Hydrogenation catalyst for dimethyl maleate and its preparation and application

Abstract

This invention discloses a hydrogenation catalyst for dimethyl maleate, its preparation method, and its application. The preparation method of the hydrogenation catalyst of this invention includes: (1) mixing soluble copper salt, soluble manganese salt, and soluble aluminum salt with dichloromethane and ethanol to obtain a mixed solution containing copper, manganese, and aluminum; then adding polylactic acid and stirring to obtain a spinning solution; (2) using a coaxial electrospinning nozzle to perform electrospinning with the spinning solution obtained in step (1), and collecting the resulting solid; (3) placing the solid obtained in step (2) in an ethanol solution of trimesic acid for reaction; after the reaction, washing and drying to obtain a catalyst precursor; (4) calcining and post-treatment of the catalyst precursor obtained in step (3) to obtain the catalyst. The catalyst prepared using the method of this invention is used in the hydrogenation of dimethyl maleate to 1,4-butanediol and the co-production of γ-butyrolactone and tetrahydrofuran, exhibiting high conversion rate and target product selectivity.

Description

Technical Field

[0001] This invention belongs to the field of catalyst technology, specifically relating to a hydrogenation catalyst for dimethyl maleate, its preparation method, and its application. Background Technology

[0002] 1,4-Butanediol (BDO) is an important raw material for organic and fine chemicals, mainly used in the production of tetrahydrofuran (THF), gamma-butyrolactone (GBL), polybutylene terephthalate (PBT), and polyurethane (PU). GBL can undergo amination with methylamine to produce N-methylpyrrolidone (NMP), which is widely used as an additive in electrolytes to improve battery conductivity and stability. THF can undergo condensation polymerization with BDO to form polytetrahydrofuran ether (PTMG) and self-condensation polymerization to form polytetramethylene ether glycol (PTMEG).

[0003] In recent years, due to the rapid growth in demand for thermoplastic elastic fibers, elastomers, and additives for new energy battery electrolytes, the demand for PTMEG, PTMG, and NMP as elastic monomers and solvents has been strong, which has led to a rapid increase in demand for upstream raw material 1,4-butanediol. Therefore, based on the huge demand for high value-added chemical products in the BDO industry chain, it is of great significance to develop technology for the co-production of BDO with GBL and THF.

[0004] Currently, the main production processes for BDO include the acetylacetonate method, the maleic anhydride method, the butadiene method, and the propylene oxide method. Among these, the maleic anhydride method can be further divided into the direct hydrogenation of maleic anhydride and the esterification hydrogenation of maleic anhydride. The esterification hydrogenation route of maleic anhydride has mild reaction conditions, economical and readily available raw materials, and the three hydrogenation products—1,4-butanediol, tetrahydrofuran, and γ-butyrolactone—can be produced in different proportions, making the route highly flexible and possessing significant market competitiveness and development potential.

[0005] CN101502803A discloses a catalyst and its preparation method for the selective hydrogenation of dimethyl maleate to 1,4-butanediol or tetrahydrofuran. The method first involves co-precipitating a Cu-Zn-MO precipitate with a soluble salt solution of Cu, Zn, etc., and a precipitant in a co-current flow. Then, aluminum hydroxide is added to obtain a catalyst precursor. After drying, calcination, and granulation, the catalyst is used to catalyze the hydrogenation reaction of dimethyl maleate, achieving a BDO yield of 73.6% at 180°C.

[0006] CN1850328A discloses a highly selective catalyst for the hydrogenation of dimethyl maleate to 1,4-butanediol and its preparation method. The catalyst is a Cu / ZnO / supported metal oxide ternary system. The catalyst is obtained by a common co-precipitation method, in which the precipitate is added dropwise under stirring conditions, followed by aging, washing, drying and calcination.

[0007] Currently, some progress has been made in the development of Cu-based catalysts for the hydrogenation of dimethyl maleate to 1,4-butanediol. However, the synthesis of these catalysts typically employs precipitation methods, which make it difficult to control the distribution of active metals during precipitation. This can easily lead to agglomeration or burial of the active metals, resulting in insufficient exposure of active sites. Adding aluminum hydroxide after precipitation can cause uneven dispersion of aluminum hydroxide during the precipitation process, leading to a higher acidity in the catalyst and consequently lower selectivity. Under the high temperature and presence of hydrogen in the reaction conditions, these problems can all lead to Cu agglomeration and sintering, resulting in a series of issues such as decreased catalyst yield, rapid deactivation, and catalyst carbon deposition, thus affecting both catalyst activity and selectivity. Summary of the Invention

[0008] To address the shortcomings of existing technologies, this invention provides a hydrogenation catalyst for dimethyl maleate, its preparation method, and its application. The catalyst prepared using the method of this invention exhibits high conversion rate and selectivity for the target products in the hydrogenation of dimethyl maleate to 1,4-butanediol, co-production of γ-butyrolactone and tetrahydrofuran.

[0009] The first aspect of this invention provides a method for preparing a hydrogenation catalyst for dimethyl maleate, comprising:

[0010] (1) Soluble copper salt, soluble manganese salt and soluble aluminum salt are mixed with dichloromethane and ethanol to obtain a mixed solution containing copper, manganese and aluminum. Polylactic acid is then added and stirred to obtain a spinning solution.

[0011] (2) Using a coaxial electrospinning nozzle, electrospinning is performed with the spinning solution obtained in step (1), and the resulting solid is collected.

[0012] (3) The solid obtained in step (2) is placed in an ethanol solution of pyromellitic acid and reacted. After the reaction is completed, it is washed and dried to obtain the catalyst precursor.

[0013] (4) The catalyst precursor obtained in step (3) is calcined and post-treated to obtain the catalyst.

[0014] Further, in step (1), the soluble copper salt is one or more of copper nitrate trihydrate, copper sulfate, copper chloride, and copper acetate. The soluble manganese salt is one or more of manganese nitrate hexahydrate, manganese sulfate, and manganese acetate. The soluble aluminum salt is one or more of aluminum nitrate nonahydrate, aluminum sulfate, and aluminum chloride.

[0015] Further, in step (1), the concentration of soluble copper salt in the copper, manganese and aluminum mixture is 0.01 to 0.2 mol / L, the concentration of soluble manganese salt is 0.0015 to 0.03 mol / L, and the concentration of soluble aluminum salt is 0.011 to 0.22 mol / L.

[0016] Further, in step (1), the volume ratio of dichloromethane to ethanol is (1-5):1.

[0017] Further, in step (1), the molecular weight of polylactic acid is 80,000 to 200,000, and the concentration of polylactic acid in the spinning solution is 0.03 to 0.3 g / mL.

[0018] Further, in step (1), the stirring conditions are: stirring speed of 100 to 1500 rpm and stirring time of 2 to 24 hours.

[0019] Further, in step (2), the conditions for electrospinning are: spinning voltage of 15-30kV, feed speed of 0.5-3.0mL / h, and receiving distance of 10-20cm.

[0020] Further, in step (2), the internal needle size of the coaxial electrospinning nozzle is 14-20G, and the external needle size is 19-25G, wherein the internal needle size is smaller than the external needle size.

[0021] Further, in step (3), the concentration of pyromellitic acid in the ethanol solution of pyromellitic acid is 0.01 to 1.0 mol / L.

[0022] Furthermore, in step (3), the concentration of the solid obtained in step (2) in the pyromellitic acid ethanol solution is 0.02 to 0.2 g / mL.

[0023] Furthermore, in step (3), the reaction conditions are: reacting at 25–80°C for 0.5–5 h.

[0024] Further, in step (3), the washing process involves first washing with ethanol 1 to 3 times, and then washing with deionized water 1 to 3 times.

[0025] Furthermore, in step (3), the drying conditions are as follows: the drying temperature is 25-80℃, and the drying time is 6-24h.

[0026] Further, in step (4), the calcination conditions are: a calcination temperature of 600–800°C and a calcination time of 2–6 hours. The calcination preferably employs a programmed temperature rise, with a heating rate of 2–10°C / min to reach the calcination temperature. The calcination atmosphere is an oxygen-containing atmosphere, such as air.

[0027] Furthermore, in step (4), the post-processing includes processes such as tableting, crushing, and sieving. The post-processing can be carried out using conventional methods in the art. An appropriate amount of graphite may be added during the tableting process. The crushing and sieving involves sieving particles of 20-40 mesh.

[0028] A second aspect of the present invention provides a hydrogenation catalyst for dimethyl maleate prepared by the above method.

[0029] Furthermore, the catalyst comprises oxides of CuO, Al2O3, and Mn.

[0030] Furthermore, based on the weight of the catalyst, the weight contents of each component are as follows: copper content (calculated as CuO) 45%–65%, manganese content (calculated as MnO) 5%–15%, and aluminum content (calculated as Al2O3) 20%–35%.

[0031] Furthermore, the catalyst also contains a forming aid, such as graphite, which accounts for less than 5% by weight in the catalyst, and more specifically 0.1% to 8%.

[0032] Furthermore, the catalyst is tested by H2-N2O titration, and the dispersion of metallic Cu is 40% to 70%, preferably 48% to 60%, for example, but not limited to 40%, 42%, 45%, 48%, 50%, 52%, 55%, 58%, 60%, 65%, 70%, etc., and any value within the range formed by any two of these values.

[0033] Furthermore, the total acidity of the catalyst is 0.30–0.55 mmol / g.

[0034] Furthermore, the specific surface area of ​​the catalyst is 45–65 m². 2 / g, pore volume 0.2~0.3cm 3 / g, with an average pore size of 15–25 nm.

[0035] The third aspect of this invention provides the application of the above-mentioned catalyst in the hydrogenation of dimethyl maleate to synthesize 1,4-butanediol and co-produce γ-butyrolactone and tetrahydrofuran.

[0036] Furthermore, the application includes: reacting dimethyl maleate with the catalyst in the presence of hydrogen to produce 1,4-butanediol, co-producing γ-butyrolactone and tetrahydrofuran.

[0037] Furthermore, the catalyst of this invention needs to be reduced and activated before use. The reducing gas is hydrogen, or a mixture of hydrogen and nitrogen, wherein the volume ratio of H2 / N2 is (1-10):(90-99). The reduction temperature is 220-300℃, and the reduction time is 6-24h.

[0038] Furthermore, the reaction conditions are as follows: reaction temperature of 150–300℃, reaction pressure of 1–10 MPa, and volume hourly space velocity of 0.1–2.0 h⁻¹. -1 The molar ratio of hydrogen to dimethyl maleate is 100–300:1.

[0039] Compared with the prior art, the present invention has the following advantages:

[0040] (1) The catalyst of the present invention is used in the reaction of hydrogenation of dimethyl maleate to produce 1,4-butanediol and co-production of γ-butyrolactone and tetrahydrofuran, and has high conversion rate and target product selectivity.

[0041] (2) The preparation method of the present invention utilizes coaxial electrospinning technology, which provides abundant mass transfer channels for reactants to enter the internal space of the catalyst, thereby improving the catalytic activity. At the same time, the active metal Cu is fixed by pyromellitic acid, forming a heterogeneous interface with Mn-Al, which improves the metal dispersion and also improves the catalyst's high conversion rate and target product selectivity in the hydrogenation of dimethyl maleate to 1,4-butanediol and the co-production of γ-butyrolactone and tetrahydrofuran. Detailed Implementation

[0042] The technical solution of the present invention will be described in detail below with reference to the embodiments, but the present invention is not limited to the following embodiments. In the present invention, wt% is a mass fraction.

[0043] In this invention, an ASAP 2425 (McClone Systems, Inc., USA) physical adsorption analyzer was used to test specific surface area, pore volume, and pore size. Specific surface area was analyzed using the BET method; pore size distribution was calculated using BJH and DFT theoretical models based on the adsorption data.

[0044] In this invention, a PANalytical Axios X-ray fluorescence spectrometer was used to analyze the types and contents of elements.

[0045] In this invention, the metal dispersion was tested using an AutoChem II 2920 (McClone Systems, Inc., USA) chemisorption analyzer via H2-N2O titration. The specific test method is as follows:

[0046] (a) Weigh 100 mg of the catalyst sample to be tested and place it in a U-shaped quartz tube. Pre-treat it at 450 °C for 1 h under an inert atmosphere, and then cool it to room temperature. Under a mixed atmosphere of 10% H2 / 90% Ar by volume, raise the temperature to 800 °C at a rate of 10 °C / min and measure the amount of H2 consumed, X, to determine the total number of Cu atoms in the catalyst sample.

[0047] (b) The reduced catalyst was purged and cooled to 50°C under an inert atmosphere. The volume fraction was changed to 10% N2O / 90% Ar and reacted for 1 h. The metal Cu on the surface of the catalyst sample was oxidized to Cu2O (2Cu+N2O→Cu2O+N2). Then, the residual N2O was purged clean under an inert atmosphere.

[0048] (c) After the oxidation step, a H2 programmed temperature reduction process is carried out. Under a mixed atmosphere of 10% H2 / 90% Ar by volume, the temperature is increased to 800℃ at a rate of 10℃ / min. The amount of H2 consumed, Y, is measured to determine the number of Cu atoms on the surface of the catalyst sample.

[0049] The formula for calculating the dispersion of metallic Cu is: Dispersion (%) = 2Y / X × 100%.

[0050] Example 1

[0051] (1) Cu(NO3)2·3H2O, Mn(NO3)2·6H2O and Al(NO3)3·9H2O were added to 15mL of dichloromethane and 5mL of anhydrous ethanol to prepare a mixed solution containing copper, manganese and aluminum. The concentration of copper salt in the mixed solution was 0.1mol / L, the concentration of manganese salt was 0.016mol / L and the concentration of aluminum salt was 0.08mol / L. 2g of polylactic acid (molecular weight 160000) was added to the solution and stirred at 1000rpm for 12h to obtain the spinning solution.

[0052] (2) Using a coaxial electrospinning nozzle (inner needle model 16G, outer needle model 21G), with the spinning solution obtained in step (1) as the shell, electrospinning is performed according to the following parameters: the spinning voltage is controlled at 20kV, the feed speed is 2.0mL / h, and the receiving distance is 15cm.

[0053] (3) Place 5g of the solid obtained in step (2) into 50mL of ethanol solution of pyromellitic acid (the concentration of pyromellitic acid is 0.1mol / L), react at 50℃ for 2h, wash with ethanol 3 times and deionized water 3 times after the reaction is completed, and dry at 50℃ for 12h to obtain the catalyst precursor.

[0054] (4) The catalyst precursor obtained in step (3) is placed in a muffle furnace for calcination under the following conditions: the calcination temperature rise rate is 5℃ / min to 700℃, and calcination is carried out at 700℃ for 4 hours. The calcination atmosphere is air. Graphite is added to the obtained catalyst powder, which is then pressed into tablets, pulverized, and sieved to obtain 20-40 mesh particles to form catalyst A1. The properties of catalyst A1 are shown in Table 1.

[0055] Example 2

[0056] (1) Cu(NO3)2·3H2O, Mn(NO3)2·6H2O and Al(NO3)3·9H2O were added to 15mL of dichloromethane and 5mL of anhydrous ethanol to prepare a mixed solution containing copper, manganese and aluminum. The concentration of copper salt in the mixed solution was 0.1mol / L, the concentration of manganese salt was 0.016mol / L and the concentration of aluminum salt was 0.08mol / L. 1.5g of polylactic acid (molecular weight 160000) was added to the solution and stirred at 1000rpm for 12h to obtain the spinning solution.

[0057] (2) Using a coaxial electrospinning nozzle (inner needle model 16G, outer needle model 21G), with the spinning solution obtained in step (1) as the shell, electrospinning is performed according to the following parameters: the spinning voltage is controlled at 20kV, the feed speed is 2.0mL / h, and the receiving distance is 15cm.

[0058] (3) The precursor obtained in step (2) was placed in 50 mL of ethanol solution of pyromellitic acid (the concentration of pyromellitic acid was 0.1 mol / L), and reacted at 50 °C for 2 h. After the reaction was completed, the precursor was washed three times with ethanol and three times with deionized water, and dried at 50 °C for 12 h to obtain the catalyst precursor.

[0059] (4) The catalyst precursor obtained in step (3) is placed in a muffle furnace for calcination under the following conditions: the calcination temperature rise rate is 5℃ / min to 700℃, and calcination is carried out at 700℃ for 4 hours. The calcination atmosphere is air. Graphite is added to the obtained catalyst powder, which is then pressed into tablets, pulverized, and sieved to obtain 20-40 mesh particles to form catalyst A2. The properties of catalyst A2 are shown in Table 1.

[0060] Example 3

[0061] (1) Cu(NO3)2·3H2O, Mn(NO3)2·6H2O and Al(NO3)3·9H2O were added to 15mL of dichloromethane and 5mL of anhydrous ethanol to prepare a mixed solution containing copper, manganese and aluminum. The concentration of copper salt in the mixed solution was 0.2mol / L, the concentration of manganese salt was 0.032mol / L and the concentration of aluminum salt was 0.16mol / L. 2g of polylactic acid (molecular weight 160000) was added to the solution and stirred at 1000rpm for 12h to obtain the spinning solution.

[0062] (2) Using a coaxial electrospinning nozzle (inner needle model 16G, outer needle model 21G), with the spinning solution obtained in step (1) as the shell, electrospinning is performed according to the following parameters: the spinning voltage is controlled at 20kV, the feed speed is 2.0mL / h, and the receiving distance is 15cm.

[0063] (3) The precursor obtained in step (2) was placed in 50 mL of ethanol solution of pyromellitic acid (the concentration of pyromellitic acid was 0.1 mol / L), and reacted at 50 °C for 2 h. After the reaction was completed, the precursor was washed three times with ethanol and three times with deionized water, and dried at 50 °C for 12 h to obtain the catalyst precursor.

[0064] (4) The catalyst precursor obtained in step (3) is placed in a muffle furnace for calcination under the following conditions: the calcination temperature rise rate is 5℃ / min to 660℃, and calcination is carried out at 660℃ for 4 hours in an air atmosphere. Graphite is added to the obtained catalyst powder, which is then pressed into tablets, pulverized, and sieved to obtain 20-40 mesh particles to form catalyst A3. The properties of catalyst A3 are shown in Table 1.

[0065] Example 4

[0066] (1) Cu(NO3)2·3H2O, Mn(NO3)2·6H2O and Al(NO3)3·9H2O were added to 15mL of dichloromethane and 5mL of anhydrous ethanol to prepare a mixed solution containing copper, manganese and aluminum. The concentration of copper salt in the mixed solution was 0.1mol / L, the concentration of manganese salt was 0.016mol / L and the concentration of aluminum salt was 0.08mol / L. 2g of polylactic acid (molecular weight 160000) was added to the solution and stirred at 1000rpm for 12h to obtain the spinning solution.

[0067] (2) Using a coaxial electrospinning nozzle (inner needle model 17G, outer needle model 22G), with the spinning solution obtained in step (1) as the shell, electrospinning is performed according to the following parameters: the spinning voltage is controlled at 15kV, the feed speed is 1.5mL / h, and the receiving distance is 10cm.

[0068] (3) Place 5g of the solid obtained in step (2) into 50mL of ethanol solution of pyromellitic acid (the concentration of pyromellitic acid is 0.1mol / L), react at 50℃ for 2h, wash with ethanol 3 times and deionized water 3 times after the reaction is completed, and dry at 50℃ for 12h to obtain the catalyst precursor.

[0069] (4) The catalyst precursor obtained in step (3) is placed in a muffle furnace for calcination under the following conditions: the calcination temperature rise rate is 5℃ / min to 700℃, and calcination is carried out at 700℃ for 4 hours in an air atmosphere. Graphite is added to the obtained catalyst powder, which is then pressed into tablets, pulverized, and sieved to obtain 20-40 mesh particles to form catalyst A4. The properties of catalyst A4 are shown in Table 1.

[0070] Example 5

[0071] (1) Cu(NO3)2·3H2O, Mn(NO3)2·6H2O and Al(NO3)3·9H2O were added to 15mL of dichloromethane and 5mL of anhydrous ethanol to prepare a mixed solution containing copper, manganese and aluminum. The concentration of copper salt in the mixed solution was 0.1mol / L, the concentration of manganese salt was 0.016mol / L and the concentration of aluminum salt was 0.08mol / L. 2g of polylactic acid (molecular weight 160000) was added to the solution and stirred at 1000rpm for 12h to obtain the spinning solution.

[0072] (2) Using a coaxial electrospinning nozzle (inner needle model 16G, outer needle model 21G), with the spinning solution obtained in step (1) as the shell, electrospinning is performed according to the following parameters: the spinning voltage is controlled at 20kV, the feed speed is 2.0mL / h, and the receiving distance is 15cm.

[0073] (3) Place 5g of the solid obtained in step (2) into 50mL of ethanol solution of pyromellitic acid (the concentration of pyromellitic acid is 0.05mol / L), react at 50℃ for 2h, wash with ethanol 3 times and deionized water 3 times after the reaction is completed, and dry at 50℃ for 12h to obtain the catalyst precursor.

[0074] (4) The catalyst precursor obtained in step (3) is placed in a muffle furnace for calcination under the following conditions: the calcination temperature rise rate is 5℃ / min to 700℃, and calcination is carried out at 700℃ for 4 hours in an air atmosphere. Graphite is added to the obtained catalyst powder, which is then pressed into tablets, pulverized, and sieved to obtain 20-40 mesh particles to form catalyst A5. The properties of catalyst A5 are shown in Table 1.

[0075] Comparative Example 1

[0076] (1) Cu(NO3)2·3H2O, Mn(NO3)2·6H2O and Al(NO3)3·9H2O were added to 15mL of dichloromethane and 5mL of anhydrous ethanol to prepare a mixed solution containing copper, manganese and aluminum. The concentration of copper salt in the mixed solution was 0.1mol / L, the concentration of manganese salt was 0.016mol / L and the concentration of aluminum salt was 0.08mol / L. 2.0g of polylactic acid (molecular weight 160000) was added to the solution and stirred at 1000rpm for 12h to obtain the spinning solution.

[0077] (2) Use a common single-channel electrospinning nozzle (needle model 21G) to perform electrospinning according to the following parameters: the spinning voltage is controlled at 20kV, the feed speed is 2.0mL / h, and the receiving distance is 15cm.

[0078] (3) Place 5g of the solid obtained in step (2) into 50mL of ethanol solution of pyromellitic acid (the concentration of pyromellitic acid is 0.1mol / L), react at 50℃ for 2h, wash with ethanol 3 times and deionized water 3 times after the reaction is completed, and dry at 50℃ for 12h to obtain the catalyst precursor.

[0079] (4) The catalyst precursor obtained in step (3) is placed in a muffle furnace for calcination under the following conditions: the calcination temperature rise rate is 5℃ / min to 700℃, and calcination is carried out at 700℃ for 4 hours. The calcination atmosphere is air. Graphite is added to the obtained catalyst powder, which is then pressed into tablets, pulverized, and sieved to obtain 20-40 mesh particles to form catalyst B1. The properties of catalyst B1 are shown in Table 1.

[0080] Comparative Example 2

[0081] (1) Cu(NO3)2·3H2O, Mn(NO3)2·6H2O and Al(NO3)3·9H2O were added to 15mL of dichloromethane and 5mL of anhydrous ethanol to prepare a mixed solution containing copper, manganese and aluminum. The concentration of copper salt in the mixed solution was 0.1mol / L, the concentration of manganese salt was 0.016mol / L and the concentration of aluminum salt was 0.08mol / L. 2.0g of polylactic acid (molecular weight 160000) was added to the solution and stirred at 1000rpm for 12h to obtain the spinning solution.

[0082] (2) Using a coaxial electrospinning nozzle (inner needle model 16G, outer needle model 21G), with the spinning solution obtained in step (1) as the shell, electrospinning is performed according to the following parameters: the spinning voltage is controlled at 20kV, the propulsion speed is 2.0mL / h, the receiving distance is 15cm, and the catalyst precursor is collected.

[0083] (3) The catalyst precursor obtained in step (2) is placed in a muffle furnace for calcination under the following conditions: the calcination temperature rise rate is 5℃ / min to 700℃, and calcination is carried out at 700℃ for 4 hours in an air atmosphere. Graphite is added to the obtained catalyst powder, which is then pressed into tablets, pulverized, and sieved to obtain 20-40 mesh particles to form catalyst B2. The properties of catalyst B2 are shown in Table 1.

[0084] Application examples

[0085] The catalysts prepared in Examples 1-5 and Comparative Examples 1-2 were used for the hydrogenation of dimethyl maleate to 1,4-butanediol, co-producing γ-butyrolactone and tetrahydrofuran. Before use, the catalysts were reduced with hydrogen under the following conditions: hydrogen pressure 0.1 MPa, reduction temperature 270 °C, and reduction time 12 h. After reduction, the reaction was carried out under the following conditions: reaction temperature 190 °C; feed hourly space velocity 0.25 h⁻¹. -1The H2 / ester molar ratio was 200:1; the reaction pressure was 6 MPa. The reaction results are shown in Table 2.

[0086] Table 1. Composition and properties of catalysts obtained in each example.

[0087]

[0088] Table 2 Evaluation results of the catalysts obtained in each example

[0089]

[0090] *Note: In Table 2, the target products are 1,4-butanediol, γ-butyrolactone, and tetrahydrofuran.

[0091] It should be emphasized that the above-mentioned content is only a specific embodiment of the present invention and should not be construed as limiting the present invention to the above description in specific implementation. For those skilled in the art, any simple deductions and improvements made without departing from the spirit and principles of the present invention should be considered within the scope of protection of the present invention.

Claims

1. A method for preparing a hydrogenation catalyst for dimethyl maleate, characterized in that, include: (1) Mix soluble copper salt, soluble manganese salt and soluble aluminum salt with dichloromethane and ethanol to obtain a mixed solution containing copper, manganese and aluminum, then add polylactic acid and stir to obtain a spinning solution. (2) Using a coaxial electrospinning nozzle, electrospinning is performed with the spinning solution obtained in step (1), and the resulting solid is collected. (3) The solid obtained in step (2) is placed in an ethanol solution of pyromellitic acid and reacted. After the reaction is completed, it is washed and dried to obtain the catalyst precursor. (4) The catalyst precursor obtained in step (3) is calcined and post-treated to obtain the catalyst.

2. The method according to claim 1, characterized in that, In step (1), the soluble copper salt is one or more of copper nitrate trihydrate, copper sulfate, copper chloride, and copper acetate; the soluble manganese salt is one or more of manganese nitrate hexahydrate, manganese sulfate, and manganese acetate; and the soluble aluminum salt is one or more of aluminum nitrate nonahydrate, aluminum sulfate, and aluminum chloride. Preferably, in step (1), the concentration of soluble copper salt in the mixed solution of copper, manganese and aluminum is 0.01-0.2 mol / L, the concentration of soluble manganese salt is 0.0015-0.03 mol / L, and the concentration of soluble aluminum salt is 0.011-0.22 mol / L.

3. The method according to claim 1, characterized in that, In step (1), the volume ratio of dichloromethane to ethanol is (1-5):1; And / or, in step (1), the molecular weight of the polylactic acid is 80,000 to 200,000, and the concentration of the polylactic acid in the spinning solution is 0.03 to 0.3 g / mL; And / or, in step (1), the stirring conditions are: stirring speed of 100 to 1500 rpm and stirring time of 2 to 24 hours.

4. The method according to claim 1, characterized in that, In step (2), the conditions for electrospinning are: spinning voltage of 15-30kV, feed speed of 0.5-3.0mL / h, and receiving distance of 10-20cm; And / or, in step (2), the internal needle size of the coaxial electrospinning nozzle is 14-20G and the external needle size is 19-25G, wherein the internal needle size is smaller than the external needle size.

5. The method according to claim 1, characterized in that, In step (3), the concentration of pyromellitic acid in the ethanol solution of pyromellitic acid is 0.01 to 1.0 mol / L; And / or, the concentration of the solid obtained in step (2) in the pyromellitic acid ethanol solution is 0.02 to 0.2 g / mL; And / or, in step (3), the reaction conditions are: reacting at 25–80°C for 0.5–5 h; And / or, in step (3), the drying conditions are as follows: the drying temperature is 25-80℃ and the drying time is 6-24h.

6. The method according to claim 1, characterized in that, In step (4), the calcination conditions are: calcination temperature of 600-800℃, calcination time of 2-6h; the calcination preferably adopts programmed heating, and the heating rate to the calcination temperature is 2-10℃ / min; the calcination atmosphere is an oxygen-containing atmosphere.

7. A hydrogenation catalyst for dimethyl maleate prepared by the method according to any one of claims 1-6.

8. The catalyst according to claim 7, characterized in that, The catalyst comprises oxides of CuO, Al2O3, and Mn; And / or, based on the weight of the catalyst, the weight contents of each component are as follows: copper content is 45% to 65% as CuO, manganese content is 5% to 15% as MnO, and aluminum content is 20% to 35% as Al2O3.

9. The catalyst according to claim 7, characterized in that, The catalyst was tested by H2-N2O titration, and the dispersion of metallic Cu was 40% to 70%, preferably 48% to 60%. And / or, the total acidity of the catalyst is 0.30–0.55 mmol / g; And / or, the specific surface area of ​​the catalyst is 45–65 m². 2 / g, pore volume 0.2~0.3cm 3 / g, with an average pore size of 15–25 nm.

10. The application of the catalyst prepared by any of the methods according to claims 1-6 or the catalyst according to any of claims 7-9 in the hydrogenation of dimethyl maleate to synthesize 1,4-butanediol and co-produce γ-butyrolactone and tetrahydrofuran.

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