Catalyst for preparing methanol through carbon dioxide hydrogenation and preparation method thereof

Abstract

The invention provides a catalyst for preparing methanol through carbon dioxide hydrogenation and a preparation method of the catalyst. The catalyst is prepared from an active component and an auxiliary agent and / or a modifier, the active component is CuO or In2O3; the auxiliary agent is one or more of ZnO (zinc oxide), ZrO2 (zirconium oxide) and Al2O3 (aluminum oxide); and the modifying agent is one or more of La2O3, Y2O3 and CeO2. The catalyst is prepared by adopting a single-step coprecipitation method, the preparation process is greatly simplified, the preparation cost is greatly reduced, the large-scale production potential is achieved, the CO2 catalytic efficiency can be improved by 1-5%, and the methanol yield can be improved by 1-10%. The composition of the catalyst can be flexibly regulated and controlled, various catalysts with excellent performance can be obtained, and the most suitable catalyst can be conveniently selected according to the working condition environment in actual production.

Description

Technical Field

[0001] The present invention relates to the technical field of catalysts and their preparation methods, and particularly to an efficient catalyst for hydrogenating carbon dioxide to methanol and its preparation method. Background Art

[0002] The extensive use of fossil fuels (coal, oil, and natural gas) has led to excessive CO2 emissions, causing environmental problems such as global warming and ecological damage. In addition, with the continuous rise in global energy demand, the resource utilization of CO2 has become a research focus. As a sustainable carbon resource, converting CO2 into CH3OH is one of the most promising renewable approaches, which can not only solve the environmental problems caused by CO2 but also address the energy crisis. Moreover, CH3OH, as a basic organic chemical raw material, can be used in the production of various chemicals such as olefins, aromatics, gasoline, formaldehyde, acetic acid, and dimethyl ether. The process of hydrogenating carbon dioxide to methanol is relatively easy to achieve, so CH3OH is expected to become an effective way for the resource utilization of CO2.

[0003] The catalysts for hydrogenating CO2 to methanol mainly include non-noble metal (Cu)-based catalysts, noble metal (Pd) catalysts, and bimetallic oxide catalysts at present. For noble metal (Pd) catalysts, due to the high price of Pd and too strong hydrogenation performance, the selectivity of catalyst products is poor. At the same time, the weak adsorption of Pd to CO2 leads to low catalytic efficiency. Non-noble metal catalysts have a certain market prospect due to their relatively low price. In addition, side reactions often occur during the reaction of hydrogenating carbon dioxide to methanol, such as the reverse water-gas shift and the decomposition of intermediate products. The hydrogenation of CH3O* during the reaction process is the rate-determining step of the catalytic reaction, but too much CH3O* in the reaction process will decompose into CO, thus reducing the methanol selectivity, which forms a competitive reaction with the hydrogenation of CH3O*. How to balance the reaction rate and methanol selectivity needs further exploration. From the perspective of catalyst design, it is also necessary to explore the changes in the active center structure and the H and C atom ratios on the catalyst surface caused by the synthesis method and doping a certain proportion of elements into different active component catalysts, so as to rationally design an efficient catalyst for hydrogenating carbon dioxide to methanol. Summary of the Invention

[0004] The present invention aims to overcome the limitations of the prior art and provide an efficient catalyst for hydrogenating carbon dioxide to methanol with excellent catalytic performance, various types, simple preparation process, and low preparation cost, as well as its preparation method.

[0005] The technical solution adopted by the present invention is as follows: A catalyst for the hydrogenation of carbon dioxide to methanol, which is composed of an active component, an auxiliary agent and / or a modifier; the active component is CuO or In2O3; the auxiliary agent is one or more of ZnO, ZrO2, and Al2O3; the modifier is one or more of La2O3, Y2O3, and CeO2; the active component accounts for 20-70% of the mass of the catalyst in terms of oxide; the auxiliary agent accounts for 20-85% of the mass of the catalyst in terms of oxide; the modifier accounts for 0-15% of the mass of the catalyst in terms of oxide.

[0006] Further, the catalyst is composed of an active component, an auxiliary agent and a modifier. The active component is CuO, and the auxiliary agent is one or two of ZnO, Al2O3, and ZrO2; in terms of oxide, CuO, ZnO, Al2O3, and ZrO2 account for 50-70%, 16-26%, 3-15%, and 3-15% of the mass of the catalyst respectively; the modifier accounts for 3-10% of the mass of the catalyst. Further, the catalyst is composed of an active component and an auxiliary agent; the active component is CuO, and the auxiliary agent is Al2O3 or ZrO2; in terms of oxide, CuO accounts for 55-65% of the mass of the catalyst; Al2O3 and ZrO2 account for 25-45% and 25-35% of the mass of the catalyst respectively; the modifier accounts for 3-10% of the mass of the catalyst.

[0007] Further, the catalyst is composed of an active component and an auxiliary agent; the active component is In2O3, and the auxiliary agent is ZrO2; in terms of oxide, In2O3 and ZrO2 account for 15-40% and 60-85% of the mass of the catalyst respectively.

[0008] Further, the catalyst is composed of an active component, an auxiliary agent and a modifier; the active component is In2O3, and the auxiliary agent is ZrO2. In terms of oxide, In2O3 and ZrO2 account for 15-25% and 60-80% of the mass of the catalyst respectively; the modifier accounts for 2-15% of the mass of the catalyst.

[0009] The preparation method of the catalyst for the hydrogenation of carbon dioxide to methanol according to the present invention uses the co-precipitation method to prepare the catalyst, and the method steps are as follows: (1) Dissolve the precursor salts of the active component, the auxiliary agent and the modifier in deionized water to prepare a mixed solution with a concentration of 0.5-2 mol / L. Among the active components, the precursor salt of CuO is one of copper nitrate, copper acetate, and copper chloride; the precursor salt of In2O3 is indium nitrate; the precursor salt of ZnO is zinc nitrate or zinc acetate. Among the auxiliary agents, the precursor salt of ZrO2 is one of zirconium nitrate, zirconium hydroxide, and zirconium sulfate; the precursor salt of Al2O3 is one of aluminum nitrate and aluminum sulfate; Among the modifiers, the precursor salt of La2O3 is lanthanum nitrate; the precursor salt of Y2O3 is yttrium nitrate; the precursor salt of CeO2 is cerium nitrate; (2) After preparing a solution of the precipitating agent with a concentration of 0.2 - 2 mol / , it is gradually added dropwise to the mixed solution prepared in step (1) and the pH is adjusted to 6 - 10 to obtain an adjusted mixed solution; the precipitating agent is one of ammonia water, sodium hydroxide, sodium carbonate, and urea; (3) The adjusted mixed solution prepared in step (2) is continuously stirred at 70 - 90 °C for 1 - 5 h and aged at 50 - 80 °C for 6 - 24 h to form a precipitate; (4) The precipitate obtained in step (3) is washed 3 - 4 times with deionized water, dried at 60 - 80 °C for 8 - 12 h, and then placed in a muffle furnace and calcined at 300 - 500 °C for 2 - 5 h in an air atmosphere to obtain the catalyst.

[0010] Further, in the above step (2), the dropping rate of the precipitating agent solution is 1 - 10 ml / min and stirring is carried out during the dropping process.

[0011] Further, in the above step (4), the heating rate of the calcination is 2 - 5 °C / min.

[0012] The present invention provides a simple and efficient catalyst for hydrogenating carbon dioxide to methanol and its synthesis method. The catalyst is composed of an active component and an auxiliary agent and / or a modifier. The active component provides active sites, and the auxiliary agent acts as a carrier to provide a high specific surface area and a porous structure, promoting the uniform dispersion of the active component and enhancing the mass transfer efficiency; in addition, when the auxiliary agent and / or the modifier is added to the catalyst for hydrogenating carbon dioxide to prepare methanol, after the active component is combined with the auxiliary agent and / or the modifier, it can effectively improve the active dispersion, surface basicity, and stability of the catalyst, increase the synergistic effect with other metal oxides, effectively improve the catalytic performance of the catalyst, change the adsorption and activation performance of the reactants, and thus improve the product selectivity and catalyst stability.

[0013] The active component, auxiliary agent, and / or modifier of the present invention constitute a new catalyst. In the process of hydrogenating CO2 to prepare methanol, this catalyst has high conversion rate, high methanol selectivity, and high stability. The catalyst preparation method of the present invention has significant advantages such as a simple preparation process, low preparation cost, and a large variety of obtained catalysts. In actual production, different types of catalysts can be selected according to the working conditions. Specific Embodiments

[0014] The content of the present invention will be further elaborated below in conjunction with embodiments.

[0015] Example 1

[0016] A highly efficient Cu-Zn-Al-Ce catalyst for hydrogenating carbon dioxide to produce methanol. In this catalyst, CuO, ZnO, Al2O3, and CeO2 account for 60 wt%, 22 wt%, 10 wt%, and 8 wt% of the catalyst mass respectively. The preparation method of the catalyst is as follows: (1) Weigh 9.11 g of Cu(NO3)2·3H2O (Sinopharm, AR), 4.02 g of Zn(NO3)2·6H2O (Sinopharm, AR), 3.68 g of Al(NO3)3·9H2O (Sinopharm, AR), and 2.01 g of Ce(NO3)3·6H2O (Sinopharm, AR) respectively and dissolve them in 65.7 ml of deionized water to form a mixed solution; (2) Take an appropriate amount of 0.2 M (mol / L) ammonia water (AR) and add it dropwise to the mixed solution while adjusting the pH to 8 to obtain an adjusted mixed solution; the dropping rate is 4 ml / min and stirring is carried out during the dropping process; (3) Continuously stir the adjusted mixed solution at 80 °C for 2 h and age it at 80 °C for 12 h to form a precipitate; (4) Wash the obtained precipitate 4 times with deionized water, dry it at 80 °C for 12 h, and then calcine it in an air atmosphere at 400 °C at a heating rate of 2 °C / min for 4 h to obtain the Cu 60 Zn 22 Al 10 Ce8 catalyst.

[0017] Example 2

[0018] A Cu-Zn-Al-Ce-Zr catalyst for hydrogenating carbon dioxide to produce methanol. In this catalyst, CuO, ZnO, Al2O3, CeO2, and ZrO2 account for 57 wt%, 20 wt%, 10 wt%, 8 wt%, and 5 wt% of the catalyst mass respectively. The preparation method of this catalyst is as follows: (1) Weigh 8.56 g of Cu(NO3)2·3H2O (Sinopharm, AR), 3.66 g of Zn(NO3)2·6H2O (Sinopharm, AR), 3.68 g of Al(NO3)3·9H2O (Sinopharm, AR), 2.01 g of Ce(NO3)3·6H2O (Sinopharm, AR), and 0.87 g of Zr(NO3)4·5H2O (Sinopharm, AR) respectively and dissolve them in 64.6 ml of deionized water to form a mixed solution; (2) An appropriate amount of 1 M ammonia water (AR) was added dropwise to the mixed solution, and the pH was adjusted to 8.5 to obtain an adjusted mixed solution; the dropping rate was 6 ml / min, and stirring was carried out during the dropping process; (3) The adjusted mixed solution was continuously stirred at 90 °C for 1 h and aged at 60 °C for 2 h to form a precipitate; (4) The obtained precipitate was washed 4 times with deionized water and dried at 80 °C for 10 h, and then calcined in an air atmosphere at 450 °C for 2 h at a heating rate of 2 °C / min to obtain Cu 57 Zn 20 Al 10 Ce8Zr5 catalyst.

[0019] Example 3

[0020] A Cu-Zn-Al-Y catalyst for the hydrogenation of carbon dioxide to methanol. In this catalyst, CuO, ZnO, Al2O3, and Y2O3 account for 55 wt%, 25 wt%, 15 wt%, and 5 wt% of the catalyst mass, respectively. The preparation method of the catalyst is as follows: (1) 8.36 g of Cu(NO3)2·3H2O (Guoyao, AR), 4.58 g of Zn(NO3)2·6H2O (Guoyao, AR), 5.51 g of Al(NO3)3·9H2O (Guoyao, AR), and 0.85 g of Y(NO3)3·6H2O (Guoyao, AR) were weighed separately and dissolved in 67 ml of deionized water to form a mixed solution; (2) An appropriate amount of 2 M sodium hydroxide solution was added dropwise to the mixed solution, and the pH was adjusted to 10 to obtain an adjusted mixed solution; the dropping rate was 10 ml / min, and stirring was carried out during the dropping process; (3) The adjusted mixed solution was continuously stirred at 70 °C for 5 h and aged at 50 °C for 24 h to form a precipitate; (4) The obtained precipitate was washed 3 times with deionized water and dried at 70 °C for 12 h, and then calcined in an air atmosphere at 500 °C for 2 h at a heating rate of 2 °C / min to obtain Cu 55 Zn 25 Al 15 Y5 catalyst.

[0021] Example 4

[0022] A Cu-Zn-Zr catalyst for the hydrogenation of carbon dioxide to methanol. In this catalyst, when CuO, ZnO, and ZrO2 account for 55 - 60 wt%, 25 - 30 wt%, and 10 - 15 wt% of the catalyst mass respectively, good catalytic effects can be obtained. The mass ratio of each elemental oxide in Cat.4 catalyst is CuO:ZnO:ZrO2 = 58:28:14. The specific preparation scheme is as follows: Weigh 8.81 g of Cu(NO3)2·3H2O (Sinopharm, AR), 5.12 g of Zn(NO3)2·6H2O (Sinopharm, AR), and 2.44 g of Zr(NO3)4·5H2O respectively and dissolve them in 60 ml of deionized water to form a mixed solution.

[0023] (2) Take an appropriate amount of sodium carbonate (Sinopharm, AR) to prepare a 0.2 M solution and add it dropwise to the mixed solution while adjusting the pH to 9; the dropping rate is 4 ml / min and stirring is carried out during the dropping process.

[0024] (3) Continuously stir the adjusted mixed solution at 80 °C for 2 h and age it at 80 °C for 12 h to form a precipitate.

[0025] (4) Wash the obtained precipitate 4 times with deionized water, dry it at 80 °C for 12 h, and then calcine it in an air atmosphere at 400 °C for 4 h at a heating rate of 2 °C / min to obtain a Cu 58 Zn 28 Zr 14 catalyst.

[0026] Example 5

[0027] Prepare an In-Zr catalyst; when In2O3 and ZrO2 account for 15 - 30 wt% and 70 - 85 wt% of the catalyst mass respectively, good catalytic effects can be obtained. The mass ratio of each elemental oxide of the Cat.5 catalyst is In2O3:ZrO2 = 20:80, and the specific production scheme is as follows: (1) Weigh 2.75 g of In(NO3)3·4.5H2O (Sinopharm, AR) and 13.95 g of Zr(NO3)4·5H2O (Sinopharm, AR) respectively and dissolve them in 40 ml of deionized water to form a mixed solution.

[0028] (2) Take an appropriate amount of urea (Sinopharm, AR) to prepare a 0.5 M urea aqueous solution and add it dropwise to the mixed solution while adjusting the pH to 9; the dropping rate is 4 ml / min and stirring is carried out during the dropping process.

[0029] (3) Continuously stir the adjusted mixed solution at 80 °C for 2 h and age it at 80 °C for 12 h to form a precipitate.

[0030] (4) Wash the obtained precipitate 4 times with deionized water, dry it at 80 °C for 12 h, and then calcine it in an air atmosphere at 400 °C for 4 h at a heating rate of 2 °C / min to obtain an In 20 Zr 80 catalyst.

[0031] Example 6

[0032] In-Zr-La catalyst for hydrogenating carbon dioxide to produce methanol. In this catalyst, when In2O3, ZrO2, and La2O3 account for 18 wt%, 65 - 75 wt%, and 8 - 12 wt% of the catalyst mass respectively, good catalytic effects can be achieved. The mass ratio of each elemental oxide of Cat.6 catalyst is In2O3:ZrO2:La2O3 = 18:72:10. The specific preparation scheme is as follows: (1) Weigh 2.47 g of In(NO3)3·4.5H2O (Sinopharm, AR), 12.53 g of Zr(NO3)4·5H2O (Sinopharm, AR), and 1.32 g of La(NO3)3·6H2O (Sinopharm, AR) respectively, and dissolve them in 38.7 ml of deionized water to form a mixed solution.

[0033] (2) Take an appropriate amount of 0.2 M ammonia water solution (AR) and add it dropwise to the mixed solution, and adjust the pH to 8.5. The dropping rate is 4 ml / min, and stirring is carried out during the dropping process.

[0034] (3) Continuously stir the adjusted mixed solution at 80 °C for 2 h, and age it at 80 °C for 12 h to form a precipitate.

[0035] (4) Wash the obtained precipitate 4 times with deionized water, then dry it at 80 °C for 12 h, and then calcine it in an air atmosphere at 400 °C for 4 h at a heating rate of 2 °C / min to obtain the In 18 Zr 72 La 10 catalyst.

[0036] Example 7

[0037] In-Zr-Y = 20:75:5 Prepare In-Zr-Y catalyst; when In2O3, ZrO2, and Y2O3 account for 15 - 25 wt%, 60 - 80 wt%, and 3 - 15 wt% of the catalyst mass respectively, good catalytic effects can be achieved. The mass ratio of each elemental oxide of Cat.7 catalyst is In2O3:ZrO2:Y2O3 = 20:75:5. The specific preparation scheme is as follows: (1) Weigh 2.75 g of In(NO3)3·4.5H2O (Sinopharm, AR), 13.05 g of Zr(NO3)4·5H2O (Sinopharm, AR), and 0.84 g of Y(NO3)3·6H2O (Sinopharm, AR) respectively, and dissolve them in 40 ml of deionized water to form a mixed solution.

[0038] (2) Take an appropriate amount of 0.2 M ammonia water solution (AR) and add it dropwise to the mixed solution, and adjust the pH to 8. The dropping rate is 4 ml / min, and stirring is carried out during the dropping process.

[0039] (3) Continuously stir the adjusted mixture at 80 °C for 2 h and age it at 80 °C for 12 h to form a precipitate.

[0040] (4) Wash the obtained precipitate 4 times with deionized water, dry it at 80 °C for 12 h, and then calcine it in an air atmosphere at 400 °C for 4 h at a heating rate of 2 °C / min to obtain the In 20 Zr 75 Y5 catalyst.

[0041] Catalyst performance test: Apply the above-mentioned Examples Cat.1 - Cat.7 to the reaction of hydrogenation of carbon dioxide to methanol.

[0042] The activation conditions before testing are as follows: The catalyst is pressed and sieved into 50 meshes and then loaded into a fixed-bed reactor. It is reduced at 280 °C (heating rate: 2 °C / min) under a reducing gas composed of a mixture of hydrogen and argon (where the hydrogen content is 10%) at atmospheric pressure for 3 h; after the reduction is completed, wait for the temperature of the fixed-bed reactor to naturally cool to room temperature before testing.

[0043] The reaction conditions for the performance test are: the reaction temperature is 260 °C, the reaction pressure is 5 MPa, the reaction space velocity is 10000 mL·g cat −1 ·h −1 , and the flow ratio of H2 and CO2 is 3:1.

[0044] The performance test results are shown in the following table:

[0045] As can be seen from the above table, the CO2 conversion rates of the catalysts prepared by the single-step coprecipitation method of the present invention are all above 17%. Compared with the existing coprecipitation method, sol-gel method, impregnation method and other preparation methods, they are complex and not suitable for large-scale industrial production, and the CO2 conversion rate is only ~20%. The method of the present invention realizes the precise ratio regulation of the active component and the auxiliary agent and / or modifier through a single-step synthesis strategy, greatly simplifies the preparation process, and has the potential for large-scale production. Through the design of the multi-element synergistic effect, the CO2 conversion rate of the catalyst is stably higher than 17%, and the methanol selectivity can be increased by 1 - 10% compared with the existing similar technologies. When the reaction temperature of the catalyst is 260 °C and the reaction space velocity is 10000 mL·gcat −1 ·h −1 , the methanol selectivity is at ~75%.

[0046] The above are only the preferred implementation schemes of the present invention. It should be noted that for those of ordinary skill in the art, without departing from the principle of the present invention, several improvements and refinements can be made, and these improvements and refinements should also be regarded as the protection scope of the present invention.

Claims

1. A catalyst for preparing methanol by hydrogenating carbon dioxide, characterized in that: The catalyst is composed of an active component and an auxiliary agent and / or a modifier; the active component is CuO or In2O3; the auxiliary agent is one or more of ZnO, ZrO2, and Al2O3; the modifier is one or more of La2O3, Y2O3, and CeO2; the active component accounts for 20-70% of the mass of the catalyst in terms of oxide; the auxiliary agent accounts for 20~85% of the mass of the catalyst in terms of oxide; and the modifier accounts for 0~15% of the mass of the catalyst in terms of oxide.

2. A catalyst for preparing methanol by hydrogenation of carbon dioxide according to claim 1, characterized in that: The catalyst consists of an active component, an auxiliary agent and a modifier, wherein the active component is CuO, and the auxiliary agent is one or two of ZnO, Al2O3, and ZrO2; in terms of oxides, CuO, ZnO, Al2O3, and ZrO2 account for 50-70%, 16-26%, 3-15%, and 3-15% of the mass of the catalyst, respectively; and the modifier accounts for 3-10% of the mass of the catalyst.

3. The catalyst for preparing methanol by hydrogenation of carbon dioxide according to claim 1, characterized in that: The catalyst consists of an active component and an auxiliary agent; the active component is CuO, and the auxiliary agent is Al2O3 or ZrO2; in terms of oxide, CuO accounts for 55-65% of the mass of the catalyst; Al2O3 and ZrO2 account for 25-45% and 25-35% of the mass of the catalyst respectively; and the modifier accounts for 3-10% of the mass of the catalyst.

4. The catalyst for preparing methanol by hydrogenation of carbon dioxide according to claim 1, characterized in that: The catalyst consists of an active component and an auxiliary agent; the active component is In2O3, and the auxiliary agent is ZrO2; in terms of oxides, In2O3 and ZrO2 account for 15-40% and 60-85% of the mass of the catalyst, respectively.

5. The catalyst for preparing methanol by hydrogenation of carbon dioxide according to claim 1, characterized in that: The catalyst consists of an active component, an auxiliary agent and a modifier; the active component is In2O3, the auxiliary agent is ZrO2, and as oxides, In2O3 and ZrO2 account for 15-25% and 60-80% of the mass of the catalyst respectively; the modifier accounts for 2-15% of the mass of the catalyst.

6. The method for preparing a catalyst for preparing methanol by hydrogenation of carbon dioxide according to any one of claims 1 to 5, characterized in that: The catalyst was prepared by coprecipitation method, and the steps are as follows: (1) Dissolving the precursor salts of the active component, auxiliary agent and modifier in deionized water to prepare a mixed solution with a concentration of 0.5-2 mol / L; Among the active components, the precursor salt of CuO is one of copper nitrate, copper acetate and copper chloride; the precursor salt of In2O3 is indium nitrate; the precursor salt of ZnO is zinc nitrate or zinc acetate; In the auxiliary agent, the precursor salt of ZrO2 is one of zirconium nitrate, zirconium hydroxide and zirconium sulfate; the precursor salt of Al2O3 is one of aluminum nitrate and aluminum sulfate; In the modifier, the precursor salt of La2O3 is lanthanum nitrate; the precursor salt of Y2O3 is yttrium nitrate; the precursor salt of CeO2 is cerium nitrate; (2) preparing a precipitant solution with a concentration of 0.2-2 mol / , adding the solution dropwise to the mixed solution prepared in step (1) and adjusting the pH to 6-10 to obtain an adjusted mixed solution; the precipitant is one of ammonia water, sodium hydroxide, sodium carbonate and urea; (3) stirring the adjusted mixed solution prepared in step (2) at 70-90° C. for 1-5 h, and aging at 50-80° C. for 6-24 h to form a precipitate; (4) The precipitate obtained in step (3) is washed with deionized water for 3 to 4 times, dried at 60 to 80° C. for 8 to 12 hours, and then placed in a muffle furnace under air atmosphere, heated to 300 to 500° C. and calcined for 2 to 5 hours to obtain the catalyst.

7. The method for preparing a catalyst for preparing methanol by hydrogenating carbon dioxide according to claim 6, characterized in that: In the above step (2), the dropping rate of the precipitant solution is 1-10 ml / min and stirring is performed during the dropping process.

8. The method for preparing a catalyst for preparing methanol by hydrogenating carbon dioxide according to claim 6 or 7, characterized in that: In the above step (4), the heating rate of calcination is 2-5°C / min.

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