Catalyst for preparing methanol through hydrogenation of carbon dioxide as well as preparation method and application of catalyst

Abstract

The invention provides a catalyst for preparing methanol through carbon dioxide hydrogenation and a preparation method and application thereof. The catalyst comprises the following components: a composite metal oxide and a spinel compound (ZnO-Cu) Mn2O4. RE containing rare earth, the molar ratio of the rare earth element to the manganese element in the rare earth-containing spinel compound is 0.001-0.1, the molar ratio of the copper element to the manganese element is 0.1-1, and the molar ratio of the zinc element to the copper element is 0.1-1; the molar ratio of a copper element to a zinc element to an aluminum element to a zirconium element to a rare earth element in the composite metal oxide is 1: (0.3-1): (0.01-0.1): (0.01-0.1): (0.001-0.1); the molar ratio of the manganese element in the spinel compound to the copper element in the composite metal oxide is (1: 9)-(9: 1). The catalyst provided by the invention significantly improves the conversion efficiency of carbon dioxide and the selectivity of methanol.

Description

Technical Field

[0001] This invention relates to a catalyst for the hydrogenation of carbon dioxide to methanol, its preparation method and application, belonging to the field of catalyst preparation. Background Technology

[0002] Currently, there are three main types of catalysts for CO2 hydrogenation to methanol: the first is copper-based catalysts, which are the most typical Cu / ZnO / Al2O3 catalytic system; the second is supported noble metal catalysts, such as Pd / ZrO2; and the third is semiconductor oxides, such as ZnO-ZrO2 and In2O3. Because noble metal catalysts are too expensive for industrial application, and ZnO-ZrO2 semiconductor catalysts have relatively low catalytic activity, most pilot and industrial-scale CO2 hydrogenation to methanol production facilities currently use copper-based Cu / ZnO / Al2O3 catalytic systems in tubular fixed-bed reactors. However, copper-based catalysts are susceptible to poisoning by impurities such as sulfur, and high-temperature sintering reduces their activity and stability. These problems hinder the industrial application of CO2 to methanol technology.

[0003] In the prior art, CN109621956A relates to a copper-aluminum spinel catalyst for the hydrogenation of carbon dioxide to methanol. The catalyst composition is as follows: copper-aluminum spinel content of 40.0 wt%-99.9 wt%, copper oxide content of 0.04 wt%-10.0 wt%, aluminum oxide content of 0.06%-50%, and other oxide content of 0-20.0%. A spinel precursor is obtained by preparing a homogeneous sol-gel solution using a sol-gel method, comprising a copper source, an aluminum source, an auxiliary metal source, a complexing agent, and a solvent. Alternatively, the spinel precursor can be obtained by directly and physically mixing the copper source, aluminum source, and auxiliary metal source using a solid-state method. The spinel precursor is then calcined at 600-1200℃ in air or an oxygen atmosphere for 0.5-10 h to obtain the copper-aluminum spinel catalyst. However, the catalyst preparation conditions are harsh, resulting in low catalytic activity.

[0004] In addition, CN101513615A relates to a catalyst for the synthesis of methanol from carbon dioxide and its preparation method. The molar ratio of its components is Cu∶Zn∶Al∶Zr∶M=43∶43∶10∶5∶2. It includes the following steps: (1) dissolving copper and zinc nitrates with a molar ratio of Cu∶Zn of 1 / 2 to 2 / 1 in water to obtain a mixed salt solution; (2) preparing a sodium carbonate solution of 0.1 to 1 mol / L and dividing it into two portions; (3) preparing a mixed aluminum nitrate / zirconium nitrate solution of 0.01 to 0.2 mol / L; (4) co-precipitating the sodium carbonate solution from step (2) and the mixed solution from step (3) in parallel flow at 50-70℃, with a pH of 7-8, to prepare a precipitate. (1) is used as a carrier precursor. The mixed solution from step (1) and the sodium carbonate solution from step (2) were added concurrently to the precipitate (1), controlling the precipitation temperature at 50-70℃ and the pH at 7-8. After titration, the precipitate was stirred for 20 minutes, allowed to stand, aged at room temperature for 1 hour, filtered, and washed with deionized water until the outflow from the bottom of the Buchner funnel was neutral. It was then dried overnight at 110℃ in air, and calcined at 350℃ for 4 hours with a temperature program of 1℃ / min from 20℃. After cooling to room temperature, it was pressed into tablets or extruded into strips. However, the catalyst activity was relatively low.

[0005] Therefore, developing a catalyst with high catalytic activity and selectivity for the hydrogenation of carbon dioxide into methanol has significant practical and industrial value. Summary of the Invention

[0006] To address the aforementioned technical problems, the present invention aims to provide a catalyst for the hydrogenation of carbon dioxide to methanol, its preparation method, and its application, which significantly improves the conversion efficiency of carbon dioxide and the selectivity of methanol.

[0007] To achieve the above objectives, in a first aspect, the present invention provides a catalyst for the hydrogenation of carbon dioxide to methanol, wherein the catalyst comprises: a composite metal oxide and a rare earth-containing spinel compound (ZnO-Cu)Mn2O4·RE;

[0008] The molar ratio of rare earth elements to manganese in the rare earth-containing spinel compound is 0.001-0.1, the molar ratio of copper to manganese is 0.1-1, and the molar ratio of zinc to copper is 0.1-1.

[0009] The molar ratio of copper, zinc, aluminum, zirconium, and rare earth elements in the composite metal oxide is 1:(0.3-1):(0.01-0.1):(0.01-0.1):(0.001-0.1).

[0010] The molar ratio of manganese in the rare earth-containing spinel compound to copper in the composite metal oxide is (1:9)-(9:1).

[0011] The rare earth elements include one or more combinations of Ce, La, Pr, Nd, Gd, and Sm. In the rare earth-containing spinel compound (ZnO-Cu)Mn2O4·RE, RE only indicates the presence of rare earth elements.

[0012] According to a specific embodiment of the present invention, preferably, the molar ratio of copper, zinc, aluminum and zirconium in the composite metal oxide is 1:(0.4-0.6):(0.02-0.04):(0.03-0.06).

[0013] According to a specific embodiment of the present invention, preferably, the surface of the rare earth-containing spinel compound (ZnO-Cu)Mn2O4·RE is covered with the composite metal oxide.

[0014] The catalyst of this invention is synthesized using a two-step precipitation method: First, a manganese-based spinel compound containing copper, zinc, and rare earth elements is prepared. This manganese-based spinel compound can act as a support and also catalyze the hydrogenation of carbon dioxide to methanol. Second, copper-zinc-aluminum-zirconium and rare earth metal compounds are deposited on the surface of the manganese-based spinel compound precursor precipitate by chemical precipitation. The content of the copper-zinc-based spinel compound accounts for about half of the entire catalyst. The manganese-based spinel compound plays a good role in dispersing the copper and zinc active components in the copper-zinc-aluminum-zirconium and rare earth metal compounds, thereby improving the catalyst activity. The copper-zinc-based spinel compound itself is rich in oxygen vacancies. With the modification of rare earth elements, the number of oxygen vacancies in the manganese-based spinel is further increased and stabilized, which significantly improves the carbon dioxide adsorption and activation capacity. It can play a synergistic catalytic role with the copper and zinc active components supported on the manganese-based spinel compound. Meanwhile, in addition to increasing oxygen vacancies, zirconium, together with aluminum, surrounds the active components copper and zinc, playing an anti-sintering role and significantly improving the stability and service life of the catalyst.

[0015] Secondly, the present invention provides a method for preparing the above-mentioned catalyst for the hydrogenation of carbon dioxide to methanol, comprising the following steps:

[0016] Step 1: Mix the first copper source, the first zinc source, the manganese source and the first rare earth additive to form the first salt solution, and then carry out the first precipitation reaction with the solution of the first precipitant to obtain the precipitate mother liquor;

[0017] Step 2: Mix the second copper source, the second zinc source, the aluminum source, the zirconium source and the second rare earth additive to form a second salt solution, and then add it together with the solution of the second precipitant to the mother liquor of the precipitate to carry out the second precipitation reaction, and obtain the catalyst for the hydrogenation of carbon dioxide to methanol.

[0018] According to a specific embodiment of the present invention, preferably, the first copper source, the first zinc source, the manganese source, the second copper source, the second zinc source, the aluminum source, and the zirconium source are selected from one or more combinations of nitrates, halides, acetates, and sulfates.

[0019] According to a specific embodiment of the present invention, preferably, the first copper source is selected from one or a combination of two or more of copper nitrate, copper sulfate, and copper chloride.

[0020] According to a specific embodiment of the present invention, preferably, the first zinc source is selected from one or a combination of two or more of zinc nitrate, zinc sulfate, and zinc acetate.

[0021] According to a specific embodiment of the present invention, preferably, the manganese source is selected from one or a combination of two or more of manganese acetate, manganese sulfate, and manganese chloride.

[0022] According to a specific embodiment of the present invention, preferably, the second copper source is selected from one or a combination of two or more of copper nitrate, copper sulfate, and copper chloride.

[0023] According to a specific embodiment of the present invention, preferably, the second zinc source is selected from one or a combination of two or more of zinc nitrate, zinc sulfate, and zinc acetate.

[0024] According to a specific embodiment of the present invention, preferably, the aluminum source is selected from one or a combination of two or more of aluminum nitrate, aluminum sulfate, and aluminum chloride.

[0025] According to a specific embodiment of the present invention, preferably, the zirconium source is selected from one or a combination of two or more of zirconium nitrate, zirconium sulfate, and zirconium oxychloride.

[0026] According to a specific embodiment of the present invention, preferably, the first rare earth additive and the second rare earth additive are selected from one or more combinations of salts of Ce, La, Pr, Nd, Gd, and Sm; the first rare earth additive and the second rare earth additive are the same rare earth additive or different rare earth additives.

[0027] According to a specific embodiment of the present invention, preferably, the first precipitant and the second precipitant are selected from one or more combinations of NaOH, KOH, Na2CO3, NaHCO3, K2CO3, KHCO3, Na2C2O4, K2C2O4, RCOONa, RCOOK, (NH4)2CO3, and NH4HCO3, wherein R is an organic functional group; the first precipitant and the second precipitant are the same precipitant or different precipitants.

[0028] According to a specific embodiment of the present invention, preferably, a first copper source, a first zinc source, a manganese source and a first rare earth additive are added to a solvent to form a first salt solution; wherein, the concentration of the first salt solution is 0.05-2 mol / L, more preferably 1 mol / L; the solvent can be water.

[0029] According to a specific embodiment of the present invention, preferably, a second copper source, a second zinc source, an aluminum source, a zirconium source and a second rare earth additive are added to a solvent to form a second salt solution; wherein, the concentration of the second salt solution is 0.05-2 mol / L, more preferably 1 mol / L; the solvent can be water.

[0030] According to a specific embodiment of the present invention, preferably, the concentration of the first precipitant solution is 0.1-5 mol / L, more preferably 1 mol / L; the concentration of the second precipitant solution is 0.1-5 mol / L, more preferably 1 mol / L.

[0031] According to a specific embodiment of the present invention, preferably, in step 1, before carrying out the first precipitation reaction, the solvent is heated to 60-80°C and stirred at a speed of 400-800 rpm / min for 0.5-3 hours. The solvent can be water. Then, the first salt solution and the first precipitant solution are added to the solvent in a parallel flow at a rate of 0.5-1.5 drops / second to carry out the first precipitation reaction, controlling the pH to be 7-9. After aging for 0.5-5 hours, more preferably 1 hour, the precipitate mother liquor is obtained.

[0032] According to a specific embodiment of the present invention, preferably, in step 2, before the second precipitation reaction, the mother liquor of the precipitate is heated to 60-80°C and stirred at a speed of 400-800 rpm / min. Then, the second salt solution and the solution of the second precipitant are added to the mother liquor of the precipitate in a co-current flow at a rate of 0.5-1.5 drops / second. After the second precipitation reaction, the pH is controlled to be 7-9, and after aging for 0.5-5 hours, preferably 1 hour, it is calcined to obtain the precursor of the catalyst. Then, it is tableted and sieved to obtain the catalyst for the hydrogenation of carbon dioxide to methanol.

[0033] According to a specific embodiment of the present invention, preferably, after the second precipitation reaction, the precipitated product is first separated from the suspension at room temperature by centrifugation or vacuum filtration, washed, and then dried. For example, it is thoroughly washed with deionized water until neutral, and then dried at 110°C for 12 hours.

[0034] According to a specific embodiment of the present invention, preferably, at 2°C·min -1 The heating rate increases from room temperature to the calcination temperature, which is 300-500℃, and the calcination time is 3-6 hours.

[0035] According to a specific embodiment of the present invention, preferably, the precursor of the catalyst is first ground for 0.5-2 hours, more preferably 1 hour; then the precursor powder of the catalyst is pressed into tablets at a pressure of 3-5 MPa for 30 minutes; and then powder with a particle size of 40-60 mesh is sieved to obtain the catalyst.

[0036] Thirdly, the present invention provides an application of the catalyst for the hydrogenation of carbon dioxide to methanol as described above in the synthesis of methanol by hydrogenation of carbon dioxide.

[0037] According to a specific embodiment of the present invention, preferably, a mixture of CO2 and H2 is used as the raw material gas, and methanol is directly converted into methanol through a reduction step and a catalytic step under the catalytic action of the catalyst for the above-mentioned carbon dioxide hydrogenation to methanol.

[0038] According to a specific embodiment of the present invention, preferably, the reaction conditions for the reduction step are: reaction time of 4-24 h, reaction temperature of 200-300 °C, and H2 space velocity of 100-5000 mL / (h·g). cat ).

[0039] According to a specific embodiment of the present invention, preferably, the reaction conditions for the catalytic step are as follows: cooling to the reaction temperature in a protective atmosphere, the reaction temperature being 200-300℃, the reaction pressure being 0.01-10.0 MPa, the feed gas being a mixture of H2 and CO2 with a molar ratio of 0.5-8.0, and the feed gas space velocity being 5000-50000 mL / (h·g) cat ).

[0040] According to a specific embodiment of the present invention, preferably, the raw material carbon dioxide is a gas containing carbon dioxide, including one or more of the following: industrial waste gas containing carbon dioxide, automobile exhaust gas, coal combustion waste gas, and carbon dioxide absorbed from the atmosphere and seawater.

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

[0042] The catalyst of this invention comprises a composite metal oxide and a rare-earth-containing spinel compound (ZnO-Cu)Mn2O4·RE. First, a spinel compound precursor precipitate containing copper, zinc, manganese, and rare earth elements is synthesized. Then, a composite metal oxide of copper, zinc, aluminum, zirconium, and rare earth metals is precipitated on the surface of the spinel compound precursor precipitate to complete the catalyst preparation. The spinel compound (ZnO-Cu)Mn2O4 exhibits high catalytic activity and abundant oxygen vacancies. Modification with rare earth elements further increases the number of oxygen vacancies in the manganese spinel, and these oxygen vacancies are stabilized, improving the carbon dioxide adsorption and activation capacity. The formed copper-zinc-manganese spinel compound (ZnO-Cu)Mn2O4 can deeply reduce ZnO to Zn. 0 Atoms form CuZn alloy, thereby forming highly active CuZn bimetallic nanoparticles, which significantly improves the reaction activity and methanol selectivity, and increases the activation ability of CO and CO2 by an order of magnitude.

[0043] By depositing and adsorbing elements such as copper, zinc, manganese, and rare earth elements onto the surface of spinel, and then reducing and activating them, highly active CuZn bimetallic nanoparticles are further formed on the spinel surface, significantly increasing the number of active centers of the catalyst. Zirconium and aluminum elements are adsorbed and surround the highly active CuZn bimetallic nanoparticles, providing isolation and protection, improving the CuZn bimetallic nanoparticles' resistance to poisoning and high-temperature sintering, and significantly enhancing the catalytic activity and stability of the catalyst. Detailed Implementation

[0044] In order to provide a clearer understanding of the technical features, objectives and beneficial effects of the present invention, the technical solution of the present invention will now be described in detail below, but it should not be construed as limiting the scope of implementation of the present invention.

[0045] Example 1:

[0046] This embodiment provides a method for preparing a catalyst for the hydrogenation of carbon dioxide to methanol, comprising the following steps:

[0047] Step 1:

[0048] Weigh 24.2g Cu(NO3)2·3H2O, 14.9g Zn(NO3)2·6H2O, 73.5g Mn(CH3COO)2·4H2O, 1.3g La(NO3)3·6H2O, and 1.3g Ce(NO3)3·6H2O, and add them to deionized water to prepare a first salt solution with a total concentration of 1mol / L; weigh 55g Na2CO3 as the precipitant, and add it to deionized water to prepare a first precipitant solution with a total concentration of 1mol / L.

[0049] The sedimentation tank containing 50 ml of deionized water was heated to 75°C and stirred at a speed of 400 rpm for 0.5 h. The solutions of the first salt and the first precipitant were added dropwise to the sedimentation tank in parallel at a rate of 1 drop / second while stirring. The pH was maintained at 7-9 until the addition was complete. The mixture was then stirred and aged at a constant temperature for 1 h to obtain the precipitate mother liquor.

[0050] Step 2:

[0051] Weigh 72.5g Cu(NO3)2·3H2O, 44.6g Zn(NO3)2·6H2O, 3.4g Al(NO3)3·9H2O, 6.4g Zr(NO3)4·5H2O, 1.3g La(NO3)3·6H2O, and 1.3g Ce(NO3)3·6H2O, and add deionized water to prepare a second salt solution with a total concentration of 1mol / L; weigh 55g Na2CO3 as the precipitant, and add deionized water to prepare a second precipitant solution with a total concentration of 1mol / L.

[0052] The sedimentation tank containing the mother liquor from step 1 was heated to 75°C and stirred at 400 rpm. The second salt solution and the second precipitant solution were added dropwise to the sedimentation tank in a parallel stream at a rate of 1 drop / second, while stirring was maintained at pH 7-9, until the addition was complete. The mixture was then stirred and aged at a constant temperature for 1 hour. After the reaction was complete, the precipitated product was separated from the suspension at room temperature by centrifugation or filtration, and thoroughly washed with deionized water until neutral. It was then dried at 110°C for 12 hours at a rate of 2°C·min. -1 The heating rate was increased from room temperature to the calcination temperature, which was 400℃, and the calcination time was 3 hours to obtain the precursor of the methanol catalyst.

[0053] The precursor of the methanol catalyst was ground for 1 hour, and then the precursor powder was pressed into tablets at a pressure of 4 MPa for 30 minutes. The powder with a particle size of 40-60 mesh was then sieved to obtain catalyst S-1 for the hydrogenation of carbon dioxide to methanol.

[0054] Example 2:

[0055] This embodiment provides a method for preparing a catalyst for the hydrogenation of carbon dioxide to methanol, which differs from Example 1 only in that:

[0056] In step 1, 72g of precipitant K2CO3 was weighed and added to deionized water to prepare a solution of the first precipitant with a total concentration of 1mol / L;

[0057] In step 2, 72g of precipitant K2CO3 was weighed and added to deionized water to prepare a solution of the second precipitant with a total concentration of 1mol / L;

[0058] The catalyst S-2 for the hydrogenation of carbon dioxide to methanol was finally obtained.

[0059] Example 3:

[0060] This embodiment provides a method for preparing a catalyst for the hydrogenation of carbon dioxide to methanol, which differs from Example 1 only in that:

[0061] In step 1, 50g of precipitant (NH4)2CO3 was weighed and added to deionized water to prepare a solution of the first precipitant with a total concentration of 1mol / L;

[0062] In step 2, 50g of precipitant (NH4)2CO3 was weighed and added to deionized water to prepare a solution of the second precipitant with a total concentration of 1mol / L;

[0063] The catalyst S-3 for the hydrogenation of carbon dioxide to methanol was finally obtained.

[0064] Example 4:

[0065] This embodiment provides a method for preparing a catalyst for the hydrogenation of carbon dioxide to methanol, which differs from Example 1 only in that:

[0066] In step 1, 21g of NaOH precipitant was weighed and added to deionized water to prepare a solution of the first precipitant with a total concentration of 1mol / L;

[0067] In step 2, 21g of NaOH precipitant was weighed and added to deionized water to prepare a solution of the second precipitant with a total concentration of 1mol / L;

[0068] The catalyst S-4 for the hydrogenation of carbon dioxide to methanol was finally obtained.

[0069] Example 5:

[0070] This embodiment provides a method for preparing a catalyst for the hydrogenation of carbon dioxide to methanol, which differs from Example 1 only in that:

[0071] In step 1, 30g of precipitant KOH is weighed and added to deionized water to prepare a solution of the first precipitant with a total concentration of 1mol / L;

[0072] In step 2, 30g of precipitant KOH is weighed and added to deionized water to prepare a solution of the second precipitant with a total concentration of 1mol / L;

[0073] The final product was catalyst S-5 for the hydrogenation of carbon dioxide to methanol.

[0074] Example 6:

[0075] This embodiment provides a method for preparing a catalyst for the hydrogenation of carbon dioxide to methanol, which differs from Example 1 only in that:

[0076] In step 1, weigh 25g CuSO4·5H2O, 9g ZnSO4·H2O, 50.7g MnSO4·H2O, 1.3g La(NO3)3·6H2O, and 1.3g Ce(NO3)3·6H2O, and add them to deionized water to prepare a first salt solution with a total concentration of 1mol / L.

[0077] In step 2, 74.9g CuSO4·5H2O, 26.9g ZnSO4·H2O, 3.1g Al2(SO4)3, 5.3g Zr(SO4)2·4H2O, 1.3g La(NO3)3·6H2O, and 1.3g Ce(NO3)3·6H2O are weighed and added to deionized water to prepare a second salt solution with a total concentration of 1mol / L.

[0078] The catalyst S-6 for the hydrogenation of carbon dioxide to methanol was finally obtained.

[0079] Example 7:

[0080] This embodiment provides a method for preparing a catalyst for the hydrogenation of carbon dioxide to methanol, which differs from Example 1 only in that:

[0081] In step 1, 24.2g Cu(NO3)2·3H2O, 14.9g Zn(NO3)2·6H2O, 73.5g Mn(CH3COO)2·4H2O, 1.3g Pr(NO3)3·6H2O, and 1.4g Gd(NO3)3·6H2O were weighed and added to deionized water to prepare a first salt solution with a total concentration of 1mol / L.

[0082] In step 2, 72.5g Cu(NO3)2·3H2O, 44.6g Zn(NO3)2·6H2O, 3.4g Al(NO3)3·9H2O, 6.4g Zr(NO3)4·5H2O, 1.3g Pr(NO3)3·6H2O, and 1.4g Gd(NO3)3·6H2O are weighed and added to deionized water to prepare a second salt solution with a total concentration of 1mol / L.

[0083] The catalyst S-7 for the hydrogenation of carbon dioxide to methanol was finally obtained.

[0084] Example 8:

[0085] This embodiment provides a method for preparing a catalyst for the hydrogenation of carbon dioxide to methanol, which differs from Example 1 only in that:

[0086] In step 1, weigh 25g CuSO4·5H2O, 9g ZnSO4·H2O, 50.7g MnSO4·H2O, 1.3g La(NO3)3·6H2O, and 1.3g Ce(NO3)3·6H2O, and add them to deionized water to prepare a first salt solution with a total concentration of 1mol / L.

[0087] In step 2, 59.9g CuSO4·5H2O, 21.5g ZnSO4·H2O, 2.5g Al2(SO4)3, 4.2g Zr(SO4)2·4H2O, 1.0g La(NO3)3·6H2O, and 1.0g Ce(NO3)3·6H2O are weighed and added to deionized water to prepare a second salt solution with a total concentration of 1mol / L.

[0088] The catalyst S-8 for the hydrogenation of carbon dioxide to methanol was finally obtained.

[0089] Example 9:

[0090] This embodiment provides a method for preparing a catalyst for the hydrogenation of carbon dioxide to methanol, which differs from Example 1 only in that:

[0091] In step 1, 17g CuCl2·2H2O, 11g Zn(CH3COO)2·2H2O, 59.4g MnCl2·4H2O, 1.1g LaCl3·6H2O, and 1.1g CeCl3·7H2O were weighed and added to deionized water to prepare a first salt solution with a total concentration of 1mol / L.

[0092] In step 2, 46.1g CuCl2·2H2O, 32.9g Zn(CH3COO)2·2H2O, 2.2g AlCl3·6H2O, 4.8g ZrOCl2·8H2O, 1.1g LaCl3·6H2O, and 1.1g CeCl3·7H2O were weighed and added to deionized water to prepare a second salt solution with a total concentration of 1mol / L.

[0093] The catalyst S-9 for the hydrogenation of carbon dioxide to methanol was finally obtained.

[0094] Comparative Example 1

[0095] This comparative example provides a method for preparing a catalyst for the hydrogenation of carbon dioxide to methanol, comprising the following steps:

[0096] Weigh 241.6g Cu(NO3)2·3H2O, 59.5g Zn(NO3)2·6H2O, 300.1g Al(NO3)3·9H2O, and 86.6g La(NO3)3·6H2O, and add them to deionized water to prepare a first salt solution with a total concentration of 1mol / L. Preheat both the first salt solution and the 1mol / L KHCO3 solution to 60℃, then add them concurrently to the 60℃ deionized water solution to maintain the pH of the solution at 7-8. After aging for 30 minutes, wash the precipitate with deionized water, and filter to obtain a filter cake.

[0097] Weigh 192.1g of citric acid and disperse it evenly in 3L of ethanol along with the filter cake. Stir at room temperature for 30min, then raise the temperature to 60℃ to evaporate and recover the ethanol. The resulting solid A is calcined at 700℃ under a nitrogen atmosphere for 1h, then the temperature is lowered to 25℃, and the nitrogen is switched to an oxygen / nitrogen atmosphere with an oxygen volume percentage of 3% and maintained for 20min. The resulting solid B is shaped into sheets and crushed into 20-40 mesh to obtain the catalyst (denoted as CZALa-1).

[0098] Comparative Example 2

[0099] This comparative example provides a method for preparing a catalyst for the hydrogenation of carbon dioxide to methanol, comprising the following steps:

[0100] Weigh 241.6g Cu(NO3)2·3H2O, 59.5g Zn(NO3)2·6H2O, 300.1g Al(NO3)3·9H2O, and 86.6g La(NO3)3·6H2O, and add them to deionized water to prepare a first salt solution with a total concentration of 1mol / L. Preheat both the first salt solution and the 1mol / L KHCO3 solution to 60℃, then add them concurrently to the 60℃ deionized water solution to maintain the pH of the solution at 7-8. After aging for 30 minutes, wash the precipitate with deionized water, filter, and obtain a filter cake.

[0101] The obtained filter cake was dried overnight in a 90℃ drying oven and calcined at 350℃ in air atmosphere for 2 hours. Graphite with a mass percentage of 2% was added, shaped into sheets, and crushed into 20-40 mesh to obtain the catalyst (denoted as CZALa-2).

[0102] Both catalysts from Comparative Examples 1 and 2 were used in the hydrogenation of carbon dioxide to methanol in a fixed-bed reactor with a catalyst loading of 5 mL. Catalyst CZALa-1 underwent no reduction activation, while CZALa-2 was reduced at 230 °C for 8 h in a hydrogen / nitrogen atmosphere with a hydrogen volume percentage of 5%. The reaction conditions were: CO2 / H2 / N2 = 23 / 69 / 8, and the gas hourly space velocity (GHSV) was 1 × 10⁻⁶. 4 h -lThe reaction temperature was 230℃ and the pressure was 5 MPa. After the reaction stabilized for 3 hours, the product was analyzed by online chromatography. The catalyst evaluation results for Comparative Examples 1-2 and Examples 1-9 are shown in Table 1.

[0103] Table 1

[0104]

[0105]

[0106] This invention provides a catalyst for the hydrogenation of carbon dioxide to methanol, which can significantly improve the conversion efficiency of carbon dioxide to 29.4%.

Claims

1. A catalyst for the hydrogenation of carbon dioxide to methanol, wherein, The catalyst comprises: a composite metal oxide and a rare earth-containing spinel compound (ZnO-Cu)Mn2O4·RE; The molar ratio of rare earth elements to manganese in the rare earth-containing spinel compound is 0.001-0.1, the molar ratio of copper to manganese is 0.1-1, and the molar ratio of zinc to copper is 0.1-1. The molar ratio of copper, zinc, aluminum, zirconium, and rare earth elements in the composite metal oxide is 1:(0.3-1):(0.01-0.1):(0.01-0.1):(0.001-0.1). The molar ratio of manganese in the rare earth-containing spinel compound to copper in the composite metal oxide is (1:9)-(9:1). The rare earth elements include one or more combinations of Ce, La, Pr, Nd, Gd, and Sm.

2. The catalyst for the hydrogenation of carbon dioxide to methanol according to claim 1, wherein, The molar ratio of copper, zinc, aluminum and zirconium in the composite metal oxide is 1:(0.4-0.6):(0.02-0.04):(0.03-0.06).

3. The catalyst for the hydrogenation of carbon dioxide to methanol according to claim 1, wherein, The surface of the rare earth-containing spinel compound (ZnO-Cu)Mn2O4·RE is covered with the composite metal oxide.

4. A method for preparing a catalyst for the hydrogenation of carbon dioxide to methanol as described in any one of claims 1-3, wherein, Includes the following steps: Step 1: Mix the first copper source, the first zinc source, the manganese source and the first rare earth additive to form the first salt solution, and then carry out the first precipitation reaction with the solution of the first precipitant to obtain the precipitate mother liquor; Step 2: Mix the second copper source, the second zinc source, the aluminum source, the zirconium source and the second rare earth additive to form a second salt solution, and then add it together with the solution of the second precipitant to the mother liquor of the precipitate to carry out the second precipitation reaction, and obtain the catalyst for the hydrogenation of carbon dioxide to methanol.

5. The method for preparing the catalyst for the hydrogenation of carbon dioxide to methanol according to claim 4, wherein the first copper source is selected from one or a combination of two or more of copper nitrate, copper sulfate, and copper chloride; And / or, the first zinc source is selected from one or more combinations of zinc nitrate, zinc sulfate, and zinc acetate; And / or, the manganese source is selected from one or more of manganese acetate, manganese sulfate, and manganese chloride; And / or, the second copper source is selected from one or more combinations of copper nitrate, copper sulfate, and copper chloride; And / or, the second zinc source is selected from one or more combinations of zinc nitrate, zinc sulfate, and zinc acetate; And / or, the aluminum source is selected from one or more combinations of aluminum nitrate, aluminum sulfate, and aluminum chloride; And / or, the zirconium source is selected from one or more combinations of zirconium nitrate, zirconium sulfate, and zirconium oxychloride.

6. The method for preparing the catalyst for the hydrogenation of carbon dioxide to methanol according to claim 4, wherein, The first rare earth additive and the second rare earth additive are selected from one or more combinations of salts of Ce, La, Pr, Nd, Gd, and Sm, respectively; the first rare earth additive and the second rare earth additive are the same rare earth additive or different rare earth additives.

7. The method for preparing the catalyst for the hydrogenation of carbon dioxide to methanol according to claim 4, wherein, The first precipitant and the second precipitant are selected from one or more combinations of NaOH, KOH, Na2CO3, NaHCO3, K2CO3, KHCO3, Na2C2O4, K2C2O4, RCOONa, RCOOK, (NH4)2CO3, and NH4HCO3, wherein R is an organic functional group; the first precipitant and the second precipitant are the same precipitant or different precipitants.

8. The method for preparing the catalyst for the hydrogenation of carbon dioxide to methanol according to claim 4, wherein, The concentration of the first salt solution is 0.05-2 mol / L, and the concentration of the first precipitant solution is 0.1-5 mol / L; And / or, the concentration of the second salt solution is 0.05-2 mol / L, and the concentration of the second precipitant solution is 0.1-5 mol / L.

9. The method for preparing the catalyst for the hydrogenation of carbon dioxide to methanol according to claim 4, wherein, In step 1, before the first precipitation reaction, the solvent is heated to 60-80℃ and stirred at 400-800 rpm / min for 0.5-3 hours. Then, the first salt solution and the first precipitant solution are added to the solvent in a co-current manner at a rate of 0.5-1.5 drops / second to carry out the first precipitation reaction, with the pH controlled at 7-9. After aging for 0.5-5 hours, the precipitate mother liquor is obtained.

10. The method for preparing the catalyst for the hydrogenation of carbon dioxide to methanol according to claim 4, wherein, In step 2, before the second precipitation reaction, the mother liquor of the precipitate is heated to 60-80℃ and stirred at a speed of 400-800 rpm / min. Then, the solution of the second salt and the solution of the second precipitant are added to the mother liquor of the precipitate in a co-current manner at a rate of 0.5-1.5 drops / second. After the second precipitation reaction, the pH is controlled to be 7-9, and the mixture is aged for 0.5-5 hours and calcined at 300-500℃ from room temperature for 3-6 hours to obtain the precursor of the catalyst. The precursor is then pressed into tablets and sieved to obtain the catalyst for the hydrogenation of carbon dioxide to methanol.

11. The application of a catalyst for the hydrogenation of carbon dioxide to methanol as described in any one of claims 1-3 in the synthesis of methanol by hydrogenation of carbon dioxide.

12. The application according to claim 11, wherein, Using a mixture of CO2 and H2 as the raw material, methanol is directly converted into methanol through a reduction and catalytic step under the catalytic action of the catalyst for the hydrogenation of carbon dioxide to methanol.

13. The application according to claim 12, wherein, The reaction conditions for the reduction step are as follows: reaction time of 4-24 h, reaction temperature of 200-300 °C, and H2 space velocity of 100-5000 mL / (h·g). cat ).

14. The application according to claim 12, wherein, The reaction conditions for the catalytic step are as follows: cooling to the reaction temperature under a protective atmosphere; the reaction temperature is 200-300℃; the reaction pressure is 0.01-10.0 MPa; the feed gas is a mixture of H2 and CO2 with a molar ratio of 0.5-8.0; and the feed gas space velocity is 5000-50000 mL / (h·g). cat ).

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