A method for preparing CuZnAlGa-based hydrotalcite-derived catalysts for methanol production from carbon dioxide-rich syngas.

Abstract

This invention discloses a method for preparing a CuZnAlGa-based layered double hydroxide (TLH)-derived catalyst for methanol production from carbon dioxide-rich syngas. Using Cu, Zn, Al, and Ga metal salts as precursors, Na₂CO₃ and NaOH as precipitants, and a mixed alcohol-water solution as an auxiliary solvent, co-precipitation is performed under controlled temperature and pH to obtain a LDH-like catalyst precursor. After high-temperature calcination and in-situ reduction in a hydrogen atmosphere, a layered framework structure of Cu nanoparticles immobilized by oxides is obtained. The LDH-like structure provides lattice confinement, preventing Cu particle aggregation, and the interaction between Cu and the oxides enhances the catalyst surface's adsorption capacity for CO and CO₂, thereby improving the activity and stability of methanol production from carbon dioxide-rich syngas.

Description

Technical Field

[0001] This invention relates to the field of catalysts, and more specifically to a method for preparing a CuZnAlGa-based hydrotalcite-derived catalyst for methanol production from carbon dioxide-rich syngas. Background Technology

[0002] With the growth of the world's population and the demands of industry and daily life, excessive carbon dioxide emissions have led to global climate change, seriously threatening normal human production and life. Methanol, as a low-carbon and clean energy source, can replace oil and gas, alleviating dependence on petroleum and natural gas, and can also be used as a raw material to produce high-value chemicals. Traditional methanol production mainly uses a CO-rich syngas route (CO, CO2, H2). Increasing the CO2 content in the syngas to form CO2-rich syngas for methanol production can effectively utilize CO2 resources. However, the mainstream Cu / ZnO / Al2O3 catalyst in this application is limited by the CO2 content. In high-concentration CO2 syngas, CO molecules and CO2 molecules compete for adsorption active sites, affecting the methanol yield. Therefore, many studies are currently modifying Cu / ZnO / Al2O3 catalysts by introducing additives. The introduced components are mostly one or more metal oxides such as MgO, La2O3, CeO2, ZrO2, Ga2O3, SiO2, and TiO2. Since the hydrogenation of CO2 to methanol is a structure-sensitive reaction, in addition to the influence of catalytic components, the structure of the catalyst is also one of the important factors affecting catalytic activity.

[0003] CN104275185A discloses a method for preparing a copper-based hydrogenation catalyst that does not require reduction activation. The preparation process includes precipitation, aging, washing, filtration, and retreatment with aliphatic hydroxy acids, followed by calcination in an inert atmosphere and passivation in an oxidizing atmosphere, resulting in a Cu-based hydrogenation catalyst that does not require reduction activation. The CZAMg, CZALa, and CZAZrGa catalysts prepared by this method have been applied in CO hydrogenation and CO2 hydrogenation to methanol, respectively. In CO2-rich syngas to methanol systems, CO2 and CO molecules undergo simultaneous hydrogenation, leading to competitive adsorption on the catalyst surface and affecting the conversion efficiency of CO2 and CO reactants. The catalyst prepared in this patent exhibits excellent catalytic activity in conventional syngas to methanol and pure CO2 hydrogenation to methanol reactions, but its catalytic performance in CO2-rich syngas is not mentioned. Furthermore, the catalyst in this patent requires calcination at temperatures exceeding 500°C, followed by passivation under specific conditions before shaping, which introduces additional energy consumption and inconvenience to the catalyst's use.

[0004] CN109289854A discloses a highly stable and strong methanol synthesis catalyst and its preparation method. This invention employs a two-step co-precipitation method using a spray method to prepare the methanol catalyst. Compared with other synthesis methods, this method significantly improves the catalyst's reactivity and thermal stability in the hydrogenation of CO to methanol. However, this method requires specific spray equipment and uses a feed gas with a high hydrogen-to-carbon ratio. The CO2 concentration in the feed gas is only 5%, and there is no clear indication of its impact on CO2 conversion rate or the catalytic activity under high CO2 feed gas conditions.

[0005] Therefore, designing and developing efficient Cu-based catalysts and processes with multiple active centers suitable for methanol production from CO2-rich syngas has significant application value in achieving efficient conversion and utilization of carbon resources under mild reaction conditions. Summary of the Invention

[0006] The purpose of this invention is to overcome the shortcomings of existing technologies and provide a method for preparing a CuZnAlGa-based layered double hydroxide (TLH)-derived catalyst for methanol production from carbon dioxide-rich syngas. The prepared catalyst possesses a layered framework structure, large specific surface area, complete crystal structure, uniform particle size, diverse active centers, and high density of active sites. This is beneficial for overcoming the limitations imposed by CO2 content in syngas-to-methanol production, improving the catalytic activity and stability of methanol synthesis, and achieving efficient conversion and utilization of carbon resources.

[0007] The technical solution of this invention to solve the technical problem is as follows:

[0008] This invention provides a method for preparing a CuZnAlGa-based hydrotalcite-derived catalyst for methanol production from carbon dioxide-rich syngas, comprising the following steps:

[0009] 1) Co-precipitation: Weigh a certain mass of Cu, Zn, Al, and Ga salts and dissolve them in a mixed alcohol-water solution. Weigh a certain amount of precipitant and dissolve it in a mixed alcohol-water solution of the same concentration. Add both solutions dropwise simultaneously to a four-necked flask, accompanied by constant-temperature hydrothermal heating and stirring, while maintaining a constant pH. Continue stirring under specific hydrothermal conditions for 6-18 hours, then stop stirring and cool to room temperature.

[0010] 2) Separation: The precipitate from step 1) is separated by vacuum filtration, and the filter cake is washed multiple times with water and ethanol to obtain a colloidal light blue precipitate.

[0011] 3) Drying: Dry the light blue precipitate from step 2) in an oven.

[0012] 4) High-temperature calcination: Grind the dried blue solid from step 3) and then calcine it at high temperature.

[0013] 5) Activation: The CuZnAlGa-type hydrotalcite-derived catalyst obtained in step 4) is reduced in a reducing atmosphere to obtain a CuZnAlGa catalyst with multiple active sites. It is composed of metallic Cu nanoparticles and ZnO, Al2O3, and Ga2O3 metal oxides, maintaining a layered framework structure and having multiple active sites. The mass ratio of (CuO+ZnO) to (Al2O3+Ga2O3) is (5-9):1, the mass ratio of CuO to ZnO is (2-5):1, and the mass ratio of Al2O3 to Ga2O3 is (1-9):1.

[0014] Further, in step 1), the Cu salt, Zn salt, Al salt, and Ga salt are one or more of the following: nitrate, acetate, halide, and sulfate.

[0015] Furthermore, the precipitant is one or more of sodium carbonate, potassium carbonate, sodium bicarbonate, potassium bicarbonate, sodium hydroxide, and potassium hydroxide.

[0016] Further, in step 1), the volume concentration of the mixed alcohol aqueous solution is 5-40%, and the mixed alcohol in the mixed alcohol aqueous solution is two or more of methanol, ethanol, n-propanol, n-butanol, ethylene glycol, and glycerol. Preferably, it is a mixed alcohol of methanol and ethylene glycol.

[0017] Further, in step 1), a peristaltic pump is used to simultaneously add salt solution and precipitant solution to a four-necked flask, with the pump head rotating at 5-30 rpm.

[0018] Furthermore, in step 1), mechanical stirring is used, with the stirring paddle rotating at 600-1000 rpm.

[0019] Furthermore, in step 1), the hydrothermal conditions are 30-60℃, and the hydrothermal time is 6h-18h. The pH range is controlled to be constant at 8-10.

[0020] Furthermore, in step 2), the filter cake is washed with deionized water until the filtrate is neutral during the filtration process, and then washed once with ethanol.

[0021] Further, in step 3), the drying temperature is 60-100℃ and the drying time is 6-12h.

[0022] Further, in step 4), the roasting includes static roasting or roasting in a flowing atmosphere. The roasting equipment includes a muffle furnace or a tube furnace. The roasting atmosphere is one or more of air, oxygen, nitrogen, and argon. The roasting temperature is 320-500℃, the roasting time is 4-6 hours, and the heating rate is 2-10℃ / min.

[0023] Furthermore, in step 5), the catalyst is activated and reduced before application. The reducing atmosphere is hydrogen or a mixture of hydrogen and nitrogen (argon). The flow rate of the reducing gas is 2-20 mL / min, the reduction temperature is 250-300℃, the heating rate is 1-10℃ / min, the pressure is atmospheric pressure, and the reduction time is 1-4 h.

[0024] The CuZnAlGa-based hydrotalcite-derived catalyst prepared in this invention is applied to the methanol production reaction from carbon dioxide-rich syngas.

[0025] Furthermore, the CuZnAlGa-based hydrotalcite-derived catalyst is used in a gas-solid fixed-bed reaction to produce methanol from carbon dioxide-rich syngas, under the following conditions: reaction pressure of 3-7 MPa, reaction temperature of 180-280 °C, and reaction space velocity of 3000-18000 mL / (g). cat h), the feed gas is CO2-rich syngas, and further, the feed gas is carbon-rich syngas with a CO2 content of 20%.

[0026] Compared with the prior art, the present invention has the following beneficial effects:

[0027] 1. The CuZnAlGa-based hydrotalcite-derived catalyst provided by this invention uses a mixed alcohol as an auxiliary solvent, providing low surface tension and high OH content. - The high root concentration environment promotes high crystallinity and a complete structure in the prepared hydrotalcite-like precursor. After catalyst reduction, the Cu particles are small and uniform in size.

[0028] 2. The CuZnAlGa-based layered double hydroxide (LDH)-derived catalyst provided by this invention enhances the co-hydrogenation capacity of CO2 and CO and improves the catalytic production of methanol from carbon dioxide-rich syngas through the synergistic effect of constructing multiple active centers at the Cu-ZnO and Cu-Ga2O3 interfaces. Zn, Al, and Ga metal oxides tightly coat Cu nanoparticles, increasing the density of active sites. Simultaneously, the calcined and reduced catalyst maintains a layered framework structure similar to LDH, and the lattice confinement effect prevents the aggregation of Cu particles.

[0029] 3. The CuZnAlGa-based hydrotalcite-derived catalyst of this invention not only possesses high activity and high methanol selectivity, but more importantly, it also exhibits high stability. Long-term stability evaluation results of the CuZnAlGa-based hydrotalcite-derived catalyst at a reaction temperature of 240℃ show that the CO2 conversion rate consistently remains at approximately 20% and the CO conversion rate consistently remains at approximately 44% within a 100-hour reaction time. The selectivity for CH3OH remains consistently above 99%. This indicates that the CuZnAlGa-based hydrotalcite-derived catalyst possesses excellent activity and stability. Attached Figure Description

[0030] Figure 1XRD patterns of the CuZnAlGa-EM, CuZnAlGa-M, and CuZnAlGa-E hydrotalcite-derived catalyst precursors (LDH) prepared in Examples 1-3;

[0031] Figure 2 TEM images of the CuZnAlGa-EM, CuZnAlGa-M, and CuZnAlGa-E hydrotalcite-derived catalysts prepared in Examples 1-3 after calcination and reduction;

[0032] Figure 3 The figures show the catalytic performance of the CuZnAlGa-EM, CuZnAlGa-M, and CuZnAlGa-E hydrotalcite-derived catalysts prepared in Examples 1-3.

[0033] Figure 4 TEM images of the CuZnAl, CuZnAlGa, and CuZnGa-based hydrotalcite-derived catalyst precursors (LDH) prepared in Examples 14, 16, and 17, and their reduced forms.

[0034] Figure 5 XRD patterns of CuZnAlGa-based hydrotalcite-derived catalyst precursors and calcination-reduction catalysts with different CuO / ZnO ratios are shown, where (a) is the XRD of the LDH precursor sample; (b) is the XRD of the sample after calcination; and (c) is the XRD of the calcined sample after reduction.

[0035] Figure 6 XRD patterns of CuZnAlGa-based hydrotalcite-derived catalyst precursors and calcined / reduced samples with different Al2O3 / Ga2O3 ratios are shown, where (a) is the XRD of the LDH precursor sample; (b) is the XRD of the sample after calcination; and (c) is the XRD of the calcined sample after reduction.

[0036] Figure 7 The figures show the catalytic performance of CuZnAlGa-based hydrotalcite-derived catalysts with different CuO / ZnO ratios, where (a) represents CO2 conversion; (b) represents CO conversion; and (c) represents methanol space-time yield.

[0037] Figure 8 The catalytic performance of CuZnAlGa-based hydrotalcite-derived catalysts with different Al2O3 / Ga2O3 ratios is shown in the figure, where (a) is the CO2 conversion rate; (b) is the CO conversion rate; and (c) is the methanol space-time yield.

[0038] Figure 9 The figures show the catalytic performance of CuZnAl, CuZnAlGa, and CuZnGa-based hydrotalcite-derived catalysts, where (a) represents CO2 conversion; (b) represents CO conversion; and (c) represents methanol space-time yield.

[0039] Figure 10The results show the long-term stability evaluation of CuZnAlGa-based hydrotalcite-derived catalysts at a reaction temperature of 240℃. Detailed Implementation

[0040] The present invention will be described below with reference to specific embodiments, but the implementation of the present invention is not limited thereto. Experimental methods not specifically described in the embodiments are generally performed under conventional conditions and conditions described in the manual, or according to the manufacturer's recommendations. The general equipment, materials, reagents, etc. used are commercially available unless otherwise specified. The raw materials required in the following embodiments and comparative examples are all commercially available.

[0041] Examples 1-3 illustrate the preparation of CuZnAlGa catalysts using one alcohol and two alcohol solvents:

[0042] Example 1

[0043] Weigh 5.5g Cu(NO3)2·3H2O, 3.5g Zn(NO3)2·6H2O, 1.9g Al(NO3)3·9H2O, and 0.8g Ga(NO3)2·3H2O into a 200mL beaker. Add 80mL deionized water, 10mL methanol, and 10mL ethylene glycol, and stir until dissolved. Weigh 0.83g Na2CO3 and 4g NaOH into a 300mL beaker. Add 120mL deionized water, 15mL methanol, and 15mL ethylene glycol, and stir until dissolved. Add 320mL deionized water, 40mL methanol, and 40mL ethylene glycol to a 1L four-necked flask while mechanically stirring at 600rpm. Using a peristaltic pump, simultaneously add the prepared salt and alkali solutions dropwise to the four-necked flask at 15rpm. Maintain hydrothermal conditions at 40℃ throughout the process, with a pH of 9.0±0.2. After the addition was complete, the hydrothermal treatment and stirring were continued for 12 hours. Afterward, the mixture was filtered, and the filter cake was washed with deionized water until the filtrate was neutral, then washed once with ethanol. It was then dried in an oven at 60℃ for 12 hours. The resulting sky-blue solid was ground into powder in an agate mortar. A certain amount of the powder was placed in a muffle furnace and calcined in air atmosphere at a heating rate of 4℃ / min, a target temperature of 320℃, and held for 4 hours. The resulting gray-green catalyst was designated CZAG-EM. The catalyst was pressed into tablets (6MPa, 1min), crushed, and screened using a 40-60 mesh sieve for catalytic performance evaluation.

[0044] The prepared catalyst was evaluated using a fixed-bed microreactor. First, 0.3 g of the screened catalyst was weighed and loaded into a reaction tube with an inner diameter of 8 mm. In-situ reduction of the catalyst was performed using pure H2 at a flow rate of 20 mL / min, with a heating rate of 4 °C / min and a target temperature of 260 °C, maintained for 3 h. After reduction, a mixed gas with n(H2):n(CO2):n(CO):n(N2) = 70:20:5:5 was used at 5 MPa and WHSV = 6000 mL / (g). cat The activity of the catalyst was evaluated at different temperatures under h) conditions.

[0045] Example 2

[0046] Weigh 5.5g Cu(NO3)2·3H2O, 3.5g Zn(NO3)2·6H2O, 1.9g Al(NO3)3·9H2O, and 0.8g Ga(NO3)2·3H2O into a 200mL beaker, add 80mL deionized water and 20mL methanol, and stir until dissolved. Weigh 0.83g Na2CO3 and 4g NaOH into a 300mL beaker, add 120mL deionized water and 30mL methanol, and stir until dissolved. Add 320mL deionized water and 80mL methanol to a 1L four-necked flask, and stir mechanically at 600rpm. Subsequent preparation and evaluation steps are the same as in Example 1, and the catalyst is designated CZAG-M.

[0047] Example 3

[0048] Weigh 5.5g Cu(NO3)2·3H2O, 3.5g Zn(NO3)2·6H2O, 1.9g Al(NO3)3·9H2O, and 0.8g Ga(NO3)2·3H2O into a 200mL beaker, add 80mL deionized water and 20mL ethylene glycol, and stir until dissolved. Weigh 0.83g Na2CO3 and 4g NaOH into a 300mL beaker, add 120mL deionized water and 30mL ethylene glycol, and stir until dissolved. Add 320mL deionized water and 80mL ethylene glycol to a 1L four-necked flask, while mechanically stirring at 600rpm. Subsequent preparation and evaluation steps are the same as in Example 1, and the catalyst is designated CZAG-E.

[0049] Examples 4-9 illustrate the preparation of CuZnAlGa catalysts with different CuO / ZnO ratios:

[0050] Example 4

[0051] The metal salts used in the catalyst preparation were 5.215 g Cu(NO3)2·3H2O, 3.138 g Zn(NO3)2·6H2O, 1.672 g Al(NO3)3·9H2O, and 0.615 g Ga(NO3)2·3H2O. The precipitants used were 0.726 g Na2CO3 and 3.787 g NaOH. The resulting catalyst was designated C2Z1AG. Other preparation and evaluation steps were the same as in Example 1.

[0052] Example 5

[0053] The metal salts used in the catalyst preparation were 5.588g Cu(NO3)2·3H2O, 2.690g Zn(NO3)2·6H2O, 1.672g Al(NO3)3·9H2O, and 0.615g Ga(NO3)2·3H2O. The precipitating agents used were 0.726g Na2CO3 and 3.787g NaOH. The resulting catalyst was denoted as C. 2.5 Z1AG. Other preparation and evaluation steps are the same as in Example 1.

[0054] Example 6

[0055] The metal salts used in the catalyst preparation were 5.867 g Cu(NO3)2·3H2O, 2.354 g Zn(NO3)2·6H2O, 1.672 g Al(NO3)3·9H2O, and 0.615 g Ga(NO3)2·3H2O. The precipitating agents used were 0.726 g Na2CO3 and 3.790 g NaOH. The resulting catalyst was designated C3Z1AG. Other preparation and evaluation steps were the same as in Example 1.

[0056] Example 7

[0057] The metal salts used in the catalyst preparation were 6.084 g Cu(NO3)2·3H2O, 2.092 g Zn(NO3)2·6H2O, 1.672 g Al(NO3)3·9H2O, and 0.615 g Ga(NO3)2·3H2O. The precipitating agents used were 0.726 g Na2CO3 and 3.792 g NaOH. The resulting catalyst is denoted as C. 3.5 Z1AG. Other preparation and evaluation steps are the same as in Example 1.

[0058] Example 8

[0059] The metal salts used in the catalyst preparation were 6.258 g Cu(NO3)2·3H2O, 1.883 g Zn(NO3)2·6H2O, 1.672 g Al(NO3)3·9H2O, and 0.615 g Ga(NO3)2·3H2O. The precipitants used were 0.726 g Na2CO3 and 3.794 g NaOH. The resulting catalyst was designated C4Z1AG. Other preparation and evaluation steps were the same as in Example 1.

[0060] Example 9

[0061] The metal salts used in the catalyst preparation were 6.519 g Cu(NO3)2·3H2O, 1.569 g Zn(NO3)2·6H2O, 1.672 g Al(NO3)3·9H2O, and 0.615 g Ga(NO3)2·3H2O. The precipitating agents used were 0.726 g Na2CO3 and 3.796 g NaOH. The resulting catalyst was designated C5Z1AG. Other preparation and evaluation steps were the same as in Example 1.

[0062] Examples 10-15 illustrate the preparation of CuZnAlGa catalysts with different Al2O3 / Ga2O3 ratios:

[0063] Example 10

[0064] The metal salts used in the catalyst preparation were 5.867 g Cu(NO3)2·3H2O, 2.354 g Zn(NO3)2·6H2O, 3.010 g Al(NO3)3·9H2O, and 0.123 g Ga(NO3)2·3H2O. The precipitants used were 0.897 g Na2CO3 and 3.790 g NaOH. The resulting catalyst was designated CZA9G1. Other preparation and evaluation steps were the same as in Example 1.

[0065] Example 11

[0066] The metal salts used in the catalyst preparation were 5.867 g Cu(NO3)2·3H2O, 2.354 g Zn(NO3)2·6H2O, 2.676 g Al(NO3)3·9H2O, and 0.246 g Ga(NO3)2·3H2O. The precipitating agents used were 0.8545 g Na2CO3 and 3.790 g NaOH. The resulting catalyst was designated CZA8G2. Other preparation and evaluation steps were the same as in Example 1.

[0067] Example 12

[0068] The metal salts used in the catalyst preparation were 5.867 g Cu(NO3)2·3H2O, 2.354 g Zn(NO3)2·6H2O, 2.341 g Al(NO3)3·9H2O, and 0.369 g Ga(NO3)2·3H2O. The precipitating agents used were 0.812 g Na2CO3 and 3.790 g NaOH. The resulting catalyst was designated CZA7G3. Other preparation and evaluation steps were the same as in Example 1.

[0069] Example 13

[0070] The metal salts used in the catalyst preparation were 5.867 g Cu(NO3)2·3H2O, 2.354 g Zn(NO3)2·6H2O, 2.007 g Al(NO3)3·9H2O, and 0.492 g Ga(NO3)2·3H2O. The precipitating agents used were 0.769 g Na2CO3 and 3.790 g NaOH. The resulting catalyst was designated CZA6G4. Other preparation and evaluation steps were the same as in Example 1.

[0071] Example 14

[0072] The metal salts used in the catalyst preparation were 5.867 g Cu(NO3)2·3H2O, 2.354 g Zn(NO3)2·6H2O, 1.672 g Al(NO3)3·9H2O, and 0.615 g Ga(NO3)2·3H2O. The precipitants used were 0.726 g Na2CO3 and 3.790 g NaOH. The resulting catalyst was designated CZA5G5. Other preparation and evaluation steps were the same as in Example 1.

[0073] Example 15

[0074] The metal salts used in the catalyst preparation were 5.867 g Cu(NO3)2·3H2O, 2.354 g Zn(NO3)2·6H2O, 1.338 g Al(NO3)3·9H2O, and 0.738 g Ga(NO3)2·3H2O. The precipitating agents used were 0.683 g Na2CO3 and 3.790 g NaOH. The resulting catalyst was designated CZA4G6. Other preparation and evaluation steps were the same as in Example 1.

[0075] Example 16 is a comparative sample of Cu / ZnO / Al2O3-based hydrotalcite-derived catalyst.

[0076] The metal salts used in the catalyst preparation were 5.867 g Cu(NO3)2·3H2O, 2.354 g Zn(NO3)2·6H2O, and 3.345 g Al(NO3)3·9H2O. The precipitating agents used were 0.941 g Na2CO3 and 3.790 g NaOH. The resulting catalyst was designated CZA. Other preparation and evaluation steps were the same as in Example 1.

[0077] Example 17 is a comparative sample of Cu / ZnO / Ga2O3-based hydrotalcite-derived catalyst.

[0078] The metal salts used in the catalyst preparation were 5.867 g Cu(NO3)2·3H2O, 2.354 g Zn(NO3)2·6H2O, and 0.738 g Ga(NO3)2·3H2O. The precipitating agents used were 0.683 g Na2CO3 and 3.790 g NaOH. The resulting catalyst was designated CZG. Other preparation and evaluation steps were the same as in Example 1.

[0079] The XRD patterns of the catalyst precursors obtained in Comparative Examples 1-3 are shown in the attached figures. Figure 1 As shown, all samples exhibited characteristic diffraction peak structures resembling hydrotalcite in their XRD patterns. The sample prepared using a mixture of methanol and ethylene glycol as an auxiliary solvent (CZAG-LDH-EM) showed the highest crystallinity. Furthermore, the TEM images of the reduced samples (see attached image) also revealed this characteristic. Figure 2 It was also observed that the sample prepared using a mixture of methanol and ethylene glycol exhibited the most uniform particle dispersion and the smallest particle size, followed by the methanol-assisted preparation, with the ethylene glycol-assisted preparation being the least effective. This is primarily because the added ethylene glycol solution provides more hydroxide ions, which is more conducive to the formation of hydrotalcite-like structures. Simultaneously, the methanol solution has low surface tension, which is beneficial for particle dispersion and particle size control in the sample.

[0080] The XRD patterns of the catalyst precursors obtained in Examples 4-9, as well as the calcined and reduced samples, are shown in the attached figures. Figure 5 As shown in the attached figure, the precursors of all samples exhibit a hydrotalcite-like structure. Figure 5 In (a), different CuO / ZnO ratios have a slight effect on the degree of crystallinity of hydrotalcite-like materials. After calcination, all samples exhibit an amorphous phase as shown in the attached figure. Figure 5 (b) In the sample, after reduction, the hydrotalcite-like structure completely collapsed, revealing characteristic peaks of CuO and ZnO as shown in the attached figure. Figure 5 (c) is used in the equation, and the Scherrer equation is used to calculate that the Cu particles in the sample will increase slightly with the increase of Cu content.

[0081] The XRD patterns of the catalyst precursors obtained in Examples 10-17, as well as the calcined and reduced samples, are shown in the attached figures. Figure 6As shown in the attached figure. Except for CZG, all samples exhibited the same characteristics as in Examples 4-9. The ratio of divalent to trivalent metal ions in the CZG precursor deviated from the ratio required for a complete hydrotalcite-like structure, resulting in reduced crystallinity. The structure was more prone to collapse after calcination and reduction, and the Cu particles showed significant growth after reduction, as shown in the attached figure. Figure 6 (c) in the middle.

[0082] The catalysts obtained in Examples 1-17 were used in the methanol production reaction from carbon dioxide-rich syngas, and their catalytic activities were compared. The test results are attached. Figure 3 Appendix Figure 7 Appendix Figure 8 .

[0083] The catalytic performance of CZAG-based hydrotalcite-derived catalysts prepared with different alcohol solutions was compared. The test results are shown in the appendix. Figure 3 Under the same conditions of 240℃, CZAG-EM prepared with the assistance of a mixture of methanol and ethylene glycol exhibited better catalytic activity than CZAG-M prepared with methanol alone and CZAG-E prepared with ethylene glycol alone.

[0084] The catalytic performance of CuZnAlGa-based layered double hydroxide (TLD) derivative catalysts with different CuO / ZnO ratios was compared. The test results are shown in the appendix. Figure 7 The CO2 conversion rate is as follows: Figure 7 The conversion rates of (a) and CO in the figure are as follows: Figure 7 (b) and methanol space-time yield (STY) are as follows: Figure 7 In (c), all showed a trend of first increasing and then decreasing with the increase of CuO / ZnO ratio. At the same time, it can be seen that the catalytic activity is consistently affected by temperature, showing a trend of first increasing and then decreasing in the temperature range of 200-260℃, and exhibiting the best catalytic activity at 240℃.

[0085] The catalytic performance of CuZnAlGa-based layered double hydroxide (TLD) derivative catalysts with different Al2O3 / Ga2O3 ratios was compared. The test results are shown in the appendix. Figure 5 The CO2 conversion rate is as follows: Figure 8 The conversion rates of (a) and CO in the figure are as follows: Figure 8 (b) and methanol space-time yield (STY) are as follows: Figure 8 In (c), most catalysts showed a trend of first increasing and then decreasing with the increase of the Al2O3 / Ga2O3 ratio. The CO conversion rate of individual catalysts may have slight deviations due to the influence of catalyst structure. At the same time, it can be seen that the catalytic activity of all catalysts is consistent with the effect of temperature, showing a trend of first increasing and then decreasing in the temperature range of 200-260℃, and exhibiting the best catalytic activity at 240℃.

[0086] To investigate the effect of Ga on catalytic performance, this invention compared the catalytic activities of three types of hydrotalcite-derived catalysts (CZA, CZAG, and CZG) obtained in Examples 14, 16, and 17. The test results are attached. Figure 9 As shown in the attached figure, the introduction of Ga into CZA significantly improved both CO2 and CO conversion rates. This is because the introduction of Ga synergistically interacts with Cu sites, forming more active centers. Based on XRD patterns and Scherrer's formula, it can be seen that the introduction of Ga also reduced the size of Cu particles. Figure 6 In (c), the interaction between Cu and ZnO is enhanced, increasing the density of active sites. The synergistic effect of Cu-Ga2O3 and Cu-ZnO promotes the non-competitive adsorption of CO and CO2 molecules, effectively improving catalytic activity. In the CZG catalyst, we can see that due to the absence of Al, on the one hand, an inappropriate metal ratio leads to an incomplete hydrotalcite-like structure; on the other hand, without Al2O3 as a structural aid, Cu particles aggregate after calcination and reduction in the CZG sample, resulting in a decrease in the density of active centers and affecting the conversion rates of CO and CO2 and the yield of methanol. Under the same reaction conditions, the STY of the CZA catalyst... MeOH 413g kg -1 cat h -1 STY of CZAG catalyst MeOH 517g kg -1 cat h -1 STY of CZAG catalyst MeOH 467g kg -1 cat h -1 .

[0087] The long-term stability evaluation results of the CuZnAlGa-based hydrotalcite-derived catalyst prepared in Example 14 at a reaction temperature of 240℃ (see appendix). Figure 10 The results showed that the CO2 conversion rate remained at approximately 18.5% and the CO conversion rate remained around 44% within a 100-hour reaction time, while the space-time yield of CH3OH remained stable at 510 g. MeOH Kg -1 Cat h -1 The presence of CuZnAlGa-based hydrotalcite-derived catalysts nearby indicates good stability.

[0088] Unless otherwise specified, the raw materials and equipment used in this invention are all commonly used in the field; unless otherwise specified, the methods used in this invention are all conventional methods in the field.

[0089] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Any simple modifications, alterations, and equivalent transformations made to the above embodiments based on the technical essence of the present invention shall still fall within the protection scope of the present invention.

Claims

1. The application of a CuZnAlGa-based hydrotalcite-derived catalyst in the methanol production reaction from carbon dioxide-rich syngas, characterized in that... The reaction pressure is 3-7 MPa, the reaction temperature is 180-280 ℃, and the gas hourly space velocity is 3000-18000 mL / (g) cat h), the feed gas is carbon-rich synthesis gas with a CO2 content of 20%, and the catalyst preparation method includes the following steps: 1) Co-precipitation: Weigh a certain mass of Cu salt, Zn salt, Al salt, and Ga salt and dissolve them in a mixed alcohol aqueous solution. Weigh a certain amount of precipitant and dissolve it in the mixed alcohol aqueous solution. Add both solutions dropwise into the container simultaneously, accompanied by constant temperature hydrothermal heating at 30-60℃ and stirring, and control the pH value at 8-10. Continue stirring under hydrothermal conditions for 6-18 hours, then stop stirring and cool to room temperature. The mixed alcohol in the mixed alcohol aqueous solution is two or more of methanol, ethanol, n-propanol, n-butanol, ethylene glycol, and glycerol. 2) Separation: The precipitate from step 1) is separated by suction filtration, and the filter cake is washed multiple times with water and ethanol to obtain a colloidal light blue precipitate. 3) Drying: Dry the light blue precipitate from step 2) in an oven; 4) High-temperature calcination: Grind the light blue solid dried in step 3) and calcine it at 320-500℃ for 4-6 hours; 5) Activation: Reduce the CuZnAlGa-type hydrotalcite-derived catalyst obtained in step 4) at 250-300℃ in a reducing atmosphere for 1-4 hours. After reduction, a CuZnAlGa catalyst with multiple active centers is obtained, which is composed of metallic Cu nanoparticles and ZnO, Al2O3, and Ga2O3 metal oxides. It maintains a layered framework structure and has multiple active sites. The mass ratio of (CuO+ZnO) to (Al2O3+Ga2O3) is (5-9):1, the mass ratio of CuO to ZnO is (2-5):1, and the mass ratio of Al2O3 to Ga2O3 is (1-9):

1.

2. The application according to claim 1, characterized in that: In step 1), the Cu salt, Zn salt, Al salt, and Ga salt are one or more of the following: nitrate, acetate, halide, and sulfate.

3. The application according to claim 1, characterized in that: The precipitant is one or more of sodium carbonate, potassium carbonate, sodium bicarbonate, potassium bicarbonate, sodium hydroxide, and potassium hydroxide.

4. The application according to claim 1, characterized in that: In step 1), the mixed alcohol in the mixed alcohol aqueous solution is methanol and ethylene glycol, and the volume concentration of the mixed alcohol aqueous solution is 5-40%.

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