 18). Through activity tests, the activity of preparing methyl acetate by carbonylation of dimethyl ether increases with the increase of the total pressure.

TABLE 6 reaction performance of H-type mordenite in catalyzing carbonylation of dimethyl ether to synthesize methyl acetate under different reaction pressures