Catalyst for preparing tetrahydrofuran through maleic anhydride hydrogenation as well as preparation method and application of catalyst

Abstract

The invention relates to the technical field of heterogeneous catalysts, and particularly discloses a catalyst for preparing tetrahydrofuran through maleic anhydride hydrogenation and a preparation method and application thereof.The catalyst for preparing tetrahydrofuran through maleic anhydride hydrogenation is a molecular sieve packaged nanocluster catalyst and is composed of a catalytic hydrogenation reaction active component and an acidic carrier, the catalytic hydrogenation reaction active components are CuO and ZnO, and the acidic carrier is a porous acidic molecular sieve with a high specific surface area; the invention innovatively constructs a multiphase synergistic hydrogenation-dehydration bifunctional catalyst system, and the core of the multiphase synergistic hydrogenation-dehydration bifunctional catalyst system is that CuO-ZnO active components are accurately anchored inside and on the outer surface of a solid acid carrier micro-channel through a molecular sieve encapsulation technology. The composite structure has dual catalytic characteristics: on one hand, the high-dispersion CuO-ZnO nanoparticles provide excellent hydrogenation catalytic activity; on the other hand, the strongly acidic sites on the surface of the carrier can efficiently catalyze the dehydration reaction.

Description

Technical Field

[0001] The present invention relates to the technical field of multiphase catalysts, and more specifically, to a catalyst for the hydrogenation of maleic anhydride to tetrahydrofuran, a preparation method thereof, and uses thereof. Background Art

[0002] Tetrahydrofuran (THF), as a bulk organic chemical intermediate with medium polarity, low boiling point and low toxicity, exhibits multi-dimensional application values in the chemical industry. As a polymerization monomer, it can be used to prepare high-performance polymer materials such as polytetrahydrofuran and polyether polyols; as a solvent, it is suitable for industrial formulation systems such as polyurethane / PVC coatings and printing inks, and also provides a key medium for organic synthesis reactions such as Grignard reagents, alkyl / aryl metal compounds, and steroid drug molecules. Currently, the main production process of tetrahydrofuran is the catalytic dehydration cyclization technical route of 1,4-butanediol (BDO), and butanediol needs to be obtained through the Reppe method or the maleic anhydride esterification hydrogenation method. Although this technical route has been industrialized, its economy is significantly restricted by the high raw material cost of 1,4-butanediol. With the breakthrough of maleic anhydride production technology, the direct hydrogenation process using maleic anhydride as the raw material, with its advantages of atom economy and cost, is gradually becoming a more promising technical path in the field of tetrahydrofuran preparation, providing an innovative solution to break through the existing production capacity bottleneck.

[0003] However, there are significant technical bottlenecks in the existing processes for the catalytic hydrogenation of maleic anhydride to produce tetrahydrofuran. For example, in the ethanol-based process using a Cu-Zn-Zr composite metal oxide catalyst disclosed in Chinese Patent CN101386608A, although a maleic anhydride conversion rate of over 96% can be achieved under the liquid-phase reaction conditions of 220-280°C and a hydrogen pressure of 1 MPa, the problem of high consumption of ethanol solvent is prominent, and by-products such as ethyl acetate and acetaldehyde are generated, resulting in a decrease in the selectivity of the target product and an increase in the subsequent separation load. Chinese Patent CN101168535A uses a n-butanol process with a Cu-Zn-Ti-Ce catalytic system, and only a tetrahydrofuran yield of 75% is obtained under optimized conditions, while by-products such as butyl butyrate and butyraldehyde are generated. In the above two types of processes, the large consumption of alcohol solvents not only increases the raw material cost, but the ester and aldehyde by-products generated by their decomposition form an azeotropic system with the target product, significantly increasing the technical difficulty and economic cost of product separation, and severely restricting the feasibility of industrial application. Chinese Patent CN108148020A uses concentrated sulfuric acid and 13X molecular sieve as catalysts to catalyze the dehydration of 1,4-butanediol to produce tetrahydrofuran. Although a tetrahydrofuran product with a tar content of less than 5% can be obtained, the strong corrosiveness of concentrated sulfuric acid causes great damage to the reaction equipment. In Chinese Patent CN102617518A previously applied by the applicant, a hydrogenation-dehydration bifunctional catalyst is prepared by directly mixing copper oxide-zinc oxide composite nanoparticles with a molecular sieve solid acid. While achieving high catalytic activity and high selectivity for tetrahydrofuran, it reduces the corrosion of the catalyst to the reaction equipment. However, in the above catalyst, the dosage of active components such as copper oxide and zinc oxide is large, and only a physical mixing method is used with the molecular sieve solid acid, resulting in a low effective utilization rate of the active components and the defect of high preparation cost. Based on the above statements, in order to reduce the preparation cost of the existing processes for the catalytic hydrogenation of maleic anhydride to produce tetrahydrofuran and reduce the corrosion of the catalyst to the reaction equipment, the present invention proposes a catalyst for the hydrogenation of maleic anhydride to tetrahydrofuran, its preparation method and use. Summary of the Invention

[0004] In order to reduce the preparation cost of the existing processes for the catalytic hydrogenation of maleic anhydride to produce tetrahydrofuran and reduce the corrosion of the catalyst to the reaction equipment, the present invention provides a catalyst for the hydrogenation of maleic anhydride to tetrahydrofuran, its preparation method and use.

[0005] The present invention provides a catalyst for the hydrogenation of maleic anhydride to tetrahydrofuran, adopting the following technical solution:

[0006] A catalyst for the hydrogenation of maleic anhydride to tetrahydrofuran, wherein the catalyst is a molecular sieve encapsulated nanocluster catalyst, composed of a catalytic hydrogenation reaction active component and an acidic support. The catalytic hydrogenation reaction active component is CuO and ZnO, and the acidic support is a porous high specific surface area acidic molecular sieve.

[0007] Preferably, the catalytic hydrogenation reaction active component and the acidic support are combined in the form of molecular sieve encapsulated active component nanoclusters.

[0008] Preferably, the catalytic hydrogenation reaction active components CuO and ZnO exist in the form of nanoclusters inside and on the outer surface of the pores of the acidic support.

[0009] Preferably, the mass ratio of the catalytic hydrogenation reaction active component CuO: the catalytic hydrogenation reaction active component ZnO: the acidic support is (0.5 - 5.0):(0.5 - 5.0):100.

[0010] Preferably, the average particle size of the active component nanoclusters is 0.8 nm - 1.5 nm.

[0011] Preferably, the porous high specific surface area acidic molecular sieve is a molecular sieve composed of silicon and aluminum, and the silicon - aluminum ratio is 25 - 100:1.

[0012] Preferably, the porous high specific surface area acidic molecular sieve is one or more of MFI, FAU, *BEA.

[0013] Preferably, the catalyst is one or more of MFI molecular sieve encapsulated nanocluster catalyst, FAU molecular sieve encapsulated nanocluster catalyst or *BEA molecular sieve encapsulated nanocluster catalyst.

[0014] The present invention provides a preparation method of a catalyst for the hydrogenation of maleic anhydride to tetrahydrofuran, adopting the following technical scheme:

[0015] A preparation method of an MFI molecular sieve encapsulated nanocluster catalyst, comprising the following steps:

[0016] A1. Add a molecular sieve template agent, a silicon source, an aluminum source, and water into a hydrothermal autoclave, and stir and mix at a temperature of 25 - 60 °C for 2 - 24 h to obtain a mixed slurry;

[0017] A2. Mix a water - soluble Cu salt, a Zn salt, and an encapsulation promoter to obtain a mixed material;

[0018] A3. Add the mixed material I into the above - mentioned mixed slurry I, perform hydrothermal synthesis, then centrifuge, wash, and dry to obtain a solid powder;

[0019] A4. Calcinate the solid powder obtained in A3 above to obtain the MFI molecular sieve encapsulated nanocluster catalyst.

[0020] Preferably, in A1, the molecular sieve template is one or more of tetrapropylammonium hydroxide, tetramethylammonium hydroxide, and tetrabutylammonium hydroxide; the silicon source is one or more of fumed silica, tetraethyl orthosilicate, and silica sol; the aluminum source is one or more of aluminum nitrate, aluminum chloride, and sodium metaaluminate; and the molar ratio of the aluminum source to the silicon source, based on the amount of aluminum element and silicon element, is 25-100:1.

[0021] Preferably, in A2, the water-soluble Cu salt is one or more of copper nitrate, copper sulfate, and copper chloride; the water-soluble Zn salt is one or more of zinc nitrate, zinc chloride, and zinc sulfate; and the encapsulation promoter is one or more of ethylenediamine, 1,4-butanediamine, and cyclohexanediamine.

[0022] Preferably, in A3, the hydrothermal synthesis temperature is 100-200 °C, and the hydrothermal time is 60-168 h; the drying temperature is 100-130 °C, and the drying time is 5-15 h.

[0023] Preferably, in A4, the calcination temperature is 400-600 °C, the calcination time is 2-10 h, and the calcination atmosphere is an air atmosphere.

[0024] A preparation method of a FAU zeolite-encapsulated nanocluster catalyst includes the following steps:

[0025] B1. Add a silicon source, an aluminum source, sodium hydroxide, and water into a hydrothermal reactor, and stir and crystallize at a temperature of 25-60 °C for 2-10 h, and perform an aging treatment for 10-15 h to obtain a structure-directing agent.

[0026] B2. Add a water-soluble Cu salt, a Zn salt, an encapsulation promoter, a silicon source, an aluminum source, and sodium hydroxide to the above structure-directing agent, perform hydrothermal synthesis, and then centrifuge, wash, and dry to obtain a solid powder.

[0027] B3. Calcinate the solid powder obtained in B2 above to obtain the FAU zeolite-encapsulated nanocluster catalyst.

[0028] Preferably, in B1 and B2, the silicon source is one or more of tetramethyl orthosilicate, tetraethyl silicate, tetrabutyl orthosilicate, and sodium silicate; the aluminum source is one or more of aluminum chloride, aluminum nitrate, and sodium metaaluminate; and the molar ratio of the aluminum source to the silicon source, based on the amount of aluminum element and silicon element, is 25-100:1.

[0029] Preferably, in B2, the water-soluble Cu salt is one or more of copper nitrate, copper sulfate, and copper chloride; the water-soluble Zn salt is one or more of zinc nitrate, zinc chloride, and zinc sulfate; the encapsulation promoter is one or more of ethylenediamine, 1,4-butanediamine, and cyclohexanediamine; the hydrothermal synthesis temperature is 80-120 °C, and the hydrothermal time is 10-15 h; the drying temperature is 100-130 °C, and the drying time is 5-15 h.

[0030] Preferably, in B3, the calcination temperature is 400-600 °C, the calcination time is 2-10 h, and the calcination atmosphere is an air atmosphere.

[0031] A preparation method of a *BEA zeolite-encapsulated nanocluster catalyst comprises the following steps:

[0032] C1. Add a silicon source, an aluminum source, sodium chloride, sodium hydroxide, a templating agent, and water into a hydrothermal reactor, and stir and mix at a temperature of 25-50 °C for 2-10 h to obtain a mixed reactant;

[0033] C2. Add a water-soluble Cu salt, a Zn salt, and an encapsulation promoter to the mixed reactant obtained in C1 above. After hydrothermal synthesis at 160-180 °C for 90-100 h, centrifuge, wash, and dry to obtain a solid powder;

[0034] C3. Calcinate the solid powder obtained in C2 above to obtain the *BEA zeolite-encapsulated nanocluster catalyst.

[0035] Preferably, in C1, the molecular sieve templating agent is tetraethylammonium hydroxide, and one or more of polyvinyl alcohol, sodium carboxymethyl cellulose, and triethanolamine; the silicon source is one or more of fumed silica, tetraethyl orthosilicate, and silica sol; the -aluminum source is one or more of aluminum nitrate, aluminum chloride, and sodium metaaluminate; the molar ratio of the aluminum source to the silicon source, based on the amount of substance of aluminum and silicon elements, is 25-100:1.

[0036] Preferably, in C2, the water-soluble Cu salt is one or more of copper nitrate, copper sulfate, and copper chloride; the water-soluble Zn salt is one or more of zinc nitrate, zinc chloride, and zinc sulfate; the encapsulation promoter is one or more of ethylenediamine, 1,4-butanediamine, and cyclohexanediamine; the hydrothermal synthesis temperature is 100-200 °C, and the hydrothermal time is 60-168 h; the drying temperature is 100-130 °C, and the drying time is 5-15 h.

[0037] Preferably, in C3, the calcination temperature is 400-600 °C, the calcination time is 2-10 h, and the calcination atmosphere is an air atmosphere.

[0038] A catalyst for the hydrogenation of maleic anhydride to tetrahydrofuran is used for the purpose of catalyzing the hydrogenation of maleic anhydride to prepare tetrahydrofuran.

[0039] Preferably, the reaction temperature of the maleic anhydride hydrogenation reaction is 180 - 280 °C, the reaction pressure is 2 - 4 Mpa, the feed mass space velocity of the maleic anhydride raw material is 0.01 - 1.0 h -1 , and the molar ratio of hydrogen to maleic anhydride is 10 - 100:1.

[0040] Preferably, the reaction for preparing tetrahydrofuran by hydrogenating maleic anhydride uses a batch production in a reaction kettle or continuous production using a fixed bed or a fluidized bed, and a target product with a higher yield can be obtained.

[0041] In summary, the present invention has the following beneficial effects:

[0042] The present invention innovatively constructs a heterogeneous cooperative hydrogenation - dehydration bifunctional catalyst system, the core of which is to precisely anchor the CuO - ZnO active component inside and on the outer surface of the micropores of a solid acid support through a molecular sieve encapsulation technology. This composite structure exhibits dual catalytic characteristics: on the one hand, highly dispersed CuO - ZnO nanoparticles provide excellent hydrogenation catalytic activity; on the other hand, the strong acidic sites on the surface of the support can efficiently catalyze the dehydration reaction. Compared with the traditional supported inorganic acid system, this design can eliminate the loading process of corrosive inorganic acids through the spatial coupling effect of metal - acid sites; secondly, due to the synergistic stabilization effect of the support acid sites, the dosage of CuO - ZnO can be significantly reduced. This structural innovation not only greatly reduces the catalyst preparation cost, but also significantly improves the equipment safety and operation stability of the reaction system by eliminating strong corrosive media, showing excellent potential for industrial application.

[0043] The present invention uses a molecular sieve to encapsulate the metal active component, achieving the acquisition of small - sized metal particles. The average size of the active metal is 0.8 nm - 1.5 nm, thereby significantly increasing the active centers on the active component and improving the catalytic activity of the catalyst.

[0044] The present invention utilizes the confinement and anchoring effect of the molecular sieve micropores on the active component, which can inhibit the migration and loss of the active component, improve the stability of the catalyst, and at the same time can significantly reduce the dosage of the active component, reducing the cost of industrial catalysts. The support used in the catalyst has strong acidity and does not have the drawback of loss, laying a foundation for industrial fixed - bed continuous reaction.

[0045] The preparation method of the present invention is an extended application of the molecular sieve encapsulation of active component technology. This preparation method has the characteristics of strong operability, good economy, and stable quality. The catalyst of the present invention can be recycled and regenerated, is very suitable for industrial production, and has high industrialization value. Detailed implementation mode

[0046] The present invention will be further described in detail below in conjunction with embodiments. The specific embodiments described herein are only for illustrating and explaining the present invention, but not for limiting the present invention.

[0047] Unless otherwise specified, the reagents, materials, and devices involved in the following embodiments are all conventional and commercially available in the art; the conventional operations involved in the following embodiments can be found in the patents, patent applications, and publications disclosed in the art (for example, edited by He Yongde, "Modern Coal Chemical Technology Handbook", Chemical Industry Press, 2003, but not limited thereto).

[0048] In Examples 1-3, a catalyst for the hydrogenation of maleic anhydride to tetrahydrofuran was provided

[0049] Example 1

[0050] An MFI zeolite-encapsulated nanocluster catalyst, with a composition of 2 wt% CuO, 2 wt% ZnO, and 96 wt% MFI zeolite, is denoted as the heterogeneous catalyst Cat1#.

[0051] A preparation method of an MFI zeolite-encapsulated nanocluster catalyst includes the following steps:

[0052] A1. Mix 4.06 g of tetrapropylammonium hydroxide solution (mass fraction 40 wt%), 4.12 g of tetraethyl orthosilicate, 325 mg of sodium metaaluminate, and 12.0 g of water in a hydrothermal autoclave according to the dosage, stir at 35 °C for 8 h to obtain a mixed slurry;

[0053] A2. Mix 56.4 g of copper nitrate and 55.8 g of zinc nitrate with 0.2 mL of ethylenediamine to obtain a mixed material;

[0054] A3. Add the mixed material in A2 to the mixed slurry in A1, perform hydrothermal synthesis at 170 °C for 96 h, then centrifuge and wash, and dry at 110 °C for 12 h to obtain a solid powder;

[0055] A4. Calcinate the solid powder in A3 in an air atmosphere at 450 °C for 6 h to obtain the heterogeneous catalyst Cat1# for the hydrogenation of maleic anhydride to tetrahydrofuran.

[0056] Charge 100 g of the above-prepared heterogeneous catalyst Cat1# into a fixed-bed reactor, use maleic anhydride and hydrogen as raw materials for hydrogenation reaction, and the reaction conditions are: 220 °C, 2.2 MPa, and the mass space velocity of maleic anhydride is 0.05 h -1 , and the reaction results are shown in Table 1.

[0057] Example 2

[0058] A FAU zeolite encapsulated nanocluster catalyst, with a composition of 2.5 wt% CuO, 2.5 wt% ZnO and 95 wt% FAU zeolite, denoted as the heterogeneous catalyst Cat2#.

[0059] A preparation method of a FAU zeolite encapsulated nanocluster catalyst, comprising the following steps:

[0060] B1. Mix 500 mg of silica sol (mass fraction 40 wt%), 105.6 mg of sodium hydroxide, 167.4 mg of aluminum nitrate and 1.8 g of water in a hydrothermal reactor, crystallize at 30 °C with stirring for 5 h, and age at 100 °C for 12 h to obtain a structure directing agent;

[0061] B2. Sequentially add 2.5 g of silica sol (mass fraction 40 wt%), 528 mg of sodium hydroxide, 837 mg of aluminum nitrate, 9.0 g of water, 98.7 mg of copper nitrate, 98.0 mg of zinc nitrate and 0.2 mL of ethylenediamine to the structure directing agent obtained in B1. After hydrothermal treatment at 100 °C for 12 h, centrifuge and wash with deionized water, and dry at 110 °C for 12 h to obtain a white dry powder;

[0062] B3. Calcinate the white dry powder obtained in B2 in an air atmosphere at 550 °C for 6 h to obtain the heterogeneous catalyst Cat2# for the hydrogenation of maleic anhydride to tetrahydrofuran.

[0063] Charge 100 g of the heterogeneous catalyst Cat2# prepared above into a fixed bed reactor, use maleic anhydride and hydrogen as raw materials for hydrogenation reaction, and the reaction conditions are: 260 °C, 1.5 MPa, and the mass space velocity of maleic anhydride is 0.1 h -1 , and the reaction results are shown in Table 1.

[0064] Example 3

[0065] A *BEA zeolite encapsulated nanocluster catalyst, with a composition of 1.5 wt% CuO, 1.5 wt% ZnO, 95 wt% *BEA zeolite, denoted as the heterogeneous catalyst Cat3#.

[0066] A preparation method of a *BEA zeolite encapsulated nanocluster catalyst, comprising the following steps:

[0067] C1. Mix 1.4 g of gaseous SiO2, 360 mg of sodium metaaluminate, 28 mg of sodium chloride, 72 mg of potassium chloride, 66 mg of sodium hydroxide, 5.12 g of tetraethylammonium hydroxide solution (mass fraction 35 wt%) and 4.0 g of water in a hydrothermal reactor according to the dosage, and stir at 30 °C for 10 h to obtain a mixed reactant;

[0068] C2. Add 64 mg of copper nitrate, 62 mg of zinc nitrate, and 0.2 mL of ethylenediamine into the above autoclave according to the measurement. Then, perform hydrothermal synthesis at 170 °C for 96 h, followed by centrifugation and washing, and drying at 110 °C for 12 h to obtain a solid powder.

[0069] C3. Calcinate the solid powder in C2 in an air atmosphere at 450 °C for 12 h to obtain a heterogeneous catalyst Cat3# for the hydrogenation of maleic anhydride to tetrahydrofuran.

[0070] Load 100 g of the above-prepared heterogeneous catalyst Cat3# into a fixed-bed reactor. Using maleic anhydride and hydrogen as raw materials, carry out a hydrogenation reaction under the reaction conditions of: 240 °C, 3 MPa, and the mass space velocity of maleic anhydride is 0.08 h -1 , and the reaction results are shown in Table 1.

[0071] To verify the comprehensive performance of the catalysts for the hydrogenation of maleic anhydride to tetrahydrofuran prepared in Examples 1-3 of the present invention, the applicant set Comparative Example 1 as follows:

[0072] Comparative Example 1

[0073] First, prepare a 1 mol / L mixed solution of copper nitrate and zinc nitrate (Cu / Zn molar ratio = 1:1), and then prepare a 1 mol / L sodium carbonate solution as a precipitant. Drop the mixed solution of copper nitrate and zinc nitrate into the sodium carbonate solution in a water bath at 80 °C, stir, and stop dropping when the pH value is 7.5. Add ZSM-5 molecular sieve (purchased from the Catalyst Factory of Nankai University, and the content of the molecular sieve is 10% of the total weight of the catalyst), age for 12 h, filter, wash, dry at 110 °C for 12 h, and calcine at 450 °C for 4 h to obtain a CuO-ZnO / ZSM-5 molecular sieve catalyst (the content ratio of each component of the catalyst is 45 / 45 / 10).

[0074] Load 100 g of the above-prepared CuO-ZnO / ZSM-5 catalyst into a fixed-bed reactor. Using maleic anhydride as a raw material, carry out a hydrogenation reaction under the process conditions of: temperature 220 °C, pressure 2.2 MPa, and the weight space velocity of maleic anhydride 0.05 h -1 When, the reaction results are shown in Table 1.

[0075] The comprehensive performance of the catalysts for the hydrogenation of maleic anhydride to tetrahydrofuran prepared in Examples 1-3 and Comparative Example 1 of the present invention is shown in Table 1 below:

[0076] Table 1 Reaction results of the hydrogenation of maleic anhydride catalyzed by various catalysts in a fixed-bed reactor

[0077]

[0078]

[0079] As can be seen from the data shown in Table 1 above: The catalysts prepared in Examples 1-3 of the present invention for the hydrogenation of maleic anhydride to tetrahydrofuran can significantly reduce the usage of copper and zinc while ensuring high catalytic activity and high selectivity for tetrahydrofuran in the reaction of hydrogenating maleic anhydride to tetrahydrofuran, thus reducing costs. In Comparative Example 1, copper oxide-zinc oxide composite nanoparticles were directly mixed with molecular sieves, and the content of the molecular sieves was only 10% of the total weight of the catalyst. A large number of copper oxide-zinc oxide composite nanoparticles had only a limited specific surface area and few exposed active sites, increasing the cost input.

[0080] This specific embodiment is only an explanation of the present invention and is not a limitation thereof. After reading this specification, those skilled in the art can make modifications to this embodiment without creative contributions as needed, but as long as it is within the scope of the claims of the present invention, it is protected by the patent law.

Claims

1. A catalyst for the hydrogenation of maleic anhydride to tetrahydrofuran, characterized in that, The catalyst is a molecular sieve encapsulated nanocluster catalyst, which is composed of a catalytic hydrogenation reaction active component and an acidic support. The catalytic hydrogenation reaction active component is CuO and ZnO, and the acidic support is a porous acidic molecular sieve with a high specific surface area.

2. The catalyst for maleic anhydride hydrogenation to tetrahydrofuran according to claim 1, characterized in that, The combination between the catalytic hydrogenation reaction active component and the acidic support is achieved in the form of molecular sieve encapsulated active component nanoclusters; The catalytic hydrogenation reaction active components CuO and ZnO exist in the form of nanoclusters inside and on the outer surface of the pores of the acidic support; The ratio of the catalytic hydrogenation reaction active component CuO: the catalytic hydrogenation reaction active component ZnO: the acidic support by mass is (0.5 - 5.0):(0.5 - 5.0):100; The average particle size of the active component nanoclusters is 0.8 nm - 1.5 nm.

3. A catalyst for the hydrogenation of maleic anhydride to tetrahydrofuran according to claim 1, characterized in that, The porous acidic molecular sieve with a high specific surface area is a molecular sieve composed of silicon and aluminum, and the silicon-aluminum ratio is 25 - 100:1; The catalyst is one or more of an MFI molecular sieve encapsulated nanocluster catalyst, an FAU molecular sieve encapsulated nanocluster catalyst, or a *BEA molecular sieve encapsulated nanocluster catalyst.

4. A method for preparing a catalyst for the hydrogenation of maleic anhydride to tetrahydrofuran according to claim 3, characterized in that, The preparation steps of the MFI molecular sieve encapsulated nanocluster catalyst are as follows: A1. Add a molecular sieve template agent, a silicon source, an aluminum source, and water into a hydrothermal kettle, and stir and mix at a temperature of 25 - 60 °C for 2 - 24 h to obtain a mixed slurry; A2. Mix a water-soluble Cu salt, a water-soluble Zn salt, and an encapsulation promoter to obtain a mixed material; A3. Add the mixed material I into the above mixed slurry I, carry out hydrothermal synthesis, then centrifuge, wash, and dry to obtain a solid powder; A4. Calcine the solid powder obtained in A3 above to obtain the MFI molecular sieve encapsulated nanocluster catalyst.

5. The preparation method of the catalyst for maleic anhydride hydrogenation to tetrahydrofuran according to claim 4, characterized in that, In A1, the molecular sieve template agent is one or more of tetrapropylammonium hydroxide, tetramethylammonium hydroxide, and tetrabutylammonium hydroxide; the silicon source is one or more of fumed silica, tetraethyl orthosilicate, and silica sol; the aluminum source is one or more of aluminum nitrate, aluminum chloride, and sodium metaaluminate; the molar ratio of the aluminum source and the silicon source, based on the amount of substance of aluminum element and silicon element, is 25 - 100:

1. In A2, the water-soluble Cu salt is one or more of copper nitrate, copper sulfate, and copper chloride; the water-soluble Zn salt is one or more of zinc nitrate, zinc chloride, and zinc sulfate; the encapsulation promoter is one or more of ethylenediamine, 1,4-butanediamine, and cyclohexanediamine; In A3, the hydrothermal synthesis temperature is 100 - 200 °C, and the hydrothermal time is 60 - 168 h; the drying temperature is 100 - 130 °C, and the drying time is 5 - 15 h; In A4, the calcination temperature is 400 - 600 °C, the calcination time is 2 - 10 h, and the calcination atmosphere is an air atmosphere.

6. A method for preparing a catalyst for the hydrogenation of maleic anhydride to tetrahydrofuran according to claim 3, characterized in that, The preparation steps of the FAU molecular sieve encapsulated nanocluster catalyst are as follows: B1. Add a silicon source, an aluminum source, sodium hydroxide, and water into a hydrothermal kettle, and stir and crystallize at a temperature of 25 - 60 °C for 2 - 10 h, and carry out an aging treatment for 10 - 15 h to obtain a structure directing agent; B2. Add water-soluble Cu salts, Zn salts, encapsulation promoter, silicon source, aluminum source, and sodium hydroxide to the above-mentioned structure-directing agent, carry out hydrothermal synthesis, then centrifuge, wash, and dry to obtain solid powder; B3. Calcinate the solid powder obtained in B2 above to obtain the FAU zeolite-encapsulated nanocluster catalyst.

7. The preparation method of the catalyst for maleic anhydride hydrogenation to tetrahydrofuran according to claim 6, characterized in that, In B1 and B2, the silicon source is one or more of tetramethyl orthosilicate, tetraethyl orthosilicate, tetrabutyl orthosilicate, and sodium silicate; the aluminum source is one or more of aluminum chloride, aluminum nitrate, and sodium metaaluminate; the molar ratio of the aluminum source to the silicon source, calculated based on the amount of substance of aluminum element and silicon element, is 25-100:1; In B2, the water-soluble Cu salt is one or more of copper nitrate, copper sulfate, and copper chloride; the water-soluble Zn salt is one or more of zinc nitrate, zinc chloride, and zinc sulfate; the encapsulation promoter is one or more of ethylenediamine, 1,4-butanediamine, and cyclohexanediamine; the hydrothermal synthesis temperature is 80-120 °C, and the hydrothermal time is 10-15 h; the drying temperature is 100-130 °C, and the drying time is 5-15 h; In B3, the calcination temperature is 400-600 °C, the calcination time is 2-10 h, and the calcination atmosphere is an air atmosphere.

8. A method for preparing a catalyst for the hydrogenation of maleic anhydride to tetrahydrofuran according to claim 3, characterized in that, The preparation steps of the *BEA zeolite-encapsulated nanocluster catalyst are as follows: C1. Add the silicon source, aluminum source, sodium chloride, sodium hydroxide, template agent, and water to a hydrothermal autoclave, and stir and mix at a temperature of 25-50 °C for 2-10 h to obtain a mixed reactant; C2. Add water-soluble Cu salts, Zn salts, and encapsulation promoter to the mixed reactant obtained in C1 above, carry out hydrothermal synthesis at 160-180 °C for 90-100 h, then centrifuge, wash, and dry to obtain solid powder; C3. Calcinate the solid powder obtained in C2 above to obtain the *BEA zeolite-encapsulated nanocluster catalyst.

9. The preparation method of the catalyst for maleic anhydride hydrogenation to tetrahydrofuran according to claim 8, characterized in that, In C1, the molecular sieve template agent is one or more of tetraethylammonium hydroxide, polyvinyl alcohol, sodium carboxymethyl cellulose, and triethanolamine; the silicon source is one or more of fumed silica, tetraethyl orthosilicate, and silica sol; the aluminum source is one or more of aluminum nitrate, aluminum chloride, and sodium metaaluminate; the molar ratio of the aluminum source to the silicon source, calculated based on the amount of substance of aluminum element and silicon element, is 25-100:1; In C2, the water-soluble Cu salt is one or more of copper nitrate, copper sulfate, and copper chloride; the water-soluble Zn salt is one or more of zinc nitrate, zinc chloride, and zinc sulfate; the encapsulation promoter is one or more of ethylenediamine, 1,4-butanediamine, and cyclohexanediamine; the hydrothermal synthesis temperature is 100-200 °C, and the hydrothermal time is 60-168 h; the drying temperature is 100-130 °C, and the drying time is 5-15 h; In C3, the calcination temperature is 400-600 °C, the calcination time is 2-10 h, and the calcination atmosphere is an air atmosphere.

10. Use of the catalyst according to any one of claims 1-3 for the hydrogenation of maleic anhydride to tetrahydrofuran as a catalyst for the hydrogenation of maleic anhydride to prepare tetrahydrofuran.

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