A ternary catalyst for carbon dioxide hydrogenation to methanol prepared by a mechanical ball milling method

Abstract

The application discloses a kind of ternary catalysts for carbon dioxide hydrogenation to methanol prepared by mechanical ball milling method and application thereof, the method is as follows: Cu (OH) 2 and Zn (OH) 2 and auxiliary metal precursor are weighed and added into ball mill jar, grinding ball is added, finally the ball mill jar is placed in ball mill to set condition and carries out ball milling, after ball milling, drying, calcination and reduction are carried out to obtain CuZn-based ternary catalyst;The catalyst preparation method of the application is simple, each component can be uniformly dispersed, and a large number of oxygen vacancies can be formed after adding the auxiliary agent, which improves the catalyst activity and is more suitable for industrialization.

Description

TECHNICAL FIELD

[0001] The present application relates to a method for preparing a ternary catalyst by mechanical ball milling and application, and belongs to the technical field of carbon dioxide hydrogenation to methanol. BACKGROUND

[0002] The rapid growth of global energy demand is driving an increase in CO2 emissions. In 2017, CO2 emissions from global energy consumption reached 33 billion tons, twice the amount of carbon dioxide sinks absorbed by land and oceans. Therefore, it is urgent to develop effective strategies to slow down or even reduce the atmospheric CO2 concentration level by effectively capturing and utilizing the CO2 to be discharged. Since methanol is a viable clean alternative fuel for gasoline and diesel and an important raw material for producing commodity chemicals, catalytic conversion of CO2 to methanol using H2 derived from renewable energy is a promising method for reducing CO2 emissions through carbon cycle and our dependence on fossil fuels, as well as storing renewable energy (solar energy, wind energy, biomass, etc.) as chemical energy. In addition, efficient CO2 hydrogenation to methanol is the core of the successful development of the recently proposed "methanol economy" and "liquid sunshine".

[0003] Although many types of metal-based catalysts can be used for CO2 hydrogenation to methanol, modified copper (Cu) catalysts are still the most effective and most widely studied. Unlike the synthesis of methanol from industrial synthesis gas (CO / H2), one of the main challenges of CO2 hydrogenation to methanol is the reverse water gas shift reaction (RWGS: CO2+H2→CO+H2O), and Cu is one of the most active catalysts. Due to the thermodynamic equilibrium limitation, the increase of CO2 conversion is always accompanied by a serious decrease of methanol selectivity. 7 Considering economic efficiency and practical application, it is crucial to develop efficient catalysts to improve methanol selectivity and have acceptable CO2 conversion. However, most supported Cu-based catalysts still suffer from low methanol selectivity (e.g., >10%) at a passable CO2 conversion. Methanol selectivity is almost less than 50% of the traditional Cu-Zn-Al catalyst. Therefore, further development of copper-based catalysts is promising to meet the requirements of high methanol selectivity at low temperature for industrial applications, in which methanol synthesis is thermodynamically more favorable. SUMMARY

[0004] The present application aims at the deficiencies of the prior art, and provides a CuZn-based ternary catalyst with high catalytic activity, which has high catalytic performance, simple preparation method, is more easy to industrialize, and has low cost.

[0005] The application discloses a ternary catalyst for methanol production by carbon dioxide hydrogenation prepared by a mechanical ball milling method, and specifically relates to the following steps: a certain amount of Cu(OH)2 and Zn(OH)2 and an auxiliary metal precursor are taken and added into a ball milling tank, matched milling balls are added in proportion, finally, the ball milling tank is placed in a ball mill to perform ball milling under set conditions, and after the ball milling is completed, the CuZn-based ternary catalyst is obtained after drying, calcination and reduction.

[0006] The application also limits the molar ratio of the Cu(OH)2 and Zn(OH)2 to 6:1-1:1, and the preferred ratio is 5:1-2:1; the molar ratio of the Zn(OH)2 and the auxiliary metal precursor is 1:0.1-1:1, and the preferred ratio is 1:0.4-1:0.8.

[0007] The application also limits the auxiliary metal precursor to be one of Zr(OH)4, Ce(OH)4, Sm(OH)3.xH2O and La(OH)3.

[0008] The application also limits the material of the ball milling tank and the milling ball to be quartz, corundum and stainless steel; the ball milling time is 0.5-6h, and the preferred ball milling time is 2-4h; the rotating speed is 200-400r / min, and the preferred rotating speed is 300r / min; and the ball-to-material ratio is 20:1-5:1, and the preferred ball-to-material ratio is 10:1.

[0009] The application also limits the drying condition to be drying at 120 DEG C for 24h; the calcination condition is to be calcination in a muffle furnace, the calcination temperature is 350-650 DEG C, the calcination time is 4-6h, the preferred calcination temperature is 450-550 DEG C, and the preferred calcination time is 5h.

[0010] The application also limits the reduction condition to be 10% H2 / N2 mixed gas, the gas flow is 50mL / min, the reduction temperature is 300 DEG C, and the reduction time is 6h.

[0011] The application also provides application of the CuZn-based ternary catalyst in methanol production by carbon dioxide hydrogenation.

[0012] The reaction condition for the CuZn-based ternary catalyst in the methanol production by carbon dioxide hydrogenation is that the reaction pressure is 3MPa, the reaction temperature is 200-300 DEG C, the reaction space velocity is 6000-24000mL / (g cat ·h), and the volume ratio of the raw gas V(H2):V(CO2) is 3:1.

[0013] Compared with the prior art, the application has the following advantages:

[0014] (1) The application adopts mechanical ball milling to prepare a multi-metal hydroxide precursor, strong interaction is generated among the three metal hydroxides by high-energy mechanical ball milling, and the three metals are complexed by hydroxyl groups to form strong interaction. Subsequently, the ternary metal hydroxide is converted into ternary metal oxide by high-temperature calcination, and a solid solution is formed among Cu, Zn and another auxiliary metal. The oxide nanoparticles of the auxiliary metal are directly embedded on the CuZn bimetallic oxide. Subsequently, the auxiliary metal oxide is converted into a metallic state by one-step reduction, and the auxiliary metal in this state is limited and stable, effectively avoiding shedding and migration during the reaction, thereby having excellent catalytic activity.

[0015] (2) The CuZn ternary catalyst prepared by the technical scheme provided in the application forms a complete solid solution structure among the three metals, and the three metals produce lattice doping among each other to generate more low-coordination metal sites, thereby generating more oxygen vacancies and more catalytic active centers, and bringing higher catalytic activity.

[0016] (3) The catalyst prepared by the application has low price, simple preparation, is suitable for large-scale preparation, and has excellent industrial application prospect. DETAILED DESCRIPTION

[0017] The application will be further described below in conjunction with specific embodiments, but the application will not be limited to these specific embodiments. Any person skilled in the art can make equivalent replacements or changes to the technical scheme and the inventive concept of the application within the technical scope disclosed in the application, and all of them should be covered within the protection scope of the application.

[0018] Example 1

[0019] 0.05 mol of Cu(OH)2, 0.01 mol of Zn(OH)2 and 0.001 mol of Zr(OH)4 were placed in a quartz ball mill jar, and then grinding balls with a ball-to-material ratio of 20:1 were added. The ball milling time was set to 0.5 h, and the rotation speed was 400 r / min. After the ball milling, the mixture was dried in an oven at 120℃ for 24 h. Subsequently, the powder was calcined in a muffle furnace at 350℃ for 4 h. Finally, the powder was reduced in a tube furnace in a 10% H2 / N2 mixed atmosphere at a flow rate of 50 mL / min at 300℃ for 6 h, and a CuZnZr ternary catalyst was finally obtained. The catalyst was used in a carbon dioxide hydrogenation reaction, and the reaction pressure was 3 MPa, the reaction temperature was 200℃, the reaction space velocity was 12000 mL / (g ca t·h), and the volume ratio of raw gas V(H2):V(CO2) was 3:1. After the reaction for 20 h, the conversion rate of CO2 was 15.1%, and the selectivity of methanol was 75.3%.

[0020] Example 2

[0021] Cu(OH)2, 0.01 mol Zn(OH)2and 0.004 mol Ce(OH)4were placed in a corundum ball mill jar, and grinding balls were added at a ball-to-material ratio of 10:1. The ball milling time was set to 4 h, and the rotation speed was 300 r / min. After the ball milling, the mixture was dried in an oven at 120 °C for 24 h, and then the powder was calcined in a muffle furnace at 550 °C for 6 h. Finally, the reduction treatment was carried out in a tube furnace at 300 °C under a 10% H2 / N2mixed atmosphere at a flow rate of 50 mL / min for 6 h, to obtain a CuZnCe ternary catalyst. The catalyst was used in a carbon dioxide hydrogenation reaction, and the reaction pressure was 3 MPa, the reaction temperature was 250 °C, the reaction space velocity was 24000 mL / (g cat ·h), and the volume ratio of the raw gas V(H2):V(CO2) was 3:1. After 20 h of reaction, the conversion of CO2was 13.2%, and the selectivity of methanol was 90.8%.

[0022] Example 3

[0023] Cu(OH)2, 0.01 mol Zn(OH)2and 0.006 mol Sm(OH)3-xH2O were placed in a stainless steel ball mill jar, and grinding balls were added at a ball-to-material ratio of 5:1. The ball milling time was set to 5 h, and the rotation speed was 200 r / min. After the ball milling, the mixture was dried in an oven at 120 °C for 24 h, and then the powder was calcined in a muffle furnace at 450 °C for 6 h. Finally, the reduction treatment was carried out in a tube furnace at 300 °C under a 10% H2 / N2mixed atmosphere at a flow rate of 50 mL / min for 6 h, to obtain a CuZnSm ternary catalyst. The catalyst was used in a carbon dioxide hydrogenation reaction, and the reaction pressure was 3 MPa, the reaction temperature was 300 °C, the reaction space velocity was 24000 mL / (g cat ·h), and the volume ratio of the raw gas V(H2):V(CO2) was 3:1. After 20 h of reaction, the conversion of CO2was 10%, and the selectivity of methanol was 96.9%.

[0024] Example 4

[0025] 0.02 mol Cu(OH)₂, 0.01 mol Zn(OH)₂, and 0.007 mol La(OH)₃ were placed in a quartz ball mill jar, and grinding balls with a ball-to-powder ratio of 10:1 were added. The ball milling time was set to 6 h at a speed of 300 r / min. After ball milling, the powder was dried in an oven at 120 °C for 24 h. Subsequently, the powder was calcined in a muffle furnace at 650 °C for 5 h. Finally, it was reduced in a tube furnace at 300 °C in a 10% H₂ / N₂ mixed atmosphere at a flow rate of 50 mL / min for 6 h to obtain the CuZnLa ternary catalyst. This catalyst was then used in the carbon dioxide hydrogenation reaction at a reaction pressure of 3 MPa, a reaction temperature of 200 °C, and a reaction space velocity of 6000 mL / (g⁻¹). cat The feed gas volume ratio V(H2):V(CO2) was 3:1. After 20 h of reaction, the CO2 conversion rate was measured to be 20.2%, and the methanol selectivity was 50.2%.

[0026] Example 5

[0027] 0.01 mol Cu(OH)₂, 0.01 mol Zn(OH)₂, and 0.01 mol Zr(OH)₄ were placed in a quartz ball mill jar, and grinding balls with a ball-to-powder ratio of 10:1 were added. The ball milling time was set to 5 h at a speed of 400 r / min. After ball milling, the powder was dried in an oven at 120 °C for 24 h. Subsequently, the powder was calcined in a muffle furnace at 350 °C for 5 h. Finally, it was reduced in a tube furnace at 300 °C in a 10% H₂ / N₂ mixed atmosphere at 50 mL / min for 6 h to obtain a CuZnZr ternary catalyst. This catalyst was then used in the hydrogenation reaction of carbon dioxide at a reaction pressure of 3 MPa, a reaction temperature of 220 °C, and a reaction space velocity of 18000 mL / (g⁻¹). ca The reaction time was t·h), and the feed gas volume ratio V(H2):V(CO2) was 3:1. After 20 h of reaction, the CO2 conversion rate was measured to be 21.2%, and the methanol selectivity was 85.1%.

[0028] Example 6

[0029] Cu(OH)2, 0.01 mol Zn(OH)2and 0.005 mol Ce(OH)4were placed in a stainless steel ball mill jar, and grinding balls with a ball-to-material ratio of 10:1 were added. The ball milling time was set to 4 h, and the rotation speed was 300 r / min. After the ball milling, the mixture was dried in an oven at 120 °C for 24 h, and then the powder was calcined in a muffle furnace at 550 °C for 5 h. Finally, the reduction treatment was carried out in a tube furnace at 300 °C under a 10% H2 / N2mixed atmosphere at a flow rate of 50 mL / min, and the reduction time was 6 h. Thus, a CuZnCe ternary catalyst was obtained. The catalyst was used in a carbon dioxide hydrogenation reaction, and the reaction pressure was 3 MPa, the reaction temperature was 240 °C, the reaction space velocity was 22000 mL / (g ca ·h), and the volume ratio of the raw gas V(H2):V(CO2) was 3:1. After 20 h of reaction, the conversion of CO2 was 15.8%, and the selectivity of methanol was 98.3%.

[0030] Example 7

[0031] Cu(OH)2, 0.01 mol Zn(OH)2and 0.005 mol La(OH)3were placed in a corundum steel ball mill jar, and grinding balls with a ball-to-material ratio of 20:1 were added. The ball milling time was set to 3 h, and the rotation speed was 400 r / min. After the ball milling, the mixture was dried in an oven at 120 °C for 24 h, and then the powder was calcined in a muffle furnace at 650 °C for 4 h. Finally, the reduction treatment was carried out in a tube furnace at 300 °C under a 10% H2 / N2mixed atmosphere at a flow rate of 50 mL / min, and the reduction time was 6 h. Thus, a CuZnLa ternary catalyst was obtained. The catalyst was used in a carbon dioxide hydrogenation reaction, and the reaction pressure was 3 MPa, the reaction temperature was 200 °C, the reaction space velocity was 12000 mL / (g cat ·h), and the volume ratio of the raw gas V(H2):V(CO2) was 3:1. After 20 h of reaction, the conversion of CO2 was 14.3%, and the selectivity of methanol was 97.9%.

[0032] Example 8

[0033] Cu(OH)2, 0.01 mol Zn(OH)2and 0.004 mol Ce(OH)4were placed in a stainless steel ball mill jar, and grinding balls were added at a ball-to-powder ratio of 10:1. The ball milling time was set to 3 h at a rotation speed of 400 r / min. After the ball milling, the mixture was dried in an oven at 120 °C for 24 h, and then the powder was calcined in a muffle furnace at 550 °C for 6 h. Finally, the reduction treatment was carried out in a tube furnace at 300 °C under a 10% H2 / N2mixed atmosphere at a flow rate of 50 mL / min for 6 h, and a CuZnCe ternary catalyst was obtained. The catalyst was used in the carbon dioxide hydrogenation reaction, and the reaction was carried out at a reaction pressure of 3 MPa, a reaction temperature of 220 °C, a reaction space velocity of 20000 mL / (g cat ·h), and a raw gas volume ratio V(H2):V(CO2) of 3:1. After 20 h of reaction, the CO2conversion rate was 18.3%, and the methanol selectivity was 90.1%.

[0034] Comparative Example 1

[0035] Cu(NO3)2, 0.01 mol Zn(NO3)2·6H2O and 0.001 mol Zr(NO3)4·5H2O were placed in a quartz ball mill jar, and grinding balls were added at a ball-to-powder ratio of 20:1. The ball milling time was set to 0.5 h at a rotation speed of 400 r / min. After the ball milling, the mixture was dried in an oven at 120 °C for 24 h, and then the powder was calcined in a muffle furnace at 350 °C for 4 h. Finally, the reduction treatment was carried out in a tube furnace at 300 °C under a 10% H2 / N2mixed atmosphere at a flow rate of 50 mL / min for 6 h, and a CuZnZr ternary catalyst was obtained. The catalyst was used in the carbon dioxide hydrogenation reaction, and the reaction was carried out at a reaction pressure of 3 MPa, a reaction temperature of 200 °C, a reaction space velocity of 12000 mL / (g cat ·h), and a raw gas volume ratio V(H2):V(CO2) of 3:1. After 20 h of reaction, the CO2conversion rate was only 3.5%, and the methanol selectivity was only 46.1%.

[0036] Comparative Example 2

[0037] Put 0.05 mol Cu(NO3)2, 0.01 mol Zn(NO3)2·6H2O and 0.001 mol Zr(NO3)4·5H2O in a 150 mL beaker, add 100 mL of deionized water to prepare solution A, put 0.155 mol NaOH in a beaker, add 100 mL of deionized water to prepare solution B. Slowly drop solution A and solution B into a three-necked flask through a constant pressure funnel respectively, then heat the three-necked flask in a 60°C water bath for 4h, thereby generating a copper-zinc-zirconium ternary metal hydroxide, then centrifugal washing, drying in an oven at 120°C for 24h, then placing the powder in a muffle furnace at 350°C for 4h, finally reducing treatment in a tube furnace at 300°C under a 10% H2 / N2 mixed gas atmosphere at a flow rate of 50 mL / min, and the reduction time is 6h, finally obtaining a CuZnZr ternary catalyst. It is used in the carbon dioxide hydrogenation reaction, the reaction pressure is 3 MPa, the reaction temperature is 200°C, the reaction space velocity is 12000 mL / (g cat ·h), and the volume ratio of raw gas V(H2):V(CO2) is 3:1. After 20h of reaction, the CO2 conversion rate is only 5.5%, and the methanol selectivity is only 50.9%.

[0038] As can be seen from Examples 1-8 and Comparative Examples 1-2, the technical scheme provided by the present application adopts adding Cu(OH)2 and Zn(OH)2 and the metal precursor of the auxiliary agent into a ball milling tank, adding grinding balls, and finally drying, calcining and reducing the CuZn-based ternary catalyst obtained after the ball milling tank is placed in a ball mill. The CuZn-based ternary catalyst prepared by the nitrate ball milling method in Comparative Example 1 has higher activity, and the CuZn-based ternary catalyst prepared by the ordinary coprecipitation method in Comparative Example 2 also has higher activity. It is possible that the strong interaction between the three metals is produced by the preparation method of hydroxide ball milling, thereby limiting the stability of the auxiliary metal, effectively avoiding the shedding and migration in the reaction process, and thus having excellent catalytic activity.

[0039] The content described in the specification is only a list of implementation forms of the inventive concept, and the protection scope of the present application should not be regarded as limited to the specific forms stated in the examples.

Claims

1. A three-way catalyst for the hydrogenation of carbon dioxide to methanol prepared by mechanical ball milling, characterized in that, Cu(OH)2 and Zn(OH)2, along with the auxiliary metal precursor, were added to a ball mill jar, grinding balls were added, and finally the ball mill jar was placed in a ball mill and ball milled at a speed of 200~400 r / min for 0.5~6 h. After ball milling, the mixture was dried, calcined, and reduced to obtain a CuZn-based ternary catalyst. The Cu(OH)₂ and Zn(OH)₂ mentioned above 2、 The molar ratio of the auxiliary metal precursor is 6-1:1:0.1-0.8; The auxiliary metal precursor is one of Zr(OH)4, Ce(OH)4, Sm(OH)3·xH2O and La(OH)3; The drying conditions are 120 ℃ for 24 h; the calcination temperature is 350~650 ℃ and the calcination time is 4~6 h. The reduction conditions were: 10% H2 / N2 mixed gas, gas flow rate of 50 mL / min, reduction temperature of 300 ℃, and reduction time of 6 h.

2. The ternary catalyst for the hydrogenation of carbon dioxide to methanol prepared by mechanical ball milling according to claim 1, characterized in that, The Cu(OH)₂ and Zn(OH)₂ mentioned above 2、 The molar ratio of the auxiliary metal precursor is 5-1:1:0.4-0.

8.

3. The ternary catalyst for the hydrogenation of carbon dioxide to methanol prepared by mechanical ball milling according to claim 1, characterized in that, The grinding jar and grinding balls are made of one of the following materials: quartz, corundum, or stainless steel.

4. The ternary catalyst for the hydrogenation of carbon dioxide to methanol prepared by mechanical ball milling according to claim 1, characterized in that, The ball milling time is 2-4 hours; the ball mill speed is 300 r / min.

5. The ternary catalyst for the hydrogenation of carbon dioxide to methanol prepared by mechanical ball milling according to claim 1, characterized in that, The ball-to-material ratio is 20:1 to 5:

1.

6. The application of the ternary catalyst for the preparation of methanol by carbon dioxide hydrogenation using the mechanical ball milling method according to any one of claims 1-5.

7. The application of the ternary catalyst for the preparation of methanol from carbon dioxide via mechanical ball milling according to claim 6, characterized in that, The catalytic hydrogenation of carbon dioxide to methanol is carried out at a pressure of 2-5 MPa, a temperature of 200-300℃, and a space velocity of 6000-24000 mL / (g). cat The volume ratio of raw gas (H2):CO2) is 3:1.