Method for improving the performance of a Cu / ZnO catalyst for carbon dioxide hydrogenation to methanol by using SiC
Cu-based catalysts with ZnO-SiC composite supports were prepared by co-precipitation, which solved the problem of insufficient performance of existing Cu-based catalysts in the process of CO2 hydrogenation to methanol, and realized the potential for efficient catalyst preparation and industrial application.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- BEIJING UNIV OF CHEM TECH
- Filing Date
- 2024-05-24
- Publication Date
- 2026-06-02
AI Technical Summary
Existing Cu-based catalysts exhibit low CO2 conversion, methanol selectivity, and methanol yield in the CO2 hydrogenation to methanol process. The lack of highly efficient catalysts limits the industrial application of CO2 hydrogenation to methanol technology.
A Cu-based catalyst with ZnO and SiC as a composite support was prepared by co-precipitation method. By adjusting the mass ratio of ZnO and SiC and the copper content, a copper-based catalyst was constructed to improve the catalytic activity.
It significantly improves the catalytic performance of CO2 hydrogenation to methanol. The catalyst preparation method is simple and low-cost, suitable for large-scale industrial production, and the catalytic activity and methanol yield are significantly improved.
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Abstract
Description
Technical Field
[0001] This invention belongs to the field of catalyst preparation technology, and relates to a method for improving the performance of Cu / ZnO catalysts in the hydrogenation of carbon dioxide (CO2) to methanol using SiC. Background Technology
[0002] Using "green hydrogen" obtained from renewable energy and CO2 emitted from industry as raw materials to produce high-value-added methanol through hydrogenation is a strategy that can both reduce greenhouse gas emissions and obtain clean energy, and has broad application prospects.
[0003] CO2 hydrogenation to methanol technology has not yet been industrialized, and one of the key bottlenecks is the lack of efficient catalysts. Currently, copper-based catalysts are the most widely studied for methanol synthesis, but their CO2 conversion, methanol selectivity, and methanol yield still need improvement. How to regulate the interface to enhance methanol synthesis performance is a current research hotspot. Studies have shown that by constructing composite supports, CO2 adsorption capacity can be enhanced on the basis of a single support, promoting the dispersion of Cu active metal, thereby improving the CO2 conversion, methanol selectivity, and methanol yield of the methanol synthesis reaction (see *Effect of TiO2, ZrO2, and TiO2-ZrO2 on the performance of CuO-ZnO catalyst for CO2 hydrogenation to methanol*, *Applied Surface Science* 2015, Vol. 338, 146–153). Furthermore, our research group discovered that using Al2O3-coated SiC as a composite support can yield Ni-based catalysts with significantly improved CO2 hydrogenation to methane performance (see An Al2O3-Coated SiC-Supported Ni Catalyst with Enhanced Activity and Improved Stability for Production of Synthetic Natural Gas, industrial & engineering chemistry research. 2018, Vol. 57, 14899-14909). Building upon this approach, we attempted to construct copper-based catalysts using SiC and metal oxides as composite supports, and by modulating the interfacial structure, thereby improving the CO2 hydrogenation to methanol performance of Cu-based catalysts.
[0004] In this invention, we prepared composite supports with different mass ratios of zinc oxide (ZnO) and silicon carbide (SiC) using a simple co-precipitation method, constructing a novel and highly efficient copper-based catalyst for CO2 hydrogenation to methanol. The preparation method employed in this invention is simple, low-cost, and suitable for large-scale industrial production, and is expected to be widely applied in the future. Furthermore, no copper-based catalysts using ZnO and SiC as composite supports have been reported in the field of CO2 hydrogenation to methanol. Summary of the Invention
[0005] The purpose of this invention is to provide a method for improving the performance of Cu / ZnO catalysts in CO2 hydrogenation to methanol using SiC. Compared with Cu / ZnO catalysts prepared by similar methods, the methanol synthesis performance of Cu / ZnO-SiC is significantly improved under the same reaction conditions, showing excellent prospects for industrial application.
[0006] To achieve the above design goals, the specific technical solutions are as follows.
[0007] This invention provides a method for improving the performance of Cu / ZnO catalysts in CO2 hydrogenation to methanol using SiC, characterized by the construction of a copper-based catalyst with ZnO and SiC as a composite support.
[0008] The catalyst of this invention was prepared by a simple co-precipitation method, mainly comprising an active component and a support; the active component is metallic copper, and the support comprises ZnO and SiC; the catalyst was prepared by a one-step co-precipitation method.
[0009] The mass ratio of ZnO to SiC is (0.1-1):(0-0.9), SiC is not 0, and the sum of ZnO and SiC is 1. The mass percentage of metallic copper is 10-70%.
[0010] Further preferred ZnO to SiC mass ratio is (0.5-0.7):(0.3-0.5), and the mass percentage of metallic copper is 20-30%.
[0011] The steps of the coprecipitation method are as follows:
[0012] (1) Preparation of precursor mixture: Weigh a certain amount of copper salt, zinc salt and SiC powder, add them to deionized water one after another, stir for 0.5-2.5h to obtain precursor mixture containing active components and carrier.
[0013] (2) Adjust the pH of the mixture: Under vigorous stirring, heat the precursor mixture in step (1) to 30-90℃ in a water bath; after the temperature of the mixture reaches the target temperature, add a certain concentration of sodium carbonate solution dropwise to the mixture until the pH of the mixture is 5-9; then keep the temperature of the mixture at 30-90℃ and the pH at 5-9, and stir vigorously for 1-5 hours.
[0014] (3) Drying the sample: After step (2) is completed, stop heating and stirring, and age for 1-3 hours; then filter the catalyst precursor mixture, wash it with water 5-6 times, and vacuum dry it at 90-150℃ for 6-24 hours to obtain the dried sample.
[0015] (4) Calcination of the sample: The dried sample is placed in a muffle furnace and heated at 3-10℃ / min for 2-10h at 300-900℃ to obtain the catalyst sample.
[0016] (5) Activation of the sample: Before the reaction, the catalyst sample is activated by hydrogen reduction.
[0017] In the above-mentioned method for preparing a highly active Cu / ZnO-SiC catalyst for the hydrogenation of CO2 to methanol via co-precipitation, the sodium carbonate solution described in step (2) is preferably 0-0.2 mol / L. -1 ;
[0018] The copper salt is copper nitrate, copper chloride, copper acetate, etc., and the zinc salt is zinc nitrate, etc., dissolved in deionized water. Preferably, the mass percentage concentration of ZnO is 0-72%. SiC is mixed with the salt solution, preferably with a mass percentage concentration of SiC of 0-72%.
[0019] In step (2) above, the pH is 5-9, preferably pH 7.
[0020] Step (5) involves reducing the CO2 to methanol reaction with hydrogen before proceeding with the CO2 hydrogenation to methanol reaction.
[0021] The catalyst was prepared using a simple co-precipitation method. The prepared copper catalyst support was a composite of ZnO and SiC, with uniform particle size, copper particle size of 5-30 nm, and specific surface area of 10-100 m². 2 / g. Following the above method, adjust the mass ratio of ZnO and SiC, and the pH of the mixed solution. Prepare a highly active Cu / ZnO-SiC catalyst for CO2 hydrogenation to methanol, preferably with a copper mass percentage of 10-70%, more preferably 20-30%.
[0022] The aforementioned composite supported catalyst Cu / ZnO-SiC is used in the CO2 hydrogenation to methanol reaction.
[0023] Based on the above scheme, a high-pressure gas-phase fixed-bed reactor is used, and the reaction steps are as follows:
[0024] (1) The Cu / ZnO-SiC catalyst sample prepared above is mixed with quartz sand in a certain mass ratio and placed in a fixed bed reactor; after heating to the target reduction temperature (200-800℃) under argon atmosphere, the atmosphere is switched to hydrogen atmosphere and reduced for 1-8h.
[0025] (2) After reduction, the temperature is lowered to the reaction temperature (200-300℃); then, a CO2 / H2 reaction gas with a volume ratio of 1 / 3 is introduced, and the pressure is increased to the target pressure (3.0-5.0 MPa) to carry out the methanol synthesis reaction. The mass hourly space velocity (HHSV) of the reaction is 24000 mL / h. -1 g cat -1 .
[0026] The present invention has the following advantages:
[0027] 1. The preparation method of the catalyst of the present invention is simple, suitable for large-scale industrial production, and the raw materials are readily available and the preparation cost is low.
[0028] 2. The Cu / ZnO-SiC catalyst prepared by this invention has the following structural advantages: a) smaller Cu particle size; b) abundant metal-oxide interfaces. Therefore, the catalyst exhibits higher catalytic activity. Attached Figure Description
[0029] Figure 1 These are transmission electron microscopy (TEM, HR-TEM) images of the Cu / ZnO-SiC catalyst synthesized in this invention and a histogram of Cu particle size distribution (Example 1). Detailed Implementation
[0030] The present invention is illustrated by the following examples, but the present invention is not limited to the specific implementations described below.
[0031] Example 1
[0032] 1. Weigh 1.2g of copper nitrate, 1.6g of zinc nitrate, and 0.4g of SiC, and add them to deionized water one after another. After stirring evenly, a precursor mixture is obtained.
[0033] 2. After heating the precursor mixture from step 1 to 70°C in a water bath, prepare a 0.1 mol / L solution. -1 A sodium carbonate solution was added dropwise to the precursor mixture in step 1 until the pH of the mixture reached 7. The mixture was then stirred vigorously for 6 hours at 70°C and pH 7.
[0034] 3. After step 2, stop heating and stirring, and age for 1 hour. The sample obtained in step 2 is filtered and washed with water 5 times, vacuum dried at 110℃ for 24 hours, and finally calcined at 350℃ for 6 hours to obtain the catalyst sample.
[0035] 4. The calcined catalyst sample from step 3 was pressed into tablets of 40-60 mesh. 0.1 g of the pressed sample was mixed with 0.4 g of quartz sand (40-60 mesh) and placed in a quartz tube. After reduction under a hydrogen atmosphere at 300℃ (the resulting catalyst had a ZnO:SiC mass ratio of 0.5:0.5 and a copper mass percentage of 28%), a CO2 / H2 (volume ratio 1:3) mixture was introduced. The methanol synthesis reaction was carried out at a pressure of 3.0 MPa and a reaction temperature of 250℃. The catalyst performance data are shown in Table 1. The CO2 conversion rate was 9.7%, the methanol selectivity was 43.7%, and the methanol space-time yield was 360.0 g. MeOH kg cat -1 h -1 ;
[0036] Example 2
[0037] 1. Weigh 1.2g of copper nitrate, 2.2g of zinc nitrate, and 0.1g of SiC. The rest is the same as step 1 in Example 1.
[0038] 2. Same as step 2 in Example 1.
[0039] 3. Same as step 3 in Example 1.
[0040] 4. Press the calcined catalyst sample from step 3 into tablets of 40-60 mesh. Take 0.1 g of the tableted sample and mix it with 0.4 g of quartz sand (40-60 mesh) in a quartz tube. After reduction under a hydrogen atmosphere at 300℃ (the resulting catalyst has a ZnO:SiC mass ratio of 0.7:0.3 and a copper mass percentage of 28%), introduce a CO2 / H2 (volume ratio 1:3) mixture. Perform a methanol synthesis reaction at a pressure of 3.0 MPa and a reaction temperature of 250℃. The catalyst performance data are shown in Table 1. The CO2 conversion rate is 9.5%, the methanol selectivity is 41.8%, and the methanol space-time yield is 335.3 g. MeOH kg cat -1 h -1 ;
[0041] Example 3
[0042] 1. Weigh 1.2g of copper nitrate, 2.7g of zinc nitrate, and 0.1g of SiC. The rest is the same as step 1 in Example 1.
[0043] 2. Same as step 2 in Example 1.
[0044] 3. Same as step 3 in Example 1.
[0045] 4. The calcined catalyst sample from step 3 was pressed into tablets of 40-60 mesh. 0.1 g of the pressed sample was mixed with 0.4 g of quartz sand (40-60 mesh) and placed in a quartz tube. After reduction under a hydrogen atmosphere at 300℃ (the resulting catalyst had a ZnO:SiC mass ratio of 0.9:0.1 and a copper mass percentage of 28%), a CO2 / H2 (volume ratio 1:3) mixture was introduced. The methanol synthesis reaction was carried out at a pressure of 3.0 MPa and a reaction temperature of 250℃. The catalyst performance data are shown in Table 1. The CO2 conversion rate was 9.3%, the methanol selectivity was 40.9%, and the methanol space-time yield was 327.7 g. MeOH kg cat -1 h -1 ;
[0046] Example 4
[0047] 1. Weigh 1.2g of copper nitrate, 0.3g of zinc nitrate, and 0.7g of SiC. The rest is the same as step 1 in Example 1.
[0048] 2. Same as step 2 in Example 1.
[0049] 3. Same as step 3 in Example 1.
[0050] 4. Press the calcined catalyst sample from step 3 into tablets of 40-60 mesh. Take 0.1 g of the tableted sample and mix it with 0.4 g of quartz sand (40-60 mesh) in a quartz tube. After reduction under a hydrogen atmosphere at 300℃ (the resulting catalyst has a ZnO:SiC mass ratio of 0.1:0.9 and a copper mass percentage of 28%), introduce a CO2 / H2 (volume ratio 1:3) mixture. Conduct a methanol synthesis reaction at a pressure of 3.0 MPa and a reaction temperature of 250℃. The catalyst performance data are shown in Table 1. The CO2 conversion rate is 8.1%, the methanol selectivity is 35.4%, and the methanol space-time yield is 245.6 g. MeOH kg cat -1 h -1 .
[0051] Example 5
[0052] 1. Same as step 1 in Example 1.
[0053] 2. After heating the precursor mixture from step 1 to 70°C in a water bath, prepare a 0.1 mol / L solution. -1A sodium carbonate solution was added dropwise to the precursor mixture in step 1 until the pH of the mixture reached 6. The mixture was then stirred vigorously for 6 hours at 70°C and pH 6.
[0054] 3. Same as step 3 in Example 1.
[0055] 4. The calcined catalyst sample from step 3 was pressed into tablets of 40-60 mesh. 0.1 g of the pressed sample was mixed with 0.4 g of quartz sand (40-60 mesh) and placed in a quartz tube. After reduction under a hydrogen atmosphere at 300℃ (the resulting catalyst had a ZnO:SiC mass ratio of 0.5:0.5 and a copper mass percentage of 28%), a CO2 / H2 (volume ratio 1:3) mixture was introduced. The methanol synthesis reaction was carried out at a pressure of 3.0 MPa and a reaction temperature of 250℃. The catalyst performance data are shown in Table 1. The CO2 conversion rate was 9.6%, the methanol selectivity was 42.1%, and the methanol space-time yield was 346.0 g. MeOH kg cat -1 h -1 ;
[0056] Example 6
[0057] 1. Same as step 1 in Example 1.
[0058] 2. After heating the precursor mixture from step 1 to 70°C in a water bath, prepare a 0.1 mol / L solution. -1 A sodium carbonate solution was added dropwise to the precursor mixture in step 1 until the pH of the mixture reached 8. The mixture was then stirred vigorously for 6 hours at 70°C and pH 8.
[0059] 3. Same as step 3 in Example 1.
[0060] 4. Press the calcined catalyst sample from step 3 into tablets of 40-60 mesh. Take 0.1 g of the tableted sample and mix it with 0.4 g of quartz sand (40-60 mesh) in a quartz tube. After reduction under a hydrogen atmosphere at 300℃ (the resulting catalyst has a ZnO:SiC mass ratio of 0.5:0.5 and a copper mass percentage of 28%), introduce a CO2 / H2 (volume ratio 1:3) mixture. Conduct a methanol synthesis reaction at a pressure of 3.0 MPa and a reaction temperature of 250℃. The catalyst performance data are shown in Table 1. The CO2 conversion rate is 9.3%, the methanol selectivity is 41.7%, and the methanol space-time yield is 338.2 g. MeOH kg cat -1 h -1 ;
[0061] Comparative Example 1
[0062] 1. Weigh out 1.2g of copper nitrate and 3.0g of zinc nitrate, and follow the same procedure as in step 1 of Example 1.
[0063] 2. Same as step 2 in Example 1.
[0064] 3. Same as step 3 in Example 1.
[0065] 4. Press the calcined catalyst sample from step 3 into tablets of 40-60 mesh. Take 0.1 g of the tableted sample and mix it with 0.4 g of quartz sand (40-60 mesh) in a quartz tube. After reduction under a hydrogen atmosphere at 300℃, a CO2 / H2 (volume ratio 1:3) mixture is introduced. The methanol synthesis reaction is carried out at a pressure of 3.0 MPa and a reaction temperature of 250℃. The catalyst performance data are shown in Table 1. The CO2 conversion rate is 6.0%, the methanol selectivity is 34.9%, and the methanol space-time yield is 179.7 g. MeOH kg cat -1 h -1 .
[0066] Comparative Example 2
[0067] 1. Weigh 1.2g of copper nitrate and 0.8g of SiC powder, and follow the same procedure as in step 1 of Example 1.
[0068] 2. Same as step 2 in Example 1.
[0069] 3. Same as step 3 in Example 1.
[0070] 4. Press the calcined catalyst sample from step 3 into tablets of 40-60 mesh. Take 0.1 g of the tableted sample and mix it with 0.4 g of quartz sand (40-60 mesh) in a quartz tube. After reduction under a hydrogen atmosphere at 300℃, a CO2 / H2 (volume ratio 1:3) mixture is introduced. The methanol synthesis reaction is carried out at a pressure of 3.0 MPa and a reaction temperature of 250℃. The catalyst performance data are shown in Table 1. The CO2 conversion rate is 0.8%, the methanol selectivity is 27.8%, and the methanol space-time yield is 19.3 g. MeOH kg cat -1 h -1 .
[0071] Comparative Example 3
[0072] 1. Weigh out a certain mass of commercial Cu / ZnO / Al2O3 catalyst.
[0073] 2. The commercial catalyst sample from step 1 was pressed into tablets of 40-60 mesh. 0.1 g of the pressed sample was mixed with 0.4 g of quartz sand (40-60 mesh) and placed in a quartz tube. After reduction under a hydrogen atmosphere at 300℃, a CO2 / H2 (volume ratio 1:3) mixture was introduced. The methanol synthesis reaction was carried out at a pressure of 3.0 MPa and a reaction temperature of 250℃. The catalyst performance data are shown in Table 1. The CO2 conversion rate was 4.9%, the methanol selectivity was 26.0%, and the methanol space-time yield was 128.0 g. MeOH kg cat -1 h -1 .
[0074] Comparative Example 4
[0075] 1. Weigh 1.2g of copper nitrate, 0.2g of zinc nitrate, and 0.8g of SiC. The rest is the same as step 1 in Example 1.
[0076] 2. Same as step 2 in Example 1.
[0077] 3. Same as step 3 in Example 1.
[0078] 4. Press the calcined catalyst sample from step 3 into tablets of 40-60 mesh. Take 0.1 g of the tableted sample and mix it with 0.4 g of quartz sand (40-60 mesh) in a quartz tube. After reduction under a hydrogen atmosphere at 300℃ (the resulting catalyst has a ZnO:SiC mass ratio of 0.083:0.917 and a copper mass percentage of 28%), introduce a CO2 / H2 (volume ratio 1:3) mixture. Perform a methanol synthesis reaction at a pressure of 3.0 MPa and a reaction temperature of 250℃. The catalyst performance data are shown in Table 1. The CO2 conversion rate is 1.1%, the methanol selectivity is 29.6%, and the methanol space-time yield is 56.6 g. MeOH kg cat -1 h -1 .
[0079] Table 1 Performance Evaluation of CO2 Hydrogenation to Methanol Catalysts
[0080]
[0081] The comparison of catalyst performance data in the table above shows that the methanol synthesis performance of the Cu / ZnO-SiC catalyst with a composite support (Example 1) is significantly improved compared to the single-support Cu / ZnO (Comparative Example 1) and Cu / SiC (Comparative Example 2) catalysts. Specifically, at a reaction temperature of 250°C and a pressure of 3.0 MPa, the methanol space-time yield of the Cu / ZnO-SiC catalyst (Example 1) is 2.0 times and 18.7 times that of the Cu / ZnO and Cu / SiC catalysts, respectively. Furthermore, Comparative Example 4 demonstrates that when the mass ratio of ZnO to SiC is too small (e.g., 0.083:0.917), the methanol synthesis performance decreases significantly. Examples 1, 5, and 6 show that the catalyst exhibits optimal methanol synthesis performance when the pH of the mixed solution is 7. Meanwhile, compared with the commercial Cu / ZnO / Al2O3 (Comparative Example 3) catalyst, this catalyst (Example 1) showed significantly improved CO2 conversion, methanol selectivity and methanol space-time yield, and has promising prospects for industrial application.
Claims
1. An application of SiC-modified Cu / ZnO catalysts, characterized in that, The SiC-modified Cu / ZnO catalyst used in the CO2 hydrogenation to methanol reaction is a copper-based catalyst with ZnO and SiC as a composite support. The active component is dispersed Cu nanoparticles, and the support includes ZnO and SiC. The mass ratio of ZnO to SiC is (0.5-0.7):(0.3-0.5), and the sum of ZnO and SiC is 1. The mass percentage of metallic copper is 20-30%. Copper particles have a size of 5-30 nm and a specific surface area of 10-100 m². 2 / g.
2. The application according to claim 1, characterized in that, The SiC-modified Cu / ZnO catalyst was prepared by a co-precipitation method, and the specific steps are as follows: (1) Preparation of precursor mixture: Weigh a certain mass of copper salt, zinc salt and SiC powder, add them to deionized water one after another, stir for 0.5-2.5 h to obtain precursor mixture containing active components and carrier; (2) Adjust the pH of the mixture: Under vigorous stirring, heat the precursor mixture in step (1) to 30-90℃ in a water bath; After the temperature of the mixture reaches the target temperature, a certain concentration of sodium carbonate solution is added dropwise to the mixture until the pH of the mixture is 5-9; then the temperature of the mixture is maintained at 30-90℃ and the pH is 5-9, and the mixture is stirred vigorously for 1-5 hours. (3) Drying the sample: After step (2) is completed, stop heating and stirring, and age for 1-3 h; then filter the catalyst precursor mixture, wash it with water 5-6 times, and vacuum dry it at 90-150℃ for 6-24 h to obtain the dried sample; (4) Calcination of samples: The dried samples are placed in a muffle furnace and heated at 300-900℃ for 2-10 h at a rate of 3-10℃ / min to obtain catalyst samples; (5) Activation of the sample: Before the reaction, the catalyst sample is activated by hydrogen reduction.
3. The application according to claim 2, characterized in that, The copper salt mentioned in step (1) is selected from copper nitrate, copper chloride, and copper acetate.
4. The application according to claim 2, characterized in that, The sodium carbonate solution mentioned in step (2) has a concentration of 0-0.2 mol / L. -1 And it is not 0.
5. The application according to claim 2, characterized in that, In step (2), the pH is 7.
6. The application according to claim 1, characterized in that, The high-pressure gas-phase fixed-bed reactor is used, and the steps are as follows: (1) The catalyst sample and quartz sand are mixed in a certain mass ratio and placed in a fixed bed reactor; the temperature is raised to the target reduction temperature of 200-800℃ under argon atmosphere, and then switched to hydrogen atmosphere for reduction for 1-8 h to obtain the corresponding Cu / ZnO-SiC. (2) After the reduction is completed, the temperature is lowered to the reaction temperature of 200-300℃; then a CO2 / H2 reaction gas with a volume ratio of 1 / 3 is introduced, and the pressure is increased to the target pressure of 3.0-5.0 MPa to carry out the methanol synthesis reaction; wherein the mass hourly space velocity of the reaction is 24000 mLh. -1 g cat -1 The methanol synthesis reaction is carried out.