Synthesis method of MCM-22 molecular sieve, synthesized MCM-22 molecular sieve and application of MCM-22 molecular sieve

Abstract

The invention discloses a synthesis method of an MCM-22 molecular sieve, the synthesized MCM-22 molecular sieve and application of the MCM-22 molecular sieve. Comprising the following steps: mixing a silicon source, an aluminum source, inorganic alkali, a structure-directing agent, water and active seed crystals, aging, crystallizing, separating and drying to obtain the MCM-22 molecular sieve. The catalyst can be used for alkylation of benzene and olefin (such as production of ethylbenzene and isopropyl benzene), isomerization, catalytic cracking and other reactions, and the production cost of the catalyst is reduced. According to the preparation method, low-toxicity and low-price cyclohexylamine is used as a structure-directing agent, an active seed crystal is introduced into a synthesis system, the active seed crystal is used as a nucleation site, the crystallization process is remarkably accelerated, the high-crystallinity MCM-22 molecular sieve is obtained through hydrothermal crystallization, and the preparation method is an economical, efficient, simple and convenient preparation method and is expected to realize large-scale commercial production.

Description

Technical Field

[0001] This application relates to a method for synthesizing MCM-22 molecular sieve, the synthesized MCM-22 molecular sieve, and its applications, belonging to the field of molecular sieve synthesis. Background Technology

[0002] MWW family molecular sieves possess a unique pore structure, comprising two relatively independent pore systems: intralayer ten-membered ring sinusoidal pores (0.41 nm × 0.51 nm) and interlayer twelve-membered ring supercages (1.82 nm × 0.71 nm × 0.71 nm). Furthermore, a twelve-membered ring semi-supercage with a depth of 0.91 nm exists on the outer surface (Science 264 (1994) 1910-1913). The coexistence of multiple pores in MWW molecular sieves makes them promising for industrial applications, and they are among the few molecular sieves that have already achieved industrialization. Their main applications include catalytic conversion of hydrocarbons and adsorption separation processes, such as alkylation of benzene and olefins for the production of ethylbenzene and isopropylbenzene (Catal. Today 73 (2002) 3-22), catalytic cracking (J. Catal. 167 (1997) 438-446), and isomerization (J. Catal. 158 (1996) 561-569).

[0003] The MWW family of molecular sieves comprises a large group of members, including MCM-22, MCM-49, MCM-56, MCM-36, ITQ-1, ITQ-2, ERB-1, SSZ-25, and SSZ-70. Current research focuses on the synthesis and modification of MCM-22, MCM-49, and MCM-56 molecular sieves. The synthesis of MCM-22 requires first hydrothermally synthesizing a layered precursor (MCM-22P), followed by calcination to further condense the interlayers into a three-dimensional layered structure.

[0004] The cell structure and synthesis method of MCM-22 molecular sieve were reported in 1994 (Science 1994, 264, 1910). The structure-directing agent used was hexamethyleneimine (HMI), which is highly toxic. It should be noted that HMI is expensive, pollutes the environment, and increases production costs. Based on the excellent catalytic performance of MCM-22 molecular sieve in alkylation and other reactions, controlling the synthesis cost can help promote the wider application of MCM-22 molecular sieve. Therefore, researchers are committed to using low-toxicity and inexpensive structure-directing agents to partially or completely replace HMI. Wu Peng et al. used piperidine as a template agent and boric acid as a crystallization aid to prepare MCM-22 molecular sieve. Compared with the product obtained by using HMI as a template agent, it has a smaller crystal size and a larger specific surface area (Chemical Reaction Engineering and Technology, 2013, 29(01):19), and the synthesis cost is reduced. Subsequently, MCM-22 molecular sieves could be synthesized using only piperidine as a template agent without the introduction of boric acid, and their catalytic performance could be improved by introducing different anions to control the aluminum landing sites (Catal. Today, 2018, 316, 71). Patent CN 117902588A reported the synthesis of MCM-22 molecular sieves using a very small amount of N,N,N-trimethyladamantane ammonium and cyclohexylamine as dual organic structure directing agents. Active seed crystals can act as nucleation sites to guide the synthesis of molecular sieves. For example, adding active seed crystals in the synthesis of MCM-49 molecular sieves can guide its synthesis, avoiding the large-scale use of structure directing agents (Inorg. Chem. Front., 2021, 8, 2575). However, the synthesis of other types of MWW molecular sieves remains quite difficult.

[0005] In summary, developing low-toxicity and inexpensive structure-directing agents that can guide MCM-22 molecular sieves remains an important research topic in the field of zeolite synthesis. Summary of the Invention

[0006] The purpose of this invention is to develop a method for synthesizing MCM-22 molecular sieves. The method uses low-toxicity and inexpensive cyclohexylamine as a structure directing agent and, with the assistance of active seed crystals, synthesizes MCM-22 molecular sieves through a simple and easy hydrothermal synthesis method.

[0007] According to one aspect of this application, a method for synthesizing MCM-22 molecular sieve is provided, comprising the following steps:

[0008] The silicon source, aluminum source, inorganic alkali, structure guiding agent, water and active seed crystals are mixed, aged, crystallized, separated and dried to obtain the MCM-22 molecular sieve.

[0009] Optionally, the following steps are included:

[0010] (1) Mix silicon source, aluminum source, inorganic base (inorganic acid to adjust pH), structure guiding agent, deionized water and active seed crystals evenly.

[0011] (2) After the raw materials are evenly mixed, they are aged at a low temperature of 0-80℃ (10-100 rpm) for 0-24 hours.

[0012] (3) The aged mixture was dynamically crystallized at 100-180℃ (10-100 rpm) for 48-240 hours to synthesize MCM-22 molecular sieve hydrothermally.

[0013] (4) Cool the reactor with tap water, and obtain the solid product by centrifugation or filtration. The solid product is washed and dried to obtain MCM-22 molecular sieve powder.

[0014] The silicon source is selected from at least one of silica, tetraethyl orthosilicate, water glass, silica sol, chromatography silica gel, or coarse-pore silica gel.

[0015] The aluminum source is selected from at least one of sodium aluminate, aluminum sulfate, aluminum chloride, aluminum nitrate, aluminum acetate, aluminum powder, or boehmite.

[0016] The structure-directing agent is cyclohexylamine;

[0017] The inorganic base is selected from at least one of sodium hydroxide, potassium hydroxide, sodium carbonate, or potassium carbonate.

[0018] The active seed crystals are characterized as follows: the active seed crystals should be highly exfoliated MCM-56 molecular sieves, which are synthesized according to the literature Microporous and Mesoporous Materials 113(2008)435–444.

[0019] The selected active seed crystals are MWW molecular sieves synthesized according to patent 202410509656.X.

[0020] Inorganic acids are added to maintain the pH of the overall reaction system between 10 and 12.

[0021] The inorganic acid is selected from at least one of sulfuric acid, hydrochloric acid, phosphoric acid, or nitric acid.

[0022] The molar ratio of the silicon source to the aluminum source is at least 10:1;

[0023] The molar ratio of the inorganic base to the silicon source is 0.01 to 1:1;

[0024] The molar ratio of the structure directing agent to the silicon source is 0.1 to 1:1;

[0025] The molar ratio of water to silicon source is 5 to 30:1;

[0026] The mass ratio of the active seed crystal to the silicon source is 0.05–0.3:1;

[0027] The molar amount of the silicon source is calculated based on the molar amount of SiO2 therein;

[0028] The molar amount of the aluminum source is calculated based on the molar amount of Al2O3 therein.

[0029] The molar amount of the inorganic base is determined by the OH groups it contains. - Calculation of molar quantity.

[0030] The aging temperature is 0–80°C;

[0031] The aging time is 0.5 to 24 hours;

[0032] The oven rotation speed during the aging process is 30-90 rpm;

[0033] The crystallization is dynamic hydrothermal crystallization;

[0034] The crystallization temperature is 100–180°C;

[0035] The crystallization time is 48–240 hours;

[0036] The rotation speed of the oven during the crystallization process is 30-90 rpm;

[0037] The drying temperature is 80–120°C;

[0038] The drying time is 10 to 24 hours.

[0039] According to another aspect of this application, an MCM-22 molecular sieve synthesized by the above-described synthesis method is provided.

[0040] According to another aspect of this application, an application of the above-mentioned MCM-22 molecular sieve is provided for alkylation reactions, alkyl transfer reactions, disproportionation reactions, isomerization reactions, aromatization reactions, and cracking reactions of hydrocarbons.

[0041] According to another aspect of this application, an application of the above-described MCM-22 molecular sieve is provided for butene pyrolysis reaction.

[0042] The beneficial effects that this application can produce include:

[0043] 1. The MCM-22 molecular sieve synthesized in this application can be used in reactions such as alkylation (production of ethylbenzene and cumene) of benzene and olefins, isomerization, and catalytic cracking, which significantly reduces the production cost of catalysts.

[0044] 2. This application uses low-toxicity and inexpensive cyclohexylamine as a structure directing agent and introduces active seed crystals into the synthesis system. The active seed crystals serve as nucleation sites, which significantly accelerate the crystallization process. High-crystallinity MCM-22 molecular sieves are obtained through hydrothermal crystallization. This is an economical, efficient, and simple preparation method that is expected to be commercially produced on a large scale. Attached Figure Description

[0045] Figure 1 The X-ray diffraction pattern is shown in Example 1.

[0046] Figure 2 The image shown is a scanning electron microscope image of Example 1, with a scale of 1 μm.

[0047] Figure 3 The nitrogen adsorption-desorption curve is shown in Example 1.

[0048] Figure 4 The X-ray diffraction pattern is shown in Example 2.

[0049] Figure 5 The image shown is a scanning electron microscope image of Example 2, with a scale of 1 μm. Detailed Implementation

[0050] The present application is described in detail below with reference to the embodiments, but the present application is not limited to these embodiments.

[0051] Unless otherwise specified, all raw materials used in the embodiments of this application were purchased through commercial channels.

[0052] Example 1 of active seed synthesis:

[0053] Synthesized according to the literature Microporous and Mesoporous Materials 113(2008)435–444.

[0054] Under stirring conditions, 19.65 g of silica sol (30.54 wt.% SiO2, 0.32 wt.% Na2O, 0.02 wt.% Al2O3, 69.12 wt.% H2O), 0.90 g of 0.1 g / ml sulfuric acid solution, 8.28 g of boric acid (H3BO3, purity ≥99.5 wt.%), 18.64 g of deionized water, and 11.92 g of piperidine (PI, purity ≥99 wt.%) were added sequentially to the reactor. The molar composition of the mixture was: H3BO3 / SiO2 = 1.34, H2O / SiO2 = 19, PI / SiO2 = 1.4. The mixture was stirred thoroughly to ensure homogeneity, and the reactor was sealed. The mixture was dynamically aged (50 rpm) at 60 °C for 2 h, and then dynamically crystallized (50 rpm) at 170 °C for 168 h. The reaction was quenched with tap water, and the solid product was obtained by centrifugation. Wash with deionized water until neutral. Dry overnight at 120℃ to obtain molecular sieve raw powder, then wash with water in 2 mol / L nitric acid solution at 30℃ for 2 h, dry, and calcine at 540℃ for 4 h to obtain MCM-56 molecular sieve.

[0055] Example 1

[0056] Under stirring conditions, 9.8 g of silica sol (30.62 wt.% SiO2, 0.32 wt.% Na2O, 0.03 wt.% Al2O3, 69.03 wt.% H2O), 0.2 g of sodium aluminate (16.8 wt.% Al2O3, 24.0 wt.% Na2O, 59.2 wt.% H2O), 0.99 g of cyclohexylamine (CHA, purity ≥99 wt.%), 0.21 g of active seed crystals, and 9 g of deionized water were added to the reactor in a specific order. The molar composition of the raw material mixture was: SiO2 / Al2O3 = 140, Na2O / SiO2 = 0.09, CHA / SiO2 = 0.2, Seed / SiO2 = 7%, H2O / SiO2 = 20. The mixture was thoroughly stirred until homogeneous, and then the reactor was sealed. The mixture was dynamically aged at 60℃ (60 rpm) for 120 min, and then dynamically crystallized at 130℃ (60 rpm) for 96 h. The reaction was quenched with tap water, and the solid product was obtained by centrifugation. The solid product was then washed with deionized water until neutral. The product was dried overnight at 120℃ to obtain the molecular sieve powder.

[0057] Figure 1 The image shows the XRD pattern of the obtained molecular sieve powder. As can be seen from the image, the product is a pure phase MCM-22 molecular sieve with good crystallinity.

[0058] Figure 2 The images are from a scanning electron microscope. The samples exhibit the typical plate-like morphology of MWW molecular sieves, with plate sizes ranging from 0.2 to 1 μm and thicknesses from 30 to 100 nm.

[0059] Figure 3 The curves show the adsorption and desorption of N2, which are typical type I isotherms.

[0060] Example 2

[0061] Under stirring conditions, 6.32 g of silica (95 wt.% dry basis), 0.12 g of aluminum nitrate (Al(NO3)3·9H2O, purity ≥99.0 wt.%), 6.24 g of 0.1 g / ml sodium hydroxide solution, 16 g of deionized water, 0.6 g of active seed crystals, 0.99 g of cyclohexylamine (CHA, purity ≥99 wt.%), and 16.09 g of deionized water were added to the reactor in a specific order. The molar composition of the raw material mixture was: SiO2 / Al2O3 = 300, Na2O / SiO2 = 0.08, CHA / SiO2 = 0.2, Seed / SiO2 = 10%, H2O / SiO2 = 20. The mixture was thoroughly stirred to ensure homogeneity, and the reactor was sealed. The mixture was then dynamically aged (50 rpm) at 50 °C for 60 min, followed by dynamic crystallization (50 rpm) at 150 °C for 120 h. The reaction was quenched with tap water, and the solid product was obtained by centrifugation. It was then washed with deionized water until neutral. The product was dried overnight at 120°C to obtain the molecular sieve powder.

[0062] Figure 4 This indicates that the product is a pure phase of MCM-22 molecular sieve.

[0063] Figure 5 The scanning electron microscope image shows that the product has the typical plate-like morphology of MWW molecular sieves, with plate sizes ranging from 0.2 to 1 μm and thicknesses from 30 to 100 nm.

[0064] Example 3

[0065] Under stirring conditions, 29.40 g of water glass (20.41 wt.% SiO2, 6.50 wt.% Na2O, 0.09 wt.% Al2O3, 73.00 wt.% H2O), 0.60 g of sodium aluminate (16.8 wt.% Al2O3, 24.0 wt.% Na2O, 59.2 wt.% H2O), 16.45 g of 0.1 g / ml hydrochloric acid solution, 6.78 g of deionized water, 1.2 g of active seed crystals, and 3.97 g of cyclohexylamine (CHA, purity ≥99 wt.%) were added to the reactor in a specific order. The molar composition of the raw materials was: SiO2 / Al2O3 = 80, Na2O / SiO2 = 0.10, CHA / SiO2 = 0.4, Seed / SiO2 = 20%, H2O / SiO2 = 25. Stir thoroughly to ensure homogeneity, then seal the synthesis vessel. Aged dynamically at 80°C (60 rpm) for 240 min, then crystallized dynamically at 150°C (60 rpm) for 96 h. Quench the reaction with tap water, and centrifuge to obtain the solid product. Wash with deionized water until neutral. Dry overnight at 120°C to obtain the molecular sieve powder.

[0066] Example 4

[0067] Under stirring conditions, 19.65 g of silica sol (30.62 wt.% SiO2, 0.32 wt.% Na2O, 0.03 wt.% Al2O3, 69.03 wt.% H2O), 2.17 g of aluminum sulfate (Al2(SO4)3·18H2O, purity ≥98 wt.%), 5.6 g of 0.1 g / ml potassium hydroxide solution, 8.90 g of deionized water, 0.3 g of active seed crystals, and 3.97 g of cyclohexylamine (CHA, purity ≥99 wt.%) were added to the reactor in a specific order. The molar composition of the raw materials was: SiO2 / Al2O3 = 30, Na2O / SiO2 = 0.05, CHA / SiO2 = 0.4, Seed / SiO2 = 5%, H2O / SiO2 = 17. The mixture was stirred thoroughly until homogeneous, and then the reactor was sealed. The mixture was dynamically aged at 80℃ (50 rpm) for 30 min, and then dynamically crystallized at 160℃ (50 rpm) for 132 h. The reaction was quenched with tap water, and the solid product was obtained by centrifugation. The solid product was then washed with deionized water until neutral. The product was dried overnight at 120℃ to obtain the molecular sieve powder.

[0068] Example 5

[0069] Under stirring conditions, 21.13 g of tetraethyl orthosilicate (28.4 wt.% SiO2), 0.30 g of sodium aluminate (16.8 wt.% Al2O3, 24.0 wt.% Na2O, 59.2 wt.% H2O), 5.05 g of 0.1 g / ml sodium hydroxide solution, 48.79 g of deionized water, 1.8 g of active seed crystals, and 0.99 g of cyclohexylamine (CHA, purity ≥99 wt.%) were added to the reactor in a specific order. The molar composition of the raw materials was: SiO2 / Al2O3 = 200, Na2O / SiO2 = 0.08, CHA / SiO2 = 0.1, Seed / SiO2 = 30%, H2O / SiO2 = 30. The mixture was stirred thoroughly until homogeneous, and then the reactor was sealed. The mixture was dynamically aged at 50℃ (60 rpm) for 300 min, and then dynamically crystallized at 150℃ (60 rpm) for 168 h. The reaction was quenched with tap water, and the solid product was obtained by centrifugation. The solid product was then washed with deionized water until neutral. The product was dried overnight at 120℃ to obtain the molecular sieve powder.

[0070] Example 6

[0071] Under stirring conditions, 21.13 g of tetraethyl orthosilicate (28.4 wt.% SiO2), 0.06 g of aluminum nitrate (Al(NO3)3·9H2O, purity ≥99.0 wt.%), 7.19 g of 0.1 g / ml sodium hydroxide solution, 33.20 g of deionized water, 0.9 g of active seed crystals, and 15.20 g of cyclohexylamine (CHA, purity ≥99 wt.%) were added to the reactor in a specific order. The molar composition of the raw materials was: SiO2 / Al2O3 = 600, Na2O / SiO2 = 0.10, CHA / SiO2 = 0.5, Seed / SiO2 = 15%, H2O / SiO2 = 20. The mixture was stirred thoroughly to ensure homogeneity, and the reactor was sealed. The mixture was then dynamically aged (60 rpm) at 70 °C for 120 min, followed by dynamic crystallization (60 rpm) at 145 °C for 144 h. The reaction was quenched with tap water, and the solid product was obtained by centrifugation. It was then washed with deionized water until neutral. The product was dried overnight at 120°C to obtain the molecular sieve powder.

[0072] Example 7

[0073] Under stirring conditions, 6.45 g of solid silica gel (93 wt.% dry basis), 20.00 g of 0.1 g / ml sodium hydroxide solution, 12.40 g of deionized water, 1.32 g of active seed crystals, and 3.97 g of cyclohexylamine (CHA, purity ≥99 wt.%) were added to the reactor in a specific order. The molar composition of the raw materials was: SiO2 / Al2O3=∞, Na2O / SiO2=0.25, CHA / SiO2=0.4, Seed / SiO2=22%, H2O / SiO2=18. The mixture was thoroughly stirred until homogeneous, and the reactor was sealed. The mixture was dynamically aged (30 rpm) at 50 °C for 150 min, and then dynamically crystallized (30 rpm) at 140 °C for 156 h. The reaction was quenched with tap water, and the solid product was obtained by centrifugation. The solid product was then washed with deionized water until neutral. The solid product was dried overnight at 120 °C to obtain the molecular sieve powder.

[0074] Test Example 1

[0075] The butene pyrolysis performance of the MCM-22 molecular sieves prepared in Examples 1-3 of this application was tested. The MCM-22 molecular sieves were placed in a fixed-bed reactor, and butene was introduced into the reactor to obtain pyrolysis products. The test conditions were: reaction temperature (T) of 590℃, and butene space velocity (WHSV). C4H8 ) is 2.5h -1 The reaction products were collected and their composition was analyzed using an Agilent 7890A chromatographic analyzer equipped with a PONA column and an FID detector.

[0076] The test results are shown in Table 1.

[0077] Table 1. Performance test results of MCM-22 molecular sieve in butene pyrolysis reaction.

[0078]

[0079] As shown in Table 1, the MCM-22 molecular sieve synthesized using cyclohexylamine as a structure-directing agent and through the addition of active seed crystals exhibits similar initial catalytic activity and stability under the same reaction conditions in the butene cracking reaction compared to the traditional MCM-22 molecular sieve synthesized using hexamethyleneimine. The selectivity for ethylene and propylene is also similar. Catalytic performance tests indicate that the MCM-22 molecular sieve synthesized by the method described in this application possesses similar textural and acidic properties to the traditional MCM-22 molecular sieve. Compared to traditional synthesis methods, the preparation method described in this application is simple, easy to implement, and controllable. By using a low-toxicity, inexpensive, and readily available structure-directing agent, production costs can be effectively reduced, demonstrating excellent prospects for industrial application.

[0080] The above description is merely a few embodiments of this application and is not intended to limit this application in any way. Although this application discloses preferred embodiments as described above, it is not intended to limit this application. Any changes or modifications made by those skilled in the art without departing from the scope of the technical solution of this application using the disclosed technical content are equivalent to equivalent implementation cases and fall within the scope of the technical solution.

Claims

1. A method for synthesizing MCM-22 molecular sieve, characterized in that, Includes the following steps: The silicon source, aluminum source, inorganic alkali, structure directing agent, water and active seed crystals are mixed, aged, crystallized, separated and dried to obtain the MCM-22 molecular sieve.

2. The synthesis method according to claim 1, characterized in that, The silicon source is selected from at least one of silica, tetraethyl orthosilicate, water glass, silica sol, chromatography silica gel, or coarse-pore silica gel. The aluminum source is selected from at least one of sodium aluminate, aluminum sulfate, aluminum chloride, aluminum nitrate, aluminum acetate, aluminum powder, or boehmite. The structure-directing agent is cyclohexylamine; The inorganic base is selected from at least one of sodium hydroxide, potassium hydroxide, sodium carbonate, or potassium carbonate.

3. The synthesis method according to claim 1, characterized in that, The active seed crystals are characterized as follows: the active seed crystals should be highly exfoliated MCM-56 molecular sieves.

4. The synthesis method according to claim 1, characterized in that, Inorganic acids are added to maintain the pH of the overall reaction system between 10 and 12. The inorganic acid is selected from at least one of sulfuric acid, hydrochloric acid, phosphoric acid, or nitric acid.

5. The synthesis method according to claim 1, characterized in that, The molar ratio of the silicon source to the aluminum source is at least 10:1; The molar ratio of the inorganic base to the silicon source is 0.01 to 1:1; The molar ratio of the structure directing agent to the silicon source is 0.1 to 1:1; The molar ratio of water to silicon source is 5 to 30:1; The mass ratio of the active seed crystal to the silicon source is 0.05–0.3:1; The molar amount of the silicon source is calculated based on the molar amount of SiO2 therein; The molar amount of the aluminum source is calculated based on the molar amount of Al2O3 therein. The molar amount of the inorganic base is determined by the OH groups it contains. - Calculation of molar quantity.

6. The synthesis method according to claim 1, characterized in that, The aging temperature is 0–80°C; The aging time is 0.5 to 24 hours; The oven rotation speed during the aging process is 30-90 rpm.

7. The synthesis method according to claim 1, characterized in that, The crystallization is dynamic hydrothermal crystallization; The crystallization temperature is 100–180°C; The crystallization time is 48–240 hours; The rotation speed of the oven during the crystallization process is 30-90 rpm; The drying temperature is 80–120°C; The drying time is 10 to 24 hours.

8. An MCM-22 molecular sieve synthesized by the synthesis method according to any one of claims 1 to 7.

9. An application of the MCM-22 molecular sieve according to claim 8, characterized in that, Used in alkylation, alkyl transfer, disproportionation, isomerization, aromatization, and cracking reactions of hydrocarbons.

10. An application of the MCM-22 molecular sieve according to claim 8, characterized in that, Used in butene pyrolysis reactions.

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