A hydrogenation catalyst, and a method for preparing dimethyl succinate by hydrogenating dimethyl maleate

Abstract

The application provides a preparation method of a hydrogenation catalyst, which comprises the following steps: mixing a complexing agent, a soluble copper salt, a buffer solution and water to obtain liquid A, mixing a silicon source, an alkali, a molecular sieve template agent and water, and hydrothermally treating to obtain liquid B, dropwise adding the liquid A into the liquid B, and transferring to a closed reaction kettle for crystallization under autogenous pressure after reaction to obtain the catalyst. In the application, the complexing agent is used as a structure directing agent to encapsulate Cu in the form of metal clusters in the pore channels of pure silicon zeolite, and the spatial restriction effect of the zeolite pore channels prevents the aggregation of Cu in the reaction process, so that the hydrogenation effect can be realized under a high dispersion degree, and the catalyst has high stability. The catalytic maleic acid dimethyl ester production butane diacid dimethyl ester reaction has high selectivity.

Description

Technical Field

[0001] This invention relates to hydrogenation catalysts, particularly catalysts for the hydrogenation of dimethyl maleate to prepare dimethyl succinate. Background Technology

[0002] Dimethyl succinate (DMS) is an important synthetic flavoring agent, mainly used in the formulation of fruit and fruit wine flavorings. It is also an important chemical intermediate widely used in the food, pharmaceutical, coating, rubber, and plastics industries. DMS can be used as a raw material for the synthesis of 1,4-butanediol, γ-butyrolactone, and tetrahydrofuran. Currently, most industrial methods for producing dimethyl succinate involve esterification of succinic acid (SA) with methanol. However, this technology uses concentrated sulfuric acid as a catalyst, resulting in numerous side reactions, low yield, demanding equipment requirements, and environmental pollution.

[0003] CN101905160A discloses a method for preparing dimethyl maleate (DMM) by hydrogenation in the presence of a Cu / ZnO / Al2O3 ternary catalyst. The method uses a fixed-bed reactor. The raw material is diluted with methanol and then enters the reactor with H2. The active components of the catalyst are composed of copper, zinc oxide and aluminum oxide, with the following mass percentages: copper 30-60%, zinc oxide 10-50%, and aluminum oxide 5-50%.

[0004] CN103464153A discloses a hydrogenation catalyst for the production of dimethyl maleate and its preparation method. The catalyst uses resin-based spherical activated carbon as a support, loads palladium nitrate by liquid-phase sedimentation, and then loads it with WO3, thereby improving the lifetime of the palladium on carbon catalyst for the production of dimethyl maleate from dimethyl maleate.

[0005] However, in the above-mentioned method for preparing dimethyl maleate by hydrogenation, the palladium-on-carbon catalyst is expensive, and as the reaction proceeds, the active components Pd or Cu that play a role in hydrogenation will aggregate, resulting in a decrease in hydrogenation efficiency and a reduction in catalyst lifetime. Therefore, preventing the aggregation of hydrogenation metals during the reaction and developing a long-life dimethyl maleate hydrogenation catalyst is of great application significance. Summary of the Invention

[0006] To address the shortcomings of existing technologies, this invention provides a hydrogenation catalyst and a method for producing dimethyl succinate from dimethyl maleate using the catalyst. The catalyst not only exhibits high stability but also high selectivity for this reaction.

[0007] The technical objective of the first aspect of this invention is to provide a method for preparing a hydrogenation catalyst, comprising the following steps:

[0008] (1) Mix the complexing agent, soluble copper salt, buffer solution and water to obtain solution A;

[0009] (2) Mix silicon source, alkali, molecular sieve template agent and water, and perform hydrothermal treatment to obtain solution B;

[0010] (3) Add solution A dropwise to solution B. After the reaction, transfer the solution to a closed reactor and crystallize it under autogenous pressure to obtain Cu@S-1 hydrogenation catalyst.

[0011] Further, the complexing agent in step (1) is selected from at least one of ethylenediaminetetraacetic acid (EDTA), disodium EDTA, and ethylenediamine; preferably, the complexing agent is disodium EDTA. The soluble copper salt is selected from at least one of copper nitrate, copper sulfate, and copper chloride; preferably, the soluble copper salt is copper nitrate. The buffer solution is at least one of a mixture of sodium carbonate and sodium bicarbonate, a mixture of disodium hydrogen phosphate and potassium dihydrogen phosphate, and a mixture of ammonium chloride and ammonia; preferably, the buffer solution is a mixture of ammonium chloride and ammonia, wherein the molar ratio of ammonium chloride to ammonia is 0.1 to 10:1.

[0012] Further, the molar ratio of each substance in solution A in step (1) is: total of conjugate acid and base in buffer solution: Cu:H2O:complexing agent = (0.15~1.5):1:(10~100):(0.2~20); preferably: total of conjugate acid and base in buffer solution: Cu:H2O:complexing agent = (0.3~1):1:(20~80):(4~8).

[0013] Furthermore, in step (1), each substance in liquid A is stirred at 30-50°C for 30-120 minutes to mix thoroughly.

[0014] Further, the silicon source in step (2) is selected from at least one of fumed silica, water glass, silica sol, and tetraethyl orthosilicate; preferably, the silicon source is tetraethyl orthosilicate. The alkali is selected from at least one of sodium hydroxide, potassium hydroxide, ammonia, and n-butylamine; preferably, the alkali is sodium hydroxide. The molecular sieve template agent is selected from at least one of n-butylamine, tetraethylammonium hydroxide, tetrapropylammonium hydroxide, tetrapropylammonium bromide, and ammonia; preferably, the molecular sieve template agent is tetrapropylammonium hydroxide.

[0015] Furthermore, in step (2) B, the silicon source is calculated as SiO2, the alkali is calculated as OH-, and the molar ratio of each substance is SiO2:OH-:template agent:H2O=1:(0.1~15):(0.05~10):(5~30); preferably SiO2:OH-:template agent:H2O=1:(0.15~3):(0.1~4):(10~20).

[0016] Furthermore, the temperature of the hydrothermal treatment in step (2) is 40-80°C, preferably 40-60°C, and the reaction time is 2-18h, preferably 4-8h.

[0017] Furthermore, in step (3), after liquid A is added dropwise to liquid B, the mixture is stirred and reacted at 40–80°C for 4–36 hours.

[0018] Furthermore, in step (3), the temperature of the crystallization reaction is 120–190°C, preferably 155–170°C, and the time is 18–96 h, preferably 48–72 h.

[0019] Furthermore, solution A and solution B are mixed at a Cu:SiO2 mass ratio of 1:5 to 1:999, preferably 1:9 to 1:19.

[0020] Furthermore, after crystallization in step (3), the process also includes collecting, filtering, washing, drying, and calcining the product to obtain the catalyst. The collection and post-processing of the product after crystallization are well known to those skilled in the art and will not be described in detail here. A specific product collection process that can be implemented but is not limited to this invention is as follows: After crystallization, the temperature of the reaction vessel is reduced to room temperature by quenching with flowing water. The crystallized product is filtered or centrifuged, wherein the solid product is washed with deionized water until the pH value is 7-8, dried, and calcined at a heating rate of 1-8℃ / min to 400-600℃ for 2-10h to remove the template agent, thereby obtaining the catalyst.

[0021] The technical objective of the second aspect of this invention is to provide a hydrogenation catalyst prepared by the above method.

[0022] The Cu content in the above-mentioned hydrogenation catalyst is 0.1–15.0 wt%; preferably, it is 5.0–10.0 wt%.

[0023] This invention encapsulates Cu in the form of metal clusters within the pores of pure silica zeolite using a complexing agent as a structure guiding agent. The spatial confinement of the zeolite pores prevents Cu from agglomerating during the reaction process, ensuring that it remains at a high degree of dispersion to achieve hydrogenation and exhibiting high stability.

[0024] The technical objective of the third aspect of this invention is to provide a method for preparing dimethyl succinate by hydrogenation of dimethyl maleate, wherein the above-mentioned Cu@S-1 hydrogenation catalyst is reacted with the raw materials.

[0025] Furthermore, the hydrogenation catalyst is subjected to reduction treatment before use. This reduction is carried out using methods well-known to those skilled in the art. Generally, this involves contacting the catalyst with hydrogen at a specific reduction temperature. A common method is to contact the catalyst with nitrogen gas containing a certain hydrogen content at 150–300°C for 2–10 hours.

[0026] Furthermore, the process conditions for the hydrogenation of dimethyl maleate to prepare dimethyl succinate are as follows: the catalyst is crushed to 20-40 mesh and loaded into a tubular reactor, with both ends filled with quartz sand. Under a hydrogen atmosphere, the raw material dimethyl maleate is introduced into the reaction tube via a horizontal flow pump. The reaction pressure is 0.5-5 MPa, the reaction temperature is 140-220℃, and the molar ratio of hydrogen to dimethyl maleate is 20-400.

[0027] Compared with the prior art, the present invention has the following beneficial effects:

[0028] (1) In the preparation method of the present invention, Cu is introduced into the pores of pure silicon molecular sieve by using a complexing agent. Pure silicon molecular sieve is not acidic and will not affect the hydrogenation reaction. By utilizing its unique pore confinement effect, Cu is prevented from agglomerating and growing during the reaction process, thus affecting its hydrogenation effect, thereby giving the catalyst strong stability and improving the catalyst life.

[0029] (2) The Cu@S-1 hydrogenation catalyst prepared in this invention catalyzes the production of dimethyl maleate from dimethyl succinate. Compared with Cu-based catalysts prepared by conventional methods, the catalyst of this invention has a longer service life and significantly improved selectivity.

[0030] Other features and advantages of the present invention will be described in detail in the following detailed description section. Attached Figure Description

[0031] Figure 1 XRD diffraction pattern of the catalyst Cu@S-1-1# prepared in Example 1;

[0032] Figure 2 TEM image of the catalyst Cu@S-1-1# prepared in Example 1;

[0033] Figure 3 STEM image of the catalyst Cu@S-1-1# prepared in Example 1;

[0034] Figure 4 The UV-Vis absorption spectra of the reactants and products in the verification experiment of Example 1. Detailed Implementation

[0035] The following non-limiting embodiments are intended to enable those skilled in the art to more fully understand the invention, but do not limit the invention in any way.

[0036] Example 1

[0037] Preparation of catalyst Cu@S-1-1#:

[0038] (1) Mix the buffer solution prepared by disodium ethylenediaminetetraacetate, copper nitrate, ammonium chloride and ammonia water with deionized water and stir at 30°C for 30 min. This mixture is called solution A. Its molar composition is: total of conjugate acid and base in the buffer solution: Cu:H2O:complexing agent = 1.5:1:10:0.2;

[0039] (2) Tetraethyl orthosilicate, ammonia, tetrapropylammonium hydroxide and deionized water are mixed to obtain solution B. The silicon source is SiO2 and the base is OH-. The molar composition is: SiO2:OH-:template agent:H2O=1:0.15:0.1:10. Solution B is hydrothermally treated at 40℃ for 4h.

[0040] (3) Add solution A slowly dropwise to solution B. Mix solution A and solution B at a Cu:SiO2 mass ratio of 1:19. Stir at 40°C for 4 hours. Transfer the resulting mixture to a hydrothermal crystallization vessel with a polytetrafluoroethylene liner. Under self-generated pressure, dynamically rotate and crystallize at 170°C for 72 hours. After crystallization, cool the reactor to room temperature by flowing water. Filter or centrifuge the crystallized product. Wash the solid product with deionized water until the pH value is 7-8. Dry at 120°C. Calcine at 540°C for 6 hours at a heating rate of 3°C / min to remove the template agent and obtain catalyst Cu@S-1-#1. The Cu loading is 5.0 wt% based on the feed amount.

[0041] The XRD diffraction pattern of the catalyst Cu@S-1-1# shows a typical MFI topology, such as... Figure 1 As shown, the relative crystallinity is 99%, and no diffraction peaks of CuO were observed, indicating that the metal is well encapsulated, uniformly dispersed, and free of CuO metal agglomerates. The TEM and STEM images of the product are shown below. Figure 2 and Figure 3 As shown, it can be observed that the metallic Cu nanoparticles are uniformly distributed in the S-1 channels, with a uniform particle size of approximately 2–4 nm.

[0042] To further demonstrate that Cu is encapsulated within the channels of pure silicon S-1 rather than deposited on the surface of pure silicon S-1, a liquid-phase hydrogenation experiment was used for verification.

[0043] 0.1 g of sodium borohydride was dissolved in 3 g of aqueous solution, and 0.1 g of catalyst Cu@S-1-1# was added. The reaction was allowed to proceed for 30 min. This step aims to reduce the hydrogenation active metal in the catalyst and provide hydrogen for the liquid-phase hydrogenation reaction. 15 mL of 3-nitrotoluene and 7 g of water were added to the above solution, and the reaction was carried out under sealed conditions for 1 h. After the reaction was complete, the reactants and products were analyzed by UV-Vis absorption spectroscopy in the range of 225-400 nm. (See attached image). Figure 4 .Depend on Figure 4It can be seen that the raw material 3-nitrotoluene was not hydrogenated to 3-aminotoluene by Cu@S-1-1#, proving that the hydrogenation active metal Cu was completely encapsulated in pure silicon S-1. Because the molecular diameter of 3-nitrotoluene is larger than the pore diameter of S-1, it cannot enter the interior of S-1 and therefore cannot undergo hydrogenation to generate 3-aminotoluene.

[0044] Example 2

[0045] Preparation of catalyst Cu@S-1-2#:

[0046] The preparation process is the same as in Example 1, except that the molar composition of solution A is: total of conjugate acid and base in the buffer solution: Cu:H2O:complexing agent = 1.2:1:40:6. The molar composition of the silicon source in solution B, calculated as SiO2, and the base, calculated as OH-, is: SiO2:OH-:template agent:H2O = 1:0.3:0.2:20. Solution A and solution B are mixed at a Cu:SiO2 mass ratio of 1:9, and the theoretical Cu loading is 10.0 wt%.

[0047] Example 3

[0048] Preparation of catalyst Cu@S-1-3#:

[0049] The preparation process is the same as in Example 1, except that the molar composition of solution A is: total of conjugate acid and base in the buffer solution: Cu:H2O:complexing agent = 0.8:1:50:6, and the molar composition of the silicon source (SiO2) and base (OH-) in solution B is: SiO2:OH-:template agent:H2O = 1:0.3:3:25. Solution A and solution B are mixed at a Cu:SiO2 mass ratio of 1:5.67. The difference is that the theoretical Cu loading is 15.0 wt%.

[0050] Example 4

[0051] Preparation of catalyst Cu@S-1-4#:

[0052] (1) Mix the buffer solution prepared with ethylenediamine, copper nitrate, sodium carbonate and sodium bicarbonate with deionized water and stir at 50°C for 120 min. This solution is called solution A. Its molar composition is: total of conjugate acid and base in the buffer solution: Cu:H2O:complexing agent = 0.25:1:20:2;

[0053] (2) Tetraethyl orthosilicate, ammonia, tetrapropylammonium hydroxide and deionized water are mixed to obtain solution B. The silicon source is SiO2 and the base is OH-. The molar composition is: SiO2:OH-:template agent:H2O=1:0.6:0.4:20. Solution B is hydrothermally treated at 60℃ for 8h.

[0054] (3) Add solution A slowly dropwise to solution B. Mix solution A and solution B at a Cu:SiO2 mass ratio of 1:9. Stir at 60°C for 12 hours. Transfer the resulting mixture to a hydrothermal crystallization vessel with a polytetrafluoroethylene liner. Under self-generated pressure, dynamically rotate and crystallize at 165°C for 56 hours. After crystallization, cool the reactor to room temperature by flowing water. Filter or centrifuge the crystallized product. Wash the solid product with deionized water until the pH value is 7-8. Dry at 120°C. Calcine at 540°C for 6 hours at a heating rate of 3°C / min to remove the template agent and obtain catalyst Cu@S-1-#4. The Cu loading is 10.0 wt% based on the feed amount.

[0055] Example 5

[0056] Preparation of catalyst Cu@S-1-5#:

[0057] The preparation process is the same as in Example 4, except that the soluble copper salt in step (1) is copper sulfate.

[0058] Example 6

[0059] Preparation of catalyst Cu@S-1-6#:

[0060] The preparation process is the same as in Example 4, except that the silicon source in step (2) is fumed silica and the alkali is sodium hydroxide.

[0061] Example 7

[0062] Preparation of catalyst Cu@S-1-7#:

[0063] (1) Mix the buffer solution prepared by disodium ethylenediaminetetraacetate, copper chloride, ammonium chloride and ammonia water with deionized water and stir at 40°C for 60 min. This mixture is called solution A. Its molar composition is: total of conjugate acid and base in the buffer solution: Cu:H2O:complexing agent = 0.75:1:30:4;

[0064] (2) Silicate sol, ammonia, tetrapropylammonium hydroxide and deionized water are mixed to obtain solution B, the molar composition of which is: SiO2:OH-:template agent:H2O=1:0.3:0.3:15. Solution B is hydrothermally treated at 50℃ for 12h.

[0065] (3) Add solution A slowly dropwise to solution B. Mix solution A and solution B at a Cu:SiO2 mass ratio of 1:11.5. Stir at 50°C for 24 hours. Transfer the resulting mixture to a hydrothermal crystallization vessel with a polytetrafluoroethylene liner. Under autogenous pressure, dynamically rotate and crystallize at 160°C for 72 hours. After crystallization, cool the reactor to room temperature by quenching with flowing water. Filter or centrifuge the crystallized product. Wash the solid product with deionized water until the pH value is 7-8. Dry at 120°C. Calcine at 540°C for 6 hours at a heating rate of 3°C / min to remove the template agent and obtain catalyst Cu@S-1-#7. The Cu loading calculated based on the feed amount is 8.0 wt%.

[0066] Example 8

[0067] Preparation of catalyst Cu@S-1-8#:

[0068] The preparation process is the same as in Example 7, except that the buffer solution in step (1) is a mixture of disodium hydrogen phosphate and potassium dihydrogen phosphate. The molar composition of solution A is: total of conjugate acid and base in the buffer solution: Cu:H2O:complexing agent = 1.2:1:50:7. Solution A and solution B are mixed at a Cu:SiO2 mass ratio of 1:9.53. The Cu loading calculated based on the amount of feed is 9.5 wt%.

[0069] Example 9

[0070] Preparation of catalyst Cu@S-1-9#:

[0071] The preparation process is the same as in Example 7, except that the molar composition of liquid B in step (2) is: SiO2:OH - Template agent:H2O = 1:0.8:0.5:25. Solution A and solution B are mixed at a Cu:SiO2 mass ratio of 1:7. The Cu loading calculated based on the amount of material fed is 12.5 wt%.

[0072] Comparative Example 1

[0073] Preparation of Cu / SiO2:

[0074] This comparative example shows the preparation of a Cu / SiO2 catalyst with a Cu content of 10.0 wt% using the traditional wet impregnation method.

[0075] Copper nitrate, a precursor of metallic Cu, was dissolved in deionized water and stirred until dissolved. Then, calcined SiO2 support was added to the solution, and the mixture was stirred at room temperature for 8 hours. The mass ratio of Cu, SiO2, and H2O in the resulting mixture was 0.1:1:10. The mixture was then transferred to an oven and dried at 120°C for 24 hours. After cooling, the product was removed, ground, and calcined at 540°C for 6 hours to obtain a Cu / SiO2 catalyst prepared by the traditional wet impregnation method, denoted as DB1.

[0076] Comparative Example 2

[0077] Cu-Zn-Al catalyst: Commercially available conventional Cu-Zn-Al catalyst with a Cu content of 10 wt% is used, denoted as DB2.

[0078] Comparative Example 3

[0079] Cu-Al2O3 catalyst: Commercially available conventional Cu-Al2O3 catalyst with a Cu content of 10 wt% is used, denoted as DB3.

[0080] The metal content of the catalysts obtained in each example and comparative example was characterized by XRF, as shown in Table 1.

[0081] Table 1

[0082]

[0083]

[0084] Catalyst evaluation

[0085] The catalyst is crushed to 20-40 mesh and loaded into the reaction tube of a micro fixed-bed reactor with an inner diameter of 10 mm. The catalyst is placed near the constant temperature section and filled with 20-40 mesh quartz sand at both ends.

[0086] Catalytic reduction was performed by introducing a mixture of 5% H2 and 95% N2 gas, and the temperature was programmed to rise to 230°C, held for 5 hours, and then lowered to the reaction temperature.

[0087] The reaction gas was switched to pure H2. Dimethyl maleate, the feedstock, was introduced into the reaction tube via a horizontal flow pump. The reaction pressure was 1.0 MPa, the reaction temperature was 170°C, the molar ratio of hydrogen to dimethyl maleate was 200, and the feed volume hourly space velocity (LHSV) was 0.2 h⁻¹. -1 The reaction products were condensed and their composition was analyzed by gas chromatography. The results are shown in Table 2.

[0088] Table 2

[0089]

[0090]

Claims

1. A method for preparing a hydrogenation catalyst, comprising the following steps: (1) Mix the complexing agent, soluble copper salt, buffer solution and water to obtain solution A; wherein the complexing agent is selected from at least one of ethylenediaminetetraacetic acid, disodium ethylenediaminetetraacetic acid and ethylenediamine; the buffer solution is at least one of a mixture of sodium carbonate and sodium bicarbonate, a mixture of disodium hydrogen phosphate and potassium dihydrogen phosphate and a mixture of ammonium chloride and ammonia; the molar ratio of each substance in solution A is: total of conjugate acid and base in buffer solution: Cu:H2O:complexing agent = 0.15~1.5:1:10~100:0.2~20; (2) Mix silicon source, alkali, molecular sieve template agent and water, and hydrothermally treat at 40-80℃ to obtain solution B; the alkali is selected from at least one of sodium hydroxide, potassium hydroxide and ammonia water; the molecular sieve template agent is selected from at least one of n-butylamine, tetraethylammonium hydroxide, tetrapropylammonium hydroxide and tetrapropylammonium bromide; (3) Add solution A dropwise to solution B. After the reaction, transfer it to a closed reactor for crystallization under autogenous pressure. The crystallization reaction temperature is 120~190℃ to obtain Cu@S-1 hydrogenation catalyst.

2. The preparation method according to claim 1, characterized in that, The soluble copper salt mentioned in step (1) is selected from at least one of copper nitrate, copper sulfate and copper chloride.

3. The preparation method according to claim 1, characterized in that, The silicon source mentioned in step (2) is selected from at least one of fumed silica, water glass, silica sol and tetraethyl orthosilicate.

4. The preparation method according to claim 1, characterized in that, In step (2), the silicon source in solution B is calculated as SiO2, and the alkali is calculated as OH-. - The molar ratio of each substance is calculated to be SiO2:OH. - Template agent:H2O=1:0.1~15:0.05~10:5~30.

5. The preparation method according to claim 1, characterized in that, The reaction time for the hydrothermal treatment described in step (2) is 2 to 18 hours.

6. The preparation method according to claim 1, characterized in that, In step (3), after liquid A is added to liquid B, the mixture is stirred at 40-80℃ for 4-36 hours.

7. The preparation method according to claim 1, characterized in that, The crystallization reaction in step (3) takes 18 to 96 hours.

8. The preparation method according to claim 1, characterized in that, Solution A and solution B are mixed at a Cu:SiO2 mass ratio of 1:5 to 1:

999.

9. The hydrogenation catalyst prepared by the preparation method according to any one of claims 1-8.

10. A method for preparing dimethyl succinate by hydrogenation of dimethyl maleate, characterized in that, The hydrogenation catalyst as described in claim 9 is used to react with the raw materials.

11. The method according to claim 10, characterized in that, The hydrogenation catalyst is reduced before use.

12. The method according to claim 10, characterized in that, The process conditions for the hydrogenation of dimethyl maleate to dimethyl succinate are as follows: the catalyst is crushed to 20-40 mesh and loaded into a tubular reactor, with both ends filled with quartz sand. Under a hydrogen atmosphere, the raw material dimethyl maleate is introduced into the reaction tube via a horizontal flow pump. The reaction pressure is 0.5-5 MPa, the reaction temperature is 140-220℃, and the molar ratio of hydrogen to dimethyl maleate is 20-400.

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