A method for the preparation and use of a silica-modified copper zinc aluminum catalyst

Abstract

This invention relates to a method for preparing and using a silica-modified copper-zinc-aluminum catalyst, comprising: dissolving copper, zinc, and aluminum salts in deionized water to obtain solution A; dissolving sodium carbonate in deionized water to obtain solution B; dissolving silicon salts or organosilicon in deionized water or anhydrous ethanol to obtain solution C; adding solutions A, B, and C dropwise into a beaker containing deionized water, adjusting the dropping rate of solution B to maintain the pH of the reaction solution in an alkaline range; aging the precipitate obtained from the reaction, washing, filtering, drying, and calcining to obtain the copper-zinc-aluminum-silicon catalyst; the molar percentages of copper, zinc, aluminum, and silicon are 20%–50%, 10%–40%, 10%–40%, and 10%–30%, respectively. This invention effectively enhances the catalyst's resistance to sintering and regulates the electronic properties of Cu nanoparticles in the catalyst, promoting the accumulation of Cu on the catalyst. δ+ The generation of species inhibits side reactions such as the decomposition of counter-current gas and methanol, significantly improves catalyst stability, and increases methanol selectivity.

Description

Technical Field

[0001] This invention pertains to the technology of synthesizing methanol by hydrogenation of carbon dioxide, and particularly relates to a method for preparing and using a silica-modified copper-zinc-aluminum catalyst for the hydrogenation of CO2 to methanol. Background Technology

[0002] Carbon dioxide is a greenhouse gas and is considered a major cause of global warming. How to efficiently utilize carbon dioxide and convert it into valuable energy and chemical products has become a research hotspot and challenge. Besides its role as a greenhouse gas, carbon dioxide is also a potential industrial raw material with broad application prospects. Through catalytic hydrogenation, carbon dioxide can be converted into methanol. Methanol is a high-value-added chemical that can be used directly as fuel, solvent, and antifreeze, and is also an important chemical intermediate used to synthesize various organic products such as formaldehyde, acetic acid, chloromethane, methylamine, and dimethyl sulfate. Driven by environmental protection factors and attracted by market prospects, companies and research institutions in many countries are actively developing and constructing carbon dioxide hydrogenation to methanol projects. These include Haldor Topsoe of Denmark, Kansai Electric Power and Mitsui Chemicals of Japan, Icelandic company of Norway, and Lurgi of Germany. Converting carbon dioxide into valuable products can not only reduce greenhouse gas emissions and resource consumption but also promote sustainable development and the development of environmentally friendly industries. Therefore, strengthening the efficient utilization and conversion of carbon dioxide has become an important research direction globally, with enormous potential and market prospects in the energy and chemical industry.

[0003] Currently, the development of catalysts for the synthesis of methanol from carbon dioxide hydrogenation is still in its early stages. Existing processes mostly rely on improvements to the catalysts used in the carbon monoxide hydrogenation synthesis of methanol. Related research primarily focuses on the reaction mechanism, the selection of active components and supports, and the influence of different preparation methods and reaction conditions on catalyst performance. However, due to thermodynamic equilibrium limitations, traditional copper-zinc-aluminum methanol catalysts suffer from drawbacks such as low CO2 conversion rates, poor methanol selectivity, and catalyst instability. To overcome these problems, modern research is increasingly focused on the design and development of novel catalysts. For example, to address the specific requirements of CO2 hydrogenation reaction conditions, novel catalysts or adjustments to catalyst structures can be considered to improve catalyst activity and selectivity. Furthermore, catalyst performance can be enhanced by improving catalyst preparation methods, optimizing reaction conditions, and exploring novel support materials. Regarding catalyst instability, research can be conducted on catalyst lifetime and stability, exploring effective regeneration and repair methods to extend catalyst lifespan. In conclusion, the development of catalysts for the synthesis of methanol from carbon dioxide hydrogenation is of great significance for reducing greenhouse gas emissions, achieving efficient resource utilization, and promoting sustainable development. Future research should continue to focus on improving catalyst activity and selectivity, solving catalyst stability and regeneration problems, to achieve the goal of efficient CO2 conversion to methanol.

[0004] Therefore, developing efficient catalysts for the hydrogenation of carbon dioxide to methanol is of great significance for the sustainable development of efficient carbon dioxide hydrogenation technology. Summary of the Invention

[0005] The purpose of this invention is to overcome the shortcomings of the prior art and provide a method for preparing and using a silica-modified copper-zinc-aluminum catalyst for the hydrogenation of CO2 to methanol.

[0006] To achieve the above objectives, the present invention employs the following technical solution:

[0007] The preparation and application methods of silica-modified copper-zinc-aluminum catalysts include the following specific details:

[0008] Take appropriate amounts of copper salt, zinc salt, and aluminum salt, and dissolve them together in deionized water to obtain solution A; take appropriate amounts of sodium carbonate, and dissolve them in deionized water to obtain solution B; take appropriate amounts of silicon salt or organosilicon, and dissolve them in deionized water or anhydrous ethanol to obtain solution C; under stirring conditions at 20–80°C, add solutions A, B, and C dropwise into a beaker containing deionized water, and maintain the pH of the reaction solution in the alkaline range by adjusting the dropping rate of solution B.

[0009] The precipitate obtained from the reaction was aged for 2–24 hours, washed with deionized water, filtered, dried, and calcined to obtain a copper-zinc-aluminum-silicon catalyst. The molar percentages of copper, zinc, aluminum, and silicon in the copper-zinc-aluminum-silicon catalyst were 20%–50%, 10%–40%, 10%–40%, and 10%–30%, respectively.

[0010] The copper salt, zinc salt, and aluminum salt are one or more of the nitrate, sulfate, and chloride salts corresponding to copper, zinc, and aluminum elements, respectively.

[0011] The silicon salt or organosilicon is one or more of sodium silicate, tetraethyl orthosilicate, dimethyldiethoxysilane, and phenyltriethoxysilane.

[0012] The stirring speed is 200-2000 rpm, the drop rate of solution A and solution C is 1-20 mL / min, the drying temperature is controlled at 60-180℃ and the time is 4-48 h; the calcination is carried out in a muffle furnace with air introduced, the temperature is controlled at 300-700℃ and the time is 2-12 h.

[0013] The method for using silica-modified copper-zinc-aluminum catalysts in the catalytic hydrogenation of CO2 to methanol, wherein the silica-modified copper-zinc-aluminum catalysts are prepared using a method for preparing silica-modified copper-zinc-aluminum catalysts for the hydrogenation of CO2 to methanol, specifically including:

[0014] A silica-modified copper-zinc-aluminum catalyst was loaded into a high-pressure fixed-bed reactor. After reduction by a mixture of hydrogen and nitrogen at a concentration of 5–99 mol% at 210–400 °C, the catalyst was further subjected to a reaction at a temperature of 200–300 °C, a pressure of 1–9 MPa, and a space velocity of 500–50000 mL / (g). cat Under the conditions of ·h), a reaction gas is introduced to achieve catalytic hydrogenation to methanol; the molar ratio of H2 to CO2 in the reaction gas is (1~10):1.

[0015] If additional CO needs to be added to the reaction gas, the molar percentage of CO compared to the reaction gas should be 0-10%.

[0016] Description of the invention principle:

[0017] This invention introduces silicon species in situ during the synthesis of copper-zinc-aluminum catalysts, ultimately obtaining silicon dioxide-modified copper-zinc-aluminum catalysts.

[0018] A series of catalysts for the hydrogenation of CO2 to methanol have been prepared. Among them, supported copper nanoparticles are favored due to their high activation and conversion activity for CO2. However, due to the low Taman temperature of copper, these copper nanoparticles are prone to sintering into larger particles, leading to the loss of active sites. For example, the extensively studied Cu / ZnO / Al2O3 catalyst exhibits a continuous decrease in activity during CO2 hydrogenation. To improve the sintering resistance of Cu nanoparticles, various metal oxides, such as ZrO, have been introduced into the Cu / ZnO / Al2O3 catalyst. x (CN118002137A and CN103272607A), GaO x (CN116899577A), LaO x (Applied catalysisA:General.2013,468:442-452.) and CeO x (CN117101669A), etc. However, due to the enhanced side reactions of the water-gas reverse conversion, the carbon dioxide conversion rate is low in many cases, and the selectivity of the target product methanol is reduced.

[0019] To overcome this limitation, silica supports are widely used to modify Cu catalysts to improve their performance in methanol synthesis. Patent CN105521775B proposes a method for synthesizing a Cu-based catalyst by mixing gaseous SiO2 and silica sol SiO2 to prepare a slurry, then synthesizing a SiO2 support using centrifugal spray drying (at 300℃), and simultaneously preparing a SiO2-modified catalyst using ammonia stripping. The resulting catalyst exhibits high metal dispersion, a large specific surface area, and excellent wear resistance, thus demonstrating high reactivity and methanol synthesis performance. However, this synthesis method involves complex SiO2 support preparation steps and requires high temperatures, hindering widespread application. Our earlier patent CN116393160A proposes a method for preparing a copper-zinc-aluminum-silica molecular sieve composite catalyst. This method utilizes a solid-phase synthesis method to prepare hydrophobic or hydrophilic SiO2 molecular sieves, and then physically mixes and packs the copper-zinc-aluminum catalyst with the SiO2 molecular sieve to form a composite catalyst, which can efficiently catalyze the conversion of CO2 to methanol. The addition of SiO2 molecular sieves in this process can effectively reduce the concentration of H2O on the catalyst surface, thereby improving catalyst stability and methanol synthesis performance. However, the synthesis of SiO2 molecular sieves requires the use of raw materials such as organosilanes, which results in high costs. Furthermore, the physical mixing of SiO2 with copper-zinc-aluminum catalysts may lead to weak interactions between the two, preventing the optimal catalytic performance for methanol synthesis from being achieved.

[0020] In summary, we have developed a silica-modified Cu / ZnO / Al2O3 catalyst (Cu / ZnO / Al2O3 / SiO2, CuZnAlSi). Compared to traditional Cu / ZnO / Al2O3 catalysts, this catalyst exhibits strong interactions between the silica and Cu nanoparticles, resulting in greater sintering resistance during CO2 hydrogenation to methanol. Furthermore, the silica electronically modulates the Cu nanoparticles, leading to the presence of more Cu on the catalyst. δ+ Species. Due to Cu δ+ The species primarily stabilizes the CH3O* intermediate, preventing its decomposition to generate the byproduct CO, thereby improving methanol selectivity. The results show a significant improvement in methanol selectivity compared to the traditional Cu / ZnO / Al2O3 catalyst.

[0021] Compared with the prior art, the beneficial effects of the present invention are:

[0022] 1) Due to the low Taman temperature of copper, sintering of copper particles is likely to occur during the reaction, leading to the deactivation of traditional CuZnAl methanol catalysts. This invention introduces silica species to enhance the interaction between copper particles and the support, thereby inhibiting their migration and aggregation during the reaction and improving the stability of the catalyst.

[0023] 2) Due to the presence of a large amount of Cu on traditional copper-zinc-aluminum methanol catalysts 0 The presence of silica species leads to severe adverse reactions in the reaction of coal gas (H2+CO2→CO+H2O) and methanol (CH3OH→CO+2H2), resulting in the formation of large amounts of CO byproducts. This invention, by introducing silica species, promotes the growth of more Cu on the catalyst. δ+ The generation of species thus inhibits side reactions such as the decomposition of counter-current gas and methanol, thereby improving the selectivity of methanol on the catalyst. Attached Figure Description

[0024] Figure 1 The in-situ reduction X-ray photoelectron spectroscopy (XPS) of the CuZnAl-1 catalyst in Example 9 is shown.

[0025] Figure 2 The in-situ reduction X-ray photoelectron spectroscopy (XPS) of the CuZnAlSi catalyst in Example 9 is shown.

[0026] Figure 3 The infrared spectrum of carbon monoxide adsorption of the CuZnAl-1 catalyst in Example 9 is shown.

[0027] Figure 4 The infrared spectrum of carbon monoxide adsorption of the CuZnAlSi catalyst in Example 9 is shown. Detailed Implementation

[0028] To make the objectives, technical solutions, and advantages of this invention clearer, the specific implementation methods of this invention will be further described below in conjunction with the embodiments. The following embodiments are used to specifically illustrate the content of this invention. These embodiments are only general descriptions of the content of this invention and do not limit the content of this invention.

[0029] Example 1: Application of silica-modified copper-zinc-aluminum catalyst in carbon dioxide hydrogenation.

[0030] (1) Comparison sample of copper-zinc-aluminum synthesis catalyst:

[0031] (1.1) The CuZnAl-1 catalyst was synthesized by co-precipitation. 12.05 g (0.050 mol) copper nitrate trihydrate, 10.40 g (0.035 mol) zinc nitrate hexahydrate, and 5.63 g (0.015 mol) aluminum nitrate nonahydrate were dissolved in 200 mL of deionized water to obtain aqueous solution A. 15.90 g (0.15 mol) sodium carbonate was dissolved in 200 mL of deionized water to obtain aqueous solution B. Heating was maintained at 60 °C and stirring speed at 700 rpm. The dropwise flow rate of solutions A and C was controlled at 3 mL / min. The dropwise flow rate of aqueous solution B was adjusted, and the pH of the liquid in the beaker was maintained within the alkaline range. After aging the resulting precipitate for 12 h, it was washed with deionized water, filtered six times, and dried at 100 °C for 12 h. The dried product was placed in a muffle furnace and calcined at 500 °C with air for 4 h to obtain the CuZnAl-1 catalyst. In this catalyst, the molar percentages of copper, zinc, and aluminum are 50%, 35%, and 15%, respectively.

[0032] (1.2) The CuZnAl₂ catalyst was synthesized by co-precipitation. 12.05 g (0.050 mol) copper nitrate trihydrate, 10.40 g (0.035 mol) zinc nitrate hexahydrate, and 5.63 g (0.015 mol) aluminum nitrate nonahydrate were dissolved in 200 mL of deionized water to obtain aqueous solution A. 15.90 g (0.15 mol) sodium carbonate was dissolved in 200 mL of deionized water to obtain aqueous solution B. Aqueous solutions A and B were simultaneously added dropwise to a beaker containing 200 mL of deionized water, while maintaining heating at 20 °C and stirring at 200 rpm. The dropwise flow rate of solution A was controlled at 1 mL / min, and the dropwise flow rate of solution B was adjusted while maintaining the pH of the liquid in the beaker within the alkaline range. After aging the resulting precipitate for 4 h, it was washed with deionized water, filtered six times, and dried at 60 °C for 48 h. The dried product was placed in a muffle furnace and calcined at 300°C with air for 12 hours to obtain the copper-zinc-aluminum catalyst CuZnAl-2. The molar percentages of copper, zinc, and aluminum in this catalyst were 50%, 35%, and 15%, respectively.

[0033] (2) Synthesis of silica-modified copper-zinc-aluminum catalysts:

[0034] (2.1) The CuZnAlSi-1 catalyst was synthesized by co-precipitation. 12.05 g (0.050 mol) copper nitrate trihydrate, 7.43 g (0.025 mol) zinc nitrate hexahydrate, and 3.62 g (0.015 mol) aluminum chloride hexahydrate were dissolved in 200 mL of deionized water to obtain aqueous solution A. 15.90 g (0.15 mol) sodium carbonate was dissolved in 200 mL of deionized water to obtain aqueous solution B. 1.22 g (0.010 mol) sodium silicate was dissolved in 200 mL of deionized water to obtain aqueous solution C. Aqueous solutions A, B, and C were simultaneously added dropwise to a beaker containing 200 mL of deionized water, while maintaining heating at 20 °C and stirring at 200 rpm. The dropwise flow rate of solution A was controlled at 1 mL / min, and the pH of the liquid in the beaker was maintained within the alkaline range by adjusting the dropwise flow rate of solution B. The obtained precipitate was aged for 4 hours, washed with deionized water, filtered six times, and dried at 60°C for 48 hours. The dried product was then placed in a muffle furnace and calcined at 300°C with air for 12 hours to obtain a silica-modified copper-zinc-aluminum catalyst CuZnAlSi-1. The molar percentages of copper, zinc, aluminum, and silicon in this catalyst were 50%, 25%, 15%, and 10%, respectively.

[0035] (2.2) The CuZnAlSi-2 catalyst was synthesized by co-precipitation. 5.00 g (0.020 mol) copper sulfate pentahydrate, 11.88 g (0.040 mol) zinc nitrate hexahydrate, and 11.25 g (0.030 mol) aluminum nitrate nonahydrate were dissolved in 200 mL of deionized water to obtain aqueous solution A. 15.90 g (0.15 mol) sodium carbonate was dissolved in 200 mL of deionized water to obtain aqueous solution B. 1.22 g (0.010 mol) sodium silicate was dissolved in 200 mL of deionized water to obtain aqueous solution C. Aqueous solutions A, B, and C were simultaneously added dropwise to a beaker containing 200 mL of deionized water, while maintaining heating at 80 °C and stirring at 2000 rpm. The dropwise flow rate of solution A was controlled at 20 mL / min, and the pH of the liquid in the beaker was maintained within the alkaline range by adjusting the dropwise flow rate of solution B. The obtained precipitate was aged for 48 hours, washed with deionized water, filtered six times, and dried at 180°C for 4 hours. The dried product was then placed in a muffle furnace and calcined at 700°C with air for 2 hours to obtain a copper-zinc-aluminum catalyst modified with silica, CuZnAlSi-2. The molar percentages of copper, zinc, aluminum, and silicon in this catalyst were 20%, 40%, 30%, and 10%, respectively.

[0036] (2.3) The CuZnAlSi-3 catalyst was synthesized by co-precipitation. 9.64 g (0.040 mol) copper nitrate trihydrate, 2.97 g (0.010 mol) zinc nitrate hexahydrate, and 15.00 g (0.040 mol) aluminum nitrate nonahydrate were dissolved in 200 mL of deionized water to obtain aqueous solution A. 15.90 g (0.15 mol) sodium carbonate was dissolved in 200 mL of deionized water to obtain aqueous solution B. 1.22 g (0.010 mol) sodium silicate was dissolved in 200 mL of deionized water to obtain aqueous solution C. Aqueous solutions A, B, and C were simultaneously added dropwise to a beaker containing 200 mL of deionized water, while maintaining heating at 20 °C and stirring at 200 rpm. The dropwise flow rate of solution A was controlled at 1 mL / min, and the dropwise flow rate of solution B was adjusted to maintain the pH of the liquid in the beaker within the alkaline range. The obtained precipitate was aged for 4 hours, washed with deionized water, filtered six times, and dried at 60°C for 48 hours. The dried product was then placed in a muffle furnace and calcined at 300°C with air for 12 hours to obtain a silica-modified copper-zinc-aluminum catalyst CuZnAlSi-3. The molar percentages of copper, zinc, aluminum, and silicon in this catalyst were 40%, 10%, 40%, and 10%, respectively.

[0037] (2.4) The CuZnAlSi-4 catalyst was synthesized by co-precipitation. 9.64 g (0.040 mol) copper nitrate trihydrate, 5.94 g (0.020 mol) zinc nitrate hexahydrate, and 11.25 g (0.030 mol) aluminum nitrate nonahydrate were dissolved in 200 mL of deionized water to obtain aqueous solution A. 15.90 g (0.15 mol) sodium carbonate was dissolved in 200 mL of deionized water to obtain aqueous solution B. 1.22 g (0.010 mol) sodium silicate was dissolved in 200 mL of deionized water to obtain aqueous solution C. Aqueous solutions A, B, and C were simultaneously added dropwise to a beaker containing 200 mL of deionized water, while maintaining heating at 20°C and stirring at 200 rpm. The dropwise flow rate of solution A was controlled at 1 mL / min, and the dropwise flow rate of solution B was adjusted to maintain the pH of the liquid in the beaker within the alkaline range. The obtained precipitate was aged for 4 hours, washed with deionized water, filtered six times, and dried at 60°C for 48 hours. The dried product was then placed in a muffle furnace and calcined at 300°C with air for 12 hours to obtain a silica-modified copper-zinc-aluminum catalyst CuZnAlSi-4. The molar percentages of copper, zinc, aluminum, and silicon in this catalyst were 50%, 30%, 10%, and 10%, respectively.

[0038] The catalytic performance of the carbon dioxide hydrogenation reaction was tested in a fixed-bed reactor, and the test procedures are as follows:

[0039] (1) The activity of the previously prepared CuZnAl-1 and CuZnAl-2 catalysts and four silica-modified CuZnAl catalysts (CuZnAlSi) in the production of methanol by CO2 hydrogenation was evaluated. First, 0.5 g of catalyst particles (20-40 mesh) and 2.0 g of inert quartz sand (20-40 mesh) were physically shaken and mixed, and then poured into a stainless steel reactor for filling. The two ends were filled with quartz wool to maintain the bed height, and a fixed bed reactor was assembled.

[0040] (2) Using a space velocity of 3000 mL / (g) cat A mixture of hydrogen and nitrogen with a hydrogen concentration of 5 mol% was used to reduce the catalyst at 400 °C for 6 h.

[0041] (3) A reaction gas with a hydrogen / carbon dioxide / argon (H2 / CO2 / Ar) molar ratio of 72.0 / 24.0 / 4.0 was introduced into a high-pressure fixed-bed reactor. The catalyst bed temperature was controlled at 240℃, the reaction pressure at 3.0 MPa, and the feed gas volume hourly space velocity at 6000 mL / (g) cat ·h).

[0042] Note: The reaction gases used here are pure CO2 / H2 / Ar, where Ar is used as an internal standard to assist in calculating the CO2 conversion rate. Because CO is generated during the reaction, additional CO needs to be added to the feed gas when simulating a cycle experiment. Experiments with CO incorporation will be listed in later examples. The experimental results are shown in Table 1:

[0043] Table 1:

[0044]

[0045] 3MPa, 240℃, SV=6000mL / (g cat ·h), H2 / CO2 / Ar=72 / 24 / 4, reaction time is 40h.

[0046] The above experimental results show that the introduction of silica can improve the selectivity of methanol. CuZnAlSi-1 has the best performance among the four samples, with a CO2 conversion rate of 15.4%, a methanol selectivity of 75.4%, and a methanol yield of 11.6%.

[0047] Example 2: Application of silica-modified copper-zinc-aluminum catalysts with different silicon contents in carbon dioxide hydrogenation.

[0048] (1) Synthesis of silicon dioxide-modified copper-zinc-aluminum catalysts with different silicon contents:

[0049] (1.1) The CuZnAlSi0.1 catalyst was synthesized by co-precipitation. 12.05 g (0.050 mol) copper nitrate trihydrate, 7.43 g (0.025 mol) zinc nitrate hexahydrate, and 5.63 g (0.015 mol) aluminum nitrate nonahydrate were dissolved in 200 mL of deionized water to obtain aqueous solution A. 15.90 g (0.15 mol) sodium carbonate was dissolved in 200 mL of deionized water to obtain aqueous solution B. 1.22 g (0.010 mol) sodium silicate was dissolved in 200 mL of deionized water to obtain aqueous solution C. Aqueous solutions A, B, and C were simultaneously added dropwise to a beaker containing 200 mL of deionized water, while maintaining heating at 60 °C and stirring at 700 rpm. The dropwise flow rate of solutions A and C was controlled at 3 mL / min. The pH of the liquid in the beaker was maintained within the alkaline range by adjusting the dropwise flow rate of solution B. The obtained precipitate was aged for 12 hours, washed with deionized water, filtered six times, and dried at 100°C for 12 hours. The dried product was then placed in a muffle furnace and calcined at 500°C with air for 4 hours to obtain a silica-modified copper-zinc-aluminum catalyst CuZnAlSi0.1. The molar percentages of copper, zinc, aluminum, and silicon in this catalyst were 50%, 25%, 15%, and 10%, respectively.

[0050] (1.2) The CuZnAlSi0.15 catalyst was synthesized by co-precipitation. 11.38 g (0.047 mol) copper nitrate trihydrate, 7.01 g (0.024 mol) zinc nitrate hexahydrate, and 5.31 g (0.014 mol) aluminum nitrate nonahydrate were dissolved in 200 mL of deionized water to obtain aqueous solution A. 15.90 g (0.15 mol) sodium carbonate was dissolved in 200 mL of deionized water to obtain aqueous solution B. 1.83 g (0.015 mol) sodium silicate was dissolved in 200 mL of deionized water to obtain aqueous solution C. Aqueous solutions A, B, and C were simultaneously added dropwise to a beaker containing 200 mL of deionized water, while maintaining heating at 60 °C and stirring at 700 rpm. The dropwise flow rate of solutions A and C was controlled at 3 mL / min. The pH of the liquid in the beaker was maintained within the alkaline range by adjusting the dropwise flow rate of solution B. The obtained precipitate was aged for 12 hours, washed with deionized water, filtered six times, and dried at 100°C for 12 hours. The dried product was then placed in a muffle furnace and calcined at 500°C with air for 4 hours to obtain a silica-modified copper-zinc-aluminum catalyst CuZnAlSi0.15. The molar percentages of copper, zinc, aluminum, and silicon in this catalyst were 47%, 24%, 14%, and 15%, respectively.

[0051] (1.3) The CuZnAlSi0.2 catalyst was synthesized by co-precipitation. 10.71 g (0.044 mol) copper nitrate trihydrate, 6.60 g (0.022 mol) zinc nitrate hexahydrate, and 5.00 g (0.013 mol) aluminum nitrate nonahydrate were dissolved in 200 mL of deionized water to obtain aqueous solution A. 15.90 g (0.15 mol) sodium carbonate was dissolved in 200 mL of deionized water to obtain aqueous solution B. 2.44 g (0.020 mol) sodium silicate was dissolved in 200 mL of deionized water to obtain aqueous solution C. Aqueous solutions A, B, and C were simultaneously added dropwise to a beaker containing 200 mL of deionized water, while maintaining heating at 60 °C and stirring at 700 rpm. The dropwise flow rate of solutions A and C was controlled at 3 mL / min. The pH of the liquid in the beaker was maintained within the alkaline range by adjusting the dropwise flow rate of solution B. The obtained precipitate was aged for 12 hours, washed with deionized water, filtered six times, and dried at 100°C for 12 hours. The dried product was placed in a muffle furnace and calcined at 500°C with air for 4 hours to obtain a silica-modified copper-zinc-aluminum catalyst CuZnAlSi0.2. The molar percentages of copper, zinc, aluminum, and silicon in this catalyst were 44.4%, 22.2%, 13.2%, and 20.2%, respectively.

[0052] (1.4) The CuZnAlSi0.25 catalyst was synthesized by co-precipitation. 10.04 g (0.042 mol) copper nitrate trihydrate, 6.19 g (0.021 mol) zinc nitrate hexahydrate, and 4.69 g (0.013 mol) aluminum nitrate nonahydrate were dissolved in 200 mL of deionized water to obtain aqueous solution A. 15.90 g (0.15 mol) sodium carbonate was dissolved in 200 mL of deionized water to obtain aqueous solution B. 3.05 g (0.025 mol) sodium silicate was dissolved in 200 mL of deionized water to obtain aqueous solution C. Aqueous solutions A, B, and C were simultaneously added dropwise to a beaker containing 200 mL of deionized water, while maintaining heating at 60 °C and stirring at 700 rpm. The dropwise flow rate of solutions A and C was controlled at 3 mL / min. The pH of the liquid in the beaker was maintained within the alkaline range by adjusting the dropwise flow rate of solution B. The obtained precipitate was aged for 12 hours, washed with deionized water, filtered six times, and dried at 100°C for 12 hours. The dried product was placed in a muffle furnace and calcined at 500°C with air for 4 hours to obtain a silica-modified copper-zinc-aluminum catalyst CuZnAlSi0.25. The molar percentages of copper, zinc, aluminum, and silicon in this catalyst were 41.6%, 20.8%, 12.8%, and 24.8%, respectively.

[0053] (1.5) The CuZnAlSi0.3 catalyst was synthesized by co-precipitation. 9.37 g (0.039 mol) copper nitrate trihydrate, 5.78 g (0.019 mol) zinc nitrate hexahydrate, and 4.38 g (0.012 mol) aluminum nitrate nonahydrate were dissolved in 200 mL of deionized water to obtain aqueous solution A. 15.90 g (0.15 mol) sodium carbonate was dissolved in 200 mL of deionized water to obtain aqueous solution B. 1.22 g (0.010 mol) sodium silicate was dissolved in 200 mL of deionized water to obtain aqueous solution C. Aqueous solutions A, B, and C were simultaneously added dropwise to a beaker containing 200 mL of deionized water, while maintaining heating at 60 °C and stirring at 700 rpm. The dropwise flow rate of solutions A and C was controlled at 3 mL / min. The pH of the liquid in the beaker was maintained within the alkaline range by adjusting the dropwise flow rate of solution B. The obtained precipitate was aged for 12 hours, washed with deionized water, filtered six times, and dried at 100°C for 12 hours. The dried product was then placed in a muffle furnace and calcined at 500°C with air for 4 hours to obtain a silica-modified copper-zinc-aluminum catalyst CuZnAlSi0.3. The molar percentages of copper, zinc, aluminum, and silicon in this catalyst were 39%, 19%, 12%, and 30%, respectively.

[0054] The catalytic performance of the carbon dioxide hydrogenation reaction was tested in a fixed-bed reactor, and the test procedures are as follows:

[0055] (1) The activity of the previously prepared CuZnAl-1 catalyst and five silica-modified CuZnAl catalysts (CuZnAlSi) in the production of methanol by CO2 hydrogenation was evaluated. First, 0.5 g of catalyst particles (20-40 mesh) and 2.0 g of inert quartz sand (20-40 mesh) were physically shaken and mixed, and then poured into a stainless steel reactor for filling. The two ends were filled with quartz wool to maintain the bed height, and a fixed bed reactor was assembled.

[0056] (2) Using a space velocity of 3000 mL / (g) cat A hydrogen-nitrogen mixture with a hydrogen concentration of 99 mol% was used to reduce the catalyst at 210 °C for 6 h.

[0057] (3) A reaction gas with a hydrogen / carbon dioxide / argon (H2 / CO2 / Ar) molar ratio of 72.0 / 24.0 / 4.0 was introduced into a high-pressure fixed-bed reactor. The catalyst bed temperature was controlled at 240℃, the reaction pressure at 3.0 MPa, and the volumetric hourly space velocity of the feed gas was in the range of 6000 mL / (g). cat •h). The experimental results are shown in Table 2.

[0058] Table 2:

[0059]

[0060] 3MPa, 240℃, SV=6000mL / (g cat ·h), H2 / CO2 / Ar=72 / 24 / 4, running time is 40h.

[0061] The above experimental results show that when the amount of silica introduced into the CuZnAlSi catalyst is 20 mol%, the catalyst has the best performance, that is, the CO2 conversion rate on the CuZnAlSi0.2 catalyst is 14.5%, the methanol selectivity is 85.1%, and the methanol yield is 12.3%.

[0062] Example 3: Application of silica-modified copper-zinc-aluminum catalysts prepared from different silicon sources in carbon dioxide hydrogenation.

[0063] (1) Synthesis of silica-modified copper-zinc-aluminum catalysts prepared using different silicon sources:

[0064] (1.1) The CuZnAlSi0.2-1 catalyst was synthesized by co-precipitation. 10.71 g (0.044 mol) copper nitrate trihydrate, 6.60 g (0.022 mol) zinc nitrate hexahydrate, and 5.00 g (0.013 mol) aluminum nitrate nonahydrate were dissolved in 200 mL of deionized water to obtain aqueous solution A. 15.90 g (0.15 mol) sodium carbonate was dissolved in 200 mL of deionized water to obtain aqueous solution B. 2.44 g (0.020 mol) sodium silicate was dissolved in 200 mL of deionized water to obtain aqueous solution C. Aqueous solutions A, B, and C were simultaneously added dropwise to a beaker containing 200 mL of deionized water, while maintaining heating at 60 °C and stirring at 700 rpm. The dropwise flow rate of solutions A and C was controlled at 3 mL / min. The pH of the liquid in the beaker was maintained within the alkaline range by adjusting the dropwise flow rate of solution B. The obtained precipitate was aged for 12 hours, washed with deionized water, filtered six times, and dried at 100°C for 12 hours. The dried product was placed in a muffle furnace and calcined at 500°C with air for 4 hours to obtain a silica-modified copper-zinc-aluminum catalyst CuZnAlSi0.2. The molar percentages of copper, zinc, aluminum, and silicon in this catalyst were 44.4%, 22.2%, 13.2%, and 20.2%, respectively.

[0065] (1.2) The CuZnAlSi0.2-2 catalyst was synthesized by co-precipitation. 10.71 g (0.044 mol) copper nitrate trihydrate, 6.60 g (0.022 mol) zinc nitrate hexahydrate, and 5.00 g (0.013 mol) aluminum nitrate nonahydrate were dissolved in 200 mL of deionized water to obtain aqueous solution A. 15.90 g (0.15 mol) sodium carbonate was dissolved in 200 mL of deionized water to obtain aqueous solution B. 4.16 g (0.020 mol) tetraethyl orthosilicate was dissolved in 200 mL of anhydrous ethanol to obtain ethanol solution C. Aqueous solutions A, B, and C were simultaneously added dropwise to a beaker containing 200 mL of deionized water, while maintaining heating at 60 °C and stirring at 700 rpm. The dropwise flow rate of solutions A and C was controlled at 3 mL / min. The pH of the liquid in the beaker was maintained within the alkaline range by adjusting the dropwise flow rate of aqueous solution B. The obtained precipitate was aged for 12 hours, washed with deionized water, filtered six times, and dried at 100°C for 12 hours. The dried product was placed in a muffle furnace and calcined at 500°C with air for 4 hours to obtain a silica-modified copper-zinc-aluminum catalyst CuZnAlSi0.2. The molar percentages of copper, zinc, aluminum, and silicon in this catalyst were 44.4%, 22.2%, 13.2%, and 20.2%, respectively.

[0066] (1.3) The CuZnAlSi0.2-3 catalyst was synthesized by co-precipitation. 10.71 g (0.044 mol) copper nitrate trihydrate, 6.60 g (0.022 mol) zinc nitrate hexahydrate, and 5.00 g (0.013 mol) aluminum nitrate nonahydrate were dissolved in 200 mL of deionized water to obtain aqueous solution A. 15.90 g (0.15 mol) sodium carbonate was dissolved in 200 mL of deionized water to obtain aqueous solution B. 2.96 g (0.020 mol) dimethyldiethoxysilane was dissolved in 200 mL of anhydrous ethanol to obtain ethanol solution C. Aqueous solutions A, B, and C were simultaneously added dropwise to a beaker containing 200 mL of deionized water, while maintaining heating at 60 °C and stirring at 700 rpm. The dropwise flow rate of solutions A and C was controlled at 3 mL / min. The pH of the liquid in the beaker was maintained within the alkaline range by adjusting the dropwise flow rate of aqueous solution B. The obtained precipitate was aged for 12 hours, washed with deionized water, filtered six times, and dried at 100°C for 12 hours. The dried product was placed in a muffle furnace and calcined at 500°C with air for 4 hours to obtain a silica-modified copper-zinc-aluminum catalyst CuZnAlSi0.2. The molar percentages of copper, zinc, aluminum, and silicon in this catalyst were 44.4%, 22.2%, 13.2%, and 20.2%, respectively.

[0067] (1.4) The CuZnAlSi0.2-4 catalyst was synthesized by co-precipitation. 10.71 g (0.044 mol) copper nitrate trihydrate, 6.60 g (0.022 mol) zinc nitrate hexahydrate, and 5.00 g (0.013 mol) aluminum nitrate nonahydrate were dissolved in 200 mL of deionized water to obtain aqueous solution A. 15.90 g (0.15 mol) sodium carbonate was dissolved in 200 mL of deionized water to obtain aqueous solution B. 4.80 g (0.020 mol) phenyltriethoxysilane was dissolved in 200 mL of anhydrous ethanol to obtain ethanol solution C. Aqueous solutions A, B, and C were simultaneously added dropwise to a beaker containing 200 mL of deionized water, while maintaining heating at 60 °C and stirring at 700 rpm. The dropwise flow rate of solutions A and C was controlled at 3 mL / min. The pH of the liquid in the beaker was maintained within the alkaline range by adjusting the dropwise flow rate of aqueous solution B. The obtained precipitate was aged for 12 hours, washed with deionized water, filtered six times, and dried at 100°C for 12 hours. The dried product was placed in a muffle furnace and calcined at 500°C with air for 4 hours to obtain a silica-modified copper-zinc-aluminum catalyst CuZnAlSi0.2. The molar percentages of copper, zinc, aluminum, and silicon in this catalyst were 44.4%, 22.2%, 13.2%, and 20.2%, respectively.

[0068] The carbon dioxide hydrogenation reaction was tested in a fixed-bed reactor. The test procedures for the catalytic reaction performance are as follows:

[0069] (1) The activity of four silica-modified CuZnAl catalysts (CuZnAlSi) prepared previously was evaluated for CO2 hydrogenation to methanol. First, 0.5 g of catalyst particles (20-40 mesh) and 2.0 g of inert quartz sand (20-40 mesh) were physically shaken and mixed, and then poured into a stainless steel reactor for filling. The two ends were filled with quartz wool to maintain the bed height, and a fixed bed reactor was assembled.

[0070] (2) Using a space velocity of 3000 mL / (g) cat A mixture of hydrogen and nitrogen with a hydrogen concentration of 10 mol% was used to reduce the catalyst at 300 °C for 6 h.

[0071] (3) A reaction gas with a hydrogen / carbon dioxide / argon (H2 / CO2 / Ar) molar ratio of 72.0 / 24.0 / 4.0 was introduced into a high-pressure fixed-bed reactor. The catalyst bed temperature was controlled at 240℃, the reaction pressure at 3.0 MPa, and the volumetric hourly space velocity of the feed gas was in the range of 6000 mL / (g). cat •h). The experimental results are shown in Table 3.

[0072] Table 3:

[0073]

[0074]

[0075] 3MPa, 240℃, SV=6000mL / (g cat ·h), H2 / CO2 / Ar=72 / 24 / 4, running time is 40h.

[0076] The experimental results of Example 3 show that the CuZnAlSi0.2 catalyst synthesized using Na2SiO3 as the silicon source has the best performance, achieving a CO2 conversion rate of 14.5%, a methanol selectivity of 85.1%, and a methanol yield of 12.3%. This is because organosilicon has strong nonpolarity and cannot be uniformly dispersed in aqueous solution, resulting in uneven distribution of Cu particles and silica support on the CuZnAlSi0.2 catalyst.

[0077] Example 4: Tests at different reaction temperatures.

[0078] The CuZnAlSi0.2 catalyst was the same as in Example 2. The carbon dioxide hydrogenation reaction was tested in a fixed-bed reactor, and the test procedures for the catalytic reaction performance are as follows:

[0079] 0.5 g of CuZnAlSi0.2 (20-40 mesh) and 2.0 g of quartz sand (20-40 mesh) were physically mixed and packed into a stainless steel reaction tube. Both ends were plugged with quartz wool to maintain the bed height, thus assembling a fixed-bed reactor. The catalyst reduction conditions were the same as in Example 1, with the reaction gas ratios of hydrogen / carbon dioxide / argon (H2 / CO2 / Ar) being 72.0 / 24.0 / 4.0. The catalyst bed temperature was controlled at 200℃, 220℃, 240℃, 260℃, 280℃, and 300℃, the reaction pressure at 3.0 MPa, and the feed gas volume hourly space velocity (VHSV) in the range of 6000 mL / (g) cat The experimental results are shown in Table 4.

[0080] Table 4:

[0081]

[0082] 3MPa, SV=6000mL / (g) cat ·h), H2 / CO2 / Ar=72 / 24 / 4, running time is 40h.

[0083] The experimental results above show that increasing the reaction temperature can improve the CO2 conversion rate of the CuZnAlSi0.2 catalyst, but it also leads to a decrease in methanol selectivity. For example, at a reaction temperature of 200℃, the CO2 conversion rate is only 6.6%, but the methanol selectivity is as high as 94.2%; when the reaction temperature rises to 300℃, although the CO2 conversion rate also increases to 21.0%, the methanol selectivity drops to 42.8%. Overall, the catalyst exhibits optimal performance at a reaction temperature of 240℃, achieving a CO2 conversion rate of 14.5% and a methanol selectivity of 85.1%, with a methanol yield of 12.3%.

[0084] Example 5: Tests under different reaction pressures.

[0085] The CuZnAlSi0.2 catalyst was the same as in Example 2. The carbon dioxide hydrogenation reaction was tested in a fixed-bed reactor, and the test procedures for the catalytic reaction performance are as follows:

[0086] 0.5 g of CuZnAlSi0.2 (20-40 mesh) and 2.0 g of quartz sand (20-40 mesh) were physically mixed and packed into a stainless steel reaction tube. Both ends were plugged with quartz wool to maintain the bed height, thus assembling a fixed-bed reactor. The catalyst reduction conditions were the same as in Example 1, with the reaction gas ratios of hydrogen / carbon dioxide / argon (H2 / CO2 / Ar) being 72.0 / 24.0 / 4.0. The catalyst bed temperature was controlled at 240℃, and the reaction pressures were 1 MPa, 2 MPa, 3 MPa, 5 MPa, 7 MPa, and 9 MPa. The feed gas volume hourly space velocity ranged from 6000 mL / (g) cat The experimental results are shown in Table 5.

[0087] Table 5:

[0088]

[0089] 240℃, SV=6000mL / (g) cat ·h), H2 / CO2 / Ar=72 / 24 / 4, running time is 40h.

[0090] The experimental results above show that increasing the reaction pressure can simultaneously improve the CO2 conversion and methanol selectivity of the CuZnAlSi0.2 catalyst. When the reaction pressure is 9 MPa, the CO2 conversion and methanol selectivity reach as high as 18.2% and 92.5%, respectively, and the methanol yield reaches 16.8%.

[0091] Example 6: Tests at different reaction flow rates.

[0092] The CuZnAlSi0.2 catalyst was the same as in Example 2. The carbon dioxide hydrogenation reaction was tested in a fixed-bed reactor, and the test procedures for the catalytic reaction performance are as follows:

[0093] 0.5 g of CuZnAlSi0.2 (20-40 mesh) and 2.0 g of quartz sand (20-40 mesh) were physically mixed and packed into a stainless steel reaction tube. Both ends were plugged with quartz wool to maintain the bed height, thus assembling a fixed-bed reactor. The catalyst reduction conditions were the same as in Example 1, with the reaction gas ratios of hydrogen / carbon dioxide / argon (H2 / CO2 / Ar) being 72.0 / 24.0 / 4.0. The catalyst bed temperature was controlled at 240°C, the reaction pressure at 3 MPa, and the feed gas volume hourly space velocity (VHSV) range at 500 mL / (g). cat ·h), 1000mL / (g cat ·h), 3000mL / (g cat ·h), 6000mL / (g cat ·h), 10000mL / (g cat ·h), 50000mL / (g cat The experimental results are shown in Table 6.

[0094] Table 6:

[0095]

[0096]

[0097] 3MPa, 240℃, H2 / CO2 / Ar=72 / 24 / 4, running time is 40h.

[0098] The experimental results above show that increasing the space velocity can improve the methanol selectivity of the CuZnAlSi0.2 catalyst, but it also leads to a decrease in CO2 conversion. For example, when the space velocity is 500 mL / (g) cat At a space velocity (h), the CO2 conversion rate reached 16.4%, and the methanol selectivity was 79.8%; at a space velocity (H), the CO2 conversion rate reached 16.4%, and the methanol selectivity was 79.8%. cat At h), although the CO2 conversion rate decreased to 13.2%, the methanol selectivity increased to 87.7%. Further increasing the space velocity to 50000 mL / (g) cat With a CO2 conversion rate of 7.2% and a methanol selectivity of 92.2%, combined with the actual methanol yield, the space velocity (SHV) is 3000–10000 mL / (g·h). cat ·h) is the appropriate reaction space velocity.

[0099] Example 7: Tests under different H2 / CO2 conditions.

[0100] The CuZnAlSi0.2 catalyst was the same as in Example 2. The carbon dioxide hydrogenation reaction was tested in a fixed-bed reactor, and the test procedures for the catalytic reaction performance are as follows:

[0101] 0.5 g of CuZnAlSi0.2 (20-40 mesh) and 2.0 g of quartz sand (20-40 mesh) were physically mixed and packed into a stainless steel reaction tube. Both ends were plugged with quartz wool to maintain the bed height, thus assembling a fixed-bed reactor. The catalyst reduction conditions were the same as in Example 1, with the following reaction conditions: a certain proportion of hydrogen / carbon dioxide / argon (H2 / CO2 / Ar) reaction gas was introduced, making H2 / CO2 = 1, 2, 3, 5, 10; the catalyst bed temperature was controlled at 240℃; the reaction pressure was 3 MPa; and the volume hourly space velocity of the feed gas was in the range of 6000 mL / (g). cat The experimental results are shown in Table 7.

[0102] Table 7:

[0103]

[0104] 3MPa, 240℃, SV=6000mL / (g cat The runtime is 40 hours.

[0105] The experimental results above show that increasing the H2 / CO2 ratio can simultaneously improve the CO2 conversion rate of the CuZnAlSi0.2 catalyst, but the methanol selectivity gradually decreases. When the H2 / CO2 ratio is 1, the CO2 conversion rate is 4.1%, and the methanol selectivity is 87.9%; when the H2 / CO2 ratio is 10, the CO2 conversion rate increases to 15.8%, but the methanol selectivity decreases to 69.8%. Therefore, an H2 / CO2 ratio of 3–5 is a suitable gas ratio.

[0106] Example 8: Tests at different CO contents.

[0107] The CuZnAlSi0.2 catalyst was the same as in Example 2. The carbon dioxide hydrogenation reaction was tested in a fixed-bed reactor, and the test procedures for the catalytic reaction performance are as follows:

[0108] 0.5g CuZnAlSi0.2 (20-40 mesh) and 2.0g quartz sand (20-40 mesh) were physically mixed and packed into a stainless steel reaction tube. Both ends were plugged with quartz wool to maintain the bed height, thus assembling a fixed-bed reactor. The catalyst reduction conditions were the same as in Example 1, with the following reaction conditions: a certain proportion of hydrogen / carbon dioxide / argon (H2 / CO2 / Ar) reaction gas was introduced to make H2 / CO2 = 3; and CO was added at molar percentages of 0, 1, 2, 3, 5, and 10% respectively. The catalyst bed temperature was controlled at 240℃, the reaction pressure at 3MPa, and the feed gas volume hourly space velocity (VHSV) ranged from 6000mL / (g) cat The experimental results are shown in Table 8.

[0109] Table 8:

[0110]

[0111] 3MPa, SV=6000mL / (g) cat ·h), H2 / CO2 / Ar=72 / 24 / 4 / x (x is the CO mol content), running time is 40h.

[0112] The experimental results above show that CO introduction reduces the CO2 conversion rate on the catalyst but increases methanol selectivity. As the CO introduction amount increases from 0 to 10 mol%, the CO2 conversion rate of the CuZnAlSi0.2 catalyst decreases from 14.5% to 5.5%, but the methanol selectivity increases from 85.1% to 95.5%. In summary, the CO introduction amount needs to be controlled between 0% and 2%.

[0113] Example 9: Catalyst lifespan test.

[0114] The CuZnAl-1 catalyst is the same as in Example 1, and the CuZnAlSi0.2 catalyst is the same as in Example 2. The carbon dioxide hydrogenation reaction was tested in a fixed-bed reactor, and the test procedures for the catalytic reaction performance are as follows:

[0115] 0.5g CuZnAlSi0.2 (20-40 mesh) and 0.5g CuZnAl-1 catalyst were physically mixed with 2.0g quartz sand (20-40 mesh) and packed into a stainless steel reaction tube. Both ends were plugged with quartz wool to maintain the bed height, and a fixed-bed reactor was assembled. The reduction and reaction conditions of the catalyst were the same as in Example 1. The reaction results are shown in Tables 9 and 10.

[0116] Table 9:

[0117]

[0118]

[0119] CuZnAlSi0.2, 3MPa, 240℃, SV=6000mL / (g cat ·h), H2 / CO2 / Ar=72 / 24 / 4.

[0120] Table 10:

[0121]

[0122] CuZnAl-1, 3MPa, 240℃, space velocity 6000mL / (g) cat ·h), H2 / CO2 / Ar=72 / 24 / 4.

[0123] Figure 1 and Figure 3 The images show the in-situ reduction X-ray photoelectron spectroscopy (XPS) and carbon monoxide adsorption infrared spectroscopy of the CuZnAl-1 catalyst, respectively. Figure 2 and Figure 4 The images show in-situ reduction X-ray photoelectron spectroscopy (XPS) and carbon monoxide adsorption infrared spectroscopy (CIR) of the CuZnAlSi catalyst, respectively. The in-situ XPS and CO adsorption infrared spectra show that the introduction of silica enhances the interaction between metallic copper and the support on the CuZnAl catalyst, inhibits Cu sintering during the reaction, and improves the catalyst's stability. Furthermore, it promotes Cu adsorption on the catalyst. δ+ Speciation. Due to Cu δ+ Species can stabilize CH3O * An intermediate is introduced to prevent its decomposition into CO. Therefore, the introduction of silica effectively reduces the CO selectivity on copper-based catalysts while improving methanol selectivity.

[0124] Meanwhile, the experimental results (Tables 9 and 10) show that the CuZnAlSi0.2 catalyst maintained a stable CO2 conversion rate of ~14.4% and a methanol selectivity of ~85.0% during the 2000-hour lifetime test. However, the CuZnAl-1 catalyst exhibited significant deactivation during the 2000-hour lifetime test, with the CO2 conversion rate decreasing from 23.5% to 12.1% and the methanol selectivity decreasing from 54.4% to 46.5%. Therefore, the introduction of silica can improve the stability of the CuZnAl catalyst.

[0125] Comparative Example 1:

[0126] (1) Comparative sample of copper-zinc-aluminum catalyst for synthesis

[0127] A CuZnAl-1 catalyst was synthesized via coprecipitation. 12.05 g (0.050 mol) copper nitrate trihydrate, 10.40 g (0.035 mol) zinc nitrate hexahydrate, and 5.63 g (0.015 mol) aluminum nitrate nonahydrate were dissolved in 200 mL of deionized water to obtain aqueous solution A. 15.90 g (0.15 mol) sodium carbonate was dissolved in 200 mL of deionized water to obtain aqueous solution B. Aqueous solutions A and B were simultaneously added dropwise to a beaker containing 200 mL of deionized water, while maintaining heating at 60 °C and stirring at 700 rpm. The dropwise flow rate of solution A was controlled at 3 mL / min, and the dropwise flow rate of solution B was adjusted while maintaining the pH of the liquid in the beaker within the alkaline range. After aging the resulting precipitate for 12 h, it was washed with deionized water, filtered six times, and dried at 100 °C for 12 h. The dried product was placed in a muffle furnace and calcined at 500°C with air for 4 hours to obtain the copper-zinc-aluminum catalyst CuZnAl-1. The molar percentages of copper, zinc, and aluminum in this catalyst were 50%, 35%, and 15%, respectively.

[0128] (1.2) The CuZnAl₂ catalyst was synthesized by co-precipitation. 15.00 g (0.060 mol) copper sulfate pentahydrate, 8.91 g (0.030 mol) zinc nitrate hexahydrate, and 1.51 g (0.010 mol) aluminum chloride hexahydrate were dissolved in 200 mL of deionized water to obtain aqueous solution A. 15.90 g (0.15 mol) sodium carbonate was dissolved in 200 mL of deionized water to obtain aqueous solution B. Aqueous solutions A and B were simultaneously added dropwise to a beaker containing 200 mL of deionized water, while maintaining heating at 60 °C and stirring at 700 rpm. The dropwise flow rate of solution A was controlled at 3 mL / min, and the dropwise flow rate of solution B was adjusted while maintaining the pH of the liquid in the beaker within the alkaline range. After aging the resulting precipitate for 12 h, it was washed with deionized water, filtered six times, and dried at 100 °C for 12 h. The dried product was placed in a muffle furnace and calcined at 500°C with air for 4 hours to obtain the copper-zinc-aluminum catalyst CuZnAl-2. The molar percentages of copper, zinc, and aluminum in this catalyst were 60%, 30%, and 10%, respectively.

[0129] (1.3) The CuZnAl-3 catalyst was synthesized by co-precipitation. 10.00 g (0.040 mol) copper sulfate pentahydrate, 2.97 g (0.010 mol) zinc nitrate hexahydrate, and 18.75 g (0.050 mol) aluminum nitrate nonahydrate were dissolved in 200 mL of deionized water to obtain aqueous solution A. 15.90 g (0.15 mol) sodium carbonate was dissolved in 200 mL of deionized water to obtain aqueous solution B. Aqueous solutions A and B were simultaneously added dropwise to a beaker containing 200 mL of deionized water, while maintaining heating at 60 °C and stirring at 700 rpm. The dropwise flow rate of solution A was controlled at 3 mL / min, and the dropwise flow rate of solution B was adjusted while maintaining the pH of the liquid in the beaker within the alkaline range. After aging the resulting precipitate for 12 h, it was washed with deionized water, filtered six times, and dried at 100 °C for 12 h. The dried product was placed in a muffle furnace and calcined at 500°C with air for 4 hours to obtain the copper-zinc-aluminum catalyst CuZnAl-3. The molar percentages of copper, zinc, and aluminum in this catalyst were 40%, 10%, and 50%, respectively.

[0130] (1.4) The CuZnAl-4 catalyst was synthesized by co-precipitation. 4.82 g (0.020 mol) copper nitrate trihydrate, 14.85 g (0.050 mol) zinc nitrate hexahydrate, and 11.25 g (0.030 mol) aluminum nitrate nonahydrate were dissolved in 200 mL of deionized water to obtain aqueous solution A. 15.90 g (0.15 mol) sodium carbonate was dissolved in 200 mL of deionized water to obtain aqueous solution B. Aqueous solutions A and B were simultaneously added dropwise to a beaker containing 200 mL of deionized water, while maintaining heating at 60 °C and stirring at 700 rpm. The dropwise flow rate of solution A was controlled at 3 mL / min, and the dropwise flow rate of solution B was adjusted while maintaining the pH of the liquid in the beaker within the alkaline range. After aging the resulting precipitate for 12 h, it was washed with deionized water, filtered six times, and dried at 100 °C for 12 h. The dried product was placed in a muffle furnace and calcined at 500°C with air for 4 hours to obtain the copper-zinc-aluminum catalyst CuZnAl-4. The molar percentages of copper, zinc, and aluminum in this catalyst were 20%, 50%, and 30%, respectively.

[0131] The synthesis steps of the copper-zinc-aluminum catalyst are the same as in Example 1. The carbon dioxide hydrogenation reaction was tested in a fixed-bed reactor, and the test steps for the catalytic reaction performance are as follows:

[0132] The four CuZnAl catalysts (20-40 mesh) synthesized above were packed into a stainless steel reaction tube, and both ends were plugged with quartz wool to maintain the bed height, thus assembling a fixed-bed reactor; the reduction and reaction conditions of the catalysts were the same as in Example 1, and the reaction results are shown in Table 11.

[0133] Table 11:

[0134]

[0135] 3MPa, 240℃, SV=6000mL / (gcath), H2 / CO2 / Ar=72 / 24 / 4, TOS=40h.

[0136] Comparative Example 2:

[0137] The synthesis steps of the CuZnAl-1 catalyst are the same as in Example 1. 2.5g of CuZnAl-1 powder is physically mixed with 0.5g of silica powder, or 2.5g of CuZnAl-1 powder is mixed with 0.5g of fine silica powder, and this mixture is named CuZnAl-1-silica or CuZnAl-1-fine silica.

[0138] The carbon dioxide hydrogenation reaction was tested in a fixed-bed reactor. The test procedures for the catalytic reaction performance are as follows:

[0139] (1) 0.5g CuZnAl-1, or 0.6g CuZnAl-1-silica (20-40 mesh) or 0.6g CuZnAl-1-fine silica gel and 2.0g quartz sand (20-40 mesh) were physically mixed and filled into a stainless steel reaction tube. Both ends were filled with quartz wool to maintain the bed height, and a fixed bed reactor was assembled. The reduction conditions and reaction conditions of the catalyst were the same as in Example 1, and the reaction results are shown in Table 12.

[0140] Table 12:

[0141]

[0142] 3MPa, 240℃, SV=6000mL / (g cat ·h), H2 / CO2 / Ar=72 / 24 / 4, TOS=40h.

[0143] The experimental results from the above examples and comparative examples show that the physical introduction of silica (i.e., physical mixing of silica with CuZnAl catalyst) does not change the performance of CuZnAl catalyst. However, the chemical introduction of silica (i.e., introducing silica during the synthesis of CuZnAl catalyst) can effectively improve the stability, methanol selectivity, and methanol yield of CuZnAl catalyst. This will greatly benefit the industrial application of traditional copper-zinc-aluminum catalysts.

[0144] Finally, it should be noted that the above examples are merely specific embodiments of the present invention. Obviously, the present invention is not limited to the above embodiments and many variations are possible. All variations that can be directly derived or conceived by those skilled in the art from the disclosure of this invention should be considered within the scope of protection of this invention.

Claims

1. A method for preparing a silica-modified copper-zinc-aluminum catalyst, characterized in that, Includes the following specific content: Take copper salt, zinc salt, and aluminum salt, and dissolve them together in deionized water to obtain solution A; take sodium carbonate, and dissolve it in deionized water to obtain solution B; take silicon salt or organosilicon, and dissolve it in deionized water or anhydrous ethanol to obtain solution C; under stirring conditions at 20~80℃, add solutions A, B, and C dropwise into a beaker containing deionized water, and maintain the pH of the reaction solution in the alkaline range by adjusting the dropping rate of solution B. The precipitate obtained from the reaction was aged for 2-24 hours, washed with deionized water, filtered, dried, and calcined to obtain a copper-zinc-aluminum-silicon catalyst. The molar percentages of copper, zinc, aluminum, and silicon in this copper-zinc-aluminum-silicon catalyst were 50%, 30%, 10%, and 10%, respectively. The silicon salt or organosilicon is one or more of tetraethyl orthosilicate, dimethyldiethoxysilane, and phenyltriethoxysilane.

2. The method for preparing a silica-modified copper-zinc-aluminum catalyst according to claim 1, characterized in that, The copper salt, zinc salt, and aluminum salt are one or more of the nitrate, sulfate, and chloride salts corresponding to copper, zinc, and aluminum elements, respectively.

3. The method for preparing a silica-modified copper-zinc-aluminum catalyst according to claim 1, characterized in that, The stirring speed is 200~2000 rpm, the drop rate of solution A and solution C is 1~20 mL / min, the drying temperature is controlled at 60~180℃ and the time is 4~48h; the calcination is carried out in a muffle furnace with air introduced, the temperature is controlled at 300~700℃ and the time is 2~12h.

4. A method for using a silica-modified copper-zinc-aluminum catalyst, characterized in that, The silica-modified copper-zinc-aluminum catalyst is prepared by the method described in any one of claims 1-3, specifically including: A silica-modified copper-zinc-aluminum catalyst was loaded into a fixed-bed reactor. After reduction by a mixture of hydrogen and nitrogen at a concentration of 5–99 mol% at 210–400 °C, the catalyst was further subjected to reaction at a temperature of 200–300 °C, a pressure of 1–9 MPa, and a space velocity of 500–50000 mL / (g). cat Under the conditions of h), a reaction gas is introduced to achieve catalytic hydrogenation to methanol; the molar ratio of H2 to CO2 in the reaction gas is (1~10):

1.

5. The method of using a silica-modified copper-zinc-aluminum catalyst according to claim 4, characterized in that, If additional CO needs to be added to the reaction gas, the molar percentage of CO compared to the reaction gas should be 0-10%.

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