Copper-chromium catalyst, method for preparing the same, and use thereof

Abstract

The application discloses a copper-chromium catalyst and a preparation method and application thereof. The preparation method of the catalyst comprises the following steps: (1) mixing a copper source solution, a chromium source solution and polyethylene glycol to obtain a mixture; (2) performing parallel flow reaction on the obtained mixture and a precipitator, aging after the reaction, drying, and obtaining a Cu-Cr precursor, and continuously feeding N2 during the parallel flow reaction and / or the aging process; (3) preparing a polyvinyl alcohol aqueous solution, mixing the obtained Cu-Cr precursor with the polyvinyl alcohol aqueous solution, and stirring to obtain a spinning solution; (4) performing electrostatic spinning on the spinning solution to obtain a catalyst precursor; and (5) performing calcination on the obtained catalyst precursor to obtain an unformed catalyst, performing tabletting on the unformed catalyst to obtain the copper-chromium catalyst. The copper-chromium catalyst obtained by the method has a low 10-particle weight, high mechanical strength and low bulk ratio, and is used in a reaction of preparing 1,4-butanediol by hydrogenating dimethyl maleate, and has high conversion rate and selectivity.

Description

Technical Field

[0001] This invention belongs to the field of catalytic materials technology, specifically relating to a copper-chromium catalyst, its preparation method, and its application. Background Technology

[0002] In catalytic reaction engineering, catalysts occupy a central position. Catalysts used in industrial production must possess excellent pore structure, high selectivity, good activity and stability, long service life, high mechanical strength, and suitable shape. All of these characteristics are related to catalyst shaping, which is an indispensable part of the industrial catalyst preparation process.

[0003] Currently, common catalyst forming methods mainly include tableting, extrusion, spray forming, rotational forming, and in-oil forming. Tableting is one of the earliest forming methods used in industrial catalysts. Compared with other catalyst forming methods, tableting produces catalyst particles with generally consistent size, a bright and smooth surface, and high mechanical strength, making it a promising forming method.

[0004] CN114768820A discloses a tableting method for an iron-based hydrogenation catalyst. In the tableting process, the iron-based catalyst powder and graphite powder are first thoroughly stirred and mixed, and then a silicon-based binder is gradually added for mixing. After drying in a forced-air oven to a constant temperature, the mixture is then fed into a tableting machine for forming.

[0005] CN103008003A discloses a method for pressing a high-strength titanium-silicon molecular sieve catalyst into tablets. The method is characterized by kneading TS-1 molecular sieve powder, silica support, binder, activated carbon fiber and boric acid into a uniform plastic body in a certain proportion, and then pressing, drying and calcining to obtain the pressed TS-1 catalyst.

[0006] Copper-chromium catalysts exhibit high carbonyl hydrogenation activity and selectivity for target alcohols. Currently, copper-chromium catalysts are widely used industrially for the hydrogenation of dimethyl maleate to 1,4-butanediol. However, the high strength and wear resistance of copper-chromium catalysts make molding chromium-doped copper-based catalysts difficult, causing significant damage to molds and limiting their industrial application. Although some progress has been made in the tableting methods for these catalysts, the introduction of binders and additives different from the catalyst components during tableting may affect the catalytic reaction. Furthermore, the universality of the tableting methods for copper-chromium catalysts needs further investigation. Therefore, developing a novel and efficient material preparation method to facilitate the molding and subsequent industrial application of copper-chromium catalysts is of paramount importance. Summary of the Invention

[0007] To address the problems of high bulk density, poor flowability, poor compressibility, low mechanical strength of molded catalysts, and high total weight of 10 catalyst particles in existing copper-chromium catalysts, this invention provides a copper-chromium catalyst, its preparation method, and its application. The copper-chromium catalyst prepared by this method exhibits high mechanical strength and a low bulk density while maintaining a relatively low weight per 10 particles. When used in the hydrogenation of dimethyl maleate to 1,4-butanediol, it can improve catalyst conversion and selectivity.

[0008] The first aspect of this invention provides a method for preparing a copper-chromium catalyst, comprising:

[0009] (1) Mix copper source and chromium source solutions with polyethylene glycol to obtain a mixture;

[0010] (2) The mixture obtained in step (1) and the precipitant are subjected to a co-current reaction. After the reaction is completed, the mixture is aged and dried to obtain Cu-Cr precursor. N2 is continuously introduced during the co-current reaction and / or aging process.

[0011] (3) Prepare a polyvinyl alcohol aqueous solution, mix it with the Cu-Cr precursor obtained in step (2), stir, and obtain a spinning solution;

[0012] (4) Electrospinning is performed using the spinning solution obtained in step (3) to obtain the catalyst precursor;

[0013] (5) The catalyst precursor obtained in step (4) is calcined to obtain an unformed catalyst, which is then pressed into tablets to obtain a copper-chromium catalyst.

[0014] Further, in step (1), the copper source is a conventional copper-containing acidic solution in the art, preferably one or more of copper nitrate, copper acetate, copper chloride, and copper sulfate. The chromium source is a conventional chromium-containing acidic solution in the art, preferably one or more of chromic anhydride, chromium nitrate, and chromium chloride.

[0015] Further, in step (1), it is preferable to first mix the copper source and the chromium source to obtain a metal salt solution, and then mix it with polyethylene glycol to obtain a mixture.

[0016] Furthermore, in step (1), the concentration of copper ions in the metal salt solution containing copper and chromium sources is 0.05–5 mol / L, and the concentration of chromium ions is 0.05–5 mol / L.

[0017] Further, in step (1), the molecular weight of the polyethylene glycol is 1000 to 10000.

[0018] Further, in step (1), the mass concentration of polyethylene glycol in the mixture is 0.05 to 0.4 g / mL.

[0019] Further, in step (2), the precipitant is one or more of sodium carbonate solution, sodium bicarbonate solution, ammonia water, and sodium hydroxide solution.

[0020] Further, in step (2), the conditions for the co-current reaction are: the reaction temperature is 25-70℃, the reaction time is 0.2-5h, and the pH value is controlled at 4.0-8.0 during the reaction process.

[0021] In step (2), the aging conditions are: the aging temperature is 25-80℃ and the aging time is 0.5-5h.

[0022] Furthermore, in step (2), the N2 flow rate is 2 to 25 mL / min relative to the volume of the mixture obtained in step (1) of 1 L.

[0023] Furthermore, in step (2), preferably, N2 is continuously introduced during both the co-current reaction and the aging process.

[0024] Further, in step (2), before drying after aging, the Cu-Cr precursor is preferably obtained through filtration, washing, and other treatments. The filtration and washing are carried out using conventional methods in the art. The drying conditions are: a drying temperature of 25–80°C and a drying time of 6–24 hours.

[0025] Further, in step (3), the preparation of the polyvinyl alcohol aqueous solution specifically involves adding polyvinyl alcohol to water (preferably deionized water) and heating it. The mass content of polyvinyl alcohol in the polyvinyl alcohol aqueous solution is 5-25 wt%, preferably 10-15 wt%; the heating conditions are: heating at 60-85°C for 0.5-5.0 h. Water bath heating is preferred.

[0026] Furthermore, in step (3), the mass of Cu-Cr precursor contained in each milliliter of polyvinyl alcohol aqueous solution is 0.025 to 0.25 g.

[0027] Further, in step (3), the stirring conditions are: stirring speed of 100-1500 rpm and stirring time of 2-24 h.

[0028] Further, in step (4), the conditions for electrospinning are: spinning voltage of 15-30kV, feed speed of 0.5-3.0mL / h, and receiving distance of 10-30cm.

[0029] Further, in step (5), the calcination conditions are: a calcination temperature of 300–500°C and a calcination time of 2–8 hours. Preferably, the calcination is performed using 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.

[0030] Further, in step (5), the unformed catalyst is mixed with graphite and then compressed into tablets. The amount of graphite used is 0.1 wt% to 5 wt% based on the weight of the unformed catalyst.

[0031] Furthermore, in step (5), after tableting, there are no special requirements for the shape of the catalyst. Generally, the catalyst is cylindrical with a diameter of 2-4 mm and a height of 2-5 mm, preferably 2.5-3.5 mm.

[0032] A second aspect of the present invention provides a copper-chromium catalyst prepared by the above method.

[0033] Furthermore, the weight contents of each component in the copper-chromium catalyst are as follows: CuO 40-60 wt%, Cr2O3 40-60 wt%.

[0034] Furthermore, the copper-chromium 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 5%.

[0035] Furthermore, the copper-chromium catalyst, based on a cylindrical shaped catalyst with a diameter of 3 mm and a height of 3.0 ± 0.4 mm, has a weight of 10 catalyst particles (total weight of 10 catalyst particles) of 0.70 to 0.90 g, preferably 0.75 to 0.85 g.

[0036] Furthermore, the catalyst side pressure strength is 80-130 N / particle, preferably 90-125 N / particle.

[0037] Furthermore, the catalyst has a bulk density of 160–195 g / 100 mL, preferably 175–190 g / 100 mL.

[0038] A third aspect of the present invention provides the application of the above-mentioned copper-chromium catalyst in the hydrogenation of dimethyl maleate to prepare 1,4-butanediol.

[0039] Furthermore, the copper-chromium catalyst is first reduced with hydrogen before use, under the following conditions: hydrogen pressure of 0-1 MPa, reduction temperature of 220-300℃, and reduction time of 6-24 h.

[0040] Furthermore, the reaction conditions for using the copper-chromium catalyst in the hydrogenation of dimethyl maleate to prepare 1,4-butanediol are as follows: reaction temperature 150–300 °C; feed volume hourly space velocity 0.1–2.0 h⁻¹. -1 H2 / ester molar ratio (100-300): 1; reaction pressure is 1-10 MPa.

[0041] Compared with the prior art, the present invention has the following advantages:

[0042] (1) In this invention, N2 bubbling is used to promote the uniform dispersion of polyethylene glycol in the system without participating in the reaction or changing the acidity or alkalinity of the solution. At the same time, polyethylene glycol is used to modify the catalyst precursor, which is combined with electrospinning to promote the uniform dispersion of the catalyst precursor in the polyvinyl alcohol spinning solution and prevent the catalyst precursor from settling prematurely during electrospinning and causing agglomeration after calcination, thereby improving the overall tableting performance of the catalyst.

[0043] (2) The catalyst of the present invention has high mechanical strength and low bulk ratio under the premise of low weight of 10 particles. When used in the hydrogenation reaction of dimethyl maleate to prepare 1,4-butanediol, it can improve the catalyst conversion rate and selectivity. Detailed Implementation

[0044] The present invention will be further described below with reference to the embodiments, but it should be understood that the scope of protection of the present invention is not limited to the embodiments.

[0045] In this invention, the weight of 10 catalyst particles was determined using a Mettler Toledo Instruments (Shanghai) Co., Ltd. AL204 electronic balance. Ten particles were selected from the test sample, and their total weight was measured. The average of three measurements was taken as the weight of 10 catalyst particles. The mechanical strength was determined using a DLⅢ intelligent particle strength tester from Dalian Chemical Research and Design Institute to measure the radial crushing force of the molded catalyst. The instrument has a range of 300N and an accuracy of 0.1N. Ten particles were selected from the test sample, and their radial crushing force was measured. The maximum and minimum values ​​were discarded, and the average of three measurements was taken as the lateral compressive mechanical strength of the catalyst. The bulk density was determined using a Mettler Toledo Instruments (Shanghai) Co., Ltd. AL204 electronic balance and a 250mL graduated cylinder. The catalyst dimensions were measured using vernier calipers. Elemental composition and content were analyzed using a PANalytical Axios (Netherlands) X-ray fluorescence spectrometer.

[0046] Example 1

[0047] (1) Prepare a metal salt solution by mixing copper nitrate and chromic anhydride with water. The concentration of copper ions in the solution is 1.0 mol / L, and the concentration of chromium ions is 1.0 mol / L. Add polyethylene glycol (molecular weight 4000) to the above metal salt solution and control the concentration of polyethylene glycol in the resulting mixture to be 0.2 g / mL.

[0048] (2) The precipitant solution was a 10wt% ammonia solution. An acid-base co-precipitation process was used. 4L of the mixture obtained in step (1) was added to the precipitant solution in a co-current manner. The reaction temperature was controlled at 30℃, the reaction pH was 7.0, and the reaction time was 2h. After the reaction, the mixture was aged at 30℃ for 2h. During the reaction and aging process, N2 (40mL / min) was introduced into the system. After aging, the mixture was filtered and washed 6 times with deionized water. It was then dried in a 60℃ oven for 12h to collect the Cu-Cr precursor.

[0049] (3) Add 6g PVA (molecular weight 80000) to 60mL of deionized water, heat in a water bath to 80℃ and stir for 2h to obtain PVA aqueous solution. Take 20mL of the above PVA aqueous solution, add 2g of Cu-Cr precursor obtained in step (2), and magnetically stir at 1000rpm for 12h to obtain spinning solution.

[0050] (4) Electrospinning was performed to prepare the catalyst precursor according to the following parameters: spinning voltage was 20kV, propulsion speed was 1.5mL / h, and receiving distance was 15cm.

[0051] (5) The catalyst precursor obtained in step (4) is placed in a muffle furnace for calcination. The calcination conditions are as follows: the heating rate to the calcination temperature is 5℃ / min, the calcination temperature is 400℃, the calcination time is 4h, and the calcination atmosphere is air, to obtain an unformed catalyst.

[0052] The unformed catalyst was mixed evenly with graphite and then automatically formed into cylindrical particles with a diameter of 3 mm and a height of 3.25 mm using a tablet press. These particles were called formed catalyst A1, which contained 49.14 wt% CuO, 47.95 wt% Cr2O3, and 2 wt% graphite, with the remainder being impurities. The properties of catalyst A1 are shown in Table 1.

[0053] The catalyst prepared in this invention is used for the hydrogenation of dimethyl maleate to 1,4-butanediol. Molded catalyst A1 is selected as the catalyst. Before the reaction, the catalyst is reduced with hydrogen under the following conditions: hydrogen pressure 0.1 MPa, reduction temperature 270℃, and reduction time 12 h. After reduction, the reaction is carried out under the following conditions: reaction temperature 190℃; feed hourly space velocity 0.25 h⁻¹. -1 H2 / ester molar ratio 200:1; reaction pressure 6.0 MPa; dimethyl maleate conversion 99.99%; 1,4-butanediol yield 89.58%.

[0054] Example 2

[0055] (1) Prepare a metal salt solution by mixing copper nitrate and chromic anhydride with water. The concentration of copper ions in the solution is 1.0 mol / L, and the concentration of chromium ions is 1.0 mol / L. Add polyethylene glycol (molecular weight 4000) to the above metal salt solution and control the concentration of polyethylene glycol in the resulting mixture to be 0.2 g / mL.

[0056] (2) The precipitant solution was a 10wt% ammonia solution. An acid-base co-precipitation process was used. 4L of the mixture obtained in step (1) was added to the precipitant solution in a co-current manner. The reaction temperature was controlled at 30℃, the reaction pH was 7.0, and the reaction time was 2h. After the reaction, the mixture was aged at 30℃ for 2h. During the reaction and aging process, N2 (60mL / min) was introduced into the system. After aging, the mixture was filtered and washed 6 times with deionized water. It was then dried in a 60℃ oven for 12h to collect the Cu-Cr precursor.

[0057] (3) Add 4g PVA (molecular weight 80000) to 60mL of deionized water, heat in a water bath to 80℃ and stir for 2h to obtain PVA aqueous solution. Take 20mL of the above PVA aqueous solution, add 2g of Cu-Cr precursor obtained in step (2), and magnetically stir at 1000rpm for 12h to obtain spinning solution.

[0058] (4) Electrospinning was performed to prepare the catalyst precursor according to the following parameters: spinning voltage was 20kV, propulsion speed was 1.5mL / h, and receiving distance was 15cm.

[0059] (5) The catalyst precursor obtained in step (4) is placed in a muffle furnace for calcination. The calcination conditions are as follows: the heating rate to the calcination temperature is 5℃ / min, the calcination temperature is 400℃, the calcination time is 4h, and the calcination atmosphere is air, to obtain an unformed catalyst.

[0060] The unformed catalyst was mixed evenly with graphite and then automatically shaped into cylindrical particles with a diameter of 3 mm and a height of 3.22 mm using a tablet press. These particles were called formed catalyst A2. The catalyst A2 contained 49.17 wt% CuO, 47.88 wt% Cr2O3, and 2 wt% graphite, with the remainder being impurities. The properties of catalyst A2 are shown in Table 1.

[0061] The catalyst reduction and reaction conditions were the same as in Example 1, with a dimethyl maleate conversion of 99.99% and a 1,4-butanediol yield of 89.41%.

[0062] Example 3

[0063] (1) Prepare a metal salt solution by mixing copper nitrate and chromic anhydride with water. The concentration of copper ions in the solution is 0.5 mol / L, and the concentration of chromium ions is 0.5 mol / L. Add polyethylene glycol (molecular weight 4000) to the above metal salt solution and control the concentration of polyethylene glycol in the resulting mixture to be 0.2 g / mL.

[0064] (2) The precipitant solution was a 10wt% ammonia solution. An acid-base co-precipitation process was used. 4L of the mixture obtained in step (1) was added to the precipitant solution in a co-current manner. The reaction temperature was controlled at 30℃, the reaction pH was 7.0, and the reaction time was 2h. After the reaction, the mixture was aged at 30℃ for 2h. During the reaction and aging process, N2 (40mL / min) was introduced into the system. After aging, the mixture was filtered and washed 6 times with deionized water. It was then dried in a 60℃ oven for 12h to collect the Cu-Cr precursor.

[0065] (3) Add 6g PVA (molecular weight 80000) to 60mL of deionized water, heat in a water bath to 80℃ and stir for 2h to obtain PVA aqueous solution. Take 20mL of the above PVA aqueous solution, add 2g of Cu-Cr precursor obtained in step (2), and magnetically stir at 1000rpm for 12h to obtain spinning solution.

[0066] (4) Electrospinning was performed to prepare the catalyst precursor according to the following parameters: spinning voltage was 20kV, propulsion speed was 1.5mL / h, and receiving distance was 15cm.

[0067] (5) The catalyst precursor obtained in step (4) is placed in a muffle furnace for calcination. The calcination conditions are as follows: the heating rate to the calcination temperature is 5℃ / min, the calcination temperature is 400℃, the calcination time is 4h, and the calcination atmosphere is air, to obtain an unformed catalyst.

[0068] The unformed catalyst was mixed evenly with graphite and then automatically formed into cylindrical particles with a diameter of 3 mm and a height of 3.26 mm using a tablet press, which is the formed catalyst A3. The catalyst A3 contains 49.18 wt% CuO, 47.96 wt% Cr2O3, and 1.5 wt% graphite, with the remainder being impurities. The properties of catalyst A3 are shown in Table 1.

[0069] The catalyst reduction and reaction conditions were the same as in Example 1, with a dimethyl maleate conversion of 99.99% and a 1,4-butanediol yield of 89.32%.

[0070] Example 4

[0071] (1) Prepare a metal salt solution by mixing copper nitrate and chromic anhydride with water. The concentration of copper ions in the solution is 1.0 mol / L, and the concentration of chromium ions is 1.0 mol / L. Add polyethylene glycol (molecular weight 4000) to the above metal salt solution and control the concentration of polyethylene glycol in the resulting mixture to be 0.2 g / mL.

[0072] (2) The precipitant solution was a 10wt% ammonia solution. An acid-base co-precipitation process was used. 4L of the mixture obtained in step (1) was added to the precipitant solution in a co-current manner. The reaction temperature was controlled at 40℃, the reaction pH was 6.0, and the reaction time was 2h. After the reaction, the mixture was aged at 40℃ for 2h. During the reaction and aging process, N2 (40mL / min) was introduced into the system. After aging, the mixture was filtered and washed 6 times with deionized water. It was then dried in a 60℃ oven for 12h to collect the Cu-Cr precursor.

[0073] (3) Add 6g PVA (molecular weight 80000) to 60mL of deionized water, heat in a water bath to 80℃ and stir for 2h to obtain PVA aqueous solution. Take 20mL of the above PVA aqueous solution, add 2g of Cu-Cr precursor obtained in step (2), and magnetically stir at 1000rpm for 12h to obtain spinning solution.

[0074] (4) Electrospinning was performed to prepare the catalyst precursor according to the following parameters: spinning voltage was 20kV, propulsion speed was 1.5mL / h, and receiving distance was 15cm.

[0075] (5) The catalyst precursor obtained in step (4) is placed in a muffle furnace for calcination. The calcination conditions are as follows: the heating rate to the calcination temperature is 5℃ / min, the calcination temperature is 400℃, the calcination time is 4h, and the calcination atmosphere is air, to obtain an unformed catalyst.

[0076] The unformed catalyst was mixed evenly with graphite and then automatically formed into cylindrical particles with a diameter of 3 mm and a height of 3.27 mm using a tablet press, which is catalyst A4. The catalyst A4 contains 49.08 wt% CuO, 48.03 wt% Cr2O3, and 2 wt% graphite, with the remainder being impurities. The properties of catalyst A4 are shown in Table 1.

[0077] The catalyst reduction and reaction conditions were the same as in Example 1, with a dimethyl maleate conversion of 99.99% and a 1,4-butanediol yield of 89.52%.

[0078] Example 5

[0079] (1) Prepare a metal salt solution by mixing copper nitrate and chromic anhydride with water. The concentration of copper ions in the solution is 1.0 mol / L, and the concentration of chromium ions is 1.0 mol / L. Add polyethylene glycol (molecular weight 4000) to the above metal salt solution and control the concentration of polyethylene glycol in the resulting mixture to be 0.2 g / mL.

[0080] (2) The precipitant solution was a 10wt% ammonia solution. An acid-base co-precipitation process was used. 4L of the mixture obtained in step (1) was added to the precipitant solution in a co-current manner. The reaction temperature was controlled at 30℃, the reaction pH was 7.0, and the reaction time was 2h. After the reaction, the mixture was aged at 30℃ for 2h. During the reaction and aging process, N2 (40mL / min) was introduced into the system. After aging, the mixture was filtered and washed 6 times with deionized water. It was then dried in a 60℃ oven for 12h to collect the Cu-Cr precursor.

[0081] (3) Add 6g of PVA (molecular weight 80000) to 60mL of deionized water, heat in a water bath to 80℃ and stir for 2h to obtain PVA aqueous solution. Take 20mL of the above PVA aqueous solution, add 4g of Cu-Cr precursor obtained in step (2), and magnetically stir at 1000rpm for 12h to obtain spinning solution.

[0082] (4) Electrospinning was performed to prepare the catalyst precursor according to the following parameters: spinning voltage was 25kV, propulsion speed was 2.0mL / h, and receiving distance was 15cm.

[0083] (5) The catalyst precursor obtained in step (4) is placed in a muffle furnace for calcination. The calcination conditions are as follows: the heating rate to the calcination temperature is 5℃ / min, the calcination temperature is 400℃, the calcination time is 4h, and the calcination atmosphere is air, to obtain an unformed catalyst.

[0084] The unformed catalyst was mixed evenly with graphite and then automatically formed into cylindrical particles with a diameter of 3 mm and a height of 3.31 mm using a tablet press. These particles were called formed catalyst A5, containing 49.22 wt% CuO, 48.05 wt% Cr2O3, and 2 wt% graphite, with the remainder being impurities. The properties of catalyst A5 are shown in Table 1.

[0085] The catalyst reduction and reaction conditions were the same as in Example 1, with a dimethyl maleate conversion of 99.99% and a 1,4-butanediol yield of 88.92%.

[0086] Comparative Example 1

[0087] (1) Prepare a metal salt solution by mixing copper nitrate and chromic anhydride with water. The concentration of copper ions in the solution is 1.0 mol / L and the concentration of chromium ions is 1.0 mol / L.

[0088] (2) The precipitant solution was a 10wt% ammonia solution. An acid-base co-precipitation process was adopted. 4L of the mixture obtained in step (1) was added to the precipitant solution in a co-current manner. The reaction temperature was controlled at 30℃, the reaction pH was 7.0, and the reaction time was 2h. After the reaction was completed, the mixture was aged at 30℃ for 2h. After aging, the mixture was filtered and separated, and washed 6 times with deionized water. The mixture was then dried in an oven at 60℃ for 12h to collect the Cu-Cr precursor.

[0089] (3) Add 6g PVA (molecular weight 80000) to 60mL of deionized water, heat in a water bath to 80℃ and stir for 2h to obtain PVA aqueous solution. Take 20mL of the above PVA aqueous solution, add 2g of Cu-Cr precursor obtained in step (2), and magnetically stir at 1000rpm for 12h to obtain spinning solution.

[0090] (4) Electrospinning was performed to prepare the catalyst precursor according to the following parameters: spinning voltage was 20kV, propulsion speed was 1.5mL / h, and receiving distance was 15cm.

[0091] (5) The catalyst precursor obtained in step (4) is placed in a muffle furnace for calcination. The calcination conditions are as follows: the heating rate to the calcination temperature is 5℃ / min, the calcination temperature is 400℃, the calcination time is 4h, and the calcination atmosphere is air, to obtain an unformed catalyst.

[0092] The unformed catalyst was mixed evenly with graphite and automatically shaped into cylindrical particles with a diameter of 3 mm and a height of 3.65 mm using a tablet press, which is catalyst B1. The catalyst B1 contains 49.12 wt% CuO, 47.96 wt% Cr2O3, and 2 wt% graphite, with the remainder being impurities. The properties of catalyst B1 are shown in Table 1.

[0093] The catalyst reduction and reaction conditions were the same as in Example 1, with a dimethyl maleate conversion of 97.45% and a 1,4-butanediol yield of 81.45%.

[0094] Comparative Example 2

[0095] (1) Prepare a metal salt solution by mixing copper nitrate and chromic anhydride with water. The concentration of copper ions in the solution is 1.0 mol / L, and the concentration of chromium ions is 1.0 mol / L. Add polyethylene glycol (molecular weight 4000) to the above metal salt solution and control the concentration of polyethylene glycol in the resulting mixture to be 0.2 g / mL.

[0096] (2) The precipitant solution was a 10wt% ammonia solution. An acid-base co-precipitation process was used. 4L of the mixture obtained in step (1) was added to the precipitant solution in a co-current manner. The reaction temperature was controlled at 30℃, the reaction pH was 7.0, and the reaction time was 2h. After the reaction, the mixture was aged at 30℃ for 2h. During the reaction and aging process, N2 (40mL / min) was introduced into the system. After aging, the mixture was filtered and washed 6 times with deionized water. It was then dried in a 60℃ oven for 12h to collect the Cu-Cr precursor.

[0097] (3) Add 6g of PVA (molecular weight 80000) to 60mL of deionized water, heat in a water bath to 80℃ and stir for 2h to obtain PVA aqueous solution. Take 20mL of the above PVA aqueous solution, add 2g of Cu-Cr precursor obtained in step (2), and magnetically stir at 1000rpm for 12h to obtain spinning solution.

[0098] (4) Electrospinning was performed to prepare the catalyst precursor according to the following parameters: spinning voltage was 5kV, propulsion speed was 5mL / h, and receiving distance was 15cm.

[0099] (5) The catalyst precursor obtained in step (4) is placed in a muffle furnace for calcination. The calcination conditions are as follows: the heating rate to the calcination temperature is 5℃ / min, the calcination temperature is 400℃, the calcination time is 4h, and the calcination atmosphere is air, to obtain an unformed catalyst.

[0100] The unformed catalyst was mixed evenly with graphite and then automatically formed into cylindrical particles with a diameter of 3 mm and a height of 3.53 mm using a tablet press. These particles were called formed catalyst B2, containing 49.23 wt% CuO, 47.91 wt% Cr2O3, and 2 wt% graphite. The properties of catalyst B2 are shown in Table 1.

[0101] The catalyst reduction and reaction conditions were the same as in Example 1, with a dimethyl maleate conversion of 98.92% and a 1,4-butanediol yield of 82.87%.

[0102] Table 1. Properties of the catalysts obtained in the examples and comparative examples.

[0103] Catalyst number Weight of 10 capsules (g) Lateral compressive strength (N) Bulk density (g / 100mL) A1 0.79 113 177.23 A2 0.77 106 176.46 A3 0.77 96 178.59 A4 0.81 118 184.05 A5 0.83 124 186.97 B1 0.92 68 196.58 B2 0.87 77 194.27

[0104] Note: The weight of 10 particles refers to the total weight of 10 catalyst particles.

[0105] 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 copper-chromium catalyst, characterized in that, include: (1) Mix copper source and chromium source solutions with polyethylene glycol to obtain a mixture; (2) The mixture obtained in step (1) and the precipitant are subjected to a co-current reaction. After the reaction is completed, the mixture is aged and dried to obtain Cu-Cr precursor. N2 is continuously introduced during the co-current reaction and / or aging process. (3) Prepare a polyvinyl alcohol aqueous solution, mix it with the Cu-Cr precursor obtained in step (2), stir, and obtain a spinning solution; (4) Electrospinning is performed using the spinning solution obtained in step (3) to obtain the catalyst precursor; (5) The catalyst precursor obtained in step (4) is calcined to obtain an unformed catalyst, which is then pressed into tablets to obtain a copper-chromium catalyst.

2. The method according to claim 1, characterized in that, In step (1), the copper source is an acidic solution containing copper, preferably one or more of copper nitrate, copper acetate, copper chloride, and copper sulfate; the chromium source is an acidic solution containing chromium, preferably one or more of chromic anhydride, chromium nitrate, and chromium chloride. And / or, in step (2), the precipitant is one or more of sodium carbonate solution, sodium bicarbonate solution, ammonia water, and sodium hydroxide solution.

3. The method according to claim 1, characterized in that, In step (1), the copper source and the chromium source are first mixed to obtain a metal salt solution, and then mixed with polyethylene glycol to obtain a mixture; in the metal salt solution, the concentration of copper ions is 0.05-5 mol / L and the concentration of chromium ions is 0.05-5 mol / L.

4. The method according to claim 1, characterized in that, In step (1), the molecular weight of the polyethylene glycol is 1000 to 10000; And / or, in the mixture, the mass concentration of polyethylene glycol is 0.05 to 0.4 g / mL.

5. The method according to claim 1, characterized in that, In step (2), the conditions for the co-current reaction are: reaction temperature of 25-70℃, reaction time of 0.2-5h, and pH value controlled at 4.0-8.0 during the reaction process; And / or, in step (2), the aging conditions are: the aging temperature is 25 to 80°C, and the aging time is 0.5 to 5 hours.

6. The method according to claim 1, characterized in that, In step (2), the N2 flow rate is 2 to 25 mL / min relative to the volume of the mixture obtained in step (1). Preferably, N2 is continuously introduced during both the co-current reaction and the aging process.

7. The method according to claim 1, characterized in that, In step (2), the drying conditions are: the drying temperature is 25-80℃ and the drying time is 6-24h.

8. The method according to claim 1, characterized in that, In step (3), the mass of Cu-Cr precursor contained in each milliliter of polyvinyl alcohol aqueous solution is 0.025 to 0.25 g.

9. The method according to claim 1, characterized in that, In step (4), the conditions for electrospinning are: spinning voltage of 15-30kV, feed speed of 0.5-3.0mL / h, and receiving distance of 10-30cm.

10. The method according to claim 1, characterized in that, In step (5), the calcination conditions are: calcination temperature of 300-500℃, calcination time of 2-8h; 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.

11. The method according to claim 1, characterized in that, In step (5), the unformed catalyst is mixed with graphite and then pressed into tablets; the amount of graphite used is 0.1wt% to 5wt% based on the weight of the unformed catalyst.

12. The method according to claim 1, characterized in that, In step (5), after tableting, the catalyst is cylindrical with a diameter of 2-4 mm and a height of 2-5 mm, preferably 2.5-3.5 mm.

13. A copper-chromium catalyst prepared by any one of claims 1-12.

14. The copper-chromium catalyst according to claim 13, characterized in that, The weight contents of each component in the copper-chromium catalyst are as follows: CuO 40-60 wt%, Cr2O3 40-60 wt%; And / or, the copper-chromium catalyst, based on a cylindrical shaped catalyst with a diameter of 3 mm and a height of 3.0 ± 0.4 mm, has a weight of 0.70 to 0.90 g for 10 catalyst particles, preferably 0.75 to 0.85 g; And / or, the catalyst side pressure strength is 80-130 N / particle, preferably 90-125 N / particle; And / or, the catalyst has a bulk density of 160–195 g / 100 mL, preferably 175–190 g / 100 mL.

15. The use of a copper-chromium catalyst prepared by any of the methods according to claims 1-12 or any of the copper-chromium catalysts according to claims 13-14 in the hydrogenation of dimethyl maleate to prepare 1,4-butanediol.