Acid solid catalyst as well as preparation method and application thereof
By introducing sulfonic acid groups and Lewis acid to form complexes on the surface of SBA-15 all-silica mesoporous molecular sieve, the problem of low conversion and yield in the production of methacrylates was solved, and a highly efficient and stable catalytic effect was achieved.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- CHINA PETROLEUM & CHEMICAL CORP
- Filing Date
- 2024-11-12
- Publication Date
- 2026-05-12
AI Technical Summary
The existing methacrylate production process suffers from problems such as low methacrylic acid conversion, low methacrylate yield, and poor catalyst stability.
Sulfonated modified SBA-15 all-silica mesoporous molecular sieve was used as an acidic solid catalyst. By introducing sulfonic acid groups and Lewis acid to form complexes on its surface, the number and stability of active centers of the catalyst were increased, thereby improving the catalytic performance.
It improves the conversion rate of methacrylic acid and the selectivity of methacrylates, has good catalyst stability, is easy to separate and recover, is suitable for high-temperature environments, has low cost, and provides mild process conditions.
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Abstract
Description
Technical Field
[0001] This invention belongs to the field of fine chemicals, specifically relating to an acidic solid catalyst and its preparation method, as well as the application of the catalyst in the synthesis reaction of methacrylate. Background Technology
[0002] As an important organic chemical product and raw material, the industrial production level and capacity of methyl methacrylate (MMA) have a significant impact on the development of my country's chemical industry. MMA is mainly used in industries such as PMMA (polymethyl methacrylate), coatings, textiles, adhesives, leather, papermaking, floor polishing, unsaturated resins, higher methacrylates, wood impregnators, printing and dyeing auxiliaries, and plasticizers. In recent years, the demand for MMA polymers, profiles, sheets, coatings, and emulsions has increased both domestically and internationally, and its application areas are constantly expanding, driving the rapid development of the MMA industry. Currently, domestic methyl methacrylate production technology is still in its initial stage. Developing methacrylate esterification catalysts and supporting processes with independent intellectual property rights is a development need facing my country's MMA production industry.
[0003] Esterification catalysts are a core technology in MMA production. The traditional catalyst used for the esterification reaction of methacrylic acid and methanol is concentrated sulfuric acid. While this catalyst is highly active and inexpensive, the strong oxidizing and dehydrating properties of concentrated sulfuric acid, as well as its solubility in the reaction system, cause problems for equipment corrosion and subsequent treatment. Therefore, seeking catalysts that combine strong catalytic activity, high selectivity, and ease of separation from the reaction system remains of significant importance. Esterification catalysts for heterogeneous reactions are currently a relatively active research area. Currently, reported catalysts that can replace concentrated sulfuric acid include strong acid ion exchange resins, heteropoly acids, ionic liquids, and solid superacids, achieving good results. Among these, strong acid ion exchange resins have attracted widespread attention due to their insolubility in the reaction system, good stability, high selectivity, low cost, and ease of separation. Strong acid cation exchange resins are a class of polymeric materials containing acidic groups. Because they are essentially solid catalysts, they are not easily corroded by production equipment and are therefore widely used in industrial production. However, these catalysts have relatively slow reaction rates and low ester yields. Cation exchange resins exhibit advantages such as good stability, high selectivity, low cost, and easy separation in esterification reactions. However, cation exchange resins themselves have poor heat resistance (generally suitable for esterification reactions below 150℃), small specific surface area and pore volume, and are prone to swelling. As catalysts for esterification reactions, they have poor activity and low ester yields.
[0004] Compared to resin catalysts, hydrogen-form zeolite molecular sieves possess a certain pore structure and surface acidity, making them suitable for catalyzing the esterification reactions of small molecules. However, the pore size of zeolite molecular sieves is relatively small (0.5-0.7 nm), which may inhibit the diffusion of large molecular products during the reaction; moreover, the number of acidic sites on the surface of zeolite molecular sieves is relatively small, resulting in lower efficiency in catalyzing esterification reactions. With the increasing demand for methyl methacrylate (MMA), green and environmentally friendly synthesis processes hold great promise. For researchers, developing high-performance catalysts for the synthesis of MMA, improving catalytic efficiency, and suppressing byproduct formation are important directions for future work. Summary of the Invention
[0005] The purpose of this invention is to overcome the problems of low methacrylic acid conversion, low methacrylic acid yield, and poor catalyst stability in current methacrylate production processes, and to provide an acidic solid catalyst, its preparation method, and its application. This catalyst, when used in the methacrylate esterification reaction, can achieve higher methacrylic acid conversion, methacrylate selectivity, and catalyst stability.
[0006] To achieve the above objectives, a first aspect of the present invention provides an acidic solid catalyst comprising a sulfonated modified SBA-15 all-silica mesoporous molecular sieve, wherein the surface sulfonic acid group content of the acidic solid catalyst is 1.6-2.8 mmol / g, preferably 1.8-2.7 mmol / g, and more preferably 2.1-2.6 mmol / g.
[0007] A second aspect of the present invention provides a method for preparing the aforementioned acidic solid catalyst, comprising the following steps:
[0008] The acidic solid catalyst is obtained by reacting SBA-15 all-silica mesoporous molecular sieve with a sulfonating agent.
[0009] A third aspect of the invention provides the application of the acidic solid catalyst in the synthesis reaction of methacrylates.
[0010] A fourth aspect of the present invention provides a method for preparing methacrylate, the method comprising: reacting methacrylic acid, a lower alcohol, and a catalyst.
[0011] Compared with the prior art, the technical solution of the present invention has the following advantages:
[0012] (1) The acidic solid catalyst provided by the present invention has a stable structure, good high temperature resistance, and is non-toxic. It does not deform or swell during the reaction and is easy to recover after the reaction.
[0013] (2) The acidic solid catalyst provided by the present invention has readily available raw materials, low preparation cost, simple preparation process, easy control of conditions, and good product repeatability.
[0014] (3) The acidic solid catalyst provided by this invention provides a mild process for the synthesis of methacrylates, with low requirements for the reaction equipment. It also exhibits high conversion rate of methacrylic acid, high ester selectivity, and good catalyst stability.
[0015] Other features and advantages of the present invention will be described in detail in the following detailed description section. Detailed Implementation
[0016] The following provides a detailed description of specific embodiments of the present invention. It should be understood that the specific embodiments described herein are for illustrative and explanatory purposes only and are not intended to limit the scope of the invention.
[0017] To achieve the above objectives, a first aspect of the present invention provides an acidic solid catalyst comprising a sulfonated modified SBA-15 all-silica mesoporous molecular sieve, wherein the surface sulfonic acid group content of the acidic solid catalyst is 1.6-2.8 mmol / g, preferably 1.8-2.7 mmol / g, and more preferably 2.1-2.6 mmol / g.
[0018] The inventors of this invention have discovered that, in the prior art, esterification catalysts used to produce methacrylates are divided into two categories: homogeneous and heterogeneous. Homogeneous catalysts mainly include inorganic acid solutions and organic acids, while heterogeneous catalysts mainly include solid acids and cation exchange resins. Homogeneous catalysts have the advantages of low cost and good catalytic activity; however, they are gradually being phased out due to drawbacks such as difficulty in separating the product from the catalyst, numerous side reactions, and easy corrosion of equipment. While solid esterification catalysts solve the problems of difficult product separation and severe equipment corrosion, they are rarely used in industrial production due to disadvantages such as poor catalytic activity, high reaction temperature, and low product selectivity. Compared with the above catalysts, using strongly acidic cation exchange resins as esterification catalysts to produce methacrylates is currently the main process in industrial applications. On the one hand, resin catalysts have advantages such as high selectivity, low cost, and ease of separation. On the other hand, the main active center of strongly acidic cation exchange resins is the sulfonic acid group. During the catalytic reaction, the sulfonic acid group may detach and dissolve in the reaction system, resulting in poor catalyst stability. Moreover, resins are organic polymers, which are prone to swelling in organic solvents and deformation or even decomposition at high temperatures. This is the main reason for the poor temperature resistance of resin catalysts. Developing novel solid catalyst systems to compensate for the performance defects of resin catalysts is a good way to solve this problem.
[0019] In recent years, acidic zeolite molecular sieve catalysts have attracted widespread attention from researchers due to their structural stability and the resistance to loss of active centers, and are frequently used as catalysts for esterification reactions. However, zeolite molecular sieves have micropores with relatively small pore sizes. If the reactant molecules, intermediates, or target products involved in the reaction are large, catalysts with small pore sizes are not conducive to diffusion, leading to a decrease in catalytic performance. Therefore, depending on the specific circumstances of the esterification reaction, catalysts with larger pore sizes should be selected when larger molecules are involved. Compared to zeolite molecular sieves, mesoporous materials are more suitable for the esterification of methacrylic acid. SBA-15 all-silica mesoporous molecular sieves have large pore sizes and volumes, making them suitable for the esterification of methacrylic acid. However, SBA-15 all-silica mesoporous molecular sieves are all-silica materials with relatively weak surface acidity, resulting in poor catalytic performance in esterification reactions. To solve this problem, it is necessary to increase the number and strength of acid centers on the surface of SBA-15 all-silica mesoporous molecular sieves.
[0020] The inventors of this invention discovered during the development of esterification catalysts that if SBA-15 all-silica mesoporous molecular sieve is sulfonated, sulfonic acid groups can be loaded onto the SBA-15 all-silica mesoporous molecular sieve, thereby effectively improving its esterification catalytic performance.
[0021] According to the present invention, preferably, the sulfonated modified SBA-15 all-silica mesoporous molecular sieve is an SBA-15 all-silica mesoporous molecular sieve treated with a sulfonating agent.
[0022] In this invention, SBA-15 all-silica mesoporous molecular sieves can be prepared using conventional methods, or the following steps can be used to prepare SBA-15 all-silica mesoporous molecular sieves:
[0023] (a) Under hydrolysis gelation conditions, a gel mixture was prepared by mixing a template solvent, a silicon source and dilute hydrochloric acid;
[0024] (b) Crystallize the gel mixture.
[0025] (c) The crystallized product is subjected to solid-liquid separation, washing, drying and calcination.
[0026] Specifically, under hydrolysis gelation conditions, the template agent, the silicon source, and the dilute hydrochloric acid are mixed to obtain a gel mixture; wherein the concentration of the dilute hydrochloric acid is 1-2 mol / L; then, the gel mixture is transferred to a polytetrafluoroethylene-lined reactor and crystallized at 80-120°C for 10-40 hours; the crystallized product is separated, washed with deionized water, and then dried in air at 70-120°C for 3-10 hours and calcined at 450-650°C for 3-12 hours to obtain all-silicon SBA-15 all-silicon mesoporous molecular sieve.
[0027] In the above-mentioned preparation method of SBA-15 all-silica mesoporous molecular sieve, the weight ratio of the template agent: the silicon source: the dilute hydrochloric acid is 1:(0.5-5.0):(5-100), preferably 1:(1.5-2.5):(15-50).
[0028] In the above-described method for preparing SBA-15 all-silica mesoporous molecular sieve, a conventional template agent used for synthesizing SBA-15 molecular sieves can be used, such as a nonionic surfactant. Preferably, the template agent is a polyoxyethylene-polyoxypropylene-polyoxyethylene triblock copolymer; wherein, the general formula of the template agent is EO. a PO b EO a Where a has a value of 5-140, b has a value of 30-100, EO is an abbreviation for ethylene oxide, and PO is an abbreviation for propylene oxide; particularly preferred is P123(EO) 20 PO 70 EO 20 Additionally, it should be noted that P123 is a trade name and can be purchased from Sigma-Aldrich Chemistry.
[0029] In the above-mentioned method for preparing SBA-15 all-silica mesoporous molecular sieve, the silicon source is an organosilicon source and / or an inorganic silicon source, wherein the organosilicon source is an organosilicone ester, preferably methyl orthosilicate and / or ethyl orthosilicate; the inorganic silicon source is an inorganic silicon-containing compound, preferably one or more of water glass, sodium metasilicate and silica sol.
[0030] In the above-mentioned method for preparing SBA-15 all-silica mesoporous molecular sieve, the present invention does not have special requirements for the hydrolysis gelation conditions. Preferably, the hydrolysis gelation conditions include a hydrolysis temperature of 20-60℃, more preferably 30-50℃, and a hydrolysis time of 12-36 hours, more preferably 18-30 hours.
[0031] In the above-mentioned preparation method of SBA-15 all-silica mesoporous molecular sieve, the crystallization conditions include: a temperature of 80-120℃ and a time of 10-40h.
[0032] In the above-described method for preparing SBA-15 all-silica mesoporous molecular sieve, there are no special requirements for the solid-liquid two-phase separation process; it can be a separation method known in the art, including gravity filtration, pressure filtration, vacuum filtration, or centrifugal filtration. Preferably, the separation process specifically includes: using a vacuum flask to create a vacuum at the bottom of the funnel or using a centrifugal filter.
[0033] In the above-mentioned preparation method of SBA-15 all-silica mesoporous molecular sieve, there are no special requirements for the method of washing the solid product. For example, deionized water can be used to wash the solid product, the volume ratio of deionized water to solid product can be 5-20, and the number of washing times can be 2-8.
[0034] In the above-mentioned preparation method of SBA-15 all-silica mesoporous molecular sieve, the drying conditions include: the temperature can be 60-150℃, preferably 70-120℃; the time can be 2-30h, preferably 3-10h.
[0035] In the above-mentioned preparation method of SBA-15 all-silica mesoporous molecular sieve, the calcination treatment conditions can be a temperature of 400-700℃, preferably 450-650℃; and a time of 2-40h, preferably 3-12h.
[0036] According to the present invention, preferably, the sulfonating agent is a halosulfonic acid, and more preferably selected from at least one of fluorosulfonic acid, chlorosulfonic acid, bromosulfonic acid and iodosulfonic acid.
[0037] In this invention, the advantage of using halosulfonic acid is that halosulfonic acid can be bonded to the surface of all-silica mesoporous material by chemical bonds during the modification process, and its properties are relatively stable, and the utilization rate of the active groups of the catalyst is high.
[0038] According to the present invention, preferably, the sulfonated modified SBA-15 all-silica mesoporous molecular sieve has an average pore size of 4.0-6.5 nm, more preferably 5.0-6.0 nm, and a specific surface area of 500-920 m². 2 / g, preferably 600-850m 2 / g, pore volume 0.9-1.3cm³ 3 / g, preferably 1.0-1.2cm 3 / g.
[0039] Under these conditions, the diffusion of raw material and product molecules during the reaction is more favorable, effectively improving the activity and selectivity of the esterification catalyst. In this invention, the use of SBA-15 all-silica mesoporous molecular sieve with the aforementioned specific parameters enables the prepared esterification catalyst to exhibit better catalytic activity and higher selectivity when used in the synthesis reaction of methacrylates.
[0040] According to the present invention, preferably, the acidic solid catalyst further includes Lewis acid that forms a complex with the sulfonic acid groups on the sulfonated modified SBA-15 all-silica mesoporous molecular sieve.
[0041] Furthermore, the inventors of this invention discovered during the development of esterification catalysts that Lewis acids can form complexes with sulfonic acid groups, not only creating highly active dual-acid centers but also significantly improving the stability of the sulfonic acid centers, effectively preventing the shedding of sulfonic acid groups during long-term reactions. Further modification of the sulfonated SBA-15 all-silica mesoporous molecular sieve with appropriate amounts of Lewis acids such as tin tetrachloride yields a high-performance esterification catalyst. On one hand, the addition of Lewis acids significantly increases the number of acidic centers on the catalyst, thereby promoting improved catalytic performance. On the other hand, the complex system formed by Lewis acids and sulfonic acid groups is relatively stable in the esterification reaction, avoiding the problem of active center shedding and dissolution, thus improving catalyst stability. Acidic solid catalysts possess characteristics such as high catalytic activity, simple preparation, and low dosage. Moreover, these catalysts are inorganic in structure, meaning they do not swell or deform in organic solvents and exhibit good temperature resistance. For these reasons, acidic solid catalysts demonstrate excellent catalytic activity, methacrylate selectivity, and stability when used in the esterification reaction of methacrylic acid. The acidic solid catalyst after the reaction is insoluble in organic systems, easily separated from the product, simple to process, and has good reusability. It is an environmentally friendly catalyst with good application prospects.
[0042] According to the present invention, preferably, the Lewis acid is selected from at least one of tin tetrachloride, aluminum trichloride and ferric bromide.
[0043] According to the present invention, preferably, based on the total mass of the acidic solid catalyst, the content of Lewis acid in the acidic solid catalyst, calculated as metal ions, is 4-16 wt%, more preferably 5-14 wt%, and more preferably 6-12 wt%.
[0044] In this invention, by using the aforementioned specific tin content and catalyst surface acidity, the prepared catalyst can exhibit better catalytic activity, ester selectivity, and catalyst stability when used in the synthesis reaction of methacrylates.
[0045] According to the present invention, preferably, the acidic solid catalyst has an average pore size of 3.5-6.0 nm, more preferably 4.0-5.5 nm, and a specific surface area of 400-900 m². 2 / g, preferably 500-750m 2 / g, pore volume 0.7-1.2cm³ 3 / g, preferably 0.8-1.1cm 3 / g, with a surface acidity of 2.0-3.5 mmol / g, preferably 2.2-3.3 mmol / g, and more preferably 2.5-3.0 mmol / g.
[0046] A second aspect of the present invention provides a method for preparing the aforementioned acidic solid catalyst, comprising the following steps:
[0047] The acidic solid catalyst is obtained by reacting SBA-15 all-silica mesoporous molecular sieve with a sulfonating agent.
[0048] In this invention, the gas generated in the reaction is absorbed by an alkaline aqueous solution; preferably, the alkaline aqueous solution can be an aqueous solution of NaOH, an aqueous solution of KOH, an aqueous solution of NaHCO3, or an aqueous solution of Na2CO3, and more preferably an aqueous solution of NaOH or an aqueous solution of KOH.
[0049] According to the present invention, preferably, the weight ratio of the SBA-15 all-silica mesoporous molecular sieve to the sulfonating agent is 1:(0.3-1.2), more preferably 1:(0.4-1.0), and more preferably 1:(0.5-0.9).
[0050] According to the present invention, preferably, the conditions for the contact reaction include: a reaction temperature of 0-40°C and a reaction time of 0.2-8 hours. Preferably, to achieve better reaction results, rapid stirring can be performed during the contact reaction between the all-silica SBA-15 all-silica mesoporous molecular sieve and the halosulfonic acid to improve reaction efficiency.
[0051] According to the present invention, preferably, the preparation method further includes the following steps:
[0052] (1) The Lewis acid solution was reacted with the sulfonated modified SBA-15 all-silica mesoporous molecular sieve.
[0053] (2) The acidic solid catalyst is obtained by filtration, washing and drying.
[0054] According to the present invention, preferably, in step (1), the solvent of the Lewis acid solution is selected from at least one of methanol, ethanol and isopropanol; the mass concentration of Lewis acid is 1.3-3.5%, preferably 1.6-2.5%.
[0055] Preferably, the weight ratio of the sulfonated modified SBA-15 all-silica mesoporous molecular sieve to Lewis acid solution is 1:(5-50), more preferably 1:(10-30).
[0056] Preferably, the contact reaction conditions include a temperature of 30-80°C and a time of 2-8 hours. Preferably, to achieve better contact reaction results, rapid stirring can be performed during the contact reaction between the sulfonated modified SBA-15 all-silica mesoporous molecular sieve and the alcohol solution to improve the reaction efficiency.
[0057] According to the present invention, the filtration can be a filtration method known in the art, including gravity filtration, pressure filtration, vacuum filtration or centrifugal filtration.
[0058] According to the present invention, the method for washing the solid product is as follows: the solid product can be washed with anhydrous methanol, the volume ratio of anhydrous methanol to the solid product can be 5-20, and the number of washing cycles can be 2-8. Preferably, in order to achieve a better washing effect, rapid stirring can be performed during the mixing of anhydrous methanol and the solid product.
[0059] According to the present invention, the drying conditions include: a temperature of 80-150°C, preferably 90-120°C; and a time of 1-20 hours, preferably 2-10 hours.
[0060] A third aspect of the invention provides the application of the acidic solid catalyst in the synthesis reaction of methacrylates.
[0061] According to the present invention, preferably, the methacrylate is methyl methacrylate.
[0062] A fourth aspect of the present invention provides a method for preparing methacrylate, the method comprising: reacting methacrylic acid, a lower alcohol, and a catalyst.
[0063] In this invention, the conditions for the contact reaction include: the contact temperature can be 40-150℃, preferably 60-120℃; the contact pressure can be 0.01-5.0 MPa, preferably 0.1-3.0 MPa; and the mass hourly space velocity (HHSV) of methacrylic acid can be 0.01-30 h⁻¹. -1 Preferably 0.1-10h -1 The mass hourly space velocity (MSV) of lower alcohols can range from 0.01 to 50 h⁻¹. -1 Preferably 0.1-30h -1 The lower alcohol is preferably a C1-C4 alcohol, and more preferably methanol.
[0064] The present invention will be further described below with reference to the embodiments, but the scope of the present invention is not limited to these embodiments.
[0065] In the following examples and comparative examples:
[0066] The pore structure parameters of the samples were analyzed using an ASAP2020-M+C adsorption analyzer manufactured by Micromeritics, USA. Before measurement, the samples were degassed under vacuum at 40°C for 4 hours. The specific surface area of the samples was calculated using the BET method, and the pore volume was calculated using the BJH model.
[0067] Elemental analysis of the samples was performed on an Eagle III energy-dispersive X-ray fluorescence spectrometer manufactured by EDAX Corporation in the United States.
[0068] The drying oven was manufactured by Shanghai Yiheng Scientific Instruments Co., Ltd., model DHG-9030A.
[0069] The muffle furnace is manufactured by CARBOLITE, model CWF1100.
[0070] P123 (EO) used in the examples and comparative examples 20 PO 70 EO 20 All reagents were purchased from Sigma-Aldrich Chemistry; other reagents used in the examples and comparative examples were purchased from Sinopharm Chemical Reagent Co., Ltd., and the reagent purity was analytical grade.
[0071] Example 1
[0072] (1) Preparation of SBA-15 all-silica mesoporous molecular sieve
[0073] 24.0 g of nonionic surfactant P123 was added to 600 g of 2M hydrochloric acid aqueous solution and stirred at 35 °C for 1 hour; 51.2 g of tetraethyl orthosilicate was added to the above solution and stirred at 35 °C for 24 hours; the mixture was transferred to a hydrothermal reactor and hydrothermally crystallized at 100 °C for 24 hours. After the hydrothermal reaction was completed, the solid product was separated from the mother liquor, washed with deionized water until neutral, dried at 110 °C for 6 hours, and calcined at 550 °C for 6 hours to obtain SBA-15 all-silica mesoporous molecular sieve A.
[0074] The specific surface area of SBA-15 all-silica mesoporous molecular sieve A is 967 m². 2 / g; average pore size 7.0nm, pore volume 1.4cm³. 3 / g.
[0075] (2) Preparation of modified SBA-15 mesoporous molecular sieve
[0076] At 30°C, 12 g of SBA-15 all-silica mesoporous molecular sieve A was added to a three-necked flask equipped with a constant-pressure funnel and a tail gas outlet pipe, and a mechanical stirrer was installed. 8.5 g of chlorosulfonic acid was added to the constant-pressure funnel, and the tail gas outlet pipe was connected to an aqueous NaOH solution. Under stirring, the chlorosulfonic acid was added dropwise to the three-necked flask, and the acidic gas generated during the reaction was absorbed by the NaOH solution. After all the chlorosulfonic acid had been added, stirring continued for 1 hour. The white solid in the three-necked flask was then removed; this was the modified SBA-15 mesoporous molecular sieve A.
[0077] The specific surface area of modified SBA-15 mesoporous molecular sieve A is 794 m². 2 / g; average pore size 5.8nm, pore volume 1.1cm³. 3 / g, with a surface sulfonic acid group content of 2.4mmol / g.
[0078] (3) Preparation of acidic solid catalysts
[0079] 4.0 g of tin tetrachloride was dissolved in 200 g of methanol to prepare a methanol solution. 10 g of modified SBA-15 mesoporous molecular sieve A was added, and the mixture was stirred at 50 °C for 4 h. After the reaction, the solid product was obtained by filtration. The solid product was washed four times with 200 ml of anhydrous methanol and dried at 110 °C for 5 h to obtain acidic solid catalyst A.
[0080] The specific surface area of acidic solid catalyst A is 721 m². 2 / g; average pore size is 5.3nm, pore volume is 1.1cm³. 3 The catalyst contains 9.4% tin by weight, 2.4 mmol / g of surface sulfonic acid groups, and 2.8 mmol / g of surface acidity.
[0081] (4) Evaluation of catalyst reaction performance
[0082] The performance of the catalyst in the methacrylilation reaction was evaluated in a fixed-bed reactor. 10 g of acidic solid catalyst A was packed into a stainless steel fixed-bed reactor with an inner diameter of 8 mm. The reaction temperature was 95 °C, the reaction pressure was 0.5 MPa, and the weight hourly space velocity (WHSV) of methacrylic acid was 0.4 h⁻¹. -1 The weight hourly space velocity (WHSV) of methanol is 1.6 h⁻¹. -1 After cooling, the product was analyzed using an Agilent 7890A gas chromatograph equipped with an FFAP capillary column and a flame ionization detector (FID). Quantitative analysis was performed using programmed temperature ramping and correction factors. The conversion of methacrylic acid and the selectivity of methyl methacrylate are listed in Table 1.
[0083] Example 2
[0084] (1) Preparation of SBA-15 all-silica mesoporous molecular sieve
[0085] 30.0 g of nonionic surfactant P123 was added to 450 g of 1 M hydrochloric acid aqueous solution and stirred at 40 °C for 1 hour. 45.0 g of methyl orthosilicate was added dropwise to the above solution and stirred at 40 °C for 24 hours. The mixture was then transferred to a hydrothermal reactor and hydrothermally crystallized at 120 °C for 10 hours. After the hydrothermal reaction was complete, the solid product was separated from the mother liquor, washed with deionized water until neutral, dried at 120 °C for 3 hours, and calcined at 450 °C for 12 hours to obtain SBA-15 all-silica mesoporous molecular sieve B.
[0086] The specific surface area of SBA-15 all-silica mesoporous molecular sieve B is 920 m². 2 / g; average pore size is 6.7nm, pore volume is 1.3cm³.3 / g.
[0087] (2) Preparation of modified SBA-15 mesoporous molecular sieve
[0088] At 25°C, 12 g of SBA-15 all-silica mesoporous molecular sieve B was added to a three-necked flask equipped with a constant-pressure funnel and a tail gas outlet pipe, and a mechanical stirrer was installed. 6.0 g of chlorosulfonic acid was added to the constant-pressure funnel, and the tail gas outlet pipe was connected to a KOH aqueous solution. Under stirring, the chlorosulfonic acid was added dropwise to the three-necked flask, and the acidic gas generated during the reaction was absorbed by the KOH aqueous solution. After all the chlorosulfonic acid had been added, stirring continued for 0.5 h. The white solid in the three-necked flask was then removed; this was the modified SBA-15 mesoporous molecular sieve B.
[0089] The specific surface area of modified SBA-15 mesoporous molecular sieve B is 806 m². 2 / g; average pore size is 6.0nm, pore volume is 1.1cm³. 3 / g, with a surface sulfonic acid group content of 2.1mmol / g.
[0090] (3) Preparation of acidic solid catalysts
[0091] 2.5 g of tin tetrachloride was dissolved in 150 g of methanol to prepare a methanol solution. 10 g of modified SBA-15 mesoporous molecular sieve B was added, and the mixture was stirred at 60 °C for 3 h. After the reaction, the solid product was obtained by filtration. The solid product was washed three times with 300 ml of anhydrous methanol and dried at 90 °C for 10 h to obtain acidic solid catalyst B.
[0092] The specific surface area of acidic solid catalyst B is 693 m². 2 / g; average pore size is 5.1nm, pore volume is 1.0cm³. 3 The catalyst contains 6.0% tin by weight, 2.1 mmol / g of surface sulfonic acid groups, and 2.5 mmol / g of surface acid.
[0093] (4) Evaluation of catalyst reaction performance
[0094] The esterification performance of catalyst B was tested according to step (4) in Example 1. The experimental results are listed in Table 1.
[0095] Example 3
[0096] (1) Preparation of SBA-15 all-silica mesoporous molecular sieve
[0097] 16.0 g of nonionic surfactant P123 was added to 800 g of 1.5 M hydrochloric acid aqueous solution and stirred at 40 °C for 1 hour. 40.0 g of water glass (SiO2 content 28.26 wt%) was added to the above solution and stirred at 40 °C for 24 hours. The mixture was then transferred to a hydrothermal reactor and hydrothermally crystallized at 80 °C for 40 hours. After the hydrothermal reaction was complete, the solid product was separated from the mother liquor, washed with deionized water until neutral, dried at 70 °C for 10 hours, and calcined at 650 °C for 3 hours to obtain SBA-15 all-silica mesoporous molecular sieve C.
[0098] The specific surface area of SBA-15 all-silica mesoporous molecular sieve C is 892 m². 2 / g; average pore size is 6.4nm, pore volume is 1.2cm³. 3 / g.
[0099] (2) Preparation of modified SBA-15 mesoporous molecular sieve
[0100] At 20°C, 12 g of SBA-15 all-silica mesoporous molecular sieve C was added to a three-necked flask equipped with a constant-pressure funnel and a tail gas outlet pipe, and a mechanical stirrer was installed. 10.8 g of chlorosulfonic acid was added to the constant-pressure funnel, and the tail gas outlet pipe was connected to a KOH aqueous solution. Under stirring, the chlorosulfonic acid was added dropwise to the three-necked flask, and the acidic gas generated during the reaction was absorbed by the KOH aqueous solution. After all the chlorosulfonic acid had been added, stirring continued for 3 hours. The white solid in the three-necked flask was then removed; this was the modified SBA-15 mesoporous molecular sieve C.
[0101] The specific surface area of modified SBA-15 mesoporous molecular sieve C is 627 m². 2 / g; average pore size is 5.2nm, pore volume is 1.0cm³. 3 / g, with a surface sulfonic acid group content of 2.6mmol / g.
[0102] (3) Preparation of acidic solid catalysts
[0103] 5.2 g of tin tetrachloride was dissolved in 250 g of methanol to prepare a methanol solution. 10 g of modified SBA-15 mesoporous molecular sieve C was added, and the mixture was stirred at 40 °C for 5 h. After the reaction, the solid product was obtained by filtration. The solid product was washed eight times with 100 ml of anhydrous methanol and dried at 120 °C for 2 h to obtain acidic solid catalyst C.
[0104] The specific surface area of acidic solid catalyst C is 538 m². 2 / g; average pore size is 4.3nm, pore volume is 0.8cm³. 3 The catalyst contains 12.0% tin by weight, 2.6 mmol / g of surface sulfonic acid groups, and 3.0 mmol / g of surface acid.
[0105] (4) Evaluation of catalyst reaction performance
[0106] The esterification performance of catalyst C was tested according to step (4) in Example 1. The experimental results are listed in Table 1.
[0107] Example 4
[0108] (1) Prepare SBA-15 all-silica mesoporous molecular sieve A according to the method of step (1) in Example 1.
[0109] (2) Preparation of modified SBA-15 mesoporous molecular sieve
[0110] At 5°C, 12 g of SBA-15 all-silica mesoporous molecular sieve A was added to a three-necked flask equipped with a constant-pressure funnel and a tail gas outlet pipe, and a mechanical stirrer was installed. 4.8 g of chlorosulfonic acid was added to the constant-pressure funnel, and the tail gas outlet pipe was connected to an aqueous NaOH solution. Under stirring, the chlorosulfonic acid was added dropwise to the three-necked flask, and the acidic gas generated during the reaction was absorbed by the NaOH solution. After all the chlorosulfonic acid had been added, stirring continued for 5 hours. The white solid in the three-necked flask was then removed; this was the modified SBA-15 mesoporous molecular sieve D.
[0111] The specific surface area of modified SBA-15 mesoporous molecular sieve D is 849 m². 2 / g; average pore size is 6.0nm, pore volume is 1.2cm³. 3 / g, with a surface sulfonic acid group content of 1.8mmol / g.
[0112] (3) Preparation of acidic solid catalysts
[0113] 2.1 g of tin tetrachloride was dissolved in 100 g of methanol to prepare a methanol solution. 10 g of modified SBA-15 mesoporous molecular sieve D was added, and the mixture was stirred at 70 °C for 3 h. After the reaction, the solid product was obtained by filtration. The solid product was washed twice with 400 ml of anhydrous methanol and dried at 90 °C for 10 h to obtain acidic solid catalyst D.
[0114] The specific surface area of acidic solid catalyst D is 750 m². 2 / g; average pore size 5.5nm, pore volume 1.1cm³. 3 The catalyst contains 5.0% tin by weight, 1.8 mmol / g of surface sulfonic acid groups, and 2.2 mmol / g of surface acidity.
[0115] (4) Evaluation of catalyst reaction performance
[0116] The esterification performance of catalyst D was tested according to step (4) in Example 1. The experimental results are listed in Table 1.
[0117] Example 5
[0118] (1) Prepare SBA-15 all-silica mesoporous molecular sieve B according to the method in step (1) of Example 2.
[0119] (2) Preparation of modified SBA-15 mesoporous molecular sieve
[0120] At 35℃, 12 g of SBA-15 all-silica mesoporous molecular sieve B was added to a three-necked flask equipped with a constant-pressure funnel and a tail gas outlet pipe, and a mechanical stirrer was installed. 12.0 g of chlorosulfonic acid was added to the constant-pressure funnel, and the tail gas outlet pipe was connected to a KOH aqueous solution. Under stirring, the chlorosulfonic acid was added dropwise to the three-necked flask, and the acidic gas generated during the reaction was absorbed by the KOH aqueous solution. After all the chlorosulfonic acid had been added, stirring continued for 0.5 h. The white solid in the three-necked flask was then removed; this was the modified SBA-15 mesoporous molecular sieve E.
[0121] The specific surface area of the modified SBA-15 mesoporous molecular sieve E is 615 m². 2 / g; average pore size 5.0nm, pore volume 1.0cm³. 3 / g, with a surface sulfonic acid group content of 2.7mmol / g.
[0122] (3) Preparation of acidic solid catalysts
[0123] 6.0 g of tin tetrachloride was dissolved in 290 g of methanol to prepare a methanol solution. 10 g of modified SBA-15 mesoporous molecular sieve F was added, and the mixture was stirred at 55 °C for 5 h. After the reaction, the solid product was obtained by filtration. The solid product was washed five times with 200 ml of anhydrous methanol and dried at 110 °C for 4 h to obtain acidic solid catalyst E.
[0124] The specific surface area of acidic solid catalyst E is 507 m². 2 / g; average pore size is 4.0nm, pore volume is 0.8cm³. 3 The catalyst contains 14.0% tin by weight, has 2.7 mmol / g of surface sulfonic acid groups, and 3.3 mmol / g of surface acidity.
[0125] (4) Evaluation of catalyst reaction performance
[0126] The esterification performance of catalyst E was tested according to step (4) in Example 1. The experimental results are listed in Table 1.
[0127] Example 6
[0128] (1) Prepare SBA-15 all-silica mesoporous molecular sieve A according to the method of step (1) in Example 1.
[0129] (2) Preparation of modified SBA-15 mesoporous molecular sieve
[0130] At 0℃, 12 g of SBA-15 all-silica mesoporous molecular sieve A was added to a three-necked flask equipped with a constant-pressure funnel and a tail gas outlet pipe, and a mechanical stirrer was installed. 3.6 g of fluorosulfonic acid was added to the constant-pressure funnel, and the tail gas outlet pipe was connected to an aqueous NaOH solution. Under stirring, the fluorosulfonic acid was added dropwise to the three-necked flask, and the acidic gas generated during the reaction was absorbed by the NaOH solution. After all the fluorosulfonic acid had been added, stirring continued for 8 hours. The white solid in the three-necked flask was then removed; this was the modified SBA-15 mesoporous molecular sieve F.
[0131] The specific surface area of the modified SBA-15 mesoporous molecular sieve F is 920 m². 2 / g; average pore size is 6.5nm, pore volume is 1.3cm³. 3 / g, with a surface sulfonic acid group content of 1.6mmol / g.
[0132] (3) Preparation of acidic solid catalysts
[0133] 1.7 g of tin tetrachloride was dissolved in 50 g of methanol to prepare a methanol solution. 10 g of modified SBA-15 mesoporous molecular sieve D was added, and the mixture was stirred at 70 °C for 3 h. After the reaction, the solid product was obtained by filtration. The solid product was washed twice with 400 ml of anhydrous methanol and dried at 90 °C for 10 h to obtain the acidic solid catalyst F.
[0134] The specific surface area of acidic solid catalyst F is 874 m². 2 / g; average pore size is 6.0nm, pore volume is 1.2cm³. 3 The catalyst contains 4.0% tin by weight, 1.6 mmol / g of surface sulfonic acid groups, and 2.0 mmol / g of surface acid.
[0135] (4) Evaluation of catalyst reaction performance
[0136] The esterification performance of catalyst F was tested according to step (4) in Example 1. The experimental results are listed in Table 1.
[0137] Example 7
[0138] (1) Prepare SBA-15 all-silica mesoporous molecular sieve C according to the method of step (1) in Example 3.
[0139] (2) Preparation of modified SBA-15 mesoporous molecular sieve
[0140] At 40℃, 12 g of SBA-15 all-silica mesoporous molecular sieve C was added to a three-necked flask equipped with a constant-pressure funnel and a tail gas outlet pipe, and a mechanical stirrer was installed. 14.4 g of bromosulfonic acid was added to the constant-pressure funnel, and the tail gas outlet pipe was connected to a KOH aqueous solution. Under stirring, the bromosulfonic acid was added dropwise to the three-necked flask, and the acidic gas generated during the reaction was absorbed by the KOH aqueous solution. After all the bromosulfonic acid had been added, stirring continued for 0.2 h. The white solid in the three-necked flask was then removed; this was the modified SBA-15 mesoporous molecular sieve G.
[0141] The specific surface area of the modified SBA-15 mesoporous molecular sieve G is 504 m². 2 / g; average pore size 4.2nm, pore volume 0.9cm³. 3 / g, with a surface sulfonic acid group content of 2.8mmol / g.
[0142] (3) Preparation of acidic solid catalysts
[0143] 6.8 g of tin tetrachloride was dissolved in 490 g of methanol to prepare a methanol solution. 10 g of modified SBA-15 mesoporous molecular sieve G was added, and the mixture was stirred at 55 °C for 5 h. After the reaction, the solid product was obtained by filtration. The solid product was washed five times with 200 ml of anhydrous methanol and dried at 110 °C for 4 h to obtain acidic solid catalyst G.
[0144] The specific surface area of acidic solid catalyst G is 400 m². 2 / g; average pore size is 3.8nm, pore volume is 0.7cm³. 3 The catalyst contains 16.0% tin by weight, 2.8 mmol / g of surface sulfonic acid groups, and 3.5 mmol / g of surface acidity.
[0145] (4) Evaluation of catalyst reaction performance
[0146] The esterification performance of catalyst G was tested according to step (4) in Example 1. The experimental results are listed in Table 1.
[0147] Example 8
[0148] SBA-15 all-silica mesoporous molecular sieve B was prepared according to the method in step (1) of Example 2.
[0149] Modified SBA-15 mesoporous molecular sieve B was prepared according to step (2) in Example 2.
[0150] Step (3) in Example 2 was omitted, and modified SBA-15 mesoporous molecular sieve B was used as catalyst H. The specific surface area of catalyst H was 806 m². 2 / g; average pore size is 6.0nm, pore volume is 1.1cm³. 3 / g, the content of sulfonic acid groups on the catalyst surface is 2.1mmol / g, and the tin content in the catalyst is 0% by weight.
[0151] Its esterification performance was tested according to the method in step (4) of Example 1. The experimental results are listed in Table 1.
[0152] Example 9
[0153] The only difference between this implementation and Example 2 is that in step (3), 2.5g of tin tetrachloride is replaced with 5.6g of ferric bromide to obtain catalyst I. The specific surface area of catalyst I is 671m². 2 / g; average pore size 4.9nm, pore volume 0.9cm³. 3 / g, the iron content in the catalyst is 5.6% by weight, the content of sulfonic acid groups on the catalyst surface is 2.0 mmol / g, and the surface acidity is 2.3 mmol / g.
[0154] Its esterification performance was tested according to the method in step (4) of Example 1. The experimental results are listed in Table 1.
[0155] Example 10
[0156] The only difference between this implementation and Example 3 is that in step (3), 250g of methanol is replaced with 350g of isopropanol to obtain catalyst J. The specific surface area of catalyst J is 549m². 2 / g; average pore size is 4.4nm, pore volume is 0.8cm³. 3 The catalyst contains 11.8% tin by weight, has 2.6 mmol / g sulfonic acid groups on its surface, and 2.8 mmol / g surface acidity.
[0157] Its esterification performance was tested according to the method in step (4) of Example 1. The experimental results are listed in Table 1.
[0158] Comparative Example 1
[0159] SBA-15 all-silica mesoporous molecular sieve A was prepared according to step (1) in Example 1.
[0160] Step (2) was omitted, and acidic solid catalyst D1 was prepared according to step (3) in Example 1. The specific process is as follows: 4.0 g of tin tetrachloride was dissolved in 200 g of methanol to prepare a methanol solution, and 10 g of SBA-15 all-silica mesoporous molecular sieve A was added. The mixture was stirred at 50 °C for 4 h. After the reaction, the solid product was obtained by filtration. The solid product was washed four times with 200 ml of anhydrous methanol and dried at 110 °C for 5 h to obtain acidic solid catalyst D1.
[0161] The specific surface area of acidic solid catalyst D1 is 851 m². 2 / g; average pore size is 6.3nm, pore volume is 1.3cm³. 3 The catalyst contains 9.8% tin by weight, has 0 mmol / g sulfonic acid groups on its surface, and has a surface acidity of 1.1 mmol / g.
[0162] The performance of the acidic solid catalyst D1 for esterification was tested according to step (4) in Example 1. The experimental results are listed in Table 1.
[0163] Comparative Example 2
[0164] In Example 1, step (1) is cancelled, and the SBA-15 all-silica mesoporous molecular sieve A in step (2) of Example 1 is replaced with commercially available silica (purchased from Nanjing Baoket New Materials Co., Ltd., with a specific surface area of 180 m²). 2 / g, pore volume is 0.3ml / g, average pore diameter is 14nm), replace the modified SBA-15 mesoporous molecular sieve A in step (3) of Example 1 with modified commercially available silica to obtain catalyst D3.
[0165] The specific surface area of acidic solid catalyst D2 is 79 m². 2 / g; average pore size is 8.2nm, pore volume is 0.1cm³. 3 The catalyst contains 3.8% tin by weight, 0.9 mmol / g of surface sulfonic acid groups, and 1.1 mmol / g of surface acidity.
[0166] The performance of the acidic solid catalyst D2 esterification reaction was tested according to the method in step (4) of Example 1. The experimental results are listed in Table 1.
[0167] Comparative Example 3
[0168] (1) Prepare SBA-15 all-silica mesoporous molecular sieve A according to the method of step (1) in Example 1.
[0169] (2) Preparation of modified SBA-15 mesoporous molecular sieve
[0170] At 0℃, 12 g of SBA-15 all-silica mesoporous molecular sieve A was added to a three-necked flask equipped with a constant-pressure funnel and a tail gas outlet pipe, and a mechanical stirrer was installed. 1.5 g of chlorosulfonic acid was added to the constant-pressure funnel, and the tail gas outlet pipe was connected to an aqueous NaOH solution. Under stirring, the chlorosulfonic acid was added dropwise to the three-necked flask, and the acidic gas generated during the reaction was absorbed by the NaOH solution. After all the chlorosulfonic acid had been added, stirring continued for 8 hours. The white solid in the three-necked flask was then removed; this was the modified SBA-15 mesoporous molecular sieve D3.
[0171] The specific surface area of modified SBA-15 mesoporous molecular sieve D3 is 951 m². 2 / g; average pore size is 6.7nm, pore volume is 1.4cm³. 3 / g, with a surface sulfonic acid group content of 0.5mmol / g.
[0172] (3) Preparation of acidic solid catalysts
[0173] 0.6 g of tin tetrachloride was dissolved in 50 g of methanol to prepare a methanol solution. 10 g of modified SBA-15 mesoporous molecular sieve D3 was added, and the mixture was stirred at 70 °C for 3 h. After the reaction, the solid product was obtained by filtration. The solid product was washed twice with 400 ml of anhydrous methanol and dried at 90 °C for 10 h to obtain the acidic solid catalyst D4.
[0174] The specific surface area of the acidic solid catalyst D3 is 908 m². 2 / g; average pore size is 6.3nm, pore volume is 1.3cm³. 3 The catalyst contains 1.5% tin by weight, 0.5 mmol / g of surface sulfonic acid groups, and 0.8 mmol / g of surface acid.
[0175] (4) Evaluation of catalyst reaction performance
[0176] The esterification performance of catalyst D3 was tested according to step (4) in Example 1. The experimental results are listed in Table 1.
[0177] Comparative Example 4
[0178] (1) Prepare SBA-15 all-silica mesoporous molecular sieve C according to the method of step (1) in Example 3.
[0179] (2) Preparation of modified SBA-15 mesoporous molecular sieve
[0180] At 40℃, 12 g of SBA-15 all-silica mesoporous molecular sieve C was added to a three-necked flask equipped with a constant-pressure funnel and a tail gas outlet pipe, and a mechanical stirrer was installed. 18.6 g of bromosulfonic acid was added to the constant-pressure funnel, and the tail gas outlet pipe was connected to a KOH aqueous solution. Under stirring, the bromosulfonic acid was added dropwise to the three-necked flask, and the acidic gas generated during the reaction was absorbed by the KOH aqueous solution. After all the bromosulfonic acid had been added, stirring continued for 3 hours. The white solid in the three-necked flask was then removed; this was the modified SBA-15 mesoporous molecular sieve D4.
[0181] The specific surface area of modified SBA-15 mesoporous molecular sieve D4 is 480 m². 2 / g; average pore size 3.9nm, pore volume 0.7cm³. 3 / g, with a surface sulfonic acid group content of 3.2mmol / g.
[0182] (3) Preparation of acidic solid catalysts
[0183] 8.5 g of tin tetrachloride was dissolved in 600 g of methanol to prepare a methanol solution. 10 g of modified SBA-15 mesoporous molecular sieve D4 was added, and the mixture was stirred at 55 °C for 5 h. After the reaction, the solid product was obtained by filtration. The solid product was washed five times with 200 ml of anhydrous methanol and dried at 110 °C for 4 h to obtain the acidic solid catalyst D4.
[0184] The specific surface area of acidic solid catalyst D4 is 310 m². 2 / g; average pore size is 3.2nm, pore volume is 0.4cm³. 3 The catalyst has a tin content of 20.0% by weight, a surface sulfonic acid group content of 3.2 mmol / g, and a surface acidity of 3.8 mmol / g.
[0185] (4) Evaluation of catalyst reaction performance
[0186] The esterification performance of catalyst D4 was tested according to step (4) in Example 1. The experimental results are listed in Table 1.
[0187] Comparative Example 5
[0188] (1) Prepare SBA-15 all-silica mesoporous molecular sieve A according to the method of step (1) in Example 1.
[0189] (2) Preparation of catalyst
[0190] 10g of SBA-15 all-silica mesoporous molecular sieve A and 20g of 20% (w / w) phosphotungstic acid aqueous solution were mixed and stirred at 60℃ for 1h. 4.4g of 10% (w / w) bismuth trichloride aqueous solution was slowly added dropwise to the mixture. After the addition was complete, the mixture was stirred at 60℃ for 4h. The solvent water in the system was removed using a rotary evaporator. The solid product was dried at 100℃ for 8h and then calcined at 280℃ for 4h to obtain catalyst D5.
[0191] The specific surface area of catalyst D5 is 425 m². 2 / g; average pore size 3.8nm, pore volume 0.6cm³. 3 The catalyst contains 0% tin by weight, 0 mmol / g of surface sulfonic acid groups, 29.1% wt% bismuth phosphotungsten, and 1.9 mmol / g of surface acidity.
[0192] The esterification performance of catalyst D5 was tested according to step (4) in Example 1. The experimental results are listed in Table 1.
[0193] Table 1
[0194]
[0195]
[0196]
[0197] The results above show that the acidic solid catalyst provided by the present invention can directly convert methacrylic acid and methanol into methyl methacrylate, achieving a high conversion rate of methacrylic acid and selectivity for methyl methacrylate, while maintaining good catalyst stability.
[0198] In Example 8, the tin tetrachloride modification step was omitted, and the prepared catalyst did not contain tin ions. The surface acidity all came from sulfonic acid groups. The stability of the active groups was slightly poor during the reaction, resulting in low conversion rate of methacrylic acid, low selectivity of methyl methacrylate, and poor catalyst stability.
[0199] In Comparative Example 1, the sulfonation step was omitted, resulting in a catalyst surface lacking sulfonic acid groups. The acidity originated solely from Lewis acids, leading to a lower surface acidity and insufficient active sites for the same weight of catalyst during the reaction. This resulted in low methacrylic acid conversion, low methyl methacrylate selectivity, and poor catalyst stability.
[0200] In Comparative Example 2, the SBA-15 all-silica mesoporous molecular sieve specifically defined in this invention was not used; instead, commercially available silica was used. Because the pore structure of commercially available silica differs significantly from that of the SBA-15 all-silica mesoporous molecular sieve, the pore volume is smaller. The acidic groups are unevenly dispersed on the surface of the commercially available silica. This results in low methacrylic acid conversion, low selectivity for methyl methacrylate, and poor catalyst stability.
[0201] In Comparative Example 3, the preparation conditions of the acidic solid catalyst were not within the scope of the claims, the content of active groups on the catalyst was too low, resulting in low conversion of methacrylic acid, low selectivity of methyl methacrylate, and poor catalyst stability.
[0202] In Comparative Example 4, the preparation conditions of the acidic solid catalyst were not within the scope of the claims. The excessive content of sulfonic acid groups on the catalyst blocked the pores, resulting in a significant decrease in the catalyst pore size, pore volume, and specific surface area. In addition, the active components on the catalyst surface were unevenly dispersed, which seriously affected the diffusion of reactant and product molecules, leading to low methacrylic acid conversion, low selectivity for methyl methacrylate, and poor catalyst stability.
[0203] In Comparative Example 5, bismuth phosphotungstenate was supported on an SBA-15 all-silica mesoporous molecular sieve. The catalyst surface lacked sulfonic acid groups, resulting in a lower surface acidity and insufficient active sites for the same weight of catalyst during the reaction. This catalyst exhibited good stability, but showed low conversion of methacrylic acid and low selectivity for methyl methacrylate.
[0204] The various embodiments of the present invention have been described above. These descriptions are exemplary and not exhaustive, nor are they limited to the disclosed embodiments. Many modifications and variations will be apparent to those skilled in the art without departing from the scope and spirit of the described embodiments.
[0205] The endpoints and any values of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values should be understood to include values close to these ranges or values. For numerical ranges, the endpoint values of the various ranges, the endpoint values of the various ranges and individual point values, and individual point values can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.
Claims
1. An acidic solid catalyst, characterized in that, The acidic solid catalyst comprises a sulfonated modified SBA-15 all-silica mesoporous molecular sieve, and the surface sulfonic acid group content of the acidic solid catalyst is 1.6-2.8 mmol / g, preferably 1.8-2.7 mmol / g, and more preferably 2.1-2.6 mmol / g.
2. The acidic solid catalyst according to claim 1, wherein, The sulfonated modified SBA-15 all-silica mesoporous molecular sieve is an SBA-15 all-silica mesoporous molecular sieve treated with a sulfonating agent.
3. The acidic solid catalyst according to claim 2, wherein, The sulfonating agent is a halosulfonic acid, preferably selected from at least one of fluorosulfonic acid, chlorosulfonic acid, bromosulfonic acid, and iodosulfonic acid.
4. The acidic solid catalyst according to claim 2, wherein, The sulfonated modified SBA-15 all-silica mesoporous molecular sieve has an average pore size of 4.0-6.5 nm, preferably 5.0-6.0 nm, and a specific surface area of 500-920 m². 2 / g, preferably 600-850m 2 / g, pore volume 0.9-1.3cm³ 3 / g, preferably 1.0-1.2cm 3 / g.
5. The acidic solid catalyst according to any one of claims 1-4, wherein, The acidic solid catalyst also includes Lewis acid that forms a complex with the sulfonic acid groups on the sulfonated SBA-15 all-silica mesoporous molecular sieve.
6. The acidic solid catalyst according to claim 5, wherein, The Lewis acid is selected from at least one of tin tetrachloride, aluminum trichloride, and ferric bromide.
7. The acidic solid catalyst according to claim 5, wherein, Based on the total mass of the acidic solid catalyst, the content of Lewis acid in the acidic solid catalyst, calculated as metal ions, is 4-16 wt%, preferably 5-14 wt%, and more preferably 6-12 wt%.
8. The acidic solid catalyst according to claim 5, wherein, The acidic solid catalyst has an average pore size of 3.5-6.0 nm, preferably 4.0-5.5 nm, and a specific surface area of 400-900 m². 2 / g, preferably 500-750m 2 / g, pore volume 0.7-1.2cm³ 3 / g, preferably 0.8-1.1cm 3 / g, with a surface acidity of 2.0-3.5 mmol / g, preferably 2.2-3.3 mmol / g, and more preferably 2.5-3.0 mmol / g.
9. A method for preparing the acidic solid catalyst according to any one of claims 1-8, characterized in that, Includes the following steps: The acidic solid catalyst is obtained by reacting SBA-15 all-silica mesoporous molecular sieve with a sulfonating agent.
10. The preparation method according to claim 9, wherein, The weight ratio of the SBA-15 all-silica mesoporous molecular sieve to the sulfonating agent is 1:(0.3-1.2), preferably 1:(0.4-1.0), and more preferably 1:(0.5-0.9).
11. The preparation method according to claim 9, wherein, The conditions for the contact reaction include: a reaction temperature of 0-40°C and a reaction time of 0.2-8 hours.
12. The preparation method according to any one of claims 9-11, wherein, The preparation method further includes the following steps: (1) The Lewis acid solution was reacted with the sulfonated modified SBA-15 all-silica mesoporous molecular sieve. (2) The acidic solid catalyst is obtained by filtration, washing and drying.
13. The preparation method according to claim 12, wherein, In step (1), the solvent of the Lewis acid solution is selected from at least one of methanol, ethanol and isopropanol; the mass concentration of Lewis acid is 1.3-3.5%; The weight ratio of the sulfonated modified SBA-15 all-silica mesoporous molecular sieve to Lewis acid solution is 1:(5-50); The conditions for the contact reaction include: a temperature of 30-80℃ and a time of 2-8h.
14. The preparation method according to claim 12, wherein, In step (2), the drying conditions include a temperature of 80-150℃ and a time of 1-20h.
15. The application of the acidic resin catalyst according to any one of claims 1-8 in the synthesis reaction of methacrylate; preferably, the methacrylate is methyl methacrylate.
16. A method for preparing methacrylate, characterized in that, The method includes: reacting methacrylic acid, lower alcohols, and a catalyst. Preferably, the conditions for the contact reaction include: a temperature of 40-150°C, more preferably 60-120°C; a pressure of 0.01-5.0 MPa, more preferably 0.1-3.0 MPa; and a mass hourly space velocity (HHSV) of methacrylic acid of 0.01-30 h⁻¹. -1 Preferably 0.1-10h -1 The mass hourly space velocity (MSV) of lower alcohols is 0.01-50 h⁻¹. -1 Preferably 0.1-30h -1 The lower alcohol is preferably a C1-C4 alcohol, and more preferably methanol.