Copper-chromium catalyst precursor, catalyst and preparation method and application thereof

Abstract

The invention discloses a copper-chromium catalyst precursor, a catalyst and a preparation method and application of the copper-chromium catalyst precursor. The precursor comprises a biological template and a copper-chromium bimetal organic framework material, the molar ratio of copper to chromium in the copper-chromium bimetal organic framework material is (0.05-5.0): 1, and the preparation method comprises the following steps: (1) mixing a copper source solution with the biological template, controlling the concentration of the biological template in the mixed solution to be 0.01-0.50 g / mL, stirring under a heating condition, and then separating and collecting a precipitate; (2) mixing the precipitate obtained in the step (1) with an organic ligand solution, reacting, washing and drying to obtain a dry solid; and (3) mixing a chromium source solution with the dried solid obtained in the step (2), reacting, washing and drying to obtain a catalyst precursor. When the catalyst obtained by roasting the precursor is used for preparing 1, 4-butanediol through dimethyl maleate hydrogenation, the conversion rate of dimethyl maleate can be increased, and the selectivity of 1, 4-butanediol can be improved.

Description

Technical Field

[0001] The invention belongs to the technical field of catalyst preparation, and specifically relates to a copper-chromium catalyst and a preparation method thereof, and application of the catalyst in preparing 1,4-butanediol by hydrogenating dimethyl maleate. Background Art

[0002] 1,4-Butanediol (BDO) is an important organic chemical and fine chemical raw material, which is widely used in the fields of medicine, daily chemical industry, textile, papermaking, etc. The process route for preparing 1,4-butanediol in industry mainly selects the maleic anhydride method, that is, the raw material maleic anhydride or dialkyl maleate (such as dimethyl maleate) is hydrogenated by gas / liquid phase to produce 1,4-butanediol while producing γ-butyrolactone and tetrahydrofuran as by-products. Copper chromium catalyst has high carbonyl hydrogenation activity and selectivity for target product alcohol, so it has been widely used in the field of preparing BDO by hydrogenation of dimethyl maleate.

[0003] CN104138762A discloses a method for preparing a copper-chromium catalyst. The method comprises dissolving copper nitrate and chromium nitrate in deionized water, adding sodium hydroxide to adjust the pH value of the solution, heating the solution to a certain temperature and stirring evenly at this temperature to obtain a suspension, then transferring the suspension to an autoclave for hydrothermal reaction, and after the reaction is completed, centrifuging, washing, drying, and grinding the product to obtain a precursor, and calcining the precursor to obtain a cubic structure CuCr2O4 catalyst.

[0004] CN105709760A discloses a method for preparing a copper-chromium catalyst. During the preparation process, a copper-chromium mixed solution and an alkaline solution are used for co-precipitation in parallel flow, citric acid is added to the remaining copper-chromium solution, and the co-precipitation in parallel flow is continued. The reaction temperature is increased by 10 to 30°C, and the reaction pH is increased by 0.5 to 1.5. Subsequently, the reaction product solution is heated to gel and dry gel, ground into fine powder, added with ethanol and ignited, and the combustion product is the copper-chromium catalyst.

[0005] CN116408096A discloses a method for preparing a CuM2O4 (M=Co, Cr, Fe) spinel catalyst. The method adopts a sol-gel method, wherein a mixed solution of copper salt, metal M salt and citric acid is initially evaporated to obtain a viscous sol, which is then dried at high temperature to obtain a fluffy dry gel, which is then calcined in an air atmosphere to obtain a CuM2O4 spinel catalyst.

[0006] Although the above method has made certain progress in the research on the preparation method of copper-chromium catalyst, since the microstructure of the catalyst is closely related to the physical and chemical properties, the materials prepared by the above method usually have problems of uneven morphology and uneven particle size distribution, which affects the performance of the copper-chromium catalyst to a certain extent. Summary of the invention

[0007] Aiming at the problems that the microstructure of the copper-chromium catalyst for preparing 1,4-butanediol by hydrogenation of dimethyl maleate in the prior art cannot be precisely controlled, the distribution of active metals is uncontrollable, and it is easy to sinter at high temperatures, the present invention provides a copper-chromium catalyst precursor, a catalyst, and a synthesis method and application thereof. When the catalyst of the present invention is used for preparing 1,4-butanediol by hydrogenation of dimethyl maleate, the conversion rate of dimethyl maleate and the selectivity of 1,4-butanediol can be improved.

[0008] The inventors have found through research that the microstructure, morphology and distribution of active metals of the copper-chromium catalyst and its precursors have a significant effect on the conversion rate of dimethyl maleate hydrogenation to 1,4-butanediol and the selectivity of 1,4-butanediol. The inventors have found through further research that when pollen with a specific morphology is used as a biological template to provide active sites for the nucleation and growth of copper-chromium metal organic framework composite materials (CuCr-MOFs), a biological template-CuCr-MOFs catalyst precursor with a highly ordered distribution of metal elements can be obtained. During the high-temperature calcination of the precursor, the organic components in the biological template and MOFs can be removed at the same time, thereby forming a copper-chromium catalyst with a uniform distribution of metal elements, thereby achieving catalyst performance improvements in terms of dimethyl maleate conversion rate and 1,4-butanediol selectivity.

[0009] The first aspect of the present invention provides a copper-chromium catalyst precursor, comprising: a biological template and a copper-chromium bimetallic organic framework material; the molar ratio of copper to chromium in the copper-chromium bimetallic organic framework material is (0.05-5.0):1.

[0010] Furthermore, the bio-template is referred to as HH, the copper-chromium bimetallic organic framework material is referred to as Cr / Cu-BTC, and the precursor is referred to as HH-Cr / Cu-BTC.

[0011] Furthermore, in the precursor, the mass content of the copper-chromium bimetallic organic framework material is 50% to 95%, and the mass content of the biological template is 5% to 50%.

[0012] Furthermore, the biological template is selected from one or more of lotus pollen, sunflower pollen, rapeseed pollen, lotus pollen, and camellia pollen.

[0013] Furthermore, the precursor is a microsphere structure.

[0014] Furthermore, the particle size of the precursor is 20 to 50 μm.

[0015] Furthermore, in the precursor, the organic ligand used in the copper-chromium bimetallic organic framework material is trimesic acid.

[0016] Furthermore, in the precursor, the copper-chromium bimetallic organic framework material is evenly distributed on the surface of the biological template, and the particle size is 50 to 500 nm.

[0017] Furthermore, in the catalyst precursor, the crystal form of the copper-chromium bimetallic organic framework material conforms to MOF-199.

[0018] Furthermore, the catalyst is a catalyst for hydrogenating dimethyl maleate to produce 1,4-butanediol.

[0019] The second aspect of the present invention provides a method for preparing the above catalyst precursor, comprising:

[0020] (1) mixing the copper source solution and the bio-template, controlling the concentration of the bio-template in the mixed solution to be 0.01-0.50 g / mL, stirring under heating conditions, and then separating and collecting the precipitate;

[0021] (2) mixing the precipitate obtained in step (1) with the organic ligand solution, reacting, washing, and drying to obtain a dry solid;

[0022] (3) mixing the chromium source solution with the dry solid obtained in step (2), reacting, washing and drying to obtain a catalyst precursor.

[0023] Furthermore, in step (1), the biological template is selected from one or more of lotus pollen, sunflower pollen, rapeseed pollen, lotus pollen, and camellia pollen. The particle size of the biological template is 20 to 50 μm.

[0024] Furthermore, preferably, the biological template may be pretreated before step (1). The pretreatment may be an ultrasonic treatment in the presence of a solvent, followed by drying. The treatment conditions are as follows: temperature 25-70°C, time 0.5-5.0h. The solvent is one or more of deionized water, low-carbon alcohol (low-carbon alcohol is selected from alcohols with a carbon number of 6 or less, preferably ethanol), and N,N-dimethylformamide, and the number of ultrasonic treatments is 3-6 times. The drying conditions are as follows: drying temperature is 25-80°C, and drying time is 6-24h.

[0025] Furthermore, in step (1), the copper source may be a conventional soluble metal salt, such as at least one of nitrate, sulfate, acetate, etc. In the copper source solution, the concentration of the copper source is 0.01 to 5.0 mol / L. The solvent used in the copper source solution may be at least one of water, methanol, ethanol, N,N-dimethylformamide, etc.

[0026] Furthermore, in step (1), the copper source solution is mixed with the biological template and stirred under heating conditions, that is, at a temperature of 25 to 60° C. and a stirring time of 0.5 to 2.0 h.

[0027] Furthermore, in step (2), the organic ligand in the organic ligand solution is selected from trimesic acid, the solvent is selected from one or more of methanol, ethanol, water, and N,N-dimethylformamide (DMF), and the concentration of the organic ligand in the organic ligand solution is 0.01-1.0 mol / L.

[0028] Furthermore, in step (2), the molar ratio of the organic ligand to the copper source in step (1) is (0.5-6.5):1 in terms of copper.

[0029] Furthermore, in step (2), the reaction conditions are as follows: reacting at 25-80° C. for 0.5-5 h.

[0030] Furthermore, in step (2), the washing solvent used in the washing is one or more of deionized water, methanol, ethanol, and N,N-dimethylformamide, and the number of washing times is preferably 3 to 6 times. The drying conditions are as follows: the drying temperature is 25 to 80° C., and the drying time is 6 to 24 hours.

[0031] Furthermore, in step (3), the chromium source may be a conventional soluble metal salt or metal oxide, such as at least one of nitrate, sulfate, chromic anhydride, etc. In the chromium source solution, the concentration of the chromium source is 0.5 to 5.0 mol / L. The solvent used in the chromium source solution may be at least one of water, methanol, ethanol, N,N-dimethylformamide, etc.

[0032] Furthermore, in step (3), the reaction conditions are as follows: reacting at 25-60° C. for 0.5-5 h.

[0033] Furthermore, in step (3), the washing solvent used in the washing is one or more of deionized water, methanol, ethanol, and N,N-dimethylformamide, and the number of washing times is preferably 3 to 6 times. The drying conditions are as follows: the drying temperature is 25 to 80° C., and the drying time is 6 to 24 hours.

[0034] The third aspect of the present invention provides a dimethyl maleate hydrogenation catalyst, wherein the catalyst is obtained by calcining the above catalyst precursor.

[0035] Furthermore, in the catalyst, the molar ratio of copper to chromium is (0.05-5.0):1.

[0036] Furthermore, the microstructure of the catalyst is a microspherical structure.

[0037] Furthermore, the calcination conditions are as follows: the heating rate to the calcination temperature is 4-8°C / min, the calcination temperature is 300-500°C, the calcination time is 2-6h, and the calcination atmosphere is an oxygen-containing atmosphere, such as air.

[0038] Furthermore, the catalyst may be a shaped body, preferably a tablet-shaped body, that is, the calcined material and graphite are pressed into tablets, and the catalyst particles are obtained by screening.

[0039] The fourth aspect of the present invention provides a method for preparing the above catalyst, comprising: calcining the above catalyst precursor and pressing it into tablets to obtain the catalyst.

[0040] Furthermore, the calcination conditions are as follows: the heating rate to the calcination temperature is 4-8°C / min, the calcination temperature is 300-500°C, the calcination time is 2-6h, and the calcination atmosphere is an oxygen-containing atmosphere, such as air.

[0041] Furthermore, during the catalyst tableting process, graphite powder accounting for 1% to 5% of the mass of the catalyst precursor after calcination is added, and catalyst solid particles of 20 to 40 mesh are screened out.

[0042] The fifth aspect of the present invention provides the use of the above catalyst in the hydrogenation of dimethyl maleate to synthesize 1,4-butanediol.

[0043] Furthermore, the application includes: in the presence of hydrogen, dimethyl maleate is contacted with the catalyst to react and produce 1,4-butanediol.

[0044] Furthermore, the catalyst of the present invention needs to be reduced and activated before use, and the reducing gas can be hydrogen or a mixture of hydrogen and nitrogen, wherein the volume ratio of H2 / N2 is (1-10): (90-99), the reducing temperature is 220-300°C, and the reducing time is 6-24h.

[0045] Furthermore, the reaction conditions are as follows: reaction temperature is 150-300°C, reaction pressure is 1-10 MPa, volume space velocity is 0.1-2.0 h -1 , the molar ratio of hydrogen to dimethyl maleate is 100-300:1.

[0046] Compared with the prior art, the present invention has the following advantages:

[0047] 1. In the preparation process of the catalyst of the present invention, the Cr / Cu-MOFs organic metal framework structure and the biological template play a multiple anchoring role on Cu, and the active metal Cu is evenly dispersed during the high-temperature calcination process, which inhibits the sintering of Cu nanoparticles and forms a strong interaction between copper and chromium. Finally, the Cu-Cr-O metal oxide is dispersed in the catalyst. The obtained catalyst is used in the process of hydrogenating dimethyl maleate to synthesize 1,4-butanediol, and has good conversion rate and 1,4-butanediol selectivity.

[0048] 2. The catalyst preparation process of the present invention successively undergoes processes such as molecular assembly, impregnation, and calcination, and the biological template used can be removed by simple calcination, without the need for subsequent treatment steps such as acid and alkali. The preparation method is simple, the conditions are mild, and it is suitable for industrial production. BRIEF DESCRIPTION OF THE DRAWINGS

[0049] Figure 1 X-ray diffraction (XRD) patterns of the catalyst precursor (HH-Cr / Cu-BTC) obtained in Example 1 and the unformed catalyst A1 (HH-CuCr2O4) after calcination;

[0050] Figure 2 This is a scanning electron microscope (SEM) image of the catalyst precursor obtained in Example 1;

[0051] Figure 3 This is a SEM image of the unformed catalyst A1 obtained in Example 1;

[0052] Figure 4 This is a SEM image of the unformed catalyst A2 obtained in Example 2;

[0053] Figure 5 This is a SEM image of the unformed catalyst A3 obtained in Example 3;

[0054] Figure 6 This is the SEM image of the unformed catalyst B1 obtained in Comparative Example 1;

[0055] Figure 7 This is a SEM image of the unformed catalyst B2 obtained in Comparative Example 2;

[0056] Figure 8 This is the SEM image of the unformed catalyst B3 obtained in Comparative Example 3. DETAILED DESCRIPTION

[0057] The present invention will be further described below in conjunction with embodiments, but it should be understood that the protection scope of the present invention is not limited by the embodiments.

[0058] Example 1

[0059] Step (1), weighing 1.8163 g of anhydrous copper acetate and dissolving it in 200 mL of ethanol to prepare solution A, adding 4 g of lotus powder (microspherical, particle size of 20-50 μm) thereto, stirring at 50° C. for 1 h, and filtering and separating the precipitate;

[0060] Step (2), weigh 8.404 g of trimesic acid and dissolve it in 200 mL of ethanol to prepare solution B. Add the precipitate obtained in step (1) thereto and react at 50° C. for 1 h, filter and separate, wash with ethanol 3 times, dry in an oven at 60° C. for 12 h, and collect the resulting solid.

[0061] Step (3), weigh 1.0 g of Cr(NO3)3 and add 2 mL of ethanol to it, mix well, add it to 2.2 g of the solid obtained in step (2), react at 50°C for 2 h, and dry at 60°C for 12 h to obtain a catalyst precursor HH-Cr / Cu-BTC, whose XRD pattern is shown in Figure 1 The crystal form of the catalyst precursor is consistent with MOF-199; SEM images are shown in Figure 2 As shown, the precursor is a microsphere structure, and particles with a diameter of 100 to 400 nm are evenly distributed on the surface of the biological template.

[0062] The catalyst precursor obtained in step (4) and step (3) was heated to the calcination temperature at a heating rate of 5°C / min, and calcined at 400°C for 4h to obtain an unformed catalyst A1 (wherein the molar ratio of Cu to Cr was 1:2), and 3% graphite was added to form the catalyst, and catalyst particles of 20 to 40 mesh were screened to obtain a formed catalyst A1. Figure 1 As shown, the XRD spectrum of the unformed catalyst A1 is consistent with the XRD diffraction peak of the CuCr2O4 standard card. Figure 3 As shown, the unformed catalyst A1 obtained after calcination is in the shape of microspheres.

[0063] Formed catalyst A1 was used for hydrogenation of dimethyl maleate. It was reduced with hydrogen before the reaction. The reduction conditions were as follows: hydrogen pressure of 0.1 MPa, reduction temperature of 270°C, and reduction time of 12 h. After the reduction, the reaction was carried out under the following conditions: reaction temperature of 190°C; feed volume space velocity of 0.25 h -1 ; H2 / ester molar ratio 200:1; reaction pressure 6.0 MPa, dimethyl maleate conversion rate 100%; 1,4-butanediol selectivity 82.3%.

[0064] Example 2

[0065] Step (1), weighing 1.8163 g of anhydrous copper acetate and dissolving it in 200 mL of ethanol to prepare solution A, adding 8 g of lotus powder (microspherical, particle size of 20-50 μm) thereto, stirring at 50° C. for 1 h, and filtering and separating the precipitate;

[0066] Step (2), weigh 8.404 g of trimesic acid and dissolve it in 200 mL of ethanol to prepare solution B. Add the precipitate obtained in step (1) thereto and react at 50° C. for 1 h, filter and separate, wash with ethanol 3 times, dry in an oven at 60° C. for 12 h, and collect the resulting solid;

[0067] Step (3), weigh 1.0g Cr(NO3)3 and add 2mL ethanol to it, mix well, add it to 2.2g of the solid obtained in step (2), react at 50°C for 2h, and dry at 60°C for 12h to obtain a catalyst precursor; from its XRD pattern, it can be seen that the crystal form of the catalyst precursor conforms to MOF-199; from SEM, it can be seen that the precursor is a microsphere structure, and particles with a particle size of 100 to 400nm are evenly distributed on the surface of the biological template.

[0068] The catalyst precursor obtained in step (4) and step (3) was heated to a calcination temperature at a heating rate of 6°C / min and calcined at 400°C for 4h to obtain an unformed catalyst A2 (wherein the molar ratio of Cu to Cr was 1:2); Figure 4 As shown, the unformed catalyst A2 obtained after calcination is in the shape of microspheres. 3% graphite is added to form the catalyst and the catalyst particles of 20 to 40 mesh are screened to obtain the formed catalyst A2;

[0069] Formed catalyst A2 was used for hydrogenation of dimethyl maleate. It was reduced with hydrogen before the reaction. The reduction conditions were as follows: hydrogen pressure of 0.1 MPa, reduction temperature of 270°C, and reduction time of 12 h. After the reduction, the reaction was carried out under the following conditions: reaction temperature of 190°C; feed volume space velocity of 0.25 h -1 ; H2 / ester molar ratio 200:1; reaction pressure 6.0 MPa, dimethyl maleate conversion 100%; 1,4-butanediol selectivity 83.5%.

[0070] Example 3

[0071] Step (1), weighing 1.8163 g of anhydrous copper acetate and dissolving it in 200 mL of ethanol to prepare solution A, adding 4 g of rapeseed pollen (microspherical, particle size of 20-50 μm) thereto, stirring at 50° C. for 1 h, and filtering and separating the precipitate;

[0072] Step (2), weigh 8.404 g of trimesic acid and dissolve it in 200 mL of ethanol to prepare solution B. Add the precipitate obtained in step (1) to the solution and react at 55° C. for 1 h, filter and separate, wash with ethanol 3 times, dry in an oven at 60° C. for 12 h, and collect the resulting solid;

[0073] Step (3), weigh 0.5g Cr(NO3)3 and add 2mL ethanol to it, mix well, add it to 2.2g of the solid obtained in step (2), react at 60°C for 2h, and dry at 60°C for 12h to obtain a catalyst precursor; from its XRD pattern, it can be seen that the crystal form of the catalyst precursor conforms to MOF-199; from SEM, it can be seen that the precursor is a microsphere structure, and particles with a particle size of 100 to 400nm are evenly distributed on the surface of the biological template.

[0074] The catalyst precursor obtained in step (4) and step (3) was heated to a calcination temperature at a heating rate of 7°C / min and calcined at 400°C for 4h to obtain an unformed catalyst A3 (wherein the molar ratio of Cu to Cr was 1:1); Figure 5 As shown, the unformed catalyst A3 obtained after calcination is in the shape of microspheres. 3% graphite is added to form the catalyst and the catalyst particles of 20 to 40 mesh are screened to obtain the formed catalyst A3;

[0075] Formed catalyst A3 was used for hydrogenation of dimethyl maleate. It was reduced with hydrogen before the reaction. The reduction conditions were as follows: hydrogen pressure of 0.1 MPa, reduction temperature of 270°C, and reduction time of 12 h. After the reduction, the reaction was carried out under the following conditions: reaction temperature of 190°C; feed volume space velocity of 0.25 h -1 ; H2 / ester molar ratio 200:1; reaction pressure 6.0 MPa, dimethyl maleate conversion rate 100%; 1,4-butanediol selectivity 81.8%.

[0076] Comparative Example 1

[0077] Step (1), weighing 1.8163 g of anhydrous copper acetate and dissolving it in 200 mL of ethanol to prepare solution A, adding 4 g of lotus powder (microspherical, particle size of 20-50 μm) thereto, stirring at 50° C. for 1 h, and filtering and separating the precipitate;

[0078] Step (2), weigh 8.404 g of trimesic acid and dissolve it in 200 mL of ethanol to prepare solution B. Add the precipitate obtained in step (1) thereto and react at 50° C. for 1 h, filter and separate, wash with ethanol 3 times, dry in an oven at 60° C. for 12 h, and collect the resulting solid;

[0079] Step (3), weigh 5.0 g of Cr(NO3)3 and add 2 mL of ethanol thereto, mix well, add the mixture to 2.2 g of the solid obtained in step (2), react at 50°C for 2 h, and dry at 60°C for 12 h after the reaction to obtain a catalyst precursor;

[0080] The catalyst precursor obtained in step (4) and step (3) was heated to a calcination temperature at a heating rate of 5°C / min and calcined at 400°C for 4h to obtain an unformed catalyst B1 (wherein the molar ratio of Cu to Cr was 1:9.5); Figure 6 As shown, the unformed catalyst B1 obtained after calcination has the morphology of irregular particle aggregates. 3% graphite is added to form the pellets and the catalyst particles of 20-40 mesh are screened to obtain the formed catalyst B1;

[0081] Formed catalyst B1 was used for hydrogenation of dimethyl maleate. It was reduced with hydrogen before the reaction. The reduction conditions were as follows: hydrogen pressure of 0.1 MPa, reduction temperature of 270°C, and reduction time of 12 h. After the reduction, the reaction was carried out under the following conditions: reaction temperature of 190°C; feed volume space velocity of 0.25 h -1 ; H2 / ester molar ratio 200:1; reaction pressure 6.0 MPa, dimethyl maleate conversion rate 97.7%; 1,4-butanediol selectivity 79.6%.

[0082] Comparative Example 2

[0083] (1) copper nitrate and chromic anhydride are used to prepare a metal salt solution in a copper:chromium molar ratio of 1:1, wherein the total concentration of metal ions in the solution is 2.0 mol / L;

[0084] (2) The precipitant solution is a 10 wt% ammonia solution. The mixture obtained in step (1) and the precipitant solution are added in parallel by an acid-base coprecipitation process. The reaction temperature is controlled at 45°C, the reaction pH is 7.0, and the reaction time is 2 hours. After the reaction is completed, the mixture is aged for 2 hours, filtered and separated, washed with deionized water for 6 times, and dried in an oven at 60°C for 12 hours to obtain a catalyst precursor;

[0085] (3) The catalyst precursor obtained in step (2) was heated to a calcination temperature at a heating rate of 5°C / min, and calcined in a muffle furnace at 400°C for 4 hours in an air atmosphere to obtain an unformed catalyst B2 (wherein the molar ratio of Cu to Cr is 1:1); Figure 7 As shown, the unformed catalyst B2 obtained after calcination has the morphology of irregular particle aggregates. 3% graphite is added to form the pellets and the catalyst particles of 20-40 mesh are screened to obtain the formed catalyst B2;

[0086] Formed catalyst B2 was used for hydrogenation of dimethyl maleate. It was reduced with hydrogen before the reaction. The reduction conditions were as follows: hydrogen pressure of 0.1 MPa, reduction temperature of 270°C, and reduction time of 12 h. After the reduction, the reaction was carried out under the following conditions: reaction temperature of 190°C; feed volume space velocity of 0.25 h -1 ; H2 / ester molar ratio 200:1; reaction pressure 6.0 MPa, dimethyl maleate conversion rate 98.4%; 1,4-butanediol selectivity 80.3%.

[0087] Comparative Example 3

[0088] Step (1), weighing 1.8163 g of anhydrous copper acetate and dissolving it in 200 mL of ethanol to prepare solution A, stirring at 50° C. for 1 h, and filtering and separating the precipitate;

[0089] Step (2), weigh 8.404 g of trimesic acid and dissolve it in 200 mL of ethanol to prepare solution B. Add the precipitate obtained in step (1) thereto and react at 50° C. for 1 h.

[0090] Step (3), weighing 1.0 g of Cr(NO3)3 and adding it to the mother liquor obtained in step (2), reacting at 50°C for 2 h, filtering and separating, washing with ethanol three times, and drying the obtained powder at 60°C for 12 h to obtain a catalyst precursor;

[0091] The catalyst precursor obtained in step (4) and step (3) was heated to the calcination temperature at a heating rate of 5°C / min and calcined at 400°C for 4h to obtain an unformed catalyst B3. 3% graphite was added to form the catalyst and the catalyst particles of 20 to 40 mesh were screened to obtain a formed catalyst B3. Figure 8 As shown, the unformed catalyst B3 obtained after calcination has the morphology of irregular particle aggregates.

[0092] The molded catalyst B3 was used for the hydrogenation reaction of dimethyl maleate. It was reduced with hydrogen before the reaction. The reduction conditions were as follows: hydrogen pressure of 0.1MPa, reduction temperature of 270℃, and reduction time of 12h. After the reduction, the reaction was carried out under the following conditions: reaction temperature of 190℃; feed volume space velocity of 0.25h -1 ; H2 / ester molar ratio 200:1; reaction pressure 6.0 MPa, dimethyl maleate conversion rate 96.6%; 1,4-butanediol selectivity 80.0%.

[0093] Comparative Example 4

[0094] Step (1), weighing 1.8163 g of anhydrous copper acetate and dissolving it in 200 mL of ethanol to prepare solution A, adding 4 g of lotus powder (microspherical, particle size of 20-50 μm) thereto, stirring at 50° C. for 1 h, and filtering and separating the precipitate;

[0095] Step (2), weigh 8.404 g of trimesic acid and dissolve it in 200 mL of ethanol to prepare solution B. Add the precipitate obtained in step (1) thereto and react at 50° C. for 1 h, filter and separate, wash with ethanol 3 times, dry in an oven at 60° C. for 12 h, and collect the resulting solid.

[0096] Step (3), weigh 1.0 g of Cr(NO3)3 and add 2 mL of ethanol to it, mix well, add it to 2.2 g of the solid obtained in step (2), react at 50°C for 2 h, and after the reaction is completed, dry at 60°C for 12 h to obtain a catalyst precursor.

[0097] The catalyst precursor obtained in step (4) and step (3) was heated to the calcination temperature at a heating rate of 2°C / min, calcined at 400°C for 4h at a calcination heating rate of 2°C / min to obtain an unformed catalyst B4, and 3% graphite was added to form a sheet and catalyst particles of 20 to 40 mesh were screened to obtain a formed catalyst B4. It can be seen from the scanning electron microscope image that the unformed catalyst B4 obtained after calcination has the morphology of irregular particle aggregates.

[0098] Formed catalyst B4 was used for hydrogenation of dimethyl maleate. It was reduced with hydrogen before the reaction. The reduction conditions were as follows: hydrogen pressure of 0.1 MPa, reduction temperature of 270°C, and reduction time of 12 h. After the reduction, the reaction was carried out under the following conditions: reaction temperature of 190°C; feed volume space velocity of 0.25 h -1 ; H2 / ester molar ratio 200:1; reaction pressure 6.0 MPa, dimethyl maleate conversion rate 98.3%; 1,4-butanediol selectivity 81.6%.

[0099] The embodiments of the present invention are only detailed descriptions of the technical solutions of the present invention, but the present invention is not limited to the above embodiments, that is, the present invention can be implemented without relying on the steps described in the above embodiments. In summary, any improvements made to the present invention by those skilled in the art, as long as they do not deviate from the content of the technical solutions of the present invention, any simple modifications, equivalent changes and modifications made to the above embodiments according to the technical essence of the present invention, shall fall within the protection scope and disclosure scope of the present invention.

Claims

1. A copper-chromium catalyst precursor, comprising: A biological template and a copper-chromium bimetallic organic framework material, wherein the molar ratio of copper to chromium in the copper-chromium bimetallic organic framework material is (0.05-5.0):

1.

2. The precursor according to claim 1, characterized in that In the precursor, the mass content of the copper-chromium bimetallic organic framework material is 50% to 95%, and the mass content of the biological template is 5% to 50%.

3. The precursor according to claim 1, characterized in that The biological template is selected from one or more of lotus pollen, sunflower pollen, rapeseed pollen, lotus pollen and camellia pollen.

4. The precursor according to claim 1, characterized in that The precursor is a microsphere structure; and / or the particle size of the precursor is 20 to 50 μm.

5. The precursor according to claim 1, characterized in that In the catalyst precursor, the copper-chromium bimetallic organic framework material has a crystal form that conforms to MOF-199.

6. The precursor according to claim 1, characterized in that In the precursor, the organic ligand used in the copper-chromium bimetallic organic framework material is trimesic acid.

7. The precursor according to claim 1, characterized in that In the precursor, the copper-chromium bimetallic organic framework material is evenly distributed on the surface of the biological template, and the particle size is 50-500nm.

8. The method for preparing the catalyst precursor according to any one of claims 1 to 7, comprising: (1) mixing the copper source solution and the bio-template, controlling the concentration of the bio-template in the mixed solution to be 0.01-0.50 g / mL, stirring under heating conditions, and then separating and collecting the precipitate; (2) mixing the precipitate obtained in step (1) with the organic ligand solution, reacting, washing, and drying to obtain a dry solid; (3) mixing the chromium source solution with the dry solid obtained in step (2), reacting, washing and drying to obtain a catalyst precursor.

9. The preparation method according to claim 8, characterized in that: In step (1), the copper source is a soluble metal salt, preferably at least one of nitrate, sulfate, and acetate; in the copper source solution, the concentration of the copper source is 0.01 to 5.0 mol / L; the solvent used in the copper source solution is at least one of water, methanol, ethanol, and N,N-dimethylformamide; and / or, in step (2), the organic ligand in the organic ligand solution is selected from trimesic acid, and the solvent is selected from one or more of methanol, ethanol, water, and N,N-dimethylformamide (DMF); the concentration of the organic ligand in the organic ligand solution is 0.01 to 1.0 mol / L; and / or, in step (2), the molar ratio of the organic ligand to the copper source in step (1) is (0.5 to 6.5):1 in terms of copper.

10. The preparation method according to claim 8, characterized in that: In step (1), the copper source solution is mixed with the biological template and stirred under heating conditions, that is, at a temperature of 25 to 60° C. and a stirring time of 0.5 to 2.0 h.

11. The preparation method according to claim 8, characterized in that: In step (2), the reaction conditions are as follows: reaction at 25-80° C. for 0.5-5.0 h; and / or, the drying conditions are as follows: drying temperature is 25-80° C., and drying time is 6-24 h.

12. The preparation method according to claim 8, characterized in that: In step (3), the chromium source is a soluble metal salt or metal oxide, preferably at least one of nitrate, sulfate, and chromic anhydride; the concentration of the chromium source in the chromium source solution is 0.5 to 5.0 mol / L; the solvent used in the chromium source solution is at least one of water, methanol, ethanol, N,N-dimethylformamide, etc.; and / or, in step (3), the reaction conditions are as follows: react at 25 to 60° C. for 0.5 to 5.0 hours; and / or, in step (3), the drying conditions are as follows: the drying temperature is 25 to 80° C., and the drying time is 6 to 24 hours.

13. A dimethyl maleate hydrogenation catalyst, characterized in that: The precursor is obtained by calcining the precursor according to any one of claims 1 to 7 or the precursor prepared by the method according to any one of claims 8 to 12.

14. The catalyst according to claim 13, characterized in that The microstructure of the catalyst is a microspherical structure; and / or, the calcination conditions are as follows: the heating rate to the calcination temperature is 4-8°C / min, the calcination temperature is 300-500°C, the calcination time is 2-6h, and the calcination atmosphere is an oxygen-containing atmosphere.

15. A method for preparing a dimethyl maleate hydrogenation catalyst, comprising: The catalyst is obtained by calcining the precursor described in any one of claims 1 to 7 or the precursor prepared by the method described in any one of claims 8 to 12 and pressing the precursor into tablets.

16. The preparation method according to claim 15, characterized in that: The calcination conditions are as follows: the heating rate to the calcination temperature is 4-8°C / min, the calcination temperature is 300-500°C, the calcination time is 2-6h, and the calcination atmosphere is an oxygen-containing atmosphere.

17. Use of the catalyst according to any one of claims 13-14 or the catalyst prepared by the method according to any one of claims 15-16 in the hydrogenation of dimethyl maleate to synthesize 1,4-butanediol.

18. The use according to claim 17, characterized in that The application includes: in the presence of hydrogen, dimethyl maleate is contacted with the catalyst to react and produce 1,4-butanediol; preferably, the reaction conditions are as follows: the reaction temperature is 150-300°C, the reaction pressure is 1-10MPa, and the volume space velocity is 0.1-2.0h -1 , the molar ratio of hydrogen to dimethyl maleate is 100-300:1.

Images