Catalyst for preparing methanol through CO2 hydrogenation as well as preparation method and application of catalyst

Abstract

The invention provides a catalyst for preparing methanol through CO2 hydrogenation as well as a preparation method and application of the catalyst. The catalyst provided by the invention has excellent low-temperature and low-pressure activity and high product selectivity when being applied to preparation of methanol through CO2 hydrogenation. The preparation method comprises the following steps: (1) adding a salt solution and a second alkali solution into a reaction device containing a first alkali solution in advance for co-precipitation, and aging after precipitation is finished; the adding of the salt solution comprises the steps of firstly adding a first salt solution for coprecipitation, then adding a second salt solution for coprecipitation, and then adding a third salt solution for coprecipitation; and (2) washing the solid obtained in the step (1), and then drying and roasting to obtain the catalyst, the catalyst is prepared from the following components in percentage by weight: 30 to 65 percent of CuO, 20 to 30 percent of ZnO, 0 to 20 percent of Al2O3 and 0 to 30 percent of Ga2O3, and the total amount of Al2O3 and Ga2O3 accounts for 8 to 40 percent of the total amount of the catalyst.

Description

Technical Field

[0001] The present invention relates to the technical field of hydrogenation of CO2 to methanol, further relates to the preparation technology of catalysts for hydrogenation of CO2 to methanol in a fixed-bed reactor, and specifically relates to a catalyst for hydrogenation of CO2 to methanol, its preparation method and application. Background Art

[0002] CN114029063B discloses a preparation method of a catalyst, which uses a metal copper mass fraction of 30 - 70%, metal zinc of 10 - 30%, a metal promoter mass fraction of 1 - 10%, and the rest is carbon material. The catalyst preparation process adopts co-precipitation, mainly introducing carbon material during the precipitation process, and introducing organic substances such as glucose, citric acid, tartaric acid, adipic acid, alanine, fructose, sucrose, etc. during the catalyst preparation. This catalyst preparation method is disadvantageous for bulk catalysts. To remove the complexing agent, a high calcination temperature is required, even as high as 550°C. At this temperature, CuO micro-nanoparticles are prone to aggregation, which is not conducive to the dispersion of active sites.

[0003] CN115254127B discloses a copper-based solid solution catalyst, its preparation method and application. The main catalyst is CuGaZrOx, using metal salts as precursors and ammonium carbonate as a precipitating agent. However, the single-pass conversion rate of CO2 of this catalyst under test conditions is 6 - 10%, and the methanol selectivity is about 22 - 25%. The overall methanol yield is relatively low.

[0004] CN104959143A discloses a catalyst for hydrogenation of CO2 to methanol in a slurry bed, its preparation method and application. The preparation method includes the following steps: (1) According to the weight ratio composition of the catalyst, prepare an aqueous copper salt solution A, a mixed solution B of zinc salt, aluminum salt, and transition metal salt, and a mixed precipitation solution C of sodium hydroxide and sodium carbonate; (2) First, perform co-precipitation on the mixed solution B and the mixed precipitation solution C. After the mixed solution B is completely precipitated, then perform co-precipitation on the aqueous copper salt solution A and the unreacted mixed precipitation solution C. After precipitation, age and wash to obtain a slurry; (3) According to the weight ratio composition of the catalyst, mix the slurry with the sol of the structural aid or the gas-phase structural aid to obtain a catalyst slurry, dry and calcine to obtain a catalyst for hydrogenation of CO2 to methanol in a slurry bed. This process introduces strong base sodium hydroxide into the precipitation system. After precipitation aging, it needs to be mixed with the sol of the structural aid and then dried and calcined to obtain a catalyst suitable for hydrogenation of CO2 to methanol in a slurry bed. The precipitation system of this scheme needs to introduce a strong base, which requires high corrosion resistance of the equipment, and the developed catalyst is a catalyst suitable for a slurry bed reactor. Summary of the Invention

[0005] The present invention provides a CO2 hydrogenation to methanol catalyst, its preparation method and application. The CO2 hydrogenation to methanol catalyst prepared by the preparation method of the present invention is particularly suitable for application in a fixed-bed reactor, and this catalyst has excellent low-temperature and low-pressure activities and high product selectivity in the application of CO2 hydrogenation to methanol.

[0006] To achieve its purpose, the present invention provides the following technical solutions:

[0007] The present invention provides a preparation method of a CO2 hydrogenation to methanol catalyst, comprising the following steps:

[0008] (1) Add a salt solution and a second alkali solution to a reaction device pre-filled with a first alkali solution for co-precipitation, and perform aging after the precipitation ends; the addition of the salt solution includes first adding a first salt solution for the co-precipitation, then adding a second salt solution for the co-precipitation, and then adding a third salt solution for the co-precipitation;

[0009] The first alkali solution is selected from an aqueous solution of carbonate and / or bicarbonate, and the second alkali solution is selected from an aqueous solution of carbonate and / or bicarbonate;

[0010] The first salt solution includes a soluble salt of zinc and also includes a soluble salt of aluminum or gallium; the second salt solution includes a soluble salt of aluminum or gallium; the third salt solution includes soluble salts of copper and zinc;

[0011] (2) Wash the solid obtained in step (1), and then obtain the catalyst through drying and calcination. Preferably, the drying temperature for the drying is 25 - 130 °C;

[0012] The catalyst includes 30 - 65 wt% of CuO, 20 - 30 wt% of ZnO, 0 - 20 wt% of Al2O3, and 0 - 30 wt% of Ga2O3, and the total amount of Al2O3 and Ga2O3 in the catalyst accounts for 8 - 40 wt%.

[0013] In some embodiments, the proportion of CuO in the catalyst is 30 wt%, 40 wt%, 50 wt%, 60 wt% or 65 wt%, etc. In some embodiments, the proportion of ZnO in the catalyst is 20 wt%, 24 wt%, 28 wt% or 30 wt%, etc. In some embodiments, the proportion of Al2O3 in the catalyst is 0 wt%, 5 wt%, 10 wt%, 15 wt% or 20 wt%, etc. In some embodiments, the proportion of Ga2O3 in the catalyst is 0 wt%, 10 wt%, 20 wt% or 30 wt%, etc. In some embodiments, the total amount of Al2O3 and Ga2O3 in the catalyst accounts for 8 wt%, 10 wt%, 20 wt%, 30 wt% or 40 wt%, etc.

[0014] The first alkali solution and the second alkali solution are the same or different.

[0015] In some preferred embodiments, one of the first alkali solution and the second alkali solution is an aqueous bicarbonate solution, and the other is an aqueous carbonate solution, or one or both of the first alkali solution and the second alkali solution are respectively aqueous solutions of a mixture of bicarbonate and carbonate. The inventors have found that in the precipitation reaction system, the combined use of aqueous bicarbonate and carbonate solutions is beneficial to further improving the catalytic activity of the obtained catalyst for the hydrogenation of CO2 to methanol and further increasing the methanol yield.

[0016] Preferably, the amount of the first alkali solution is 0.08 - 0.5 times, preferably 0.1 - 0.3 times, the volume of the second alkali solution;

[0017] Preferably, the total amount of the carbonate and the bicarbonate is 0.8 - 1.5 times, such as 0.8, 0.9, 1.0, 1.2 or 1.5 times, etc., preferably 0.9 - 1.2 times, the total molar amount of each soluble salt in the salt solution.

[0018] In the present invention, during the precipitation process, the precipitation reaction of the salt solution is carried out in a specific order. First, the soluble salts of zinc and aluminum or gallium and the second alkali solution are added to the system for coprecipitation. After the precipitation is complete, the soluble salts of aluminum or gallium and the second alkali solution are added to the system for coprecipitation. After the precipitation is complete, the soluble salts of copper and zinc and the second alkali solution are added to the system for coprecipitation; at the same time, no strong base is introduced during the precipitation process, and it is carried out under mild weak alkaline conditions. The inventors have found that the catalyst prepared by coprecipitation using the specific process of the present invention is particularly suitable for use as a catalyst for the hydrogenation of CO2 to methanol in a fixed bed reactor and has better catalytic activity and product selectivity.

[0019] In the preparation method of the present invention, during the coprecipitation process, the soluble zinc salt is fed in two parts, and is coprecipitated with the soluble salt of aluminum or gallium in the first precipitation step and with the soluble salt of copper in the third precipitation step, and the prepared catalyst has improved catalytic activity for the hydrogenation of CO2 to methanol; in some embodiments, in step (1), the mass of the soluble zinc salt used in the first salt solution is 11 - 30% of the total amount of the soluble zinc salt used in step (1), such as 11%, 15%, 19%, 25% or 30%, etc., preferably 19 - 30%. The stepwise feeding of the soluble zinc salt according to the preferred ratio is beneficial to further improving the performance of the obtained catalyst.

[0020] In some embodiments, it is preferred that the catalyst contains both Al2O3 and Ga2O3. In step (1), a soluble salt of aluminum is added to the first salt solution and a soluble salt of gallium is added to the second salt solution, or a soluble salt of gallium is added to the first salt solution and a soluble salt of aluminum is added to the second salt solution.

[0021] In some embodiments, the catalyst contains Al2O3 but does not contain Ga2O3. In step (1), the soluble salt of aluminum is added to the first salt solution and the second salt solution respectively; preferably, the amount of the soluble salt of aluminum in the first salt solution accounts for 40-50% of the total amount of the soluble salt of aluminum, such as 40%, 45% or 50%, etc.

[0022] In some embodiments, the catalyst contains Ga2O3 but does not contain Al2O3. In step (1), the soluble salt of gallium is added to the first salt solution and the second salt solution respectively; preferably, the amount of the soluble salt of gallium in the first salt solution accounts for 40-50% of the total amount of the soluble salt of gallium, such as 40%, 45% or 50%, etc.

[0023] In the present invention, the drying temperature in step (2) is controlled to be 25-130 °C, such as 25 °C, 40 °C, 60 °C, 90 °C, 110 °C or 130 °C, etc. The inventors have found that in the catalyst preparation system of the present invention, removing free water in a slow drying manner can significantly improve the catalyst performance compared to drying at a higher temperature. In a preferred embodiment, in step (2), the drying is a slow drying method such as forced air drying, natural air drying at room temperature, or natural air drying in an environment with sunlight as the heat source (such as natural air drying in a sunroom or greenhouse or similar environment) or floor heating drying, and the drying temperature is controlled to be 25-130 °C. The present invention preferably adopts the above drying method to ensure that free water is removed by slow drying, which can significantly improve the catalyst performance compared to drying methods such as spray drying.

[0024] In some embodiments, the carbonate is selected from one or more of sodium carbonate, potassium carbonate, and ammonium carbonate.

[0025] In some embodiments, the bicarbonate is selected from one or more of sodium bicarbonate, potassium bicarbonate, and ammonium bicarbonate.

[0026] In some embodiments, the soluble salt is a nitrate.

[0027] In some embodiments, the concentration in the first alkali solution is 0.005-0.05 mol / L, such as 0.005, 0.01, 0.03 or 0.05 mol / L, etc., and it is an aqueous solution, for example.

[0028] In some embodiments, the concentration of the second alkali solution is 0.4 - 2 mol / L, such as 0.4 mol / L, 0.8 mol / L, 1 mol / L, or 2 mol / L, etc., and for example, it is an aqueous solution.

[0029] In some embodiments, the concentration of the first salt solution is 0.4 - 2 mol / L, such as 0.4 mol / L, 0.8 mol / L, 1 mol / L, or 2 mol / L, etc., and for example, it is an aqueous solution.

[0030] In some embodiments, the concentration of the second salt solution is 0.1 - 2 mol / L, such as 0.1 mol / L, 0.2 mol / L, 0.4 mol / L, 1 mol / L, or 2 mol / L, etc., and for example, it is an aqueous solution.

[0031] In some embodiments, the concentration of the third salt solution is 0.4 - 2 mol / L, and for example, it is an aqueous solution.

[0032] In some embodiments, the catalyst may further optionally include other divalent metal oxides, and the metal element in the other divalent metal oxides is selected from one or more of the elements La, Ce, Zr, Ni, Mg, Pd, Pt, Ru, and Rh; preferably, the mass percentage of the other divalent metal oxides in the catalyst is 0 - 5%, preferably 0.05 - 5%. When the catalyst includes the other divalent metal oxides, preferably, in step (1), the corresponding soluble salts of the other divalent metal oxides are added to the first salt solution or the third salt solution; more preferably, when the metal element in the other divalent metal oxides is a noble metal element, the soluble salt of the noble metal element is added to the third salt solution. The corresponding soluble salts of the other divalent metal oxides are, for example, nitrates, chlorides, or acetates of the corresponding metal elements.

[0033] In a preferred embodiment, in step (1), when performing the coprecipitation, the temperature of the reaction system is controlled to be 60 - 80°C, such as 60°C, 65°C, 70°C, 75°C, or 80°C, etc., preferably 65 - 75°C, and the pH is controlled to be 6 - 9; the pH during the aging is 7 - 8, and the aging time is, for example, 1 - 24 h, such as 1, 2, 4, 8, 10, 12, 16, or 24 h, etc.

[0034] In some embodiments, in step (2), the calcination is carried out at a calcination temperature of 300 - 400 °C (such as 300 °C, 350 °C or 400 °C, etc.), and the calcination time is, for example, 3 - 8 h, such as 3, 5 or 8 h, etc. In some embodiments, after calcination, operations such as tabletting and screening are further included, for example, screening to a desired particle size, such as 20 - 40 mesh.

[0035] The present invention also provides a catalyst prepared by the preparation method described above. The catalyst comprises 30 - 65 wt% of CuO, 20 - 30 wt% of ZnO, 0 - 20 wt% of Al2O3, and 0 - 30 wt% of Ga2O3, and the total amount of Al2O3 and Ga2O3 accounts for 8 - 40 wt% in the catalyst.

[0036] The present invention also provides an application of the catalyst described above. The catalyst is used in the hydrogenation of CO2 to methanol. Preferably, the catalyst is used in the process of hydrogenating CO2 to methanol in a fixed - bed reactor. In the application, the catalyst can be mixed with an inert filler and then loaded into the fixed - bed reactor for use. The inert filler is, for example, silica that does not participate in the reaction and / or a metal block that can play a heat - dissipation role, etc. The particle size of the inert filler can be, for example, similar to that of the catalyst.

[0037] The technical solution provided by the present invention has the following beneficial effects:

[0038] The catalyst provided by the present invention is used for the application test of hydrogenating CO2 to methanol on a micro - reactor. At 3 MPa, 240 °C, and 3000 h -1 the single - pass conversion rate of CO2 reaches or approaches the chemical equilibrium under this condition, and the catalyst exhibits excellent low - temperature, low - pressure activity and high product selectivity. Detailed Embodiments

[0039] To facilitate the understanding of the present invention, the present invention will be further described below in conjunction with embodiments. It should be understood that the following embodiments are only for better understanding the present invention, and do not mean that the present invention is limited only to the following embodiments.

[0040] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the art to which the present invention belongs. The term "and / or" as used herein may include any and all combinations of one or more of the related listed items.

[0041] For those parts in the embodiments where specific experimental steps or conditions are not indicated, the operations or conditions of the corresponding conventional experimental steps in the technical field can be followed. For reagents or instruments not indicated by the manufacturer, they are all conventional products that can be obtained through commercial purchase.

[0042] Example 1

[0043] Dissolve 11 g of aluminum nitrate containing crystal water (Al(NO3)3·9H2O) and 5 g of zinc nitrate (Zn(NO3)2·6H2O) in deionized water to prepare a first salt solution of 40 mL.

[0044] Dissolve 2 g of gallium nitrate (Ga(NO3)3) in deionized water to prepare a second salt solution of 40 mL.

[0045] Dissolve 23 g of copper nitrate (Cu(NO3)2·6H2O) and 12 g of zinc nitrate (Zn(NO3)2·6H2O) in 120 mL of deionized water to prepare a third salt solution.

[0046] Dissolve 25 g of sodium carbonate in deionized water at 40 °C to prepare a 200 mL second alkali solution.

[0047] Under stirring, add the first salt solution and the second alkali solution into a 1 L reactor in a parallel flow manner (30 mL of 0.01 mol / L potassium bicarbonate aqueous solution (i.e., the first alkali solution) was added to the bottom of the reactor in advance) for precipitation reaction; after the precipitation of the first salt solution is complete, continue to add the second salt solution and the second alkali solution into the reactor in a parallel flow manner for precipitation reaction; after the precipitation of the second salt solution is complete, continue to add the third salt solution and the second alkali solution into the reactor in a parallel flow manner for precipitation reaction until the precipitation is complete. During the above precipitation reaction process, control the temperature of the precipitation reaction system to be 70 °C, the pH of the precipitation reaction system gradually decreases from 9 to 7, the precipitation rate (i.e., the feed rate of the feed liquid) is 5 mL / min, after the precipitation is completed, continue to age for 2 h under the same temperature and pH of 7, then filter to obtain a precipitate, wash the precipitate with deionized water until the conductivity of the last filtrate is less than 50 μS / cm.

[0048] Dry the washed precipitate in a blast drying oven at 120 °C until all free water is removed, then calcine at 320 °C for 5 h. The specific surface area of the obtained catalyst is 114 m 2 / g, then tablet and screen to 20 - 40 mesh, and then carry out the activity evaluation of the catalyst.

[0049] The composition of the obtained catalyst includes: CuO 50 wt%, ZnO 30 wt%, Al2O3 10 wt%, Ga2O3 10 wt%.

[0050] Example 2

[0051] Dissolve 11 g of aluminum nitrate containing crystal water (Al(NO3)3·9H2O) and 5 g of zinc nitrate (Zn(NO3)2·6H2O) in deionized water to prepare a first salt solution of 50 mL.

[0052] Dissolve 4 g of gallium nitrate (Ga(NO3)3) in deionized water to prepare a 50 mL second salt solution;

[0053] Dissolve 18 g of copper nitrate (Cu(NO3)2·6H2O) and 12 g of zinc nitrate (Zn(NO3)2·6H2O) in 100 mL of deionized water to prepare a third salt solution;

[0054] Dissolve 25 g of sodium carbonate in deionized water at 40 °C to prepare a 200 mL second alkali solution;

[0055] Under stirring, add the first salt solution and the second alkali solution in parallel into a 1 L reaction kettle (30 mL of 0.01 mol / L potassium bicarbonate aqueous solution (i.e., the first alkali solution) was previously added to the bottom of the kettle) for precipitation reaction; after the precipitation of the first salt solution is complete, continue to add the second salt solution and the second alkali solution in parallel into the reaction kettle for precipitation reaction; after the precipitation of the second salt solution is complete, continue to add the third salt solution and the second alkali solution in parallel into the reaction kettle for precipitation reaction until the precipitation is complete. During the above precipitation reaction process, control the temperature of the precipitation reaction system to be 70 °C, the pH of the precipitation reaction system gradually decreases from 9 to 7, the precipitation rate is 5 mL / min, and after the precipitation is completed, continue to age for 2 h under the same temperature and pH of 7, then filter to obtain a precipitate, and wash the precipitate with deionized water until the conductivity of the last filtrate is less than 50 μS / cm.

[0056] Dry the washed precipitate in a forced-air drying oven at 120 °C until all free water is removed, then calcine at 320 °C for 5 h. The specific surface area of the obtained catalyst is 137 m 2 / g, then tablet and screen to 20 - 40 mesh, and then conduct the activity evaluation of the catalyst.

[0057] The composition of the obtained catalyst includes: 40 wt% CuO, 30 wt% ZnO, 10 wt% Al2O3, 20 wt% Ga2O3.

[0058] Example 3

[0059] Dissolve 11 g of aluminum nitrate containing crystal water (Al(NO3)3·9H2O) and 5 g of zinc nitrate (Zn(NO3)2·6H2O) in deionized water to prepare a 50 mL first salt solution;

[0060] Dissolve 6 g of gallium nitrate (Ga(NO3)3) in deionized water to prepare a 50 mL second salt solution;

[0061] Dissolve 14 g of copper nitrate (Cu(NO3)2·6H2O) and 12 g of zinc nitrate (Zn(NO3)2·6H2O) in 100 mL of deionized water to prepare a third salt solution;

[0062] Dissolve 22 g of sodium carbonate in deionized water at 40 °C to prepare 200 mL of a second alkali solution;

[0063] While stirring, add the first salt solution and the second alkali solution in a parallel flow into a 1 L reactor (50 mL of 0.01 mol / L potassium bicarbonate aqueous solution (i.e., the first alkali solution) was previously added to the bottom of the reactor) for precipitation reaction; after the precipitation of the first salt solution is complete, continue to add the second salt solution and the second alkali solution in a parallel flow into the reactor for precipitation reaction; after the precipitation of the second salt solution is complete, continue to add the third salt solution and the second alkali solution in a parallel flow into the reactor for precipitation reaction until the precipitation is complete. During the above precipitation reaction process, control the temperature of the precipitation reaction system to 70 °C, the pH of the precipitation reaction system gradually decreases from 9 to 7, the precipitation rate is 5 mL / min, and after the precipitation is completed, continue to age for 2 h under the same temperature and pH of 7, then filter to obtain a precipitate, and wash the precipitate with deionized water until the conductivity of the last filtrate is less than 50 μS / cm.

[0064] Dry the washed precipitate in a blast drying oven at 120 °C until all free water is removed, and then calcine at 320 °C for 5 h. The specific surface area of the obtained catalyst is 136 m 2 / g, then tablet and screen to 20 - 40 mesh, and then conduct the activity evaluation of the catalyst.

[0065] The composition of the obtained catalyst includes: 30 wt% CuO, 30 wt% ZnO, 10 wt% Al2O3, 30 wt% Ga2O3.

[0066] Example 4

[0067] Dissolve 11 g of aluminum nitrate containing crystal water (Al(NO3)3·9H2O) and 5 g of zinc nitrate (Zn(NO3)2·6H2O) in deionized water to prepare 50 mL of a first salt solution;

[0068] Dissolve 4 g of gallium nitrate (Ga(NO3)3) in deionized water to prepare 50 mL of a second salt solution;

[0069] Dissolve 18 g of copper nitrate (Cu(NO3)2·6H2O) and 12 g of zinc nitrate (Zn(NO3)2·6H2O) in 100 mL of deionized water to prepare a third salt solution;

[0070] Dissolve 24 g of sodium carbonate in deionized water at 40 °C to prepare 200 mL of a second alkali solution;

[0071] With stirring, the first brine solution and the second alkali solution were added in parallel into a 1L reaction kettle (50 mL of 0.01 mol / L potassium bicarbonate aqueous solution (i.e., the first alkali solution) was previously added to the bottom of the kettle) for precipitation reaction; after the precipitation of the first salt solution was complete, the second salt solution and the second alkali solution were continuously added in parallel into the reaction kettle for precipitation reaction; after the precipitation of the second salt solution was complete, the third salt solution and the second alkali solution were continuously added in parallel into the reaction kettle for precipitation reaction until the precipitation was complete. During the above precipitation reaction process, the temperature of the precipitation reaction system was controlled at 70 °C, the pH of the precipitation reaction system gradually decreased from 9 to 7, the precipitation rate was 5 mL / min, and after precipitation, it was aged for 2 h under the same temperature and pH of 7, and then the precipitate was obtained by filtration. The precipitate was washed with deionized water until the conductivity of the final filtrate was less than 50 μS / cm.

[0072] The washed precipitate was dried in a forced-air drying oven at 120 °C until all free water was removed, and then calcined at 320 °C for 5 h. The specific surface area of the obtained catalyst was 135 m 2 / g. It was then tableted and sieved to 20 - 40 mesh, and then the activity evaluation of the catalyst was carried out.

[0073] The composition of the obtained catalyst included: 40 wt% CuO, 30 wt% ZnO, 10 wt% Al2O3, and 20 wt% Ga2O3.

[0074] Example 5 (compared with Example 1, sodium carbonate aqueous solution was not used)

[0075] 11 g of aluminum nitrate containing crystal water (Al(NO3)3·9H2O) and 5 g of zinc nitrate (Zn(NO3)2·6H2O) were dissolved in deionized water to prepare a 40 mL first salt solution;

[0076] 2 g of gallium nitrate (Ga(NO3)3) was dissolved in deionized water to prepare a 40 mL second salt solution;

[0077] 23 g of copper nitrate (Cu(NO3)2·6H2O) and 12 g of zinc nitrate (Zn(NO3)2·6H2O) were dissolved in 120 mL of deionized water to prepare a third salt solution;

[0078] 25 g of potassium bicarbonate was dissolved in deionized water at 40 °C to prepare 200 mL of a second alkali solution;

[0079] While stirring, the first salt solution and the second alkali solution were added into a 1 L reaction kettle in a concurrent flow manner (30 mL of 0.01 mol / L potassium bicarbonate aqueous solution (i.e., the first alkali solution) was previously added to the bottom of the kettle) for precipitation reaction; after the precipitation of the first salt solution was complete, the second salt solution and the second alkali solution were continuously added into the reaction kettle in a concurrent flow manner for precipitation reaction; after the precipitation of the second salt solution was complete, the third salt solution and the second alkali solution were continuously added into the reaction kettle in a concurrent flow manner for precipitation reaction until the precipitation was complete. During the above precipitation reaction process, the temperature of the precipitation reaction system was controlled at 70 °C, the pH of the precipitation reaction system gradually decreased from 9 to 7, the precipitation rate was 5 mL / min, and after the precipitation was completed, it was aged for another 2 h under the same temperature and pH of 7, and then the precipitate was filtered out, and the precipitate was washed with deionized water until the conductivity of the last filtrate was less than 50 μS / cm.

[0080] The washed precipitate was dried in a forced-air drying oven at 120 °C until all the free water was removed, and then calcined at 320 °C for 5 h. The specific surface area of the obtained catalyst was 95 m 2 / g. It was then tableted and sieved to 20 - 40 mesh, and then the activity evaluation of the catalyst was carried out.

[0081] The composition of the obtained catalyst included: 50 wt% CuO, 30 wt% ZnO, 10 wt% Al2O3, and 10 wt% Ga2O3.

[0082] Example 6 (compared with Example 1, potassium bicarbonate aqueous solution was not used)

[0083] 11 g of aluminum nitrate containing crystal water (Al(NO3)3·9H2O) and 5 g of zinc nitrate (Zn(NO3)2·6H2O) were made into a 40 mL first salt solution with deionized water;

[0084] 2 g of gallium nitrate (Ga(NO3)3) was made into a 40 mL second salt solution with deionized water;

[0085] 23 g of copper nitrate (Cu(NO3)2·6H2O) and 12 g of zinc nitrate (Zn(NO3)2·6H2O) were dissolved in 120 mL of deionized water to make a third salt solution;

[0086] 25 g of sodium carbonate was dissolved in deionized water at 40 °C to make 200 mL of the second alkali solution;

[0087] With stirring, the first salt solution and the second alkali solution were added into a 1 L reaction kettle in a parallel flow manner (30 mL of 0.01 mol / L sodium carbonate aqueous solution (i.e., the first alkali solution) was previously added to the bottom of the kettle) for precipitation reaction; after the precipitation of the first salt solution was complete, the second salt solution was continuously added to the reaction kettle in a parallel flow manner with the second alkali solution for precipitation reaction; after the precipitation of the second salt solution was complete, the third salt solution was continuously added to the reaction kettle in a parallel flow manner with the second alkali solution for precipitation reaction until the precipitation was complete. During the above precipitation reaction process, the temperature of the precipitation reaction system was controlled at 70 °C, the pH of the precipitation reaction system gradually decreased from 9 to 7, the precipitation rate was 5 mL / min, and after precipitation, it was aged for another 2 h under the same temperature and pH of 7, and then the precipitate was filtered, and the precipitate was washed with deionized water until the conductivity of the final filtrate was less than 50 μS / cm.

[0088] The washed precipitate was dried in a forced-air drying oven at 120 °C until all the free water was removed, and then calcined at 320 °C for 5 h. The specific surface area of the obtained catalyst was 90 m 2 / g. It was then tableted and sieved to 20 - 40 mesh, and then the activity evaluation of the catalyst was carried out.

[0089] The composition of the obtained catalyst included: 50 wt% CuO, 30 wt% ZnO, 10 wt% Al2O3, and 10 wt% Ga2O3.

[0090] Example 7 (compared with Example 1, without Ga2O3)

[0091] 11 g of aluminum nitrate containing crystal water (Al(NO3)3·9H2O) and 5 g of zinc nitrate (Zn(NO3)2·6H2O) were dissolved in deionized water to prepare a 40 mL first salt solution;

[0092] 11 g of aluminum nitrate (Al(NO3)3·9H2O) was dissolved in deionized water to prepare a 40 mL second salt solution;

[0093] 23 g of copper nitrate (Cu(NO3)2·6H2O) and 12 g of zinc nitrate (Zn(NO3)2·6H2O) were dissolved in 120 mL of deionized water to prepare a third salt solution;

[0094] 25 g of sodium carbonate was dissolved in deionized water at 40 °C to prepare a 200 mL second alkali solution;

[0095] With stirring, the first salt solution and the second alkali solution were added into a 1 L reaction kettle in a parallel flow manner (30 mL of 0.01 mol / L potassium bicarbonate aqueous solution (i.e., the first alkali solution) was previously added to the bottom of the kettle) for precipitation reaction; after the precipitation of the first salt aqueous solution was complete, the second salt aqueous solution was continuously added into the reaction kettle in a parallel flow manner with the second alkali solution for precipitation reaction; after the precipitation of the second salt aqueous solution was complete, the third salt aqueous solution was continuously added into the reaction kettle in a parallel flow manner with the second alkali solution for precipitation reaction until the precipitation was complete. During the above precipitation reaction process, the temperature of the precipitation reaction system was controlled at 70 °C, the pH of the precipitation reaction system gradually decreased from 9 to 7, the precipitation rate was 5 mL / min, and after precipitation, it was aged for another 2 h under the same temperature and pH of 7, and then the precipitate was filtered out, and the precipitate was washed with deionized water until the conductivity of the last filtrate was less than 50 μS / cm.

[0096] The washed precipitate was dried in a forced-air drying oven at 120 °C until all the free water was removed, and then calcined at 320 °C for 5 h. The specific surface area of the obtained catalyst was 104 m 2 / g, then tableted and sieved to 20 - 40 mesh, and then the activity evaluation of the catalyst was carried out.

[0097] The composition of the obtained catalyst included: 50 wt% CuO, 30 wt% ZnO, and 20 wt% Al2O3.

[0098] Example 8 (compared with Example 1, without Al2O3)

[0099] 2 g of gallium nitrate (Ga(NO3)3) containing crystal water and 5 g of zinc nitrate (Zn(NO3)2·6H2O) were made into a 40 mL first salt solution with deionized water;

[0100] 2 g of gallium nitrate (Ga(NO3)3) was made into a 40 mL second salt solution with deionized water;

[0101] 23 g of copper nitrate (Cu(NO3)2·6H2O) and 12 g of zinc nitrate (Zn(NO3)2·6H2O) were dissolved in 120 mL of deionized water to make a third salt solution;

[0102] 25 g of sodium carbonate was dissolved in deionized water at 40 °C to make a 200 mL second alkali solution;

[0103] Under stirring, the first salt solution and the second alkali solution were added into a 1L reaction kettle in a concurrent flow manner (30 mL of 0.01 mol / L potassium bicarbonate aqueous solution (i.e., the first alkali solution) was previously added to the bottom of the kettle) for precipitation reaction; after the precipitation of the first salt solution was complete, the second salt solution and the second alkali solution were continuously added into the reaction kettle in a concurrent flow manner for precipitation reaction; after the precipitation of the second salt solution was complete, the third salt solution and the second alkali solution were continuously added into the reaction kettle in a concurrent flow manner for precipitation reaction until the precipitation was complete. During the above precipitation reaction process, the temperature of the precipitation reaction system was controlled at 70 °C, the pH of the precipitation reaction system gradually decreased from 9 to 7, the precipitation rate was 5 mL / min, and after the precipitation was over, it was aged for 2 h under the same temperature and pH of 7, and then the precipitate was filtered out, and the precipitate was washed with deionized water until the conductivity of the final filtrate was less than 50 μS / cm.

[0104] The washed precipitate was dried in a forced-air drying oven at 120 °C until all free water was removed, and then calcined at 320 °C for 5 h. The specific surface area of the obtained catalyst was 95 m 2 / g. It was then tableted and sieved to 20 - 40 mesh, and then the activity evaluation of the catalyst was carried out.

[0105] The composition of the obtained catalyst included: 50 wt% CuO, 30 wt% ZnO, and 20 wt% Ga2O3.

[0106] Comparative Example 1: (One-step precipitation and without gallium nitrate)

[0107] 22 g of aluminum nitrate containing crystal water (Al(NO3)3·9H2O), 23 g of copper nitrate (Cu(NO3)2·6H2O), and 17 g of zinc nitrate (Zn(NO3)2·6H2O) were dissolved in 200 mL of deionized water to obtain a salt solution;

[0108] 24 g of sodium carbonate was dissolved in deionized water at 40 °C to obtain 200 mL of an alkali solution;

[0109] Under stirring, the salt solution and the alkali solution were added into a 1L reaction kettle in a concurrent flow manner (30 mL of 0.01 mol / L potassium bicarbonate aqueous solution was previously added to the bottom of the kettle). The temperature of the precipitation reaction system was controlled at 70 °C, the pH of the precipitation reaction system gradually decreased from 9 to 7, the precipitation rate was 5 mL / min, and after the precipitation was over, it was aged for 2 h under the same temperature and pH of 7, and then the precipitate was filtered out, and the precipitate was washed with deionized water until the conductivity was less than 50 μS / cm.

[0110] The washed precipitate was dried in a forced-air drying oven at 120 °C until all free water was removed, and then calcined at 320 °C for 5 h. The specific surface area of the obtained catalyst was 96 m 2per g, then tableted and sieved to 20 - 40 mesh, and then the activity evaluation of the catalyst was carried out.

[0111] The composition of the obtained catalyst includes: 50 wt% CuO, 30 wt% ZnO, and 20 wt% Al2O3.

[0112] Comparative Example 2 (compared with Example 1, zinc nitrate was not added step by step)

[0113] 11 g of aluminum nitrate containing crystal water (Al(NO3)3·9H2O) and 17 g of zinc nitrate (Zn(NO3)2·6H2O) were made into a 40 mL first salt solution with deionized water;

[0114] 2 g of gallium nitrate (Ga(NO3)3) was made into a 40 mL second salt solution with deionized water;

[0115] 23 g of copper nitrate (Cu(NO3)2·6H2O) was dissolved in 120 mL of deionized water to make a third salt solution;

[0116] 25 g of sodium carbonate was dissolved in deionized water at 40 °C to make a 200 mL second alkali solution;

[0117] Under stirring, the first salt solution and the second alkali solution were added into a 1 L reaction kettle in a parallel flow manner (30 mL of 0.01 mol / L potassium bicarbonate aqueous solution (i.e., the first alkali solution) was added to the bottom of the kettle in advance) for precipitation reaction; after the precipitation of the first salt solution was complete, the second salt solution was continuously added into the reaction kettle in a parallel flow manner with the second alkali solution for precipitation reaction; after the precipitation of the second salt solution was complete, the third salt solution was continuously added into the reaction kettle in a parallel flow manner with the second alkali solution for precipitation reaction until the precipitation was complete. During the above precipitation reaction process, the temperature of the precipitation reaction system was controlled at 70 °C, the pH of the precipitation reaction system gradually decreased from 9 to 7, the precipitation rate was 5 mL / min, and after precipitation, it was aged for 2 h at the same temperature and pH of 7, and then the precipitate was filtered, and the precipitate was washed with deionized water until the conductivity of the last filtrate was less than 50 μS / cm.

[0118] The washed precipitate was dried in a forced-air drying oven at 120 °C until all free water was removed, and then calcined at 320 °C for 5 h. The specific surface area of the obtained catalyst was 97 m 2 per g, then tableted and sieved to 20 - 40 mesh, and then the activity evaluation of the catalyst was carried out.

[0119] The composition of the obtained catalyst includes: 50 wt% CuO, 30 wt% ZnO, 10 wt% Al2O3, and 10 wt% Ga2O3.

[0120] Comparative Example 3 (compared with Example 1, the proportion of stepwise addition of zinc nitrate is different)

[0121] Dissolve 11 g of aluminum nitrate containing crystal water (Al(NO3)3·9H2O) and 2 g of zinc nitrate (Zn(NO3)2·6H2O) in deionized water to prepare a first salt solution of 40 mL;

[0122] Dissolve 2 g of gallium nitrate (Ga(NO3)3) in deionized water to prepare a second salt solution of 40 mL;

[0123] Dissolve 23 g of copper nitrate (Cu(NO3)2·6H2O) and 15 g of zinc nitrate (Zn(NO3)2·6H2O) in 120 mL of deionized water to prepare a third salt solution;

[0124] Dissolve 25 g of sodium carbonate in deionized water at 40 °C to prepare a 200 mL second alkali solution;

[0125] Under stirring, add the first salt solution and the second alkali solution into a 1 L reactor in a co-current manner (30 mL of 0.01 mol / L potassium bicarbonate aqueous solution (i.e., the first alkali solution) is added to the bottom of the reactor in advance) for precipitation reaction; after the precipitation of the first salt solution is complete, continue to add the second salt solution and the second alkali solution into the reactor in a co-current manner for precipitation reaction; after the precipitation of the second salt solution is complete, continue to add the third salt solution and the second alkali solution into the reactor in a co-current manner for precipitation reaction until the precipitation is complete. During the above precipitation reaction process, control the temperature of the precipitation reaction system to be 70 °C, the pH of the precipitation reaction system gradually decreases from 9 to 7, the precipitation rate is 5 mL / min, and after the precipitation is completed, continue to age for 2 h under the same temperature and pH of 7, then filter to obtain a precipitate, wash the precipitate with deionized water until the conductivity of the last filtrate is less than 50 μS / cm.

[0126] Dry the washed precipitate in a forced-air drying oven at 120 °C until all free water is removed, and then calcine it at 320 °C for 5 h. The specific surface area of the obtained catalyst is 106 m 2 / g, then tablet it and screen it to 20 - 40 mesh, and then conduct the activity evaluation of the catalyst.

[0127] The composition of the obtained catalyst includes: CuO 50 wt%, ZnO 30 wt%, Al2O3 10 wt%, Ga2O3 10 wt%.

[0128] Comparative Example 4 (compared with Example 1, the drying conditions are different)

[0129] Dissolve 11 g of aluminum nitrate containing crystal water (Al(NO3)3·9H2O) and 5 g of zinc nitrate (Zn(NO3)2·6H2O) in deionized water to prepare a first salt solution of 40 mL;

[0130] Dissolve 2 g of gallium nitrate (Ga(NO3)3) in deionized water to prepare a 40 mL second salt solution;

[0131] Dissolve 23 g of copper nitrate (Cu(NO3)2·6H2O) and 12 g of zinc nitrate (Zn(NO3)2·6H2O) in 120 mL of deionized water to prepare a third salt solution;

[0132] Dissolve 25 g of sodium carbonate in deionized water at 40 °C to prepare a 200 mL second alkali solution;

[0133] Under stirring, add the first salt solution and the second alkali solution into a 1 L reactor in a co-current manner (30 mL of 0.01 mol / L potassium bicarbonate aqueous solution (i.e., the first alkali solution) was added to the bottom of the reactor in advance) for precipitation reaction; after the precipitation of the first salt solution is complete, continue to add the second salt solution and the second alkali solution into the reactor in a co-current manner for precipitation reaction; after the precipitation of the second salt solution is complete, continue to add the third salt solution and the second alkali solution into the reactor in a co-current manner for precipitation reaction until the precipitation is complete. During the above precipitation reaction process, control the temperature of the precipitation reaction system to be 70 °C, the pH of the precipitation reaction system gradually decreases from 9 to 7, the precipitation rate is 5 mL / min, and after the precipitation is completed, continue to age for 2 h under the same temperature and pH of 7, then filter to obtain the precipitate, and wash the precipitate with deionized water until the conductivity is less than 50 μS / cm.

[0134] Spray-dry the washed precipitate at 150 °C until all free water is removed, and then calcine it at 320 °C for 5 h. The specific surface area of the obtained catalyst is 85 m 2 / g, then tablet it and screen it to 20 - 40 mesh, and then conduct the activity evaluation of the catalyst.

[0135] The composition of the obtained catalyst includes: CuO 50 wt%, ZnO 30 wt%, Al2O3 10 wt%, Ga2O3 10 wt%.

[0136] The catalyst activity evaluation method for each example and comparative example: Use a fixed-bed micro-reactor to evaluate the catalyst performance. The catalyst loading is 1 g (20 - 40 mesh), and the raw material gas composition (volume percentage): H2 71%, CO2 23%, N2 6%. The test conditions are: reaction temperature 240 - 260 °C, reaction pressure 3 Mpa, volume space velocity 3000 - 10000 h -1 .

[0137] The catalyst activity evaluation results of each example and comparative example are shown in Table 1.

[0138] Table 1

[0139]

[0140]

[0141] Note: The equilibrium conversion rate of CO2 at 240°C and 3 MPa is approximately 21 ± 0.5%.

[0142] It is easy to understand that the above embodiments are merely examples for clear illustration and do not mean that the present invention is limited thereto. For those of ordinary skill in the art, other different forms of changes or variations can be made based on the above description. It is not necessary and impossible to enumerate all the implementation manners here. And the obvious changes or variations derived therefrom are still within the protection scope of the present invention.

Claims

1. A preparation method of a CO2 hydrogenation to methanol catalyst, characterized in that, It includes the following steps: (1) Add a salt solution and a second alkali solution to a reaction device pre-filled with a first alkali solution for co-precipitation, and perform aging after the precipitation ends; the feeding of the salt solution includes first adding a first salt solution for the co-precipitation, then adding a second salt solution for the co-precipitation, and then adding a third salt solution for the co-precipitation; The first alkali solution is selected from aqueous solutions of carbonates and / or bicarbonates, and the second alkali solution is selected from aqueous solutions of carbonates and / or bicarbonates; The first salt solution includes a soluble salt of zinc and also includes a soluble salt of aluminum or gallium; the second salt solution includes a soluble salt of aluminum or gallium; the third salt solution includes soluble salts of copper and zinc; (2) Wash the solid obtained in step (1), and then obtain the catalyst through drying and calcination. Preferably, the drying temperature for the drying is 25 - 130 °C; The catalyst includes 30 - 65 wt% of CuO, 20 - 30 wt% of ZnO, 0 - 20 wt% of Al2O3, and 0 - 30 wt% of Ga2O3, and the total amount of Al2O3 and Ga2O3 accounts for 8 - 40 wt% in the catalyst.

2. The preparation method according to claim 1, characterized in that, The first alkali solution and the second alkali solution are the same or different; Preferably, one of the first alkali solution and the second alkaline solution is an aqueous solution of bicarbonate, and the other is an aqueous solution of carbonate, or one or both of the first alkali solution and the second alkaline solution are aqueous solutions of a mixture of bicarbonate and carbonate; Preferably, the dosage of the first alkali solution is 0.08 - 0.5 times, preferably 0.1 - 0.3 times, the volume of the second alkali solution; Preferably, the total dosage of the carbonate and the bicarbonate is 0.8 - 1.5 times, preferably 0.9 - 1.2 times, the total molar amount of each soluble salt in the salt solution.

3. The preparation method according to any one of claims 1-2, characterized in that, In step (1), the mass of the soluble salt of zinc used in the first salt solution is 11 - 30%, preferably 19 - 30%, of the total amount of the soluble salt of zinc used in step (1).

4. The preparation method according to any one of claims 1-3, characterized in that, Both Al2O3 and Ga2O3 are contained in the catalyst. In step (1), the soluble salt of aluminum is added to the first salt solution and the soluble salt of gallium is added to the second salt solution, or the soluble salt of gallium is added to the first salt solution and the soluble salt of aluminum is added to the second salt solution; Or, Al2O3 is contained in the catalyst but Ga2O3 is not. In step (1), the soluble salt of aluminum is added to the first salt solution and the second salt solution respectively. Preferably, the dosage of the soluble salt of aluminum in the first salt solution accounts for 40 - 50% of the total dosage of the soluble salt of aluminum; Or, Ga2O3 is contained in the catalyst but Al2O3 is not. In step (1), the soluble salt of gallium is added to the first salt solution and the second salt solution respectively. Preferably, the dosage of the soluble salt of gallium in the first salt solution accounts for 40 - 50% of the total dosage of the soluble salt of gallium.

5. The preparation method according to any one of claims 1-4, characterized in that, In step (2), the drying is carried out by blowing air drying, natural air drying at room temperature, natural air drying in an environment with sunlight as the heat source, or floor heating drying.

6. The preparation method according to any one of claims 1-5, characterized in that, The carbonate is selected from one or more of sodium carbonate, potassium carbonate, and ammonium carbonate; and / or, the bicarbonate is selected from one or more of sodium bicarbonate, potassium bicarbonate, and ammonium bicarbonate; and / or, the soluble salt is a nitrate; and / or, the concentration of the first alkali solution is 0.005 - 0.05 mol / L; and / or, the concentration of the second alkali solution is 0.4 - 2 mol / L; and / or, the concentration of the first salt solution is 0.4 - 2 mol / L; and / or, the concentration of the second salt solution is 0.1 - 2 mol / L; and / or, the concentration of the third salt solution is 0.4 - 2 mol / L.

7. The preparation method according to any one of claims 1-6, characterized in that, The catalyst may further optionally include other divalent metal oxides, and the metal element in the other divalent metal oxides is selected from one or more of La, Ce, Zr, Ni, Mg, Pd, Pt, Ru, and Rh elements; Preferably, in step (1), the corresponding soluble salt of the other divalent metal oxide is added to the first salt solution or the third salt solution; further preferably, when the metal element in the other divalent metal oxide is a noble metal element, the soluble salt of the noble metal element is added to the third salt solution; Preferably, the mass percentage of the other divalent metal oxide in the catalyst is 0 - 5%, preferably 0.05 - 5%.

8. The preparation method according to any one of claims 1 to 7, characterized in that, In step (1), when carrying out the coprecipitation, the temperature of the reaction system is controlled to be 60 - 80 °C, preferably 65 - 75 °C, and the pH is controlled to be 6 - 9; when carrying out the aging, the pH is 7 - 8, and the aging time is, for example, 1 - 24 h; and / or, in step (2), the calcination is carried out at a calcination temperature of 300 - 400 °C, and the calcination time is, for example, 3 - 8 h.

9. A catalyst prepared by the preparation method according to any one of claims 1-8, characterized in that, The catalyst comprises 30 - 65 wt% of CuO, 20 - 30 wt% of ZnO, 0 - 20 wt% of Al2O3, and 0 - 30 wt% of Ga2O3, and the total amount of Al2O3 and Ga2O3 accounts for 8 - 40 wt% in the catalyst.

10. Use of the catalyst according to claim 9, characterized in that, The catalyst is applied in the hydrogenation of CO2 to methanol. Preferably, the catalyst is applied in the process of hydrogenation of CO2 to methanol in a fixed bed reactor.

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