A hydrophobic copper-based molecular sieve catalyst and methods for making and using the same

Abstract

The present application relates to a kind of hydrophobic copper-based molecular sieve catalyst and its preparation method and use method, belong to copper-based catalyst technical field.The present application discloses a kind of hydrophobic copper-based molecular sieve catalyst, the hydrophobic copper-based molecular sieve catalyst includes the copper nanoparticle of mass ratio 1 :(0.3~1.2) :(1~10), methyl functional group, silica molecular sieve framework;The methyl functional group is located on the surface of silica molecular sieve framework, and copper nanoparticle exists in silica molecular sieve channel and / or cavity.This application also discloses the preparation method of hydrophobic copper-based molecular sieve catalyst and the use method of hydrophobic copper-based molecular sieve catalyst.This application will be evenly distributed in the copper nanoparticle in silica molecular sieve channel and / or cavity, and there is methyl functional group on the outside of urchin-shaped structure molecular sieve, in maleic anhydride selective hydrogenation make by-product water quickly leave catalyst surface, reduce the occurrence of hydrolysis side reaction, improve catalyst activity and reduce the selectivity of acid product.

Description

Technical Field

[0001] This invention belongs to the field of copper-based catalyst technology, and relates to a hydrophobic copper-based molecular sieve catalyst and its preparation and application methods. Background Technology

[0002] Currently, the main methods for preparing γ-butyrolactone are the direct hydrogenation of maleic anhydride and the indirect hydrogenation of maleic anhydride esterification. The indirect hydrogenation method involves first esterifying maleic anhydride to generate maleate ester before hydrogenation, followed by hydrogenation using a copper-based catalyst to produce γ-butyrolactone. The direct hydrogenation method eliminates the intermediate esterification step, resulting in a shorter process flow and lower investment costs. However, both methods require copper-based catalysts. In the maleic anhydride hydrogenation system, H2O is generated, and water, being acidic at high temperatures, causes the loss of the active copper component, leading to catalyst deactivation. Therefore, to address the hydrolysis side reactions, reduce the selectivity of byproducts such as maleic acid, succinic acid, and butyric acid, and improve catalyst lifespan, a hydrophobic catalyst needs to be developed to allow for rapid efflux of H2O during the reaction. Furthermore, the catalyst needs to possess high stability, as existing catalysts often exhibit copper particle agglomeration during use, affecting their lifespan.

[0003] Chinese patent application (publication number CN107519883A) discloses a hydrophobic copper-based catalyst composed of 45-65% CuO, 25-35% ZnO, and 10-30% SiO2. The catalyst's stability is improved by coating the active sites of Cu and ZnO with unmodified or modified (hydrophobic) silica, which prevents the crystallization and growth of Cu and ZnO during the reaction. However, this catalyst is used for methanol synthesis, and the silica coating of the active sites partially covers them, resulting in a reduced effective active surface area and affecting the catalyst's catalytic performance. Summary of the Invention

[0004] The purpose of this invention is to address the aforementioned problems in the existing technology by proposing a preparation method that combines ammonia stripping and chemical modification. The surface of the support is modified through a chemical reaction without affecting the catalytic activity. The resulting hydrophobic copper-based molecular sieve catalyst has a highly stable structure. During catalytic application, the generated H2O can be rapidly evaporated, thus extending the service life of the hydrophobic copper-based molecular sieve catalyst.

[0005] The objective of this invention can be achieved through the following technical solutions:

[0006] A hydrophobic copper-based molecular sieve catalyst, wherein the hydrophobic copper-based molecular sieve catalyst comprises copper nanoparticles, methyl functional groups, and a silica molecular sieve framework in a mass ratio of 1:(0.3-1.2):(1-10).

[0007] The methyl functional group is located on the surface of the silica molecular sieve framework, and the copper nanoparticles exist in the silica molecular sieve channels and / or cavities.

[0008] The hydrophobic copper-based molecular sieve catalyst of the present invention comprises a silica molecular sieve framework, copper nanoparticles present in the channels and / or cavities of the silica molecular sieve, and methyl functional groups on the surface of the silica molecular sieve framework. Both the copper nanoparticles and the methyl functional groups need to be strictly controlled. If there are too few methyl functional groups, the hydrophobicity / hydrophobicity will decrease, the surface will be prone to hydrolysis, resulting in more byproducts and low selectivity for the target product. If there are too many methyl functional groups, it will hinder maleic anhydride molecules from contacting the catalytic active site, thereby affecting the catalytic activity and resulting in low conversion rate. If there are too many copper nanoparticles, it will lead to aggregation, thus affecting the catalytic activity.

[0009] Existing hydrophobic catalysts typically obtain their hydrophobic groups through physical methods such as impregnation and deposition. In contrast, this invention modifies the molecular sieve surface with methyl functional groups via a chemical modification method combining ultrasound and room-temperature rotational reaction. The methyl functional groups react chemically with the support surface to modify it, making them less prone to detachment. Furthermore, this method enhances the dispersibility of the active ingredient, resulting in high catalytic activity. Additionally, this invention involves a second calcination under an inert atmosphere to prevent further oxidation of the active ingredient, which could lead to volume changes and affect catalytic activity.

[0010] Preferably, the content of silica molecular sieve framework in the hydrophobic copper-based molecular sieve catalyst is 35-85 wt.%.

[0011] The content of the copper nanoparticles is 10-40 wt.%.

[0012] The content of the methyl functional group is 3-18 wt.%.

[0013] More preferably, the content of silica molecular sieve framework in the hydrophobic copper-based molecular sieve catalyst is 70-85 wt.%.

[0014] The content of the copper nanoparticles is 10-20 wt.%.

[0015] The content of the methyl functional group is 3-15 wt.%.

[0016] Preferably, the size of the copper nanoparticles is 10–25 nm.

[0017] Preferably, the hydrophobic copper-based molecular sieve catalyst has a specific surface area of ​​450–520 m². 2 / g.

[0018] Preferably, the hydrophobic copper-based molecular sieve catalyst has a sea urchin-like structure with a methyl functional group on the outermost side.

[0019] A method for preparing a hydrophobic copper-based molecular sieve catalyst includes:

[0020] S1. Dissolve soluble copper salts and add concentrated ammonia and additives to prepare copper-ammonia complexes;

[0021] S2. Add all-silica molecular sieve to the copper ammonia complex and control the pH to 10-12;

[0022] S3. Ammonia is evaporated at 60-90℃, and the precipitate is washed and dried.

[0023] S4. The dried solid is placed in a muffle furnace and calcined for the first time at 270-480℃ for 3-8 hours to obtain the intermediate product.

[0024] S5. Mix the intermediate product with toluene and sonicate at room temperature for 5-30 min. Add the organosilicon precursor and perform a room temperature rotational reaction for 0.5-10 h. Filter, remove the solid and dry it.

[0025] S6. The solid is calcined for a second time at 200-340℃ for 1-10 hours under nitrogen protection to obtain a hydrophobic copper-based molecular sieve catalyst.

[0026] This invention involves mixing a copper-ammonia complex with an all-silica molecular sieve, followed by ammonia stripping and a first calcination. This allows a greater amount of the active ingredient (copper) to enter the multi-mesoporous all-silica molecular sieve, maintaining good dispersibility. Then, methyl functional groups are modified on the surface of the molecular sieve through chemical modification, and a second calcination is performed under an inert atmosphere to prevent further oxidation of the active ingredient, which would lead to volume changes and thus affect catalytic activity.

[0027] Preferably, the mass ratio of the soluble copper salt to the all-silica molecular sieve in step S1 is (0.2-1.5):1.

[0028] Further preferred, the mass ratio of the soluble copper salt to the all-silica molecular sieve in step S1 is (0.8-1.2):1.

[0029] Preferably, the soluble copper salt in step S1 includes one or more of copper nitrate, copper chloride, copper sulfate, copper acetate, and copper sulfate.

[0030] Preferably, the mass ratio of the soluble copper salt to the additive in step S1 is (3-20):1.

[0031] Preferably, the amount of concentrated ammonia added in step S1 is 21–29 wt.%.

[0032] Preferably, the additive in step S1 is a metal-soluble salt, including chloride salts, nitrates, and sulfates.

[0033] More preferably, the metal elements in the metal compound include zinc and molybdenum.

[0034] In metal compound additives, zinc reduces the acidity of the catalyst, while molybdenum promotes the reduction of copper.

[0035] Without the addition of additives, the catalyst will have low catalytic activity and low selectivity.

[0036] Preferably, the all-silica molecular sieve in step S2 includes one or more of Silicalite-1, Silicalite-2, and MCM-41.

[0037] This invention uses all-silica molecular sieves as a carrier. The mesoporous channels of all-silica molecular sieves can effectively limit the growth of active components and prevent them from becoming too large and agglomerating. However, this does not mean that adding more soluble copper salts to the raw materials is more beneficial to the catalytic effect of the catalyst. In this invention, if too much soluble copper salt is added, it will cause the active components to agglomerate and affect the catalytic activity.

[0038] Preferably, the organosilicon precursor in step S5 includes one or both of trimethylchlorosilane and 3-aminopropyl(diethoxy)methylsilane.

[0039] Preferably, the mass ratio of the intermediate product to the organosilicon precursor in step S5 is (0.2-5):1.

[0040] Preferably, the product after the second calcination in step S6 is first activated by hydrogen reduction before being used in the selective hydrogenation process of maleic anhydride.

[0041] A method for using a hydrophobic copper-based molecular sieve catalyst, the method comprising: filling the middle of a continuous reaction tube for a selective hydrogenation process of maleic anhydride with the hydrophobic copper-based molecular sieve catalyst, fixing the upper and lower ends of the catalyst bed with inert alumina, and then using the mixed catalyst after reducing it with hydrogen to the reaction temperature.

[0042] Preferably, the reduction temperature of the catalyst is 200–400°C, and the time is 5–15 h.

[0043] Preferably, after selective hydrogenation of maleic anhydride, the maleic anhydride conversion rate is ≥99.5%, the yield is ≥99%, and the total acid selectivity is ≤0.5%.

[0044] Compared with the prior art, the present invention has the following beneficial effects:

[0045] 1. This invention uses an ammonia stripping method to uniformly distribute copper nanoparticles within the pores and / or cavities of a silica molecular sieve; chemical modification replaces some of the functional groups on the outer side of the molecular sieve with methyl functional groups; using the molecular sieve as a silicon source, the copper nanoparticles are uniformly distributed within the pores and / or cavities of the silica molecular sieve, surrounded by the molecular sieve framework, making them less prone to sintering; furthermore, the presence of methyl functional groups on the outer side of the urchin-like molecular sieve allows the byproduct water to quickly leave the catalyst surface during application, reducing the occurrence of hydrolysis side reactions, improving catalyst activity, and reducing the selectivity of acid products, thereby increasing catalyst lifetime.

[0046] 2. In this invention, copper nanoparticles are uniformly distributed in the channels and / or cavities of silica molecular sieves by ammonia stripping. Compared with ordinary silica sources, the all-silica molecular sieve used in this invention has a greater number of defect sites and can accommodate more copper nanoparticles.

[0047] 3. Unlike physical coating methods such as impregnation and deposition, this invention modifies the surface of molecular sieves with methyl functional groups through chemical modification. The surface of the support is modified by chemical reaction between the functional groups and the support surface, which does not affect the active sites (i.e., catalytic activity) and the modified groups are not easy to fall off.

[0048] 4. This invention uses all-silica molecular sieve as the matrix. All-silica molecular sieve itself has good high temperature resistance and can maintain performance and structural stability during two calcination processes, effectively accommodating the active ingredient copper nanoparticles and ensuring their dispersion. Ordinary silica sol will encapsulate some of the active ingredients during the preparation process of this invention, reducing the exposure of the active ingredients and reducing catalytic performance.

[0049] 5. The hydrophobic copper-based molecular sieve catalyst of the present invention is used for selective hydrogenation of maleic anhydride, with a maleic anhydride conversion rate ≥99.5% and a yield ≥99%. Attached Figure Description

[0050] Figure 1 This is a flowchart illustrating the preparation process of the hydrophobic copper-based molecular sieve catalyst in Example 1 of the present invention.

[0051] Figure 2 The image shows the XRD pattern of the hydrophobic copper-based molecular sieve catalyst in Example 1 of this invention.

[0052] Figure 3 This is a SEM image of the hydrophobic copper-based molecular sieve catalyst in Example 1 of the present invention. Detailed Implementation

[0053] The following are specific embodiments of the present invention, which further describe the technical solution of the present invention, but the present invention is not limited to these embodiments.

[0054] Unless otherwise specified, the materials used in this invention are commercially available products, and the methods used are conventional technical means.

[0055] Example 1

[0056] In this embodiment, the mass ratio of copper nanoparticles, methyl functional groups, and silica molecular sieve framework in the hydrophobic copper-based molecular sieve catalyst is 1:0.3:6; the copper nanoparticles are uniformly dispersed in the channels and / or cavities of the silica molecular sieve, and the methyl functional groups are located on the surface of the silica molecular sieve framework.

[0057] Dissolve 5.4g of soluble copper salt (copper nitrate) in 100ml of water, then add 25wt.% concentrated ammonia and 0.5g of auxiliary agent (zinc nitrate and molybdenum nitrate in a mass ratio of 1:1) and stir until homogeneous to prepare a copper-ammonia complex.

[0058] Add 6g of all-silica molecular sieve Silicalite-1 to the copper ammonia complex and mix well, controlling the pH to 10.5±0.3;

[0059] Next, the ammonia was evaporated at 80°C, the precipitate was removed, washed, and dried.

[0060] The dried solid was placed in a muffle furnace and calcined for the first time at 300°C for 6 hours to obtain the intermediate product.

[0061] 2g of intermediate product was mixed with 10ml of toluene and sonicated at room temperature for 20min. 1g of organosilicon precursor (trimethylchlorosilane) was added and the mixture was rotated at room temperature for 3h. The solid was then filtered and dried.

[0062] The solid was heated to 240℃ and calcined for 5 hours under nitrogen protection to obtain a hydrophobic copper-based molecular sieve catalyst.

[0063] Figure 1 This is a flowchart of the preparation process; Figure 2 The image shows the XRD pattern of the hydrophobic copper-based molecular sieve catalyst. Figure 3 Its SEM image.

[0064] Example 2

[0065] In this embodiment, the mass ratio of copper nanoparticles, methyl functional groups, and silica molecular sieve framework in the hydrophobic copper-based molecular sieve catalyst is 1:0.4:6; the copper nanoparticles are uniformly dispersed in the channels and / or cavities of the silica molecular sieve, and the methyl functional groups are located on the surface of the silica molecular sieve framework.

[0066] Compared with Example 1, the difference is that the mass ratio of intermediate product to organosilicon precursor is 2g:2g.

[0067] Dissolve 5.4g of soluble copper salt (copper nitrate) in 100ml of water, then add 25wt.% concentrated ammonia and 0.5g of auxiliary agent (zinc nitrate and molybdenum nitrate in a mass ratio of 1:1) and stir until homogeneous to prepare a copper-ammonia complex.

[0068] Add 6g of all-silica molecular sieve Silicalite-1 to the copper ammonia complex and mix well, controlling the pH to 10.5±0.3;

[0069] Next, the ammonia was evaporated at 80°C, the precipitate was removed, washed, and dried.

[0070] The dried solid was placed in a muffle furnace and calcined for the first time at 300°C for 6 hours to obtain the intermediate product.

[0071] 2g of intermediate product was mixed with 10ml of toluene and sonicated at room temperature for 20min. 2g of organosilicon precursor (trimethylchlorosilane) was added and the mixture was rotated at room temperature for 3h. The solid was then filtered and dried.

[0072] The solid was heated to 240℃ and calcined for 4 hours under nitrogen protection to obtain a hydrophobic copper-based molecular sieve catalyst.

[0073] Example 3

[0074] In this embodiment, the mass ratio of copper nanoparticles, methyl functional groups, and silica molecular sieve framework in the hydrophobic copper-based molecular sieve catalyst is 1:0.6:6; the copper nanoparticles are uniformly dispersed in the channels and / or cavities of the silica molecular sieve, and the methyl functional groups are located on the surface of the silica molecular sieve framework.

[0075] Compared with Example 1, the difference is that the mass ratio of intermediate product to organosilicon precursor is 2g:4g.

[0076] Dissolve 5.4g of soluble copper salt (copper nitrate) in 100ml of water, then add 25wt.% concentrated ammonia and 0.5g of auxiliary agent (zinc nitrate and molybdenum nitrate in a mass ratio of 1:1) and stir until homogeneous to prepare a copper-ammonia complex.

[0077] Add 6g of all-silica molecular sieve to the copper ammonia complex and mix well, controlling the pH to 10.5±0.2;

[0078] Next, the ammonia was evaporated at 80°C, the precipitate was removed, washed, and dried.

[0079] The dried solid was placed in a muffle furnace and calcined for the first time at 300°C for 6 hours to obtain the intermediate product.

[0080] 2g of intermediate product was mixed with 10ml of toluene and sonicated at room temperature for 20min. 4g of organosilicon precursor (trimethylchlorosilane) was added and the mixture was rotated at room temperature for 3h. The solid was then filtered and dried.

[0081] The solid was heated to 240℃ and calcined for 4 hours under nitrogen protection to obtain a hydrophobic copper-based molecular sieve catalyst.

[0082] Example 4

[0083] In this embodiment, the mass ratio of copper nanoparticles, methyl functional groups, and silica molecular sieve framework in the hydrophobic copper-based molecular sieve catalyst is 1:1.1.6; the copper nanoparticles are uniformly dispersed in the channels and / or cavities of the silica molecular sieve, and the methyl functional groups are located on the surface of the silica molecular sieve framework.

[0084] Compared with Example 1, the difference is that the mass ratio of intermediate product to organosilicon precursor is 2g:10g.

[0085] Dissolve 5.4g of soluble copper salt (copper nitrate) in 100ml of water, then add 25wt.% concentrated ammonia and 0.5g of auxiliary agent (zinc nitrate and molybdenum nitrate in a mass ratio of 1:1) and stir until homogeneous to prepare a copper-ammonia complex.

[0086] Add 6g of all-silica molecular sieve to the copper ammonia complex and mix well, controlling the pH to 10.5±0.2;

[0087] Next, the ammonia was evaporated at 80°C, the precipitate was removed, washed, and dried.

[0088] The dried solid was placed in a muffle furnace and calcined for the first time at 300°C for 6 hours to obtain the intermediate product.

[0089] 2g of intermediate product was mixed with 10ml of toluene and sonicated at room temperature for 20min. 10g of organosilicon precursor (trimethylchlorosilane) was added and the mixture was rotated at room temperature for 3h. The solid was then filtered and dried.

[0090] The solid was heated to 240℃ and calcined for 4 hours under nitrogen protection to obtain a hydrophobic copper-based molecular sieve catalyst.

[0091] Example 5

[0092] Compared with Example 1, the difference is that the first roasting temperature is 500°C and the time is 7 hours.

[0093] In this embodiment, the excessively high temperature and long duration of the first calcination resulted in an excessively large volume of the copper-containing active components, a decrease in the specific surface area of ​​the active sites, and low catalyst efficiency; in addition, partial sintering occurred.

[0094] Example 6

[0095] Compared with Example 1, the difference is that silica sol is used instead of all-silica molecular sieve.

[0096] In this embodiment, the silica sol encapsulates part of the active ingredient, reducing the exposure of active sites and thus decreasing catalytic performance.

[0097] Example 7

[0098] The difference from Example 1 is that the second roasting is carried out in air.

[0099] In this embodiment, the second calcination is carried out in air, which leads to further oxidation of the active components in the molecular sieve, increasing the volume and reducing the specific surface area of ​​the active sites, resulting in low catalyst efficiency.

[0100] Comparative Example 1

[0101] Compared with Example 3, the difference is that the copper-based molecular sieve catalyst has no methyl functional groups on its surface.

[0102] Dissolve 5.4g of soluble copper salt (copper nitrate) in 100ml of water, then add 25wt.% concentrated ammonia and 0.5g of auxiliary agent (zinc nitrate and molybdenum nitrate in a mass ratio of 1:1) and stir until homogeneous to prepare a copper-ammonia complex.

[0103] Add 6g of all-silica molecular sieve Silicalite-1 to the copper ammonia complex and mix well, controlling the pH to 11±0.3;

[0104] Next, the ammonia was evaporated at 80°C, the precipitate was removed, washed, and dried.

[0105] The dried solid was placed in a muffle furnace and calcined at 300°C for 6 hours to obtain a copper-based molecular sieve catalyst.

[0106] Application Example 1

[0107] The copper-based catalyst prepared in Example 1 was granulated (20-40 mesh) and mixed with an appropriate amount of quartz sand. This mixture was then packed into the middle of a continuous reaction tube for the selective hydrogenation of maleic anhydride. The catalyst bed was fixed at both ends with inert alumina. Under normal pressure, the catalyst was reduced with 99.9% hydrogen at 300°C for 10 hours. The temperature was then lowered to the reaction temperature, and a mixture of maleic anhydride and γ-butyrolactone at a mass ratio of 1:3 was injected using a high-pressure plunger pump. The product was collected in a cold trap and analyzed by offline FID chromatography.

[0108] The results of maleic anhydride conversion and γ-butyrolactone selectivity are shown in Table 1.

[0109] Application Examples 2-7

[0110] The copper-based catalysts prepared in Examples 2-7 were used according to the method described in Application Example 1. Results such as maleic anhydride conversion and γ-butyrolactone selectivity are shown in Table 1.

[0111] Application Comparative Example 1

[0112] The copper-based catalyst prepared in Comparative Example 1 was used according to the method in Application Example 1. Results such as maleic anhydride conversion and γ-butyrolactone selectivity are shown in Table 1.

[0113] Table 1. Performance of copper-based catalysts in selective hydrogenation of maleic anhydride

[0114] maleic anhydride conversion rate / % γ-Butyrolactone selectivity / % Succinic anhydride selectivity / % Total acid selectivity / % Example 1 99.8 50.2 42.1 5.6 Example 2 99.9 51.3 42.4 4.3 Example 3 99.9 55.8 43.3 0.5 Example 4 99.6 48.7 41.8 6.1 Example 5 97.8 41.6 36.9 10.9 Example 6 99.2 46.8 40.4 7.7 Example 7 98.7 45.4 39.8 8.2 Comparative Example 1 99.7 50.1 41.9 5.8

[0115] As shown in the table above, the hydrophobic copper-based molecular sieve catalyst of the present invention contains 12.3–13.7 wt.% copper nanoparticles, 4.1–13.6 wt.% methyl functional groups, and 74.1–82.2 wt.% silica molecular sieve framework. The copper nanoparticles are uniformly dispersed in the channels and / or cavities of the silica molecular sieve, exhibiting high dispersion and good catalyst activity. The presence of methyl functional groups on the surface of the silica molecular sieve framework allows the byproduct water to quickly leave the catalyst surface, reducing the occurrence of hydrolysis side reactions, improving catalyst activity, and reducing the selectivity of acid products, thereby increasing catalyst lifetime.

[0116] As can be seen from Examples 1 to 4, as the amount of organosilicon precursor added increases, the content of methyl functional groups increases. However, excessive methyl functional groups hinder maleic anhydride molecules from contacting catalytic active sites, thereby affecting catalytic activity.

[0117] The catalyst in Comparative Example 1 lacks methyl functional groups on its surface, which prevents the byproduct water from leaving the catalyst surface quickly. This mainly affects the long-term service life of the catalyst and also has a certain impact on its catalytic activity.

[0118] The silica source selected in this invention is an all-silica molecular sieve, which has a larger specific surface area, making it less prone to copper nanoparticle aggregation and resistant to sintering; compared with other silica sources, it can expose more active sites.

[0119] In the hydrophobic copper-based molecular sieve catalyst of the present invention, if there are too few methyl functional groups, the hydrophobicity will be poor, the surface will be prone to hydrolysis, there will be more by-products, and the selectivity of the target product will be low; if there are too many methyl functional groups, it will hinder maleic anhydride molecules from contacting the catalytic active sites, thereby affecting the catalytic activity and the conversion rate will be low; if there are too many copper nanoparticles, it will lead to agglomeration and affect the catalytic activity; if there are too few copper nanoparticles, there will be fewer active sites and the conversion rate will be low.

[0120] In summary, this invention achieves uniform distribution of copper nanoparticles within the pores and / or cavities of a silica molecular sieve via ammonia stripping; it replaces some functional groups on the outer side of the molecular sieve with methyl functional groups through chemical modification; using the molecular sieve as a silicon source ensures that the copper nanoparticles are uniformly distributed within the pores and / or cavities of the silica molecular sieve, surrounded by the molecular sieve framework, making them less prone to sintering; furthermore, the presence of methyl functional groups on the outer side of the urchin-like molecular sieve structure allows the byproduct water to quickly leave the catalyst surface, reducing the occurrence of hydrolysis side reactions, improving catalyst activity, and reducing the selectivity of acid products, thereby increasing catalyst lifetime.

[0121] The specific embodiments described herein are merely illustrative of the spirit of the invention. Those skilled in the art to which this invention pertains may make various modifications or additions to the described specific embodiments or use similar methods to substitute them, without departing from the spirit of the invention or exceeding the scope defined by the appended claims.

Claims

1. A hydrophobic copper-based molecular sieve catalyst for selective hydrogenation of maleic anhydride, characterized in that, The hydrophobic copper-based molecular sieve catalyst for selective hydrogenation of maleic anhydride comprises copper nanoparticles, methyl functional groups, and a silica molecular sieve framework in a mass ratio of 1:0.6:

6. The methyl functional group is located on the surface of the silica molecular sieve framework, and the copper nanoparticles exist in the silica molecular sieve channels and / or cavities. The preparation method of the hydrophobic copper-based molecular sieve catalyst for selective hydrogenation of maleic anhydride includes: 5.4 g of soluble copper salt copper nitrate was dissolved in 100 mL of water, and then 25 wt.% concentrated ammonia and 0.5 g of additive were added and stirred until homogeneous to prepare a copper-ammonia complex. The additive was zinc nitrate and molybdenum nitrate in a mass ratio of 1:

1. 6 g of all-silica molecular sieve Silicalite-1 was added to the copper-ammonia complex and mixed well, controlling the pH to 10.5 ± 0.

3. Then, ammonia was evaporated at 80 °C, the precipitate was removed, washed, and dried. The dried solid was placed in a muffle furnace and calcined for the first time at 300 °C for 6 h to obtain an intermediate product. 2 g of the intermediate product was mixed with 10 mL of toluene and sonicated at room temperature for 20 min. 4 g of organosilicon precursor trimethylchlorosilane was added, and the mixture was rotated at room temperature for 3 h. The solid was filtered, dried, and then heated to 240 °C for a second calcination for 4 h under nitrogen protection to obtain a hydrophobic copper-based molecular sieve catalyst.

2. A method for preparing a hydrophobic copper-based molecular sieve catalyst for selective hydrogenation of maleic anhydride as described in claim 1, characterized in that, The preparation method includes: 5.4 g of soluble copper salt copper nitrate was dissolved in 100 mL of water, and then 25 wt.% concentrated ammonia and 0.5 g of additive were added and stirred until homogeneous to prepare a copper-ammonia complex. The additive was zinc nitrate and molybdenum nitrate in a mass ratio of 1:

1. 6 g of all-silica molecular sieve Silicalite-1 was added to the copper-ammonia complex and mixed well, controlling the pH to 10.5 ± 0.

3. Then, ammonia was evaporated at 80 °C, the precipitate was removed, washed, and dried. The dried solid was placed in a muffle furnace and calcined for the first time at 300 °C for 6 h to obtain an intermediate product. 2 g of the intermediate product was mixed with 10 mL of toluene and sonicated at room temperature for 20 min. 4 g of organosilicon precursor trimethylchlorosilane was added, and the mixture was rotated at room temperature for 3 h. The solid was filtered, dried, and then heated to 240 °C for a second calcination for 4 h under nitrogen protection to obtain a hydrophobic copper-based molecular sieve catalyst.

3. A method for using a hydrophobic copper-based molecular sieve catalyst for selective hydrogenation of maleic anhydride, characterized in that, The method of use includes: filling the middle of the continuous reaction tube of the selective hydrogenation process of maleic anhydride with the hydrophobic copper-based molecular sieve catalyst of selective hydrogenation of maleic anhydride as described in claim 1, and / or the hydrophobic copper-based molecular sieve catalyst of selective hydrogenation of maleic anhydride prepared by the preparation method described in claim 2; fixing the upper and lower ends of the catalyst bed with inert alumina; reducing it with 99.9% hydrogen at 300°C for 10 hours under normal pressure; then lowering the temperature to the reaction temperature; and injecting a mixture of maleic anhydride and γ-butyrolactone in a mass ratio of 1:3 by a high-pressure plunger pump.

4. The method of use according to claim 3, characterized in that, After selective hydrogenation of maleic anhydride, the maleic anhydride conversion rate is ≥99.5%, the yield is ≥99%, and the total acid selectivity is ≤0.5%.

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