Modified macroporous / mesoporous molecular sieve catalyst, preparation method thereof and application of modified macroporous / mesoporous molecular sieve catalyst in production of methyl methacrylate

Abstract

The invention relates to the field of fine chemical engineering, and further relates to a modified macroporous / mesoporous molecular sieve catalyst, a preparation method thereof and application of the catalyst in methyl methacrylate synthesis reaction. The catalyst comprises a carrier and lanthanum chloride loaded on the carrier, wherein the carrier is a modified macroporous / mesoporous molecular sieve; the weight content of the lanthanum element in the catalyst is 8-22%, and the weight of the catalyst is 100%; the surface acid content of the catalyst is 3 to 4.5 mmol / g. The catalyst provided by the invention is used for the synthetic reaction of methyl methacrylate, the operation process conditions are mild, the methacrylic acid conversion rate is high, the ester selectivity is high, and the catalyst stability is good.

Description

Technical Field

[0001] This invention relates to the field of fine chemicals, and more specifically, to a modified macroporous mesoporous molecular sieve catalyst and its preparation method, as well as the application of the catalyst in the synthesis reaction of methyl 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, acidic 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 the current methacrylic acid production process, and to provide a modified macroporous mesoporous molecular sieve catalyst, its preparation method, and its application. This catalyst, when used in the methacrylic acid esterification reaction, can achieve higher methacrylic acid conversion, methacrylic acid selectivity, and catalyst stability.

[0006] The inventors of this invention have discovered that, in the prior art, esterification catalysts used to produce methyl methacrylate 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 methyl methacrylate is currently the main process used 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.

[0007] 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. For reactant and product molecules to diffuse easily within the pores during the reaction, larger pore sizes in mesoporous materials are more beneficial for the esterification reaction. Ultra-large pore mesoporous molecular sieves with an average pore size greater than 10 nm are clearly suitable for the esterification of methacrylic acid. However, ultra-large pore mesoporous molecular sieves are all-silica materials with 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 the mesoporous molecular sieve.

[0008] The inventors of this invention discovered during the development of esterification catalysts that acidification modification of macroporous mesoporous molecular sieves can load sulfonic acid groups onto the sieves, thereby effectively improving their esterification catalytic performance. Furthermore, the inventors also discovered that lanthanum chloride, possessing Lewis acidity, 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 macroporous mesoporous molecular sieve with an appropriate amount of lanthanum chloride yields a high-performance esterification catalyst. On one hand, the addition of Lewis acid significantly increases the number of acidic centers on the catalyst, thereby promoting improved catalytic performance. On the other hand, the complex system formed by lanthanum chloride and sulfonic acid groups is relatively stable during the esterification reaction, avoiding the problem of active center shedding and dissolution, thus improving catalyst stability. Modified macroporous and mesoporous molecular sieve catalysts possess advantages such as high catalytic activity, simple preparation, and low dosage. Furthermore, as inorganic catalysts, they do not swell or deform in organic solvents and exhibit good temperature resistance. For these reasons, modified macroporous and mesoporous molecular sieve catalysts demonstrate excellent catalytic activity, methyl methacrylate selectivity, and stability in the esterification reaction of methacrylate. The reacted modified macroporous and mesoporous molecular sieve catalyst is insoluble in organic systems, easily separated from the product, and undergoes simple post-processing and good reusability, making it an environmentally friendly catalyst with promising application prospects.

[0009] Based on the above research and invention, the first aspect of the present invention is to provide a modified macroporous mesoporous molecular sieve catalyst, the catalyst comprising a support and lanthanum chloride supported on the support, wherein the support is a modified macroporous mesoporous molecular sieve.

[0010] The catalyst contains 8%-22% lanthanum by weight, based on 100% of the catalyst's weight; the surface acidity of the catalyst is 3-4.5 mmol / g.

[0011] According to the present invention, preferably, the lanthanum content in the catalyst is 10%-20% by weight, and the surface acidity of the catalyst is 3.2-4.2 mmol / g based on 100% by weight; more preferably,

[0012] The catalyst contains 13%-18% lanthanum by weight, and the surface acidity of the catalyst is 3.5-4 mmol / g, calculated as 100% by weight.

[0013] In this invention, by using the aforementioned preferred lanthanum 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 methyl methacrylate.

[0014] According to the present invention, preferably, the catalyst has a specific surface area of ​​170-420 m². 2 / g, and / or, pore volume of 0.7-1.6cm³ 3 / g, and / or, with an average pore size of 6-11nm;

[0015] More preferably, the catalyst has a specific surface area of ​​220-370 m². 2 / g, and / or, pore volume of 0.8-1.4cm³ 3 / g, and / or, with an average pore size of 7-10 nm. Under these conditions, the diffusion of feedstock and product molecules during the reaction is more favorable, which can effectively improve the activity and selectivity of the esterification catalyst.

[0016] In this invention, by using the specific surface area and / or pore volume and / or average pore size of the aforementioned preferred catalyst, the prepared catalyst can exhibit better catalytic activity, ester selectivity and catalyst stability when used in the synthesis reaction of methyl methacrylate.

[0017] A second aspect of the present invention provides a method for preparing the catalyst described above, comprising:

[0018] 1) The macroporous mesoporous molecular sieve was reacted with concentrated sulfuric acid under pressure. The resulting solid product was washed and dried to obtain the modified macroporous mesoporous molecular sieve.

[0019] 2) A methanol solution containing lanthanum chloride was reacted with a modified macroporous mesoporous molecular sieve. The resulting solid product was washed and dried to obtain the catalyst.

[0020] According to the present invention, preferably, the specific surface area of ​​the macroporous mesoporous molecular sieve (macroporous mesoporous molecular sieve raw powder) is 300-500 m². 2 / g, and / or, pore volume of 1.2-2.0ml / g, and / or, pore size of 11-16nm;

[0021] More preferably, the specific surface area of ​​the macroporous mesoporous molecular sieve is 350-450 m². 2 / g, and / or, pore volume of 1.4-1.8 ml / g, and / or, pore size of 12-14 nm.

[0022] According to the present invention, macroporous mesoporous molecular sieves (macroporous mesoporous molecular sieve raw powder) can be obtained commercially, and preferably, are prepared by the following method. According to the present invention, preferably, the method for preparing the catalyst further includes the step of preparing macroporous mesoporous molecular sieves by the following method:

[0023] In the presence of a template agent and water, a silicon source, an acid agent, ammonium fluoride, and heptane are mixed and contacted. The resulting mixture is then subjected to crystallization, filtration, washing, drying, and template removal treatment to obtain a macroporous mesoporous molecular sieve.

[0024] According to the present invention, in the above-described steps for preparing macroporous and mesoporous molecular sieves, more preferably:

[0025] The silicon source is selected from at least one of tetraethyl orthosilicate, methyl orthosilicate, propyl orthosilicate, sodium orthosilicate and silica sol, preferably tetraethyl orthosilicate;

[0026] And / or, the acid agent may be a substance conventional in the art that can provide acidic conditions, such as at least one of hydrochloric acid and sulfuric acid, preferably hydrochloric acid.

[0027] And / or, the heptane refers to a straight-chain or branched alkane with 7 carbon atoms, preferably n-heptane;

[0028] And / or, the template agent is a triblock copolymer of polyethylene oxide-polypropylene oxide-ethylene oxide (EO). 20 PO 70 EO 20 This template agent is commercially available (e.g., it can be purchased from Aldrich under the trade name P123, with the molecular formula EO). 20 PO 70 EO 20 It can also be prepared using various existing methods.

[0029] According to the present invention, in the method for preparing macroporous and mesoporous molecular sieves, the molar ratio of the template agent, the ammonium fluoride, the acid agent, the heptane, the silicon source and distilled water is 1:(0.5-6):(150-800):(300-1500):(30-300):(5000-20000); further, the molar ratio of the template agent, the ammonium fluoride, the acid agent, the heptane, the silicon source and distilled water is 1:(1-3):(200-500):(400-1000):(50-200):(7000-15000).

[0030] According to the present invention, in the method for preparing macroporous and mesoporous molecular sieves, the mixing contact conditions include a temperature of 20-60°C; more preferably, the mixing contact conditions include stirring for 0.2-6 hours at a temperature of 20-60°C, followed by standing for 1-48 hours. To further facilitate uniform mixing of the substances, according to a preferred embodiment of the present invention, the mixing contact is carried out under stirring conditions. Preferably, the mixing contact method includes stirring for 0.5-2 hours at a temperature of 30-50°C, followed by standing for 4-24 hours.

[0031] According to the present invention, the crystallization conditions for preparing macroporous and mesoporous molecular sieves include: a temperature of 90-120°C and / or a time of 10-40 h; preferably, the crystallization temperature is 95-105°C and the crystallization time is 20-36 h.

[0032] According to the present invention, in the method for preparing macroporous and mesoporous molecular sieves, the conditions for the stripping agent treatment include: a temperature of 400-600℃ and / or a time of 8-50 h; preferably, calcination at 400-600℃ for 8-50 h in a static air atmosphere. More preferably, the conditions for the stripping agent treatment include: a temperature of 450-550℃ and a time of 16-30 h.

[0033] According to the present invention, the method for preparing macroporous and mesoporous molecular sieves does not have special requirements for the filtration method, and can be a filtration method known in the art, including gravity filtration, pressure filtration, vacuum filtration, or centrifugal filtration. Preferably, the filtration process specifically includes: using a vacuum flask to create a vacuum at the bottom of a funnel or using a centrifugal filter.

[0034] According to the present invention, the washing conditions for preparing macroporous and mesoporous molecular sieves are not particularly limited. For example, the washing process may include: after filtration, obtaining a solid product, repeatedly washing the solid product with distilled water (the number of washing times may be 2-10), and then performing vacuum filtration.

[0035] According to the present invention, in the method for preparing macroporous and mesoporous molecular sieves, the drying process can be carried out in a drying oven, and the drying conditions may include: a temperature of 70-150°C and a time of 2-30 hours; preferably, the drying conditions include: a temperature of 90-130°C and a time of 6-20 hours.

[0036] According to the present invention, in the catalyst preparation method, preferably, the modified macroporous mesoporous molecular sieve obtained in step 1) has a specific surface area of ​​200-450 m². 2 / g, and / or, pore volume of 0.8-1.7cm³ 3 / g, and / or, with an average pore size of 7-12 nm; more preferably,

[0037] The modified macroporous and mesoporous molecular sieve has a specific surface area of ​​250-400 m². 2 / g, and / or, pore volume of 1.0-1.5cm³ 3 / g, and / or, with an average pore size of 8-11 nm. In this invention, the use of modified macroporous and mesoporous molecular sieves with the aforementioned preferred parameters enables the prepared esterification catalyst to exhibit better catalytic activity and higher selectivity when used in the synthesis reaction of methyl methacrylate.

[0038] According to the present invention, the catalyst preparation method involves reacting a macroporous mesoporous molecular sieve with concentrated sulfuric acid under pressure, and then washing and drying the resulting solid product to obtain a modified macroporous mesoporous molecular sieve.

[0039] Preferably, in step 1) (i.e., in the preparation step of modified macroporous mesoporous molecular sieve):

[0040] The weight ratio of the macroporous mesoporous molecular sieve to the concentrated sulfuric acid is 1:(0.2-10), preferably 1:(0.5-5); more preferably, the weight ratio of the macroporous mesoporous molecular sieve to the concentrated sulfuric acid is 1:(1-3).

[0041] Preferably, the contact conditions in step 1) include: a temperature of 80-180°C, more preferably 100-150°C; and a time of 4-30 hours, more preferably 8-20 hours.

[0042] Preferably, the pressurization conditions in step 1) include: a pressure of 0.2-10 MPa, preferably 0.5-5 MPa.

[0043] According to the present invention, preferably, the contact between the macroporous mesoporous molecular sieve and concentrated sulfuric acid is carried out in an autoclave. Rapid stirring can be performed during the contact process to improve contact efficiency and uniformity. In this invention, the conditions for rapid stirring are not specifically limited; preferably, it is carried out at a stirring rate of 200-800 rpm.

[0044] According to the present invention, the preparation method of the modified macroporous mesoporous molecular sieve includes the following washing conditions: the washing medium is preferably distilled water; the temperature of the washing medium can be 60-100℃, preferably 80-95℃; the weight ratio of distilled water to solid product can be 5-30, preferably 10-20; and the number of washing cycles can be 3-12, preferably 5-10.

[0045] According to the present invention, the drying conditions in the preparation method of the modified macroporous mesoporous molecular sieve include: a temperature of 60-120°C, preferably 80-100°C; and a time of 3-16 hours, preferably 5-12 hours.

[0046] According to the present invention, preferably, lanthanum chloride is dissolved in methanol to obtain an alcoholic solution, which is then reacted with a modified macroporous mesoporous molecular sieve. After the reaction, the product is filtered to obtain a solid product, which is then washed and dried sequentially to obtain the modified macroporous mesoporous molecular sieve catalyst.

[0047] In the method for preparing the catalyst according to the present invention, step 2) preferably includes:

[0048] The methanol solution contains lanthanum chloride at a mass concentration of 1%-5%, preferably 2%-3.5%; and / or,

[0049] The weight ratio of the modified macroporous / mesoporous molecular sieve to the methanol solution is 1:(5-50), preferably 1:(10-30); and / or,

[0050] The conditions for the contact reaction between the modified macroporous mesoporous molecular sieve and the methanol solution include: a temperature of 30-80℃ and / or a time of 2-8 hours. Preferably, to achieve a better contact reaction effect, rapid stirring can be performed during the contact reaction between the modified macroporous mesoporous molecular sieve and the alcohol solution to improve the reaction efficiency.

[0051] 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.

[0052] 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.

[0053] 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.

[0054] A third aspect of the present invention is to provide the application of the catalyst described above or the catalyst obtained by the preparation method described above in the synthesis reaction of methyl methacrylate, wherein the application of the catalyst includes: simultaneously contacting the catalyst with methacrylic acid and methanol.

[0055] According to the present invention, preferably, the contact conditions between the methacrylic acid and methanol and the catalyst include:

[0056] The contact temperature is 40-150℃, preferably 60-120℃; and / or, the contact pressure is 0.01-5.0 MPa, preferably 0.1-3.0 MPa; and / or, the mass hourly space velocity of methacrylic acid is 0.01-30 h⁻¹. -1 Preferably 0.1-10h -1 ; and / or, the mass hourly space velocity (MSV) of methanol is 0.01-50 h⁻¹. -1 Preferably 0.1-30h -1 .

[0057] Compared with the prior art, the technical solution of the present invention has the following advantages through the above technical solution:

[0058] (1) The modified macroporous and mesoporous molecular sieve 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.

[0059] (2) The modified macroporous and mesoporous molecular sieve 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.

[0060] (3) The modified macroporous and mesoporous molecular sieve catalyst provided by this invention provides mild process conditions and low requirements for reaction equipment when used in the synthesis of methyl methacrylate. It also features high conversion rate of methacrylic acid, high ester selectivity, and good catalyst stability. Attached Figure Description

[0061] The accompanying drawings are provided to further illustrate the invention and form part of the specification. They are used together with the following detailed description to explain the invention, but do not constitute a limitation thereof. In the drawings:

[0062] Figure 1 These are the small-angle X-ray diffraction (XRD) spectra of the ultra-large-pore mesoporous molecular sieve A and the modified macroporous mesoporous molecular sieve catalyst A prepared in the examples; wherein,

[0063] Figure 1 (a) is the small-angle X-ray diffraction (XRD) pattern of the ultra-large pore mesoporous molecular sieve A prepared in Example 1;

[0064] Figure 1 (b) is the small-angle X-ray diffraction (XRD) pattern of the modified macroporous mesoporous molecular sieve catalyst A prepared in Example 1. Detailed Implementation

[0065] The present invention will now be described in detail with reference to specific embodiments. It should be noted that the following embodiments are only used to further illustrate the present invention and should not be construed as limiting the scope of protection of the present invention. Some non-essential improvements and adjustments made by those skilled in the art based on the content of the present invention are still within the scope of protection of the present invention.

[0066] The present invention will be described in detail below through embodiments.

[0067] In the following examples and comparative examples:

[0068] Small-angle XRD tests of the samples were performed on a BRUKER AXS D8 ADVANCE high-power rotating target X-ray diffractometer, with a scanning range of 0.5-10°.

[0069] 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.

[0070] Elemental analysis of the samples was performed using an Eagle III energy-dispersive X-ray fluorescence spectrometer manufactured by EDAX Corporation, USA. In the following examples and comparative examples, the lanthanum content in the catalyst refers to the weight content based on lanthanum elemental content, with the weight of the catalyst being 100%.

[0071] The acidity on the catalyst surface was determined by neutralization titration.

[0072] The drying oven was manufactured by Shanghai Yiheng Scientific Instruments Co., Ltd., model DHG-9030A.

[0073] The muffle furnace is manufactured by CARBOLITE, model CWF1100.

[0074] 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.

[0075] In the following examples and comparative examples, the conversion rate of methacrylic acid (MAA) was calculated as follows:

[0076] MAA conversion rate = (moles of MAA before reaction - moles of MAA remaining after reaction) / moles of MAA in feed * 100%

[0077] The method for calculating the selectivity of methyl methacrylate (MMA) is as follows:

[0078] MMA selectivity = (Number of moles of MMA generated / Number of moles of MAA consumed) * 100%.

[0079] Example 1

[0080] (1) Preparation of ultra-large pore mesoporous molecular sieves

[0081] 0.02 mol of template agent P123 and 0.035 mol of ammonium fluoride were added to 3.8 L of a 1.75 mol / L hydrochloric acid solution, and stirred at 40 °C until P123 and ammonium fluoride were completely dissolved. Then, 15 mol of n-heptane and 2.4 mol of tetraethyl orthosilicate were added to the above solution, and the mixture was stirred vigorously at 40 °C for 1 hour and then allowed to stand for 16 hours. The resulting solution was transferred to a polytetrafluoroethylene-lined reactor and crystallized at 100 °C for 24 hours. The resulting solid was washed eight times with distilled water, dried at 110 °C for 12 hours, and then calcined at 500 °C for 24 hours to remove the template agent, yielding ultraporous mesoporous molecular sieve A.

[0082] The specific surface area of ​​the ultra-large pore mesoporous molecular sieve A is 392 m². 2 / g, pore volume 1.6cm³ 3 / g, average pore size 13nm.

[0083] Figure 1 (a) is the small-angle XRD pattern of the mesoporous molecular sieve A. The pattern shows three clearly visible diffraction peaks at small angles below 2°, proving that the mesoporous material in the catalyst has a typical two-dimensional hexagonal phase mesoporous channel structure.

[0084] (2) Preparation of modified ultraporous mesoporous molecular sieves

[0085] 5g of macroporous molecular sieve A and 12g of concentrated sulfuric acid were mixed and transferred to a 100ml autoclave. The mixture was heated to 120℃, and high-purity nitrogen was introduced into the autoclave to maintain a pressure of 3MPa. The mixture was stirred for 15 hours at a stirring rate of 600 rpm. After cooling and depressurization, the solid product was removed and washed eight times with 95℃ distilled water. The product was then dried in air at 90℃ for 10 hours to obtain modified macroporous molecular sieve A.

[0086] The specific surface area of ​​modified ultra-large pore mesoporous molecular sieve A is 327 m². 2 / g, pore volume 1.3cm³ 3 / g, with an average pore size of 10nm.

[0087] (3) Preparation of modified macroporous and mesoporous molecular sieve catalysts

[0088] 5.6 g of lanthanum chloride was dissolved in 200 g of methanol to prepare a methanol solution. 10 g of modified macroporous 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 modified macroporous mesoporous molecular sieve catalyst A.

[0089] The specific surface area of ​​modified macroporous and mesoporous molecular sieve catalyst A is 288 m². 2 / g, pore volume 1.1cm³ 3 / g, with an average pore size of 9nm, a lanthanum content of 16% by weight in the catalyst, and a surface acidity of 3.7mmol / g.

[0090] Figure 1 Image (b) is the small-angle XRD pattern of modified macroporous / mesoporous molecular sieve catalyst A. (Compared to...) Figure 1 Similar to (a), three clearly visible diffraction peaks appear in the spectrum. This indicates that the ultra-large pore mesoporous molecular sieve still retains a relatively regular mesoporous channel structure after being prepared into an esterification catalyst, and the basic structure of the mesoporous molecular sieve was not destroyed during the catalyst preparation process.

[0091] (4) Evaluation of catalyst reaction performance

[0092] The performance of the catalyst in the methacrylilation reaction was evaluated in a fixed-bed reactor. 10 g of modified macroporous mesoporous molecular sieve 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. -1After 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.

[0093] Example 2

[0094] (1) Preparation of ultra-large pore mesoporous molecular sieves

[0095] 0.02 mol of template agent P123 and 0.06 mol of ammonium fluoride were added to 5.7 L of a 1.75 mol / L hydrochloric acid solution, and stirred at 50 °C until P123 and ammonium fluoride were completely dissolved. Then, 20 mol of n-heptane and 4.0 mol of tetraethyl orthosilicate were added to the above solution, and the mixture was stirred vigorously at 50 °C for 0.5 hours, then allowed to stand for 24 hours. The resulting solution was transferred to a polytetrafluoroethylene-lined reactor and crystallized at 105 °C for 20 hours. The resulting solid was washed 10 times with distilled water, dried at 130 °C for 6 hours, and then calcined at 550 °C for 16 hours to remove the template agent, yielding ultraporous mesoporous molecular sieve B.

[0096] The specific surface area of ​​the ultra-large pore mesoporous molecular sieve B is 350 m². 2 / g, pore volume 1.4cm³ 3 / g, average pore size 12nm.

[0097] (2) Preparation of modified ultraporous mesoporous molecular sieves

[0098] 5g of macroporous molecular sieve B and 5g of concentrated sulfuric acid were mixed and transferred to a 100ml autoclave. The mixture was heated to 150℃, and high-purity nitrogen was introduced into the autoclave to maintain a pressure of 5MPa. The mixture was stirred for 20 hours at a stirring rate of 400 rpm. After cooling and depressurization, the solid product was removed and washed five times with 95℃ distilled water. The product was then dried in air at 80℃ for 12 hours to obtain modified macroporous molecular sieve B.

[0099] The modified ultra-large pore mesoporous molecular sieve B has a specific surface area of ​​250 m². 2 / g, pore volume 1.0cm³ 3 / g, with an average pore size of 8nm.

[0100] (3) Preparation of modified macroporous and mesoporous molecular sieve catalysts

[0101] 4.8 g of lanthanum chloride was dissolved in 150 g of methanol to prepare a methanol solution. 10 g of modified macroporous mesoporous molecular sieve B was added, and the mixture was stirred at 60 °C for 3 h. The reaction was then filtered to obtain a solid product. The solid product was washed three times with 300 ml of anhydrous methanol and dried at 90 °C for 10 h to obtain the modified macroporous mesoporous molecular sieve catalyst B.

[0102] The modified macroporous and mesoporous molecular sieve catalyst B has a specific surface area of ​​220 m². 2 / g, pore volume 0.8cm³ 3 / g, with an average pore size of 7nm, a lanthanum content of 13% by weight in the catalyst, and a surface acidity of 3.5mmol / g.

[0103] (4) Evaluation of catalyst reaction performance

[0104] The esterification performance of catalyst B was tested according to step (4) in Example 1. The experimental results are listed in Table 1.

[0105] Example 3

[0106] (1) Preparation of ultra-large pore mesoporous molecular sieves

[0107] 0.02 mol of template agent P123 and 0.02 mol of ammonium fluoride were added to 2.5 L of a 1.6 mol / L hydrochloric acid solution, and stirred at 30 °C until P123 and ammonium fluoride were completely dissolved. Then, 8 mol of n-heptane and 1.0 mol of tetraethyl orthosilicate were added to the above solution, and the mixture was stirred vigorously at 30 °C for 2 hours and then allowed to stand for 4 hours. The resulting solution was transferred to a polytetrafluoroethylene-lined reactor and crystallized at 95 °C for 36 hours. The resulting solid was washed six times with distilled water, dried at 90 °C for 20 hours, and then calcined at 450 °C for 30 hours to remove the template agent, yielding ultraporous mesoporous molecular sieve C.

[0108] The specific surface area of ​​the ultra-large pore mesoporous molecular sieve C is 450 m². 2 / g, pore volume 1.8cm³ 3 / g, average pore size 14nm.

[0109] (2) Preparation of modified ultraporous mesoporous molecular sieves

[0110] 5g of macroporous molecular sieve C and 15g of concentrated sulfuric acid were mixed and transferred to a 100ml autoclave. The mixture was heated to 100℃, and high-purity nitrogen was introduced into the autoclave while maintaining a pressure of 1MPa. The mixture was stirred for 8 hours at a stirring rate of 800 rpm. After cooling and depressurization, the solid product was removed and washed 10 times with distilled water at 80℃. The product was then dried in air at 100℃ for 5 hours to obtain modified macroporous molecular sieve C.

[0111] The specific surface area of ​​the modified ultra-large pore mesoporous molecular sieve C is 400 m². 2 / g, pore volume 1.5cm³ 3 / g, with an average pore size of 11nm.

[0112] (3) Preparation of modified macroporous and mesoporous molecular sieve catalysts

[0113] 6.2 g of lanthanum chloride was dissolved in 250 g of methanol to prepare a methanol solution. 10 g of modified macroporous 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 the modified macroporous mesoporous molecular sieve catalyst C.

[0114] The specific surface area of ​​the modified macroporous and mesoporous molecular sieve catalyst C is 304 m². 2 / g, pore volume 1.2cm³ 3 / g, with an average pore size of 8nm, a lanthanum content of 18% by weight in the catalyst, and a surface acidity of 4.0mmol / g.

[0115] (4) Evaluation of catalyst reaction performance

[0116] The esterification performance of catalyst C was tested according to step (4) in Example 1. The experimental results are listed in Table 1.

[0117] Example 4

[0118] (1) Ultra-large pore mesoporous molecular sieve A was prepared according to the method in step (1) of Example 1.

[0119] (2) Preparation of modified ultraporous mesoporous molecular sieves

[0120] 5g of macroporous molecular sieve A and 2.5g of concentrated sulfuric acid were mixed and transferred to a 100ml autoclave. The mixture was heated to 150℃, and high-purity nitrogen was introduced into the autoclave while maintaining a pressure of 5MPa. The mixture was stirred for 20 hours at a stirring rate of 400 rpm. After cooling and depressurization, the solid product was removed and washed five times with 95℃ distilled water. The product was then dried in air at 80℃ for 12 hours to obtain modified macroporous molecular sieve D.

[0121] The specific surface area of ​​the modified ultra-large pore mesoporous molecular sieve D is 276 m². 2 / g, pore volume 1.2cm³ 3 / g, with an average pore size of 9nm.

[0122] (3) Preparation of modified macroporous and mesoporous molecular sieve catalysts

[0123] 7.0 g of lanthanum chloride was dissolved in 290 g of methanol to prepare a methanol solution. 10 g of modified macroporous 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 modified macroporous mesoporous molecular sieve catalyst D.

[0124] The modified macroporous and mesoporous molecular sieve catalyst D has a specific surface area of ​​225 m². 2 / g, pore volume 0.8cm³3 / g, with an average pore size of 7nm, a lanthanum content of 20% by weight in the catalyst, and a surface acidity of 4.2mmol / g.

[0125] (4) Evaluation of catalyst reaction performance

[0126] The esterification performance of catalyst D was tested according to step (4) in Example 1. The experimental results are listed in Table 1.

[0127] Example 5

[0128] (1) Ultra-large pore mesoporous molecular sieve C was prepared according to the method in step (1) of Example 3.

[0129] (2) Preparation of modified ultraporous mesoporous molecular sieves

[0130] 5g of macroporous molecular sieve C and 25g of concentrated sulfuric acid were mixed and transferred to a 100ml autoclave. The mixture was heated to 100℃, and high-purity nitrogen was introduced into the autoclave while maintaining a pressure of 0.5MPa. The mixture was stirred for 8 hours at a stirring rate of 800 rpm. After cooling and depressurization, the solid product was removed and washed 10 times with distilled water at 80℃. The product was then dried in air at 100℃ for 5 hours to obtain modified macroporous molecular sieve E.

[0131] The specific surface area of ​​the modified ultra-large pore mesoporous molecular sieve E is 382 m². 2 / g, pore volume 1.5cm³ 3 / g, with an average pore size of 10.5nm.

[0132] (3) Preparation of modified macroporous and mesoporous molecular sieve catalysts

[0133] 3.4 g of lanthanum chloride was dissolved in 100 g of methanol to prepare a methanol solution. 10 g of modified macroporous mesoporous molecular sieve E 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 modified macroporous mesoporous molecular sieve catalyst E.

[0134] The modified macroporous and mesoporous molecular sieve catalyst E has a specific surface area of ​​370 m². 2 / g, pore volume 1.4cm³ 3 / g, with an average pore size of 10nm, a lanthanum content of 10% by weight in the catalyst, and a surface acidity of 3.2mmol / g.

[0135] (4) Evaluation of catalyst reaction performance

[0136] The esterification performance of catalyst E was tested according to step (4) in Example 1. The experimental results are listed in Table 1.

[0137] Example 6

[0138] (1) Preparation of ultra-large pore mesoporous molecular sieves.

[0139] 0.02 mol of template agent P123 and 0.12 mol of ammonium fluoride were added to 7.3 L of a 2.2 mol / L hydrochloric acid solution, and stirred at 60 °C until P123 and ammonium fluoride were completely dissolved. Then, 30 mol of n-heptane and 6.0 mol of tetraethyl orthosilicate were added to the above solution, and the mixture was stirred vigorously at 60 °C for 0.2 hours and then allowed to stand for 48 hours. The resulting solution was transferred to a polytetrafluoroethylene-lined reactor and crystallized at 120 °C for 10 hours. The resulting solid was washed 10 times with distilled water, dried at 150 °C for 2 hours, and then calcined at 600 °C for 8 hours to remove the template agent, yielding ultraporous mesoporous molecular sieve D.

[0140] The specific surface area of ​​the ultra-large pore mesoporous molecular sieve D is 300 m². 2 / g, pore volume 1.2cm³ 3 / g, average pore size 11nm.

[0141] (2) Preparation of modified ultraporous mesoporous molecular sieves

[0142] 5g of macroporous molecular sieve D and 50g of concentrated sulfuric acid were mixed and transferred to a 100ml autoclave. The mixture was heated to 80℃, and high-purity nitrogen was introduced into the autoclave while maintaining a pressure of 0.2MPa. The mixture was stirred for 4 hours at a stirring rate of 700 rpm. After cooling and depressurization, the solid product was removed and washed 12 times with distilled water at 60℃. The product was then dried in air at 120℃ for 3 hours to obtain modified macroporous molecular sieve F.

[0143] The specific surface area of ​​the modified ultra-large pore mesoporous molecular sieve F is 200 m². 2 / g, pore volume 0.8cm³ 3 / g, with an average pore size of 7nm.

[0144] (3) Preparation of modified macroporous and mesoporous molecular sieve catalysts

[0145] 2.6 g of lanthanum chloride was dissolved in 50 g of methanol to prepare a methanol solution. 10 g of modified macroporous mesoporous molecular sieve F 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 modified macroporous mesoporous molecular sieve catalyst F.

[0146] The modified macroporous and mesoporous molecular sieve catalyst F has a specific surface area of ​​170 m². 2 / g, pore volume 0.7cm³ 3 / g, with an average pore size of 6nm, a lanthanum content of 8% by weight in the catalyst, and a surface acidity of 3.0mmol / g.

[0147] (4) Evaluation of catalyst reaction performance

[0148] The esterification performance of catalyst F was tested according to step (4) in Example 1. The experimental results are listed in Table 1.

[0149] Example 7

[0150] (1) Preparation of ultra-large pore mesoporous molecular sieves.

[0151] 0.02 mol of template agent P123 and 0.01 mol of ammonium fluoride were added to 1.8 L of a 1.67 mol / L hydrochloric acid solution, and stirred at 20 °C until P123 and ammonium fluoride were completely dissolved. Then, 6 mol of n-heptane and 0.6 mol of tetraethyl orthosilicate were added to the above solution, and the mixture was stirred vigorously at 20 °C for 6 hours and then allowed to stand for 1 hour. The resulting solution was transferred to a polytetrafluoroethylene-lined reactor and crystallized at 90 °C for 40 hours. The resulting solid was washed four times with distilled water, dried at 70 °C for 30 hours, and then calcined at 400 °C for 50 hours to remove the template agent, yielding ultraporous mesoporous molecular sieve E.

[0152] The specific surface area of ​​the ultra-large pore mesoporous molecular sieve E is 500 m². 2 / g, pore volume 2.0cm³ 3 / g, average pore size 16nm.

[0153] (2) Preparation of modified ultraporous mesoporous molecular sieves

[0154] 5g of macroporous molecular sieve E and 1g of concentrated sulfuric acid were mixed and transferred to a 100ml autoclave. The mixture was heated to 180℃, and high-purity nitrogen was introduced into the autoclave while maintaining a pressure of 10MPa. The mixture was stirred for 30 hours at a stirring rate of 300 rpm. After cooling and depressurization, the solid product was removed and washed six times with 90℃ distilled water. The product was then dried in air at 80℃ for 8 hours to obtain modified macroporous molecular sieve G.

[0155] The modified ultra-large pore mesoporous molecular sieve G has a specific surface area of ​​450 m². 2 / g, pore volume 1.7cm³ 3 / g, with an average pore size of 12nm.

[0156] (3) Preparation of modified macroporous and mesoporous molecular sieve catalysts

[0157] 7.8 g of lanthanum chloride was dissolved in 490 g of methanol to prepare a methanol solution. 10 g of modified macroporous 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 the modified macroporous mesoporous molecular sieve catalyst G.

[0158] The modified macroporous and mesoporous molecular sieve catalyst G has a specific surface area of ​​420 m². 2 / g, pore volume 1.6cm³ 3 / g, with an average pore size of 11nm, a lanthanum content of 22% by weight in the catalyst, and a surface acidity of 4.5mmol / g.

[0159] (4) Evaluation of catalyst reaction performance

[0160] The esterification performance of catalyst G was tested according to step (4) in Example 1. The experimental results are listed in Table 1.

[0161] Comparative Example 1

[0162] Ultra-large pore mesoporous molecular sieve A was prepared according to step (1) in Example 1.

[0163] Modified mesoporous molecular sieve A was prepared according to step (2) in Example 1.

[0164] Step (3) was omitted, and the modified macroporous molecular sieve A was used as catalyst D1. Its esterification reaction performance was tested according to the method in step (4) of Example 1. The experimental results are listed in Table 1.

[0165] Comparative Example 2

[0166] Ultra-large pore mesoporous molecular sieve A was prepared according to step (1) in Example 1.

[0167] Step (2) was omitted, and the modified macroporous mesoporous molecular sieve catalyst D2 was prepared according to the method in step (3) of Example 1. The specific process is as follows: 5.6 g of lanthanum chloride was dissolved in 200 g of methanol to prepare a methanol solution, and 10 g of ultra-macroporous 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 the modified macroporous mesoporous molecular sieve catalyst D2.

[0168] The modified macroporous and mesoporous molecular sieve catalyst D2 has a specific surface area of ​​307 m². 2 / g, pore volume 1.3cm³ 3 / g, average pore size 11nm, lanthanum content in the catalyst is 11% by weight, and surface acidity is 1.0mmol / g.

[0169] The performance of the modified macroporous mesoporous molecular sieve catalyst for D2 esterification reaction was tested according to step (4) in Example 1. The experimental results are listed in Table 1.

[0170] Comparative Example 3

[0171] Step (1) in Example 1 is cancelled, and the ultra-large pore 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 ultra-large pore mesoporous molecular sieve A in step (3) of Example 1 with modified commercially available silica to obtain catalyst D3.

[0172] The modified macroporous and mesoporous molecular sieve catalyst D3 has a specific surface area of ​​56 m². 2 / g; average pore size is 7nm, pore volume is 0.1cm³. 3 / g, the catalyst contains 7% lanthanum by weight and has a surface acidity of 1.4 mmol / g.

[0173] The esterification reaction performance of the modified macroporous mesoporous molecular sieve catalyst D3 was tested according to the method in step (4) of Example 1. The experimental results are listed in Table 1.

[0174] Comparative Example 4

[0175] (1) Ultra-large pore mesoporous molecular sieve C was prepared according to the method in step (1) of Example 3.

[0176] (2) Preparation of modified ultraporous mesoporous molecular sieves

[0177] 5g of macroporous molecular sieve C and 0.2g of concentrated sulfuric acid were mixed and transferred to a 100ml autoclave. The mixture was heated to 180℃, and high-purity nitrogen was introduced into the autoclave while maintaining a pressure of 10MPa. The mixture was stirred for 30 hours at a stirring rate of 100 rpm. After cooling and depressurization, the solid product was removed and washed six times with distilled water at 90℃. The product was then dried in air at 80℃ for 8 hours to obtain modified macroporous molecular sieve D4.

[0178] The specific surface area of ​​the modified ultra-large pore mesoporous molecular sieve D4 is 431 m². 2 / g, pore volume 1.7cm³ 3 / g, with an average pore size of 13nm.

[0179] (3) Preparation of modified macroporous and mesoporous molecular sieve catalysts

[0180] 1.5 g of lanthanum chloride was dissolved in 200 g of methanol to prepare a methanol solution. 10 g of modified macroporous mesoporous molecular sieve D4 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 modified macroporous mesoporous molecular sieve catalyst D4.

[0181] The modified macroporous and mesoporous molecular sieve catalyst D4 has a specific surface area of ​​417 m². 2 / g, pore volume 1.7cm³ 3 / g, with an average pore size of 12nm, a lanthanum content of 5% by weight in the catalyst, and a surface acidity of 1.2mmol / g.

[0182] (4) Evaluation of catalyst reaction performance

[0183] The esterification performance of catalyst D4 was tested according to step (4) in Example 1. The experimental results are listed in Table 1.

[0184] Comparative Example 5

[0185] (1) Ultra-large pore mesoporous molecular sieve B was prepared according to the method in step (1) of Example 2.

[0186] (2) Preparation of modified ultraporous mesoporous molecular sieves

[0187] 5g of macroporous molecular sieve B and 85g of concentrated sulfuric acid were mixed and transferred to a 100ml autoclave. The mixture was heated to 80℃, and high-purity nitrogen was introduced into the autoclave while maintaining a pressure of 0.2MPa. The mixture was stirred for 4 hours at a stirring rate of 900 rpm. After cooling and depressurization, the solid product was removed and washed 12 times with distilled water at 60℃. The product was then dried in air at 120℃ for 3 hours to obtain modified macroporous molecular sieve D5.

[0188] The specific surface area of ​​the modified ultra-large pore mesoporous molecular sieve D5 is 184 m². 2 / g, pore volume 0.7cm³ 3 / g, average pore size 6nm.

[0189] (3) Preparation of modified macroporous and mesoporous molecular sieve catalysts

[0190] 9.8 g of lanthanum chloride was dissolved in 600 g of methanol to prepare a methanol solution. 10 g of modified macroporous mesoporous molecular sieve D5 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 modified macroporous mesoporous molecular sieve catalyst D5.

[0191] The modified macroporous and mesoporous molecular sieve catalyst D5 has a specific surface area of ​​152 m². 2 / g, pore volume 0.6cm³ 3 / g, with an average pore size of 5nm, a lanthanum content of 27% by weight in the catalyst, and a surface acidity of 4.9mmol / g.

[0192] (4) Evaluation of catalyst reaction performance

[0193] The esterification performance of catalyst D5 was tested according to step (4) in Example 1. The experimental results are listed in Table 1.

[0194] Table 1

[0195]

[0196]

[0197] The results above show that the modified macroporous and mesoporous molecular sieve catalyst provided by the present invention can directly convert methacrylic acid and methanol into methyl methacrylate, resulting in a high conversion rate of methacrylic acid and a high selectivity for methyl methacrylate. After 50 hours of operation, the conversion rate of methacrylic acid and the selectivity for methyl methacrylate remain stable compared with those after 6 hours of operation, indicating that the catalyst of the present invention maintains good catalyst stability.

[0198] In Comparative Example 1, the lanthanum chloride modification step was omitted. The sulfonic acid groups on the surface of the prepared catalyst were more easily detached during the long reaction process, resulting in insufficient active sites on the catalyst in the later stages of the reaction. Therefore, this catalyst exhibited high conversion rates of methacrylic acid and high selectivity for methyl methacrylate in the initial stage of the reaction, but its catalyst stability was poor.

[0199] In Comparative Example 2, the acidification step was omitted, resulting in a lack of sulfonic acid groups on the catalyst surface. Consequently, the subsequently supported lanthanum could not form stable complexed active centers with these groups, leading to a lower acid content on the catalyst surface. This resulted in insufficient active sites for the same weight of catalyst during the reaction, and the active component readily dissolved in the reaction system. Therefore, this catalyst exhibited low methacrylic acid conversion, low selectivity for methyl methacrylate, and poor catalyst stability.

[0200] In Comparative Example 3, the ultra-large pore mesoporous molecular sieve used in this invention was not employed; instead, commercially available silica was used. Because the pore structure of commercially available silica differs significantly from that of the ultra-large pore mesoporous molecular sieve, it has a smaller specific surface area, smaller pore volume, and uneven pore size. The acidic groups are unevenly dispersed on the surface of the commercially available silica, resulting in insufficient lanthanum content and surface acidity in the catalyst. Consequently, the conversion rate of methacrylic acid is low, the selectivity for methyl methacrylate is low, and the catalyst stability is poor.

[0201] In Comparative Example 4, the lanthanum content and surface acidity in the catalyst were both outside the scope of this invention, and the content was insufficient. The content of active groups on the catalyst was too low, resulting in low conversion of methacrylic acid and low selectivity of methyl methacrylate.

[0202] In Comparative Example 5, the lanthanum content and surface acidity in the catalyst were both outside the range of this invention, being excessively high. This resulted in an excessively high content of active groups on the catalyst, uneven dispersion on the support, and severe blockage of mesoporous channels, affecting product diffusion during the reaction. Consequently, the conversion rate of methacrylic acid was low, and the selectivity of methyl methacrylate was also low.

[0203] A comparison of Examples 1-3 and Examples 4-7 of the present invention shows that, under the preferred conditions of lanthanum content and surface acidity of the catalyst, the obtained catalyst exhibits higher methacrylic acid conversion and methyl methacrylate selectivity, as well as higher catalyst stability. Under the preferred conditions of lanthanum content and surface acidity of the catalyst, if the catalyst has a better average pore size, pore volume, or a preferred specific surface area, the obtained catalyst exhibits even higher methacrylic acid conversion and methyl methacrylate selectivity, and the catalyst stability will also be further improved.

[0204] The preferred embodiments of the present invention have been described in detail above; however, the present invention is not limited thereto. Within the scope of the inventive concept, various simple modifications can be made to the technical solutions of the present invention, including combinations of various technical features in any other suitable manner. These simple modifications and combinations should also be considered as the content disclosed in the present invention and are all within the protection scope of the present invention.

[0205] It should be noted that the embodiments described above are only for explaining the present invention and do not constitute any limitation on the present invention. The present invention has been described with reference to typical embodiments, but it should be understood that the words used therein are descriptive and explanatory terms, not limiting terms. Modifications can be made to the present invention within the scope of the claims, and revisions can be made to the present invention without departing from the scope and spirit of the present invention. Although the present invention described herein relates to specific methods, materials, and embodiments, it does not mean that the present invention is limited to the specific examples disclosed herein; on the contrary, the present invention can be extended to all other methods and applications with the same function.

[0206] All publications, patent applications, patents, and other references mentioned in this specification are incorporated herein by reference. Unless otherwise defined, all technical and scientific terms used in this specification have the meanings commonly understood by those skilled in the art. In case of conflict, the definitions in this specification shall prevail.

[0207] When this specification uses the prefixes “known to those skilled in the art,” “prior art,” or similar terms to derive materials, substances, methods, steps, apparatus, or components, the objects derived from such prefixes cover those commonly used in the art at the time of this application, but also include those that are not currently commonly used but will become generally recognized in the art as suitable for similar purposes.

[0208] The endpoints and any values ​​of the ranges disclosed in this application are not limited to the precise ranges or values; such ranges or values ​​should be understood to include values ​​close to them. 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. In principle, various technical solutions can be combined with each other to obtain new technical solutions, which should also be considered as specifically disclosed herein.

[0209] In the context of this specification, except where expressly stated otherwise, any matters or issues not mentioned shall apply directly to those known in the art without any modification.

[0210] Furthermore, any implementation described herein can be freely combined with one or more other implementations described herein, and the resulting technical solutions or technical ideas shall be regarded as part of the original disclosure or original record of the present invention, and should not be regarded as new content not disclosed or anticipated herein, unless those skilled in the art consider the combination to be obviously unreasonable.

Claims

1. A modified macroporous mesoporous molecular sieve catalyst, the catalyst comprising a support and lanthanum chloride supported on the support, said support being a modified macroporous mesoporous molecular sieve; The catalyst contains 8%-22% lanthanum by weight, based on 100% of the catalyst's weight; the surface acidity of the catalyst is 3-4.5 mmol / g.

2. The catalyst according to claim 1, characterized in that: The catalyst contains 10%-20% lanthanum by weight, and based on 100% of the catalyst's weight, the surface acidity of the catalyst is 3.2-4.2 mmol / g; preferably, The catalyst contains 13%-18% lanthanum by weight, and the surface acidity of the catalyst is 3.5-4 mmol / g, calculated as 100% by weight.

3. The catalyst according to claim 1 or 2, characterized in that: The catalyst has a specific surface area of ​​170-420 m². 2 / g, and / or, pore volume of 0.7-1.6cm³ 3 / g, and / or, with an average pore size of 6-11nm; Preferably, the catalyst has a specific surface area of ​​220-370 m². 2 / g, and / or, pore volume of 0.8-1.4cm³ 3 / g, and / or, with an average pore size of 7-10nm.

4. A method for preparing a catalyst according to any one of claims 1-3, comprising: 1) The macroporous mesoporous molecular sieve was reacted with concentrated sulfuric acid under pressure. The resulting solid product was washed and dried to obtain the modified macroporous mesoporous molecular sieve. 2) A methanol solution containing lanthanum chloride was reacted with a modified macroporous mesoporous molecular sieve. The resulting solid product was washed and dried to obtain the catalyst.

5. The preparation method according to claim 4, characterized in that: The specific surface area of ​​the macroporous mesoporous molecular sieve is 300-500 m². 2 / g, and / or, pore volume of 1.2-2.0ml / g, and / or, pore size of 11-16nm; Preferably, the specific surface area of ​​the macroporous mesoporous molecular sieve is 350-450 m². 2 / g, and / or, pore volume of 1.4-1.8 ml / g, and / or, pore size of 12-14 nm.

6. The preparation method according to claim 5, characterized in that, It also includes the step of preparing macroporous mesoporous molecular sieves using the following methods: In the presence of a template agent and water, a silicon source, an acid agent, ammonium fluoride, and heptane are mixed and contacted. The resulting mixture is then subjected to crystallization, filtration, washing, drying, and template agent removal treatment to obtain a macroporous mesoporous molecular sieve; preferably: The silicon source is selected from at least one of tetraethyl orthosilicate, methyl orthosilicate, propyl orthosilicate, sodium orthosilicate and silica sol, preferably tetraethyl orthosilicate; And / or, the acid is selected from at least one of hydrochloric acid and sulfuric acid; And / or, the template agent is a triblock copolymer of polyethylene oxide-polypropylene oxide-polyethylene oxide; And / or, the molar ratio of the template agent, the ammonium fluoride, the acid agent, the heptane, the silicon source and distilled water is 1:(0.5-6):(150-800):(300-1500):(30-300):(5000-20000); And / or, the conditions for the mixed contact include: a temperature of 20-60°C; And / or, the crystallization conditions include: a temperature of 90-120°C, and / or a time of 10-40 h; And / or, the conditions for the template release agent treatment include: a temperature of 400-600°C, and / or a time of 8-50 hours.

7. The preparation method according to claim 4, characterized in that: The modified macroporous mesoporous molecular sieve obtained in step 1) has a specific surface area of ​​200-450 m². 2 / g, and / or, pore volume of 0.8-1.7cm³ 3 / g, and / or, with an average pore size of 7-12nm; preferably, The modified macroporous and mesoporous molecular sieve has a specific surface area of ​​250-400 m². 2 / g, and / or, pore volume of 1.0-1.5cm³ 3 / g, and / or, with an average pore size of 8-11nm.

8. The preparation method according to claim 4, characterized in that: In step 1): The weight ratio of the macroporous mesoporous molecular sieve to the concentrated sulfuric acid is 1:(0.2-10), preferably 1:(0.5-5); and / or, The contact conditions include: a temperature of 80-180°C, and / or a time of 4-30 hours; and / or, The pressurization conditions include a pressure of 0.2-10 MPa, preferably 0.5-5 MPa.

9. The preparation method according to claim 4, characterized in that: In step 2): The methanol solution contains lanthanum chloride at a mass concentration of 1%-5%; and / or, The weight ratio of the modified macroporous / mesoporous molecular sieve to the methanol solution is 1:(5-50); and / or, The contact reaction conditions include: a temperature of 30-80℃, and / or a time of 2-8 hours; and / or, The drying conditions include a temperature of 80-150°C and / or a time of 1-20 hours.

10. The use of a catalyst according to any one of claims 1-3 or a catalyst obtained by the preparation method according to any one of claims 4-9 in the synthesis reaction of methyl methacrylate, wherein, The application of the catalyst includes: simultaneously contacting and reacting methacrylic acid and methanol with the catalyst.

11. The application according to claim 10, characterized in that: The conditions for the contact reaction include: The contact temperature is 40-150℃, preferably 60-120℃; and / or, the contact pressure is 0.01-5.0 MPa, preferably 0.1-3.0 MPa; and / or, the mass hourly space velocity of methacrylic acid is 0.01-30 h⁻¹. -1 Preferably 0.1-10h -1 ; and / or, the mass hourly space velocity (MSV) of methanol is 0.01-50 h⁻¹. -1 Preferably 0.1-30h -1 .

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