Solid solution catalyst for preparing methanol through carbon dioxide hydrogenation and preparation method of solid solution catalyst
The CdZrOx solid solution catalyst is modified by modifier Ga(NO3)3, increasing the oxygen vacancy and specific surface area, solving the problems of the by-product generation and short service life of existing catalysts at high temperatures, and achieving efficient conversion of carbon dioxide into methanol The process significantly improves the stability of the catalyst and methanol yield.
Patent Information
- Application Number
- CN202410941847.3
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2024-07-15
- Publication Date
- 2024-12-20
AI Technical Summary
The existing carbon dioxide hydrogenation catalysts have a counterwater gas conversion reaction at high temperatures, resulting in the generation of by-product CO, reducing methanol selectivity, and the catalyst is inactivated and sintered at high temperatures, resulting in a short service life.
The modifier Ga(NO3)3 is used to modify the CdZrOx solid solution catalyst. Through Ga, Ga promotes changes in electron structure, increases the oxygen vacancies and specific surface area on the catalyst surface, enhances the adsorption and activation of CO2 and H2, and improves the synergistic effect of the catalyst.
The methanol yield and catalyst stability were significantly improved. The catalyst CO2 conversion rate reached nearly 9% at 320°C, and the methanol yield was as high as 457 mg·gcat-1h-1, and it remained basically unchanged during the continuous stability test for 100 hours. .
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Figure CN119158563A_ABST
Abstract
Description
Technical Field
[0001] The invention relates to a catalyst and a preparation method thereof, in particular to a solid solution catalyst for preparing methanol by hydrogenating carbon dioxide and a preparation method thereof. Background Art
[0002] Over the past century, with the continuous increase in the use of fossil fuels, greenhouse gas emissions, represented by CO2, have also gradually increased. Excessive emissions of carbon dioxide have accelerated a series of environmental problems such as global warming, land desertification, and ocean acidification. Therefore, carbon dioxide emission reduction and resource utilization have become hot issues in current research.
[0003] The catalytic conversion of CO2 into a series of high value-added fuels and chemicals, such as methanol, low-carbon olefins, dimethyl ether, methane, gasoline, etc., is a reasonable means of resource utilization of CO2. Among various hydrogenation products, methanol has attracted much attention because methanol, as a green fuel, can be mixed with gasoline, which can alleviate the problem of energy crisis to a great extent. At the same time, methanol, as an important chemical raw material, is widely used in the synthesis of various fine chemicals, which makes CO2 resource utilization one of the most promising research directions.
[0004] High-efficiency catalysts are the core of CO2 hydrogenation to methanol. Currently, copper-based catalysts represented by copper-zinc-aluminum systems are widely used in the industry. However, due to the relatively serious reverse water-gas shift reaction of copper-based catalysts at high temperatures, a large amount of byproduct CO is generated in the carbon dioxide hydrogenation reaction, which greatly reduces the methanol selectivity. In addition, the process also produces a large amount of water, which accelerates the deactivation and sintering of the catalyst. Therefore, how to improve the methanol yield and service life of carbon dioxide hydrogenation to methanol catalysts is the key to high-efficiency catalysts. Summary of the invention
[0005] Purpose of the invention: In order to overcome the deficiencies in the prior art, the purpose of the present invention is to provide a method for preparing a solid solution catalyst for producing methanol by hydrogenation of carbon dioxide with high methanol yield and simple and convenient operation. Another purpose of the present invention is to provide a solid solution catalyst for producing methanol by hydrogenation of carbon dioxide with long service life.
[0006] Technical solution: The method for preparing a solid solution catalyst for hydrogenating carbon dioxide to methanol described in the present invention comprises weighing a modifier and dissolving Cd(NO3)2·6H2O and Zr(NO3)4·5H2O in water to form a uniform solution, then adding a precipitant, and obtaining a solid solution catalyst after drying and calcining the obtained precipitate; the modifier is one or more of La(NO3)3, Ga(NO3)3, In(NO3)3, Cu(NO3)2, and Ce(NO3)3 hydrates.
[0007] Further, the molar ratio of the metal cations in the modifier to the total metal cations in the solution is 1% to 20%. Preferably, the molar ratio of the metal cations in the modifier to the total metal cations in the solution is 5%.
[0008] Further, the molar ratio of Cd to Cd+Zr is 5% to 50%. Preferably, the molar ratio of Cd to Cd+Zr is 20%.
[0009] Furthermore, the precipitant is ammonium carbonate, and the concentration of the precipitant is 0.1-10M.
[0010] Furthermore, the drying temperature is 80 to 120° C., and the drying time is 6 to 24 hours.
[0011] Furthermore, the calcination temperature is 300-800° C., and the calcination time is 1-10 hours.
[0012] Preferably, the modifier is Ga(NO3)3.
[0013] The solid solution catalyst obtained by the preparation method of the solid solution catalyst for preparing methanol by hydrogenation of carbon dioxide is reduced and then subjected to the reaction of hydrogenation of carbon dioxide to prepare methanol at 200-500°C and 2-7MPa, and the methanol yield reaches 390-457mg·g cat -1 h -1 .
[0014] Preparation principle: CdZrO is treated with metal additive Ga x The solid solution catalyst was modified, and Ga was used as a promoter, resulting in CdZrO x The electronic structure of the solid solution changes, and a large number of oxygen vacancies are generated on the catalyst surface, thereby promoting the production of methanol. x Compared with solid solution catalysts, the Ga, Cd and Zr components in the Ga-modified solid solution catalyst have a stronger synergistic effect, which can enhance the adsorption and activation of CO2 and H2. The enhancement of the synergistic effect of the solid solution structure and the increase of oxygen vacancies jointly promote the adsorption of CO2 and the rapid generation of intermediates during the hydrogenation reaction.
[0015] Beneficial effects: Compared with the prior art, the present invention has the following significant features:
[0016] 1. The catalyst preparation method is simple and low-cost. The activity and methanol yield of the catalyst are significantly improved. At 320°C, the CO2 conversion rate can reach nearly 9%, and the methanol yield is as high as 457 mg·g cat -1 h -1 ;
[0017] 2. The surface oxygen vacancy content of the catalyst is greatly increased after the use of the modifier, providing more surface active sites;
[0018] 3. The specific surface area of the catalyst is greatly increased after the modifier is used. The larger specific surface area also provides more surface active sites. At the same time, the adsorption capacity of carbon dioxide on the catalyst surface is enhanced, which is beneficial to the catalytic conversion of carbon dioxide.
[0019] 4. The life of the catalyst is significantly improved after the use of the modifier. Under the stability test for 100 hours, the CO2 conversion rate and methanol yield of the catalyst remain basically unchanged and are very stable. BRIEF DESCRIPTION OF THE DRAWINGS
[0020] Figure 1 It is a dotted line graph of CO2 conversion rate of the catalyst prepared by the present invention and comparative example 1;
[0021] Figure 2 A bar graph showing the methanol yield of the catalysts prepared in the present invention and comparative example 1 at 320°C;
[0022] Figure 3 This is a performance diagram of the stability test of the catalyst prepared in Example 1 of the present invention;
[0023] Figure 4 The XRD characterization results of the solid solution catalysts prepared in Example 1 and Comparative Example 1 of the present invention are shown;
[0024] Figure 5 N2 adsorption-desorption curves of the solid solution catalysts prepared in Example 1 and Comparative Example 1 of the present invention;
[0025] Figure 6 Oxygen temperature-programmed desorption curves (O2-TPD) of the solid solution catalysts prepared in Example 1 and Comparative Example 1 of the present invention;
[0026] Figure 7 The oxygen vacancy characterization result diagram (EPR) of the solid solution catalyst prepared in Example 1 and Comparative Example 1 of the present invention; DETAILED DESCRIPTION
[0027] The experimental methods described in the examples are conventional methods unless otherwise specified; reagents and materials are commercially available unless otherwise specified. All raw materials were obtained from Sinopharm Chemical Reagent Co., Ltd.
[0028] Example 1
[0029] A method for preparing a solid solution catalyst for preparing methanol by hydrogenating carbon dioxide comprises the following steps:
[0030] Cd(NO3)2·6H2O and Zr(NO3)4·5H2O were weighed at a molar ratio of Cd / (Cd+Zr) of 1:5, and the modifier Ga(NO3)3 hydrate was weighed at a molar ratio of Ga / (Ga+Cd+Zr) of 5:100. After the three nitrates were evenly mixed, a 1M ammonium carbonate precipitant was added dropwise in a 70°C water bath. After the precipitant was added dropwise, the obtained solid solution was aged at 70°C for 2h, then the solid solution was taken out for centrifugation and washed, and the obtained precipitate was dried at 105°C for 16h, and then placed in a muffle furnace for calcination at 500°C for 3h to obtain the catalyst.
[0031] Example 2
[0032] A method for preparing a solid solution catalyst for preparing methanol by hydrogenating carbon dioxide comprises the following steps:
[0033] Cd(NO3)2·6H2O and Zr(NO3)4·5H2O were weighed according to the molar ratio of Cd / (Cd+Zr) of 1:5, and the modifier Ga(NO3)3 hydrate was weighed according to the molar ratio of Ga / (Ga+Cd+Zr) of 2.5:100. After the three nitrates were evenly mixed, a 1M ammonium carbonate precipitant was added dropwise in a 70°C water bath. After the precipitant was added dropwise, the obtained solid solution was aged at 70°C for 2h, then the solid solution was taken out for centrifugation and washed, and the obtained precipitate was dried at 105°C for 16h, and then placed in a muffle furnace for calcination at 500°C for 3h to obtain the catalyst.
[0034] Example 3
[0035] A method for preparing a solid solution catalyst for preparing methanol by hydrogenating carbon dioxide comprises the following steps:
[0036] Cd(NO3)2·6H2O and Zr(NO3)4·5H2O were weighed according to the molar ratio of Cd / (Cd+Zr) of 1:5, and the modifier Ga(NO3)3 hydrate was weighed according to the molar ratio of Ga / (Ga+Cd+Zr) of 7.5:100. After the three nitrates were evenly mixed, a 1M ammonium carbonate precipitant was added dropwise in a 70°C water bath. After the precipitant was added dropwise, the obtained solid solution was aged at 70°C for 2h, then the solid solution was taken out for centrifugation and washed, and the obtained precipitate was dried at 105°C for 16h, and then placed in a muffle furnace for calcination at 500°C for 3h to obtain the catalyst.
[0037] Example 4
[0038] A method for preparing a solid solution catalyst for preparing methanol by hydrogenating carbon dioxide comprises the following steps:
[0039] Cd(NO3)2·6H2O and Zr(NO3)4·5H2O were weighed according to the molar ratio of Cd / (Cd+Zr) of 1:2, and the modifier La(NO3)3 hydrate was weighed according to the molar ratio of La / (La+Cd+Zr) of 1:100. After the three nitrates were evenly mixed, a 0.1M ammonium carbonate precipitant was added dropwise in a 70°C water bath. After the precipitant was added dropwise, the obtained solid solution was aged at 70°C for 2h, then the solid solution was taken out for centrifugation and washed, and the obtained precipitate was dried at 80°C for 24h, and then placed in a muffle furnace for calcination at 3000°C for 10h to obtain the catalyst.
[0040] Example 5
[0041] A method for preparing a solid solution catalyst for preparing methanol by hydrogenating carbon dioxide comprises the following steps:
[0042] Weigh Cd(NO3)2·6H2O and Zr(NO3)4·5H2O according to the molar ratio of Cd / (Cd+Zr) of 1:20, and weigh the modifier Ce(NO3)3 hydrate according to the molar ratio of Ce / (Ce+Cd+Zr) of 1-20:100. After the three nitrates are evenly mixed, add 10M ammonium carbonate precipitant dropwise in a 70°C water bath. After the precipitant is added dropwise, age the obtained solid solution at 70°C for 2h, then take out the solid solution, centrifuge and wash, dry the obtained precipitate at 120°C for 6h, and then put it into a muffle furnace and calcine at 800°C for 1h to obtain the catalyst.
[0043] The Ce(NO3)3 hydrate in this embodiment can be replaced by one or more of La(NO3)3, Ga(NO3)3, In(NO3)3, Cu(NO3)2, and Ce(NO3)3 hydrates.
[0044] Comparative Example 1
[0045] Cadmium nitrate and zirconium nitrate were weighed according to the molar ratio of Cd / (Cd+Zr) of 1:5. After the two nitrates were evenly mixed, a precipitant of ammonium carbonate with a concentration of 1M was added dropwise in a 70°C water bath. After the precipitant was added dropwise, the obtained solid solution was aged at 70°C for 2h, then the solid solution was taken out for centrifugation and washed, and the obtained precipitate was dried at 105°C overnight, and then placed in a muffle furnace for calcination at 500°C for 3h to obtain the catalyst.
[0046] Comparative Example 2
[0047] The same preparation method as in Example 2 was adopted, and other conditions were the same as in Example 2, except that the modifier was copper nitrate, that is, the molar ratio of Cu / (Cu+Cd+Zr) was 2.5:100.
[0048] Comparative Example 3
[0049] The same preparation method as in Example 2 was adopted, and other conditions were the same as in Example 2, except that the modifier was cerium nitrate, that is, the molar ratio of Ce / (Ce+Cd+Zr) was 2.5:100.
[0050] Comparative Example 4
[0051] The same preparation method as in Example 2 was adopted, and other conditions were the same as in Example 2, except that the modifier was lanthanum nitrate, that is, the molar ratio of La / (La+Cd+Zr) was 2.5:100.
[0052] Comparative Example 5
[0053] The same preparation method as in Example 2 was adopted, and other conditions were the same as in Example 2, except that the modifier was indium nitrate, that is, the molar ratio of In / (In+Cd+Zr) was 2.5:100.
[0054] The catalysts obtained in Examples 1 to 5 and Comparative Examples 1 to 5 were applied to the reaction of hydrogenating carbon dioxide to produce methanol, and the specific steps were as follows:
[0055] A vertical tubular heating furnace reactor with an inner diameter of 10 mm and a temperature control system is used. 100 mg of catalyst is loaded into the reactor, and a mixture of hydrogen and nitrogen is introduced. The catalyst is reduced at 200-600° C. for 1-6 hours. Then, the reaction mixture is introduced, and the carbon dioxide hydrogenation to methanol reaction is carried out at 200-500° C. and 2-7 MPa.
[0056] The total nitrogen intake was 40 mL / min, the volume concentration ratio of the reaction mixture CO2 to H2 was 1:3, each test reaction temperature point was continuously tested for 2 hours, and each test reaction temperature point was 20°C apart. The activity results of the catalyst were expressed as CO2 conversion rate and methanol yield, and the CO2 concentration and methanol concentration were detected using online gas chromatography. The test results are shown in Table 1 below.
[0057] Table 1 Performance test results of the solid solution catalysts obtained in Examples 1 to 5 and the catalysts obtained in Comparative Examples 1 to 5
[0058] catalyst <![CDATA[CO2 conversion rate / %]]> <![CDATA[CH3OH yield / mg·g cat -1 h -1 > Example 1 8.6 457 Example 2 8.1 394 Example 3 8.3 450 Example 4 8.0 390 Example 5 8.1 392 Comparative Example 1 5.8 285 Comparative Example 2 6.2 264 Comparative Example 3 4.8 228 Comparative Example 4 5.2 259 Comparative Example 5 4.3 222
[0059] It can be seen from Table 1 that the solid solution catalyst prepared by the preparation method of the present application has a high CO2 conversion rate and excellent methanol yield, among which the solid solution catalyst prepared in Example 1 has the best performance, which is significantly better than Comparative Examples 1-5, indicating that the type and content of the modifier play an important role in improving the performance of the solid solution catalyst.
[0060] Depend on Figures 1-2It can be seen that the catalytic performance of the solid solution catalyst prepared in Example 1 is the best. The CO2 conversion rate reaches 8.6% at 320°C, and the methanol yield is as high as 457 mg·g cat -1 h -1 As the reaction temperature increases, the conversion rate gradually increases. However, due to thermodynamic limitations, the reverse water gas reaction is more favorable when the temperature increases, resulting in an increase in byproduct CO and a decrease in methanol selectivity. Therefore, the data in Table 1 are selected from the results at the optimal temperature of the embodiments and comparative examples.
[0061] Depend on Figure 3 It can be seen that the solid solution catalyst for producing methanol from carbon dioxide hydrogenation prepared by the present invention has strong stability. After 100 hours of continuous testing, the CO2 conversion rate and methanol yield of the catalyst remained basically unchanged, and no deactivation phenomenon was found.
[0062] Figure 4 The XRD test results of Comparative Example 1 and Example 1 are shown in Figure 1. The center of the diffraction peak observed at 30.26° corresponds to the (011) plane, which is a typical t-ZrO2 diffraction peak. The center of the diffraction peak observed at 35.25° corresponds to the (111) plane, which is a typical m-ZrO2 diffraction peak. It can be clearly seen that the main crystal form of the prepared solid solution catalyst is t-ZrO2.
[0063] Figure 5 The N2 adsorption-desorption curve test results of Comparative Example 1 and Example 1 are shown in FIG. Figure 5 It can be seen that both Comparative Example 1 and Example 1 follow the IV type isotherm, indicating that the catalysts are mainly mesoporous, and the BET test results show that the specific surface area of Comparative Example 1 is 45.25 m 2 / g, while the specific surface area of Example 1 is 73.57m 2 / g, a larger specific surface area is conducive to the generation of more active sites and adsorption sites on the surface, thereby enhancing the adsorption and activation of CO2.
[0064] Figure 6 and Figure 7 The oxygen temperature-programmed desorption curves and oxygen vacancy characterization result diagrams of Comparative Example 1 and Example 1 are shown respectively. Figure 6The O2-TPD results show that the peaks at 124°C and 135°C correspond to the surface adsorbed oxygen content, that is, the relative content of oxygen vacancies. The relative content of oxygen vacancies in Example 1 is 0.72 mmol / g, which is significantly higher than 0.68 mmol / g in Comparative Example 1. In addition, the solid solution catalyst in Comparative Example 1 has an obvious desorption peak at 610°C (2.49 mmol / g). This peak can be attributed to lattice oxygen, which is much higher than the lattice oxygen content in Example 1 (0.15 mmol / g). More lattice oxygen will limit the reaction activity of the solid solution catalyst, which is consistent with the test result of the lower CO2 conversion rate in Comparative Example 1. Figure 7 It can be clearly seen from the oxygen vacancy characterization result diagram that the relative content of oxygen vacancies in the solid solution catalyst in Example 1 is significantly greater than that in Comparative Example 1. A larger oxygen vacancy content will produce more surface active oxygen, and surface active oxygen plays a vital role in the catalytic reaction, thereby significantly improving the catalyst performance in Example 1.
[0065] In summary, the solid solution catalysts prepared in Examples 1 to 5 have higher CO2 conversion rate and methanol yield as well as better stability. Among them, Example 1 is the best example.
Claims
1. A method for preparing a solid solution catalyst for hydrogenating carbon dioxide to methanol, characterized in that: The modifier is weighed and dissolved in water with Cd(NO3)2·6H2O and Zr(NO3)4·5H2O to form a uniform solution, and then a precipitant is added. The obtained precipitate is dried and calcined to obtain a solid solution catalyst; the modifier is one or more of La(NO3)3, Ga(NO3)3, In(NO3)3, Cu(NO3)2, and Ce(NO3)3 hydrates.
2. The method for preparing a solid solution catalyst for producing methanol by hydrogenation of carbon dioxide according to claim 1, characterized in that: The molar ratio of the metal cations in the modifier to the total metal cations in the solution is 1% to 20%.
3. The method for preparing a solid solution catalyst for preparing methanol by hydrogenation of carbon dioxide according to claim 1, characterized in that: The molar ratio of the metal cations in the modifier to the total metal cations in the solution is 5%.
4. The method for preparing a solid solution catalyst for preparing methanol by hydrogenation of carbon dioxide according to claim 1, characterized in that: The molar ratio of Cd to Cd+Zr is 5% to 50%.
5. The method for preparing a solid solution catalyst for preparing methanol by hydrogenation of carbon dioxide according to claim 1, characterized in that: The molar ratio of Cd to Cd+Zr is 20%.
6. The method for preparing a solid solution catalyst for preparing methanol by hydrogenation of carbon dioxide according to claim 1, characterized in that: The precipitant is ammonium carbonate.
7. The method for preparing a solid solution catalyst for preparing methanol by hydrogenation of carbon dioxide according to claim 1, characterized in that: The concentration of the precipitant is 0.1-10M.
8. The method for preparing a solid solution catalyst for preparing methanol by hydrogenation of carbon dioxide according to claim 1, characterized in that: The drying temperature is 80-120° C., and the drying time is 6-24 hours.
9. The method for preparing a solid solution catalyst for preparing methanol by hydrogenation of carbon dioxide according to claim 1, characterized in that: The calcination temperature is 300-800° C., and the calcination time is 1-10 hours.
10. A solid solution catalyst obtained by the method for preparing a solid solution catalyst for preparing methanol by hydrogenation of carbon dioxide according to any one of claims 1 to 9, characterized in that: After reduction, carbon dioxide is hydrogenated to produce methanol at 200-500℃ and 2-7MPa, with a methanol yield of 390-457mg·g cat -1 h -1 .