Preparation method and application of aluminum-copper-based ternary catalyst for carbon dioxide hydrogenation to methanol

Abstract

The application discloses a preparation method and application of an aluminum-copper-based ternary catalyst for carbon dioxide hydrogenation to methanol, and the method is as follows: pseudo-boehmite is dispersed in a solvent, hydrochloric acid is added, copper nitrate and an auxiliary metal precursor are added into the mixture, and then the aluminum-copper-based ternary catalyst is obtained after stirring, aging, drying and calcination. The aluminum-copper-based ternary catalyst preparation method is simple, the carbon dioxide conversion rate is close to the equilibrium conversion rate under high space velocity, the selectivity of methanol is close to 100%, and the catalyst has an industrial application prospect.

Description

Technical Field

[0001] This invention relates to a method for preparing and applying an aluminum-copper based ternary catalyst for the hydrogenation of carbon dioxide to methanol, belonging to the field of carbon dioxide resource conversion technology. Background Technology

[0002] Methanol is an important basic chemical raw material. It can be used to produce bulk chemicals such as olefins and aromatics, as well as gasoline and diesel. It can also be used directly as a fuel or fuel additive.

[0003] In the research of CO2 catalytic hydrogenation to methanol synthesis, CuZnAl has been regarded as a widely used commercial catalyst, which can be used to catalyze the production of methanol from a mixture of CO2, CO2, and H2 under reaction conditions of 5-10 MPa and 200-350℃. However, this catalyst has insufficient activity for the hydrolysis of pure CO2. Noble metal catalysts have the advantages of high activity and good stability, but the catalyst cost is high. Composite oxide catalysts have been developed in recent years, and the reaction temperature only needs to be around 300℃. Among them, Chinese patent application number 202110417516.6 discloses a solid solution Zn-CdZrOx catalyst for the hydrogenation of carbon dioxide to methanol, but Cd metal has high toxicity, which does not conform to the concept of green environmental protection.

[0004] Chinese patent application CN202010258502.X discloses a graphitic carbon nitride-supported CuZnAl catalyst for the hydrogenation of carbon dioxide to methanol. This catalyst uses graphitic carbon nitride as a support, effectively increasing the specific surface area of ​​the catalyst and making it easier for the reactant gas to be adsorbed onto the catalyst surface. This CuZnAl solid solution catalyst, under conditions of 3 MPa, 200 °C, and a contact time W / F (contact time between catalyst and feed gas or gas flow rate of feed gas entering the reaction tube) = 10 g·h / mol, can achieve a methanol selectivity exceeding 88%, but the single-pass conversion rate of carbon dioxide is less than 10%. Therefore, developing a carbon dioxide hydrogenation catalyst with mild reaction conditions, low cost, green and non-toxic properties, and high catalytic activity is an urgent problem to be solved for this process route. Summary of the Invention

[0005] To address the shortcomings of existing technologies, this invention provides a highly active aluminum-copper based ternary catalyst. This catalyst exhibits high catalytic activity, high methanol selectivity, simple preparation method, and low cost, and has promising prospects for industrial application.

[0006] Therefore, the first technical solution provided by this invention is as follows:

[0007] A method for preparing an aluminum-copper-based ternary catalyst for the hydrogenation of carbon dioxide to methanol involves dispersing boehmite in a solvent, then adding hydrochloric acid, and then adding copper nitrate and an auxiliary metal precursor. After stirring, aging, drying, calcining, and reduction, the aluminum-copper-based ternary catalyst is obtained.

[0008] Furthermore, the solvent of the present invention is water, ethylene glycol, or a mixture of both.

[0009] Furthermore, the present invention limits the solvent to a mixture of water and ethylene glycol, wherein the mass ratio of water to ethylene glycol is 0.5:1 to 2:1, preferably 1:1.

[0010] Furthermore, the present invention limits the mass ratio of the pseudoboehmite to the mixed solvent to 1:30 to 1:10, preferably 1:25 to 1:15.

[0011] Furthermore, the present invention limits the auxiliary metal precursor to one of zinc nitrate, cerium nitrate, or zirconium nitrate;

[0012] Furthermore, the present invention limits the mass ratio of the pseudoboehmite to copper nitrate to 8:1 to 1:1, with a preferred ratio of 5:1 to 2:1.

[0013] Furthermore, the present invention limits the mass ratio of the pseudoboehmite to the auxiliary metal precursor to 20:1 to 5:1, with a preferred ratio of 15:1 to 10:1.

[0014] Furthermore, the present invention limits the hydrochloric acid to a concentrated hydrochloric acid with a mass fraction of 37%; the mass ratio of the concentrated hydrochloric acid to the mixed solvent is 1:100.

[0015] Furthermore, the present invention also limits the stirring aging conditions to a 60°C water bath, a stirring speed of 300 r / min, and a stirring time of 6 h; the drying conditions are drying at 130°C for 48 h.

[0016] Furthermore, the present invention limits the calcination conditions to calcination in a muffle furnace, calcination time of 4 hours, and calcination temperature of 300–650°C, preferably 400–550°C.

[0017] Furthermore, the present invention also limits the reduction conditions to a 20% H2 / N2 mixture, a gas flow rate of 50 mL / min, a reduction temperature of 400 °C, and a reduction time of 4 h.

[0018] This invention also provides the application of the above-mentioned aluminum-copper based ternary catalyst in the catalytic hydrogenation of carbon dioxide to methanol.

[0019] Preferably, the aluminum-copper based ternary catalyst is used in the following reaction conditions for the hydrogenation of carbon dioxide to methanol: reaction pressure of 2-5 MPa, reaction temperature of 180-340℃, and reaction space velocity of 6000-24000 mL / (g) cat The volume ratio of raw gas (H2) to CO2 is 3:1.

[0020] Compared with the prior art, the present invention has the following advantages:

[0021] (1) This invention uses a mixed solvent-mediated multimetallic gel method to prepare a multimetallic oxide precursor, which enables strong interactions between Cu species and Al and another metal promoter, directly embedding CuO nanoparticles onto Al and another metal oxide. Subsequently, CuO is converted into metallic Cu through a one-step reduction process. This metallic Cu is confined and stabilized, which can effectively prevent the shedding and migration of Cu species during the reaction, thus exhibiting excellent catalytic activity.

[0022] (2) The AlCu-based ternary catalyst prepared allows the three metals to form a complete solid solution structure, and the three metals generate lattice doping between each other, resulting in more low-coordination metal sites, thus having more catalytic active centers and bringing higher catalytic activity.

[0023] (3) The catalyst prepared by this invention is inexpensive, simple to prepare, suitable for large-scale preparation, and has excellent prospects for industrial application. Detailed Implementation

[0024] The present invention will be further described below with reference to specific embodiments, but the invention is not limited to these specific embodiments. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the protection scope of the present invention.

[0025] Example 1

[0026] 10g of pseudoboehmite was added to a mixed solvent of water and ethylene glycol (mass ratio 1:1), with a total solvent mass of 250g. Then, 2.5g of concentrated hydrochloric acid (37% by mass) was added, followed by 2g of copper nitrate and 0.67g of zinc nitrate. The mixture was then stirred in a 60℃ water bath for 6 hours at a stirring speed of 300r / min. Afterward, it was transferred to an oven and dried at 130℃ for 48 hours. Following drying, it was calcined in a muffle furnace at 400℃ for 4 hours, and then reduced in a tube furnace under a 20% H2 / N2 mixed atmosphere at a gas flow rate of 50mL / min, a reduction temperature of 400℃, and a reduction time of 4 hours. The resulting AlCuZn ternary catalyst was then used in the carbon dioxide hydrogenation reaction at a reaction pressure of 3MPa, a reaction temperature of 250℃, and a reaction space velocity of 15000mL / (g⁻¹). cat The reaction time was 3 h, with a feed gas volume ratio of V(H2):V(CO2) of 3:1. After 30 h of reaction, the conversion rate of carbon dioxide was 15.9%, and the selectivity of methanol was 99.4%.

[0027] Example 2

[0028] 10g of pseudoboehmite was added to a mixed solvent of water and ethylene glycol (mass ratio of water to ethylene glycol: 0.8:1), with a total solvent mass of 300g. Then, 3g of concentrated hydrochloric acid (37% by mass) was added, followed by 1.25g of copper nitrate and 0.5g of zirconium nitrate. The mixture was then stirred in a 60℃ water bath for 6 hours at a stirring speed of 300r / min. Afterward, it was transferred to an oven and dried at 130℃ for 48 hours. Following drying, it was calcined in a muffle furnace at 300℃ for 4 hours, and then reduced in a tube furnace under a 20% H2 / N2 mixed atmosphere at a gas flow rate of 50mL / min, a reduction temperature of 400℃, and a reduction time of 4 hours. The resulting AlCuZr ternary catalyst was then used in the carbon dioxide hydrogenation reaction at a reaction pressure of 2MPa, a reaction temperature of 180℃, and a reaction space velocity of 6000mL / (g⁻¹). cat The feed gas volume ratio V(H2):V(CO2) was 3:1. After 30 hours of reaction, the conversion rate of carbon dioxide was 12.9%, and the selectivity of methanol was 96.3%.

[0029] Example 3

[0030] 10g of pseudoboehmite was added to a mixed solvent of water and ethylene glycol (mass ratio 1.5:1, mass of solvent 100g). Then, 1g of 37% hydrochloric acid was added, followed by 10g of copper nitrate and 2g of zinc nitrate. The mixture was then stirred in a 60℃ water bath for 6 hours at 300 rpm. Afterward, it was transferred to an oven and dried at 130℃ for 48 hours. Following drying, it was calcined in a muffle furnace at 650℃ for 4 hours, and then reduced in a tube furnace under a 20% H2 / N2 mixed atmosphere at a gas flow rate of 50mL / min, a reduction temperature of 400℃, and a reduction time of 4 hours. The resulting AlCuZn ternary catalyst was then used in the carbon dioxide hydrogenation reaction at a pressure of 5MPa, a temperature of 340℃, and a space velocity of 24000mL / (g). cat The feed gas volume ratio V(H2):V(CO2) was 3:1. After 30 hours of reaction, the conversion rate of carbon dioxide was 12.1%, and the selectivity of methanol was 95.7%.

[0031] Example 4

[0032] 10g of pseudoboehmite was added to a mixed solvent of water and ethylene glycol (mass ratio of water to ethylene glycol: 0.5:1), with a total solvent mass of 150g. Then, 1.5g of concentrated hydrochloric acid (37% by mass) was added, followed by 5g of copper nitrate and 1g of cerium nitrate. The mixture was then stirred in a 60℃ water bath for 6 hours at a stirring speed of 300 r / min. Afterward, it was transferred to an oven and dried at 130℃ for 48 hours. Following drying, it was calcined in a muffle furnace at 550℃ for 4 hours, and then reduced in a tube furnace under a 20% H2 / N2 mixed atmosphere at a gas flow rate of 50 mL / min, a reduction temperature of 400℃, and a reduction time of 4 hours. The resulting AlCuCe ternary catalyst was then used in the carbon dioxide hydrogenation reaction at a reaction pressure of 3 MPa, a reaction temperature of 250℃, and a reaction space velocity of 15000 mL / (g⁻¹). cat The reaction time was 3 h, with a feed gas volume ratio of V(H2):V(CO2) of 3:1. After 30 h of reaction, the conversion rate of carbon dioxide was 16.1%, and the selectivity of methanol was 98.9%.

[0033] Example 5

[0034] 10g of pseudoboehmite was added to a mixed solvent of water and ethylene glycol (mass ratio 1:1, mass of solvent 200g). Then, 2g of concentrated hydrochloric acid (37% by mass) was added, followed by 2.5g of copper nitrate and 0.83g of zirconium nitrate. The mixture was then stirred in a 60℃ water bath for 6 hours at a stirring speed of 300 r / min. Afterward, it was transferred to an oven and dried at 130℃ for 48 hours. Following drying, it was calcined in a muffle furnace at 500℃ for 4 hours, and then reduced in a tube furnace under a 20% H2 / N2 mixed atmosphere at a gas flow rate of 50 mL / min, a reduction temperature of 400℃, and a reduction time of 4 hours. The resulting AlCuZr ternary catalyst was then used in the carbon dioxide hydrogenation reaction at a reaction pressure of 3 MPa, a reaction temperature of 300℃, and a reaction space velocity of 20000 mL / (g⁻¹). cat The reaction time was 3 h, with a feed gas volume ratio of V(H2):V(CO2) of 3:1. After 30 h of reaction, the conversion rate of carbon dioxide was 15.3%, and the selectivity of methanol was 99.1%.

[0035] Example 6

[0036] 10g of pseudoboehmite was added to a mixed solvent of water and ethylene glycol (mass ratio 1:1, mass of solvent 270g). Then, 2.7g of concentrated hydrochloric acid (37% by mass) was added, followed by 3.3g of copper nitrate and 0.77g of cerium nitrate. The mixture was then stirred in a 60℃ water bath for 6 hours at a stirring speed of 300 r / min. Afterward, it was transferred to an oven and dried at 130℃ for 48 hours. Following drying, it was calcined in a muffle furnace at 450℃ for 4 hours, and then reduced in a tube furnace under a 20% H2 / N2 mixed atmosphere at a gas flow rate of 50 mL / min, a reduction temperature of 400℃, and a reduction time of 4 hours. The resulting AlCuCe ternary catalyst was then used in the carbon dioxide hydrogenation reaction at a reaction pressure of 4 MPa, a reaction temperature of 280℃, and a reaction space velocity of 16000 mL / (g⁻¹). cat The reaction time was 3 h, with a feed gas volume ratio of V(H2):V(CO2) of 3:1. After 30 h of reaction, the conversion rate of carbon dioxide was 15.7%, and the selectivity of methanol was 99.3%.

[0037] Example 7

[0038] 10g of pseudoboehmite was added to a mixed solvent of water and ethylene glycol (mass ratio 2:1, mass of solvent 250g). Then, 2.5g of concentrated hydrochloric acid (37% by mass) was added, followed by 3g of copper nitrate and 1g of zinc nitrate. The mixture was then stirred in a 60℃ water bath for 6 hours at a stirring speed of 300 r / min. Afterward, it was transferred to an oven and dried at 130℃ for 48 hours. Following drying, it was calcined in a muffle furnace at 500℃ for 4 hours, and then reduced in a tube furnace under a 20% H2 / N2 mixed atmosphere at a gas flow rate of 50 mL / min, a reduction temperature of 400℃, and a reduction time of 4 hours. The resulting AlCuZn ternary catalyst was then used in the carbon dioxide hydrogenation reaction at a reaction pressure of 4 MPa, a reaction temperature of 320℃, and a reaction space velocity of 22000 mL / (g). cat The feed gas volume ratio V(H2):V(CO2) was 3:1. After 30 hours of reaction, the conversion rate of carbon dioxide was 15.5%, and the selectivity of methanol was 99.2%.

[0039] Example 8

[0040] 10g of pseudoboehmite was added to a mixed solvent of water and ethylene glycol (mass ratio 1:1, mass of solvent 240g). Then, 2.4g of concentrated hydrochloric acid (37% by mass) was added, followed by 5g of copper nitrate and 0.72g of zirconium nitrate. The mixture was then stirred in a 60℃ water bath for 6 hours at a stirring speed of 300 r / min. Afterward, it was transferred to an oven and dried at 130℃ for 48 hours. Following drying, it was calcined in a muffle furnace at 550℃ for 4 hours, and then reduced in a tube furnace under a 20% H2 / N2 mixed atmosphere at a gas flow rate of 50 mL / min, a reduction temperature of 400℃, and a reduction time of 4 hours. The resulting AlCuZr ternary catalyst was then used in the carbon dioxide hydrogenation reaction at a reaction pressure of 3.5 MPa, a reaction temperature of 320℃, and a reaction space velocity of 10000 mL / (g⁻¹). ca The reaction time was t·h), and the feed gas volume ratio V(H2)∶V(CO2) was 3∶1. After 30 h of reaction, the conversion rate of carbon dioxide was 15.8%, and the selectivity of methanol was 99.1%.

[0041] Example 9

[0042] 10g of pseudoboehmite was added to 250g of water, followed by 2.5g of concentrated hydrochloric acid (37% by mass), then 2g of copper nitrate and 0.67g of zinc nitrate. The mixture was then stirred in a 60℃ water bath for 6 hours at a stirring speed of 300 rpm. Afterward, it was transferred to an oven and dried at 130℃ for 48 hours. Once dried, it was calcined in a muffle furnace at 400℃ for 4 hours, and then reduced in a tube furnace under a 20% H2 / N2 mixed atmosphere at a gas flow rate of 50mL / min, a reduction temperature of 400℃, and a reduction time of 4 hours. The resulting AlCuZn ternary catalyst was then used in the carbon dioxide hydrogenation reaction at a reaction pressure of 3MPa, a reaction temperature of 250℃, and a reaction space velocity of 15000mL / (g⁻¹). cat The feed gas volume ratio V(H2):V(CO2) was 3:1. After 30 hours of reaction, the conversion rate of carbon dioxide was 8.3%, and the selectivity of methanol was 82.1%.

[0043] Example 10

[0044] 10g of pseudoboehmite was added to 250g of ethylene glycol, followed by 2.5g of concentrated hydrochloric acid (37% by mass), then 2g of copper nitrate and 0.67g of zinc nitrate. The mixture was then stirred in a 60℃ water bath for 6 hours at a stirring speed of 300 r / min. Afterward, it was transferred to an oven and dried at 130℃ for 48 hours. Following drying, it was calcined in a muffle furnace at 400℃ for 4 hours, and then reduced in a tube furnace under a 20% H2 / N2 mixed atmosphere at a gas flow rate of 50 mL / min, a reduction temperature of 400℃, and a reduction time of 4 hours. The resulting AlCuZn ternary catalyst was then used in the carbon dioxide hydrogenation reaction at a reaction pressure of 3 MPa, a reaction temperature of 250℃, and a reaction space velocity of 15000 mL / (g⁻¹). cat The feed gas volume ratio V(H2):V(CO2) was 3:1. After 30 hours of reaction, the conversion rate of carbon dioxide was 7.8%, and the selectivity of methanol was 25.8%.

[0045] Comparative Example 1

[0046] 10g aluminum nitrate, 2g copper nitrate, and 0.67g zinc nitrate were placed in a 200mL beaker, and 150mL of deionized water was added to prepare solution A. 4g sodium hydroxide was placed in a 200mL beaker, and 150mL of deionized water was added to prepare solution B. Solutions A and B were slowly added dropwise to a three-necked flask, and then the flask was heated in an 80℃ water bath for 4 hours. The resulting precipitate was centrifuged and washed, and then dried and aged in an oven at 130℃ for 48 hours. It was then calcined in a muffle furnace at 400℃ for 4 hours, followed by reduction in a tube furnace under a 20% H2 / N2 mixed atmosphere at a gas flow rate of 50mL / min, a reduction temperature of 400℃, and a reduction time of 4 hours. The final AlCuZn ternary catalyst was obtained. It was used in the hydrogenation reaction of carbon dioxide at a reaction pressure of 3MPa, a reaction temperature of 250℃, and a reaction space velocity of 15000mL / (g⁻¹). cat The feed gas volume ratio V(H2):V(CO2) was 3:1. After 30 hours of reaction, the carbon dioxide conversion rate was 4.2%, and the methanol selectivity was 20.8%.

[0047] Through the above Examples 1-10, the catalytic performance of the catalysts provided in Examples 1-8 of the present invention is higher than that of the catalysts prepared in Examples 8-9. The possible reason is that in Example 9, only water was used as a solvent, resulting in an insufficient number of hydroxyl groups in the entire system. As a result, many Al species could not complex with the hydroxyl groups, leading to a lack of strong interaction between Al and Cu species. Consequently, the active species were detached during the reaction, resulting in a low catalyst conversion rate. In Example 10, only ethylene glycol was used as a solvent, which resulted in a high carbon content in the final synthesized catalyst. The active species were buried in carbon, resulting in a low catalyst conversion rate. Furthermore, due to the high carbon content, a large number of byproducts such as CO were generated during the reaction, resulting in low catalyst selectivity.

[0048] Compared to Comparative Example 1, which only uses the ordinary co-precipitation method to prepare catalysts, Examples 1-10 of this invention use a mixed solvent-mediated multi-metal gel method to prepare multi-metal oxide precursors, which enables strong interactions between metals. Furthermore, the use of a mixed solvent makes the metals more uniformly dispersed, thereby stably confining Cu species and effectively preventing the shedding and migration of Cu species during the reaction process.

[0049] The contents described in this specification are merely an enumeration of the implementation forms of the inventive concept, and the scope of protection of this invention should not be regarded as limited to the specific forms described in the embodiments.

Claims

1. A method for preparing an aluminum-copper-based ternary catalyst for the methanol synthesis from carbon dioxide and hydrogen, characterized in that, The pseudo-boehmite is dispersed in a solvent, hydrochloric acid is added, copper nitrate and an auxiliary metal precursor are added, and then stirring, aging, drying, calcination and reduction are carried out to obtain the aluminum-copper-based ternary catalyst. The mass ratio of the pseudo-boehmite to the mixed solvent is 1:30-1:

10. The mass ratio of the pseudo-boehmite to copper nitrate is 8:1-1:

1. The mass ratio of the pseudo-boehmite to the auxiliary metal precursor is 20:1-5:

1. The solvent is a mixture of water and ethylene glycol in a mass ratio of 0.5:1-2:

1. The auxiliary metal precursor is one of zinc nitrate, cerium nitrate or zirconium nitrate.

2. The preparation method of the aluminum-copper-based ternary catalyst for carbon dioxide hydrogenation to methanol according to claim 1, characterized in that, The mass ratio of the pseudo-boehmite to the mixed solvent is 1:25-1:15; the mass ratio of the pseudo-boehmite to copper nitrate is 5:1-2:1; and the mass ratio of the pseudo-boehmite to the auxiliary metal precursor is 15:1-10:

1.

3. The preparation method of the aluminum-copper-based ternary catalyst for carbon dioxide hydrogenation to methanol according to claim 1, characterized in that, The hydrochloric acid is concentrated hydrochloric acid with a mass fraction of 37%; and the mass ratio of the concentrated hydrochloric acid to the mixed solvent is 1:

100.

4. The preparation method of the aluminum-copper-based ternary catalyst for carbon dioxide hydrogenation to methanol according to claim 1, characterized in that, The stirring and aging conditions are a water bath at 60℃, a stirring speed of 300r / min and a stirring time of 6h; and the drying conditions are drying at 130℃ for 48h.

5. The method for preparing aluminum-copper-based ternary catalyst for carbon dioxide hydrogenation to methanol according to claim 1, characterized in that, The calcination conditions are calcination in a muffle furnace for 4h at a temperature of 300-650℃.

6. The method for preparing aluminum-copper-based ternary catalyst for carbon dioxide hydrogenation to methanol according to claim 1, characterized in that, The reduction conditions are a 20% H2 / N2 mixed gas, a gas flow of 50mL / min, a reduction temperature of 400℃ and a reduction time of 4h.

7. The aluminum-copper-based ternary catalyst according to any one of claims 1-6 for use in the catalytic hydrogenation of carbon dioxide to produce methanol.

8. Use of the aluminium copper-based ternary catalyst according to claim 7 for the catalytic hydrogenation of carbon dioxide to methanol, characterised in that, The carbon dioxide catalytic hydrogenation reaction pressure is 2-5 MPa, the reaction temperature is 180-340℃, the reaction space velocity is 6000-24000 mL / (g cat ·h), and the raw material gas volume ratio V(H2):V(CO2) is 3:1.