Catalyst for preparing ethylene and co-producing ethylene oxide from carbon dioxide and preparation method thereof

Abstract

The invention provides a catalyst for preparing ethylene and co-producing ethylene oxide from carbon dioxide and a preparation method of the catalyst, and belongs to the field of nano-alloy electrocatalyst preparation, carbon dioxide (CO2) is reduced into ethylene (C2H2) by utilizing an electrocatalysis process, and the catalyst has efficient electrocatalysis activity and selectivity, and can be used for preparing ethylene and co-producing ethylene oxide. The energy required by the reaction can be effectively reduced; and the yield of the target product is improved. Low-concentration carbon dioxide is efficiently converted into ethylene and ethylene oxide. The supported Cu-based catalyst is modified by using the Cu-Ag alloy, so that the dispersity and the stability of the catalyst are enhanced, and the selectivity of ethylene is improved. According to the method, CO2 is converted into ethylene and ethylene oxide, the method serves as an important way for resource utilization, remarkable potential is shown, the greenhouse effect can be relieved through reasonable utilization, the problem of resource shortage can be solved, and huge economic value is brought.

Description

Technical Field

[0001] The invention belongs to the technical field of preparation of nano alloy electrocatalysts, and specifically relates to a catalyst for producing ethylene from carbon dioxide and co-producing ethylene oxide and a preparation method thereof. Technical Background

[0002] As one of the main greenhouse gases, the increasing concentration of carbon dioxide (CO2) has had a significant impact on the global climate system, leading to a series of chain reactions such as rising global average temperatures and increasing extreme weather events, which seriously threaten the natural ecological balance and the sustainable development of human society. At the same time, considering CO2 as a potential carbon resource and making effective use of it is an important way to cope with the challenges of climate change and promote green and low-carbon transformation. Its rational use can not only alleviate the greenhouse effect, but also solve the problem of resource shortage and has huge economic value. The conversion of CO2 into ethylene (C2H2) and ethylene oxide (EO) as an important way of resource utilization has shown significant potential. Ethylene (C2H2) is an important basic chemical in the global chemical industry. It is in huge demand and occupies an important position in the chemical industry. It is not only a monomer for the synthesis of a variety of polymer materials (such as polyethylene and polyvinyl chloride), but also a key raw material for the production of a series of organic compounds, such as ethanol, ethylene oxide, acetaldehyde, acetic acid, etc.

[0003] The traditional method of producing ethylene mainly relies on petroleum cracking. Specifically, it can be divided into the following methods:

[0004] Steam cracking: This is the most mainstream method for producing ethylene. It involves cracking light crude oil fractions or natural gas condensate at high temperature (about 750°C to 950°C) and high pressure (usually using superheated steam as a diluent and heat carrier) to produce a mixed gas including ethylene. Ethylene is then purified through cooling, compression, separation and other steps.

[0005] Ethane dehydrogenation: For natural gas resources rich in ethane, ethylene can be produced directly through the ethane dehydrogenation process. This method is relatively cleaner, but it requires a higher purity of the raw materials.

[0006] However, the shortcomings of traditional ethylene production are also obvious:

[0007] 1. Strong dependence on resources: Traditional ethylene production is heavily dependent on oil and natural gas resources, which not only exacerbates the consumption of non-renewable resources, but also makes the ethylene industry vulnerable to fluctuations in oil prices.

[0008] 2. Environmental pollution: The oil cracking process produces a large amount of by-products and greenhouse gas emissions, including carbon dioxide, sulfide and other harmful pollutants, which put pressure on the environment.

[0009] 3. High energy consumption: The high temperature and high pressure cracking process consumes a lot of energy, which increases production costs and is not conducive to the sustainable use of energy.

[0010] 4. Large carbon emissions: The entire chain from raw material mining, transportation to processing has large carbon emissions, which does not meet the global carbon reduction goals.

[0011] Ethylene oxide (EO) is an important petrochemical product with a wide range of applications and significant value. Ethylene oxide is one of the commonly used low-temperature sterilization methods in the sterile industry, and is particularly suitable for medical equipment, medical devices, pharmaceutical packaging materials, etc. that cannot withstand high temperature, wet heat or radiation sterilization. EO is an important raw material for the production of ethylene glycol, which is further used to synthesize polyester fibers (such as polyester) and polyester resins, etc. These materials are widely used in textiles, beverage bottles, packaging materials and other fields. With its unique chemical properties and efficient functions, ethylene oxide has demonstrated huge economic value and social benefits in many fields such as medical and health, chemical production, and materials science, and is one of the indispensable chemicals in modern industry.

[0012] Ethylene oxide is usually produced by ethylene oxidation. Its production process is highly dependent on petroleum, and also faces the problems of limited resources and environmental pollution. In addition, the production process of ethylene oxide releases harmful substances such as acetaldehyde, posing a threat to the health of production personnel and environmental safety. Their preparation and production need to develop new clean, efficient and gentle pathways.

[0013] The traditional route for preparing ethylene requires high temperature and high pressure reaction conditions or relies on fossil raw materials. The traditional method for preparing ethylene is prone to release toxic substances and relies on petroleum. A mature industrial system has been formed in the preparation process of converting carbon dioxide (CO2) into ethylene. To prepare ethylene and ethylene oxide, a complete set of new, efficient and environmentally friendly carbon dioxide conversion and utilization paths can be designed. Since traditional ethylene production is heavily dependent on oil and natural gas resources and the amount of energy is very limited, a large amount of carbon dioxide will be released during its combustion process, causing serious pollution to the environment. Therefore, green and efficient new preparation and conversion methods have become the main research directions. In the present invention, a suitable carrier material (such as silicon carbide with a high specific surface area) is selected, and the dispersibility and stability of the catalyst are improved by a specific surface modification technology. Using innovative loading methods (such as impregnation, coprecipitation, spray drying, etc.), the copper source and the silver source are loaded on the carrier separately or together. Subsequently, the structure and performance of the catalyst are further improved by an optimized heat treatment process.

[0014] However, in the preparation method of traditional electrocatalysts, there are roughly two systems, preparing oxygen reduction (ORR) electrocatalysts through pure water phase system or oil phase system. This method is relatively cumbersome, the reaction is carried out in multiple steps, impurities are easily introduced, there will be a large amount of product loss, and the dispersion of the obtained catalyst particles on the core-shell is not uniform. Summary of the invention

[0015] The present invention aims to overcome the deficiencies of the prior art, and aims to solve the problems of easy sintering and aggregation of catalyst particles, low catalyst instability and low reuse rate, and low ethylene selectivity in the existing carbon dioxide catalytic hydrogenation to produce ethylene and ethylene oxide. A catalyst for producing ethylene and ethylene oxide from carbon dioxide and a preparation method thereof are proposed.

[0016] Through quantum chemical calculations and density functional theory (DFT) studies, possible active sites and catalyst structures are screened out. The electronic structures of transition metals (such as copper, silver, gold) and their oxides and alloys, as well as their interactions with CO2 molecules, are analyzed in detail to predict which structures have high activity and selectivity for the conversion of CO2 to ethylene. On this basis, a method for preparing a supported Cu-based catalyst modified by 3D printed Cu-Ag alloy for catalytic hydrogenation of carbon dioxide to produce ethylene and ethylene oxide is proposed, which solves the problems in the above-mentioned background technology. Carbon dioxide (CO2) is reduced to ethylene (C2H2) and ethylene oxide (EO) is co-produced using an electrocatalytic process. The catalyst has high electrocatalytic activity and selectivity, can effectively reduce the energy required for the reaction and increase the yield of the target product. A method for preparing an electrocatalyst that complies with the principles of green chemistry, reduces dependence on fossil fuels, and promotes environmental sustainability.

[0017] In order to solve the above technical problems, the technical solution adopted by the present invention is:

[0018] A catalyst for producing ethylene from carbon dioxide and co-producing ethylene oxide, the catalyst consists of an active component, an auxiliary agent and a carrier, the general structural formula is Cu-Ag / X, X is the carrier silicon carbide, the loading mass percentage of metal Cu and Ag in the catalyst is 20-70%, the auxiliary agent is potassium carbonate, the mass percentage of potassium carbonate is 5%, and the rest is the carrier.

[0019] Furthermore, the surface area of ​​metal Cu in the catalyst powder is 14.5 to 25.8 m 2 / g, the surface area of ​​metal Ag is 18.7~31.4m 2 / g, the catalyst specific surface area is 118~209m 2 / g, the dispersion of Cu in the catalyst is 67.8-74.3%, the dispersion of Ag is 72.6-81.9%, and the catalyst zero-valent copper Cu 0 Surface area 14.7~17.6m 2 / g, catalyst zero-valent silver Ag 0 Surface area 17.1~23.9m 2 / g, the average size of Cu particles in the catalyst is 1.8-3.3nm, and the average size of Ag particles in the catalyst is 1.6-2.9nm.

[0020] The present invention also provides a method for preparing the catalyst for producing ethylene from carbon dioxide and co-producing ethylene oxide, comprising the following steps:

[0021] (1) Weighing a certain amount of copper precursor salt, silver precursor salt and deionized water, stirring and mixing to obtain a mixed salt solution A;

[0022] (2) washing the SiC carrier with deionized water until the pH is close to neutral, drying the washed SiC carrier until the water is completely removed, adding the washed SiC carrier to the mixed salt solution A, and centrifugally dispersing the solution to form a solid-liquid mixture;

[0023] (3) adding an alkaline agent dropwise to the solid-liquid mixture obtained in (2) at a constant rate of 2 ml / min, stirring until the pH is ≥ 8, and ultrasonically shaking to obtain a suspension, adding an auxiliary salt K2CO3 to the obtained suspension, and centrifugally dispersing it on a magnetic stirrer to obtain a precipitate;

[0024] (4) placing the precipitate sample after centrifugal dispersion in a constant temperature water bath for aging, washing the obtained precipitate with deionized water until the pH value is neutral, and transferring the washed precipitate to a muffle furnace for calcination after drying;

[0025] (5) After calcination, the calcined sample is ground and sieved (60-180 mesh), and the sieved calcined sample is reduced and activated in a hydrogen atmosphere to obtain a catalyst precursor, and the catalyst precursor is ground and sieved to obtain a catalyst powder;

[0026] (6) Using computer-aided design software to construct a three-dimensional model of the required catalyst, placing the catalyst powder obtained in step (5) into a 3D printer powder cylinder for selective sintering and cooling, and subjecting the printed catalyst body to heat treatment under a reducing atmosphere to activate the metal active sites and improve the catalytic performance; taking out the finished catalyst, and performing powder removal, surface cleaning, polishing, and quality inspection.

[0027] Furthermore, the copper precursor salt in step (1) is any one of copper sulfate, copper nitrate and copper chloride, and the silver precursor salt is silver nitrate.

[0028] Furthermore, the drying temperature in step (2) is 80°C-120°C.

[0029] Furthermore, the alkaline agent in step (3) is a sodium hydroxide solution with a concentration of 1.5 mol / L.

[0030] Furthermore, the aging temperature in step (4) is 70-90°C, the aging time is 4-5h, and the water bath temperature is preferably 80°C.

[0031] Furthermore, the calcination in step (4) is carried out in a nitrogen atmosphere at a temperature of 400-800° C. and a calcination time of 4 hours.

[0032] Furthermore, in step (5), the calcined sample is reduced and activated in a hydrogen atmosphere at 400° C. for 3 hours.

[0033] Furthermore, in step (6), the printed catalyst body is subjected to heat treatment under a reducing atmosphere by reduction activation in a hydrogen atmosphere at 400° C. for 3 hours.

[0034] Beneficial effects of the present invention:

[0035] 1. The synergistic effect between the two metals in the copper-silver alloy used in the present invention enhances the activation ability of the catalyst for CO2, thereby improving the conversion rate of CO2. The presence of silver can adjust the electronic structure of the copper surface, making the reaction intermediates easier to form or stabilize, thereby promoting the reaction. SiC, as a material with excellent thermal stability and good corrosion resistance, can effectively prevent the catalyst from sintering and deactivation at high temperatures as a carrier, prolong the life of the catalyst, and optimize the interaction between copper, silver and SiC. The raw materials are easy to obtain, the cost is low, the process is simple and controllable, the structure is stable, the operability is strong, and it has good industrial application prospects.

[0036] 2. The catalyst prepared by the coprecipitation method (CP) of the present invention can deposit metal ions uniformly on the SiC surface under relatively mild conditions, ensuring that the active components are well dispersed on the entire catalyst and avoiding agglomeration, thereby maintaining efficient mass transfer and heat transfer efficiency. The catalyst can not only achieve efficient conversion of CO2 to ethylene, but also co-produce ethylene oxide in the same reaction system, simplifying the process flow and improving economic benefits. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0038] Figure 1 The present invention is a process flow chart for preparing a catalyst for producing ethylene from carbon dioxide and co-producing ethylene oxide.

[0039] Figure 2It is a performance evaluation chart of catalyst powders (Examples 1-8) prepared by different methods.

[0040] Figure 3 It is a comparison chart of the changes in the yield of each product participating in the reaction under different average particle sizes of metal particles and zero-valent metal surface areas under TEM observation.

[0041] Figure 4 It is a performance evaluation chart of catalyst powders prepared with different alloys at different metal mass ratios.

[0042] Figure 5 It is a schematic diagram of the core-shell catalyst model structure.

[0043] Figure numerals: 501. Catalyst shell, 502. Holes, 503. Internal catalyst. DETAILED DESCRIPTION

[0044] The present invention is further described in detail below in conjunction with the accompanying drawings and examples. It is intended to deepen understanding rather than limit the scope of protection. Parameters such as quality, reaction conditions, process parameters, etc. are only examples, and some non-essential improvements and adjustments made by those skilled in the art based on the above content of the present invention all belong to the scope of protection of the present invention. The experimental methods for which specific conditions are not indicated in the embodiments are generally in accordance with conventional conditions and the conditions described in the manual. The general equipment, materials, reagents, etc. used, unless otherwise specified, can be obtained from commercial sources.

[0045] Example 1

[0046] The catalyst for producing ethylene from carbon dioxide and co-producing ethylene oxide in this embodiment is prepared by an impregnation method (IM), and the steps are as follows:

[0047] Weigh 7.60g of copper nitrate trihydrate and 3.16g of silver nitrate into a round-bottom flask, add 125mL of distilled water and stir to dissolve to obtain a copper-silver mixed solution, wash 16g of SiC carrier with deionized water several times until the pH is close to neutral. Dry the cleaned SiC carrier at 80°C until the water is completely removed. Add the SiC carrier to the copper-silver mixed solution for impregnation at room temperature, impregnate it on a magnetic stirrer for 2 to 3 hours, place the impregnated catalyst sample in an oven at 150°C for 8 hours, and calcine it in a muffle furnace at 500°C nitrogen flow for 3 hours. Grind and sieve (60-180 mesh). The sieved calcined sample is reduced and activated in a hydrogen atmosphere at 400°C for 3 hours to obtain an active catalyst powder, which is recorded as 20% Cu-Ag / SiC-IM, where 20% represents the loading amount of Cu-Ag in the catalyst.

[0048] Example 2

[0049] The catalyst for producing ethylene from carbon dioxide and co-producing ethylene oxide in this embodiment is prepared by an impregnation method (IM), and the steps are as follows:

[0050] The operation is the same as that of Example 1, except that 11.4 g of copper nitrate trihydrate is used instead of 7.60 g of copper nitrate trihydrate, 4.74 g of silver nitrate is used instead of 3.16 g of silver nitrate, and 14 g of SiC is used instead of 16 g of SiC carrier, to obtain active catalyst 2, recorded as 30% Cu-Ag / SiC-IM, wherein 30% represents the loading amount of Cu-Ag in the catalyst.

[0051] Example 3

[0052] The catalyst for producing ethylene from carbon dioxide and co-producing ethylene oxide in this embodiment is prepared by an impregnation method (IM), and the steps are as follows:

[0053] The operation was the same as in Example 1, except that 19.00 g of copper nitrate trihydrate was used instead of 7.60 g of copper nitrate trihydrate, 7.90 g of silver nitrate was used instead of 3.16 g of silver nitrate, and 10 g of SiC was used instead of 16 g of SiC carrier, to obtain active catalyst 3, recorded as 50% Cu-Ag / SiC-IM, wherein 50% represents the loading amount of Cu-Ag in the catalyst.

[0054] Example 4

[0055] The catalyst for producing ethylene from carbon dioxide and co-producing ethylene oxide in this embodiment is prepared by an impregnation method (IM), and the steps are as follows:

[0056] The operation is the same as that of Example 1, except that 26.60 g of copper nitrate trihydrate is used instead of 7.60 g of copper nitrate trihydrate, 11.06 g of silver nitrate is used instead of 3.16 g of silver nitrate, and 6 g of SiC is used instead of 16 g of SiC carrier, to obtain active catalyst 4, recorded as 70% Cu-Ag / SiC-IM, wherein 70% represents the loading amount of Cu-Ag in the catalyst.

[0057] Example 5

[0058] The catalyst for the co-production of ethylene oxide from carbon dioxide in this embodiment is prepared by a precipitation method (CP), and the steps are as follows:

[0059] Weigh 7.60 g of copper nitrate trihydrate and 3.16 g of silver nitrate into a round-bottom flask, add 125 mL of distilled water and stir to dissolve to obtain a copper-silver mixed solution, wash 16 g of SiC carrier with deionized water several times until the pH is close to neutral, and dry the washed SiC carrier at 80°C until the water is completely removed. The SiC carrier is added to a copper-silver mixed solution and a 10wt% sodium hydroxide solution is dropped thereinto and stirred to precipitate until the pH value is ≥8. After adding 5.00g of a 20% K2CO3 solution by mass, the mixture is centrifugally dispersed on a magnetic stirrer, heated to 80°C in a water bath and aged for 4h. After aging, the obtained precipitate is washed with deionized water until the pH value is neutral, dried at 120°C for 12h, calcined in a muffle furnace at 500°C in a nitrogen flow for 4h, ground and sieved (60-80 mesh) to obtain a catalyst powder, and reduced and activated in a hydrogen atmosphere at 400°C for 3h to obtain the active catalyst 5 provided by the present invention, recorded as 20% Cu-Ag / SiC-CP, wherein 20% represents the loading amount of Cu-Ag in the catalyst.

[0060] Example 6

[0061] The catalyst for the co-production of ethylene oxide from carbon dioxide in this embodiment is prepared by a precipitation method (CP), and the steps are as follows:

[0062] 11.4 g of copper nitrate trihydrate and 4.74 g of silver nitrate were weighed and added to a round-bottom flask, and 125 mL of distilled water was added and stirred to dissolve, and 14 g of SiC carrier was washed several times with deionized water until the pH was close to neutral. The washed SiC carrier was dried at 80°C until the water was completely removed. The SiC carrier is added to a copper-silver mixed solution and 10wt% sodium hydroxide solution is dropped and stirred to precipitate until the pH value is ≥8. After adding 5.00g of 20% K2CO3 solution by mass, it is centrifugally dispersed on a magnetic stirrer, heated to 80°C in a water bath and aged for 4h. After aging, the obtained precipitate is washed with deionized water until the pH value is neutral, dried at 120°C for 12h, calcined in a muffle furnace at 500°C in a nitrogen flow for 4h, ground and sieved (60-80 mesh) to obtain a catalyst powder, and reduced and activated in a hydrogen atmosphere at 400°C for 3h to obtain the active catalyst 6 provided by the present invention, recorded as 30% Cu-Ag / SiC-CP, wherein 30% represents the loading amount of Cu-Ag in the catalyst.

[0063] Example 7

[0064] The catalyst for the co-production of ethylene oxide from carbon dioxide in this embodiment is prepared by a precipitation method (CP), and the steps are as follows:

[0065] Weigh 19.00 g of copper nitrate trihydrate and 7.90 g of silver nitrate into a round-bottom flask, add 125 mL of distilled water and stir to dissolve, wash 10 g of SiC carrier with deionized water several times until the pH is close to neutral, and dry the washed SiC carrier at 80°C until the water is completely removed. The SiC carrier is added to a copper-silver mixed solution and 10wt% sodium hydroxide solution is dropped and stirred to precipitate until the pH value is ≥8. After adding 5.00g of 20% K2CO3 solution by mass, the mixture is centrifugally dispersed on a magnetic stirrer, heated to 80°C in a water bath and aged for 4h. After aging, the obtained precipitate is washed with deionized water until the pH value is neutral, dried at 120°C for 12h, calcined in a muffle furnace at 500°C in a nitrogen flow for 4h, ground and sieved (60-80 mesh) to obtain a catalyst powder, and reduced and activated in a hydrogen atmosphere at 400°C for 3h to obtain the active catalyst 7 provided by the present invention, recorded as 50% Cu-Ag / SiC-CP, wherein 50% represents the loading amount of Cu-Ag in the catalyst.

[0066] Example 8

[0067] The catalyst for the co-production of ethylene oxide from carbon dioxide in this embodiment is prepared by a precipitation method (CP), and the steps are as follows:

[0068] Weigh 26.60 g of copper nitrate trihydrate and 11.06 g of silver nitrate (Cu:Ag mass ratio = 1:1) into a round-bottom flask, add 125 mL of distilled water and stir to dissolve, wash 6 g of SiC carrier with deionized water several times until the pH is close to neutral, and dry the washed SiC carrier at 80°C until the water is completely removed. The SiC carrier is added to a copper-silver mixed solution and 10wt% sodium hydroxide solution is dropped and stirred to precipitate until the pH value is ≥8. After adding 5.00g of 20% K2CO3 solution by mass, the mixture is centrifuged and dispersed on a magnetic stirrer. The mixture is heated to 80°C in a water bath and aged for 4h. After aging, the obtained precipitate is washed with deionized water until the pH value is neutral, dried at 120°C for 12h, calcined in a muffle furnace at 500°C in a nitrogen flow for 4h, ground and sieved (60-80 mesh) to obtain a catalyst powder, and reduced and activated in a hydrogen atmosphere at 400°C for 3h to obtain the active catalyst 8 provided by the present invention, recorded as 70% Cu-Ag / SiC-CP, wherein 70% represents the loading amount of Cu-Ag in the catalyst.

[0069] Evaluation of catalytic effect of catalysts prepared by different methods:

[0070] The carbon dioxide catalytic reaction in the present invention is carried out in a vertical fixed bed reactor.

[0071] 3.2 g of catalyst powder with a particle size of (60-80) mesh was loaded into a stainless steel tubular reactor, and a thermocouple was inserted into the catalyst bed to ensure uniform heating. The reaction was carried out at 160 ° C with a CO2:H2 ratio of 1:10 and pressurized to 3 MPa. The weight hourly space velocity (WHSV) of carbon dioxide was set to 0.2 h -1 During the reaction, the reaction pressure was maintained by supplementing H2, and the reaction time was 4h. Then an appropriate amount of oxygen was added to start the oxidation reaction. The O2:H2 ratio was 1:10, and the pressure was increased to 3MPa at 250℃. The weight hourly space velocity (WHSV) of oxygen was set to 0.15h -1 During the reaction, the reaction pressure was maintained by adding H2. The reaction was finished with ice bath cooling. The reaction time was 2h. The product was qualitatively and quantitatively analyzed by gas chromatography-mass spectrometry. The results are as follows Figure 2 And as shown in Table 1.

[0072] Table 1 Performance evaluation of catalyst powders prepared by different methods

[0073]

[0074] It can be seen from Table 1 that by comparing Examples 1 to 4 with Examples 5 to 8, the catalyst powder prepared by the coprecipitation method (CP) has a higher conversion rate and product selectivity than the impregnation method (IM) catalyst. Figure 2 It can be seen that with the increase of Cu-Ag loading, under the same preparation method, the conversion rate and selectivity generally show an upward trend. Catalysts prepared by CP (co-precipitation method) generally show higher conversion rate and selectivity than catalysts prepared by IM (impregnation method). Under high loading conditions, the catalyst prepared by co-precipitation method (CP) has better conversion rate and selectivity than IM (impregnation method). The catalyst exhibits better catalytic activity when the Cu-Ag loading is 50-70%, and it is better at 70%.

[0075] Example 9

[0076] The catalyst for the co-production of ethylene oxide from carbon dioxide in this embodiment is prepared by a precipitation method (CP), and the steps are as follows:

[0077] According to the Cu:Ag mass ratio of 1:2 and the Cu-Ag loading of 70%, 18.07g of copper nitrate trihydrate and 14.64g of silver nitrate were weighed and added to a round-bottom flask. 125mL of distilled water was added and stirred to dissolve. 6g of SiC carrier was washed several times with deionized water until the pH was close to neutral. The washed SiC carrier was dried at 80°C until the water was completely removed. The SiC carrier was added to a copper-silver mixed solution and 10wt% sodium hydroxide solution was dropped and stirred to precipitate until the pH value was 10. After adding 5.00g of 20% K2CO3 solution by mass, the mixture was dispersed by centrifugation on a magnetic stirrer, heated to 80°C in a water bath and aged for 4h. After aging, the precipitate was washed with deionized water until the pH value was neutral, dried at 120°C for 12h, calcined in a muffle furnace at 500°C in a nitrogen flow for 4h, ground and sieved (60-80 mesh) to obtain a catalyst powder, and reduced and activated in a hydrogen atmosphere at 400°C for 3h to obtain catalyst 9.

[0078] Example 10

[0079] According to the Cu:Ag mass ratio of 1:3 and the Cu-Ag loading of 70%, 13.46 g of copper nitrate trihydrate and 16.38 g of silver nitrate were weighed, and the remaining operations were the same as those in Example 9 to obtain catalyst 10.

[0080] Embodiment 11

[0081] According to the Cu:Ag mass ratio of 2:1 and the Cu-Ag loading of 70%, 35.21 g of copper nitrate trihydrate and 7.32 g of silver nitrate were weighed, and the remaining operations were the same as those in Example 9 to obtain catalyst 11.

[0082] Example 12

[0083] According to the Cu:Ag mass ratio of 3:1 and the Cu-Ag loading of 70%, 40.15 g of copper nitrate trihydrate and 5.46 g of silver nitrate were weighed, and the remaining operations were the same as those in Example 9 to obtain catalyst 12.

[0084] Embodiment 13

[0085] According to the Cu:Ag mass ratio of 2:3 and the Cu-Ag loading of 70%, 21.68 g of copper nitrate trihydrate and 13.08 g of silver nitrate were weighed, and the remaining operations were the same as those in Example 9 to obtain catalyst 13.

[0086] Examples 14-18 are catalysts prepared with a Cu-Zn metal alloy structure, and the steps are the same as above, except that zinc nitrate (Zn(NO3)2) is used instead of silver nitrate (AgNO3).

[0087] Embodiment 14

[0088] According to the Cu:Zn mass ratio of 1:1 and the Cu-Zn loading of 70%, 26.67 g of copper nitrate trihydrate and 32.04 g of zinc nitrate hexahydrate were weighed, and the remaining operations were the same as those in Example 9 to obtain catalyst 14.

[0089] Embodiment 15

[0090] According to the Cu:Zn mass ratio of 1:2 and the Cu-Zn loading of 70%, 18.07 g of copper nitrate trihydrate and 42.23 g of zinc nitrate hexahydrate were weighed, and the remaining operations were the same as those in Example 9 to obtain catalyst 15.

[0091] Example 16

[0092] According to the Cu:Zn mass ratio of 1:3 and the Cu-Zn loading of 70%, 13.46 g of copper nitrate trihydrate and 47.29 g of zinc nitrate hexahydrate were weighed, and the remaining operations were the same as those in Example 9 to obtain catalyst 16.

[0093] Embodiment 17

[0094] According to the Cu:Zn mass ratio of 2:1 and the Cu-Zn loading of 70%, 35.21 g of copper nitrate trihydrate and 21.12 g of zinc nitrate hexahydrate were weighed, and the remaining operations were the same as those in Example 9 to obtain catalyst 17.

[0095] Embodiment 18

[0096] According to the Cu:Zn mass ratio of 2:3 and the Cu-Zn loading of 70%, 21.68 g of copper nitrate trihydrate and 39.47 g of zinc nitrate hexahydrate were weighed, and the remaining operations were the same as those in Example 9 to obtain catalyst 18.

[0097] Evaluation of catalytic effects of catalysts with different alloy types:

[0098] The carbon dioxide electrode reaction in the present invention is carried out in a fixed bed reactor in a closed hydrogen atmosphere environment. The prepared alloy catalyst is used as a working electrode, and a potassium carbonate (K2CO3) aqueous solution is used as an electrolyte. A silver / silver chloride (Ag / AgCl) electrode is used as a reference electrode, a platinum mesh (Pt mesh) is used as a counter electrode, and a three-electrode system and an electrochemical workstation are used to apply a constant voltage of -0.8V vs. RHE at room temperature for electrochemical testing. A sufficient amount of CO2 is passed through the reaction electrode, and the flow rate of CO2 is controlled to be 50mL / min. After 10 minutes of reaction, a sufficient amount of O2 is passed through the reaction electrode, and the flow rate of O2 is controlled to be 50mL / min. After 10 minutes of reaction, a qualitative and quantitative analysis is performed by observing the Faraday efficiency and current density of the electrode where the catalyst is located.

[0099] Table 2: Performance evaluation of catalyst powders prepared from different alloys at different metal mass ratios

[0100]

[0101] From Table 2 and Figure 4 It can be seen that by comparing Examples 9 to 13 with 14 to 18, it can be seen that the selectivity for the target product can be effectively improved by adjusting different mass ratios. The ethylene selectivity varies significantly with the metal ratio. Cu:Ag=2:1 is the best ratio with the highest ethylene selectivity, which shows that an appropriate amount of Ag can significantly improve the surface properties of Cu. Although Cu-Zn alloy can also provide good performance at certain ratios, its overall performance is not as good as that of Cu-Ag alloy, especially at a ratio rich in Zn, where the performance decreases more significantly. Compared with Cu-Zn alloy, the catalyst prepared using Cu-Ag alloy has a better ability to improve the selectivity of ethylene.

[0102] The average particle size of Cu and Ag particles and Cu 0 、Ag 0 Surface area. Under low temperature conditions, argon is used as a protective gas to gradually introduce CO gas into the reaction chamber, control its partial pressure, monitor the adsorption of CO, and track the consumption of CO through a mass spectrometer to observe the adsorption behavior of CO on the metal surface and record the change of adsorption amount over time. The coverage data is combined with TEM images to infer the number of active sites on the copper surface, and the average particle size of Cu and Ag particles and Cu 0 、Ag 0 The yields of various products of the catalyst prepared in Example 11 of the present invention participating in the reaction were measured under different average metal particle sizes and zero-valent metal surface areas. The test conditions were the same as those for the catalyst evaluation.

[0103] The test results are as follows Figure 3 .from Figure 3 It can be seen that the average particle size of the catalyst Cu is 2.8-3.3nm, the average particle size of Ag is 2.2-2.9nm, and the catalyst zero-valent copper Cu 0 Surface area 10~18m 2 / g, catalyst zero-valent silver Ag 0 Surface area 15~25m 2 / g, the conversion rate of the reaction is high and the catalytic reaction state is good.

[0104] Embodiment 19

[0105] The catalyst of Example 11 was used as the base powder, and a three-dimensional catalyst model was constructed using computer-aided design software. The catalyst powder was placed in a 3D printer powder cylinder for selective sintering and cooling, and a cubic structure catalyst (edge ​​length 15 mm) was printed. The catalyst blank was taken out and reduced and activated in a hydrogen atmosphere at 400°C for 3 hours. After completion, the catalyst product was taken out for surface powder treatment, surface cleaning, and polishing to obtain catalyst 19.

[0106] Embodiment 20

[0107] The catalyst of Example 11 was used as the base powder and the operation was the same as that of Example 19, except that the cubic structure was replaced by a flake-like structure (30 mm in length, 15 mm in width, and 1 mm in thickness) to obtain Catalyst 20.

[0108] Embodiment 21

[0109] The catalyst of Example 11 was used as the base powder and the operation was the same as that of Example 19, except that a sphere with a radius of 15 mm was used instead of the cubic structure to obtain Catalyst 21.

[0110] Embodiment 22

[0111] The catalyst of Example 11 was used as the base powder and the operation was the same as that of Example 20, except that the cubic structure was replaced by a core-shell structure (a spherical core-shell structure with a radius of 15 mm, and uniform holes with an average diameter of 1 mm were opened on the outer shell of the sphere) to obtain catalyst 22.

[0112] like Figure 5 As shown, the catalyst shell 501 is made of silicon carbide, which can protect the core catalyst inside from the influence of the external environment, improve the chemical stability of the overall catalyst, and prevent the active metal particles from sintering or deactivation, which helps to ensure that the reaction is carried out under optimal conditions. The hole 502 provides a fast transmission path for reactants and products as an internal and external liquid exchange channel, reduces diffusion resistance, and improves mass transfer efficiency. The channel ensures that the reactants can be evenly distributed on the catalyst surface, avoiding local concentrations that are too high or too low, thereby improving the reaction rate and selectivity. Effective internal and external liquid exchange channels can help remove the heat generated during the reaction, prevent hot spots from forming, and keep the catalyst temperature stable. As the reaction process changes, the internal and external liquid exchange channels can adjust the fluid flow rate as needed, maintain the dynamic balance of the reaction system, and ensure continuous and efficient catalytic reactions. The internal catalyst 503 particles are evenly dispersed, reducing agglomeration, improving the effective utilization of active sites, and reducing the risk of catalyst deactivation, thereby optimizing catalytic performance. Silicon carbide with a high specific surface area is used to evenly disperse Cu and Ag nanoparticles on its surface, providing more maximized active sites while maintaining good thermal stability and anti-deactivation capabilities.

[0113] The catalyst evaluation process and operation are the same as those for catalyst powder evaluation. The catalyst is evaluated after the same process. The performance evaluation results of the catalyst are shown in Table 3.

[0114] Table 3: Catalyst performance evaluation of different geometries

[0115]

[0116] It can be seen from Table 3 that the core-shell structure catalyst printed by selective sintering of basic powders showed the highest conversion rate and high selectivity for ethylene oxide. The core-shell structure not only helps to improve catalytic performance, but also optimizes production processes and reduces costs. The core-shell structure is very beneficial for the separation and multiple use of catalysts. It has balanced comprehensive performance and is suitable for large-scale industrial applications and is easy to use in industrial production.

[0117] The embodiments of the present invention are described in detail above, but the present invention is not limited to the described embodiments. For those skilled in the art, various changes, modifications, substitutions and variations of these embodiments are made without departing from the principles and spirit of the present invention, and still fall within the protection scope of the present invention.

Claims

1. A catalyst for producing ethylene from carbon dioxide and co-producing ethylene oxide, characterized in that: The catalyst is composed of an active component, an auxiliary agent and a carrier, and has a general structural formula of Cu-Ag / X, wherein X is the carrier silicon carbide, the loading mass percentage of metal Cu and Ag in the catalyst is 20-70%, the auxiliary agent is potassium carbonate, the mass percentage of potassium carbonate is 5%, and the rest is the carrier.

2. The catalyst for producing ethylene from carbon dioxide and co-producing ethylene oxide according to claim 1, characterized in that: The surface area of ​​metal Cu in the catalyst powder is 14.5~25.8m² / g, the surface area of ​​metal Ag is 18.7~31.4m² / g, the specific surface area of ​​the catalyst is 118~209 m² / g, the dispersion of Cu in the catalyst is 67.8~74.3%, the dispersion of Ag is 72.6~81.9%, and the catalyst zero-valent copper Cu 0 The surface area is 14.7~17.6m² / g, the catalyst is zero-valent silver Ag 0 The surface area is 17.1~23.9m² / g, the average size of Cu particles in the catalyst is 1.8~3.3nm, and the average size of Ag particles in the catalyst is 1.6~2.9nm.

3. The catalyst for producing ethylene from carbon dioxide and co-producing ethylene oxide according to claim 1 or 2, characterized in that The steps include: (1) Weigh a certain amount of copper precursor salt, silver precursor salt and deionized water, and stir and mix to obtain a mixed salt solution A; (2) washing the SiC carrier with deionized water until the pH is close to neutral, drying the washed SiC carrier until the water is completely removed, adding it to the mixed salt solution A, and centrifugally dispersing the solution to form a solid-liquid mixture; (3) adding an alkaline agent dropwise to the solid-liquid mixture obtained in (2) at a constant speed, stirring the mixture until the pH value is ≥ 8, and performing ultrasonic oscillation to obtain a suspension, adding an auxiliary salt K2CO3 to the obtained suspension, and performing centrifugal dispersion on a magnetic stirrer to obtain a precipitate; (4) placing the precipitate sample after centrifugal dispersion in a constant temperature water bath for aging, washing the obtained precipitate with deionized water until the pH value is neutral, and transferring the washed precipitate to a muffle furnace for calcination after drying; (5) After calcination, the calcined sample is ground and sieved, and the sieved calcined sample is reduced and activated in a hydrogen atmosphere to obtain a catalyst precursor, and the catalyst precursor is ground and sieved to obtain a catalyst powder; (6) Using computer-aided design software to construct a three-dimensional model of the desired catalyst, placing the catalyst powder obtained in step (5) into a 3D printer powder cylinder for selective sintering and cooling, and subjecting the printed catalyst body to heat treatment under a reducing atmosphere to activate the metal active sites and improve the catalytic performance; taking out the finished catalyst, and performing powder removal, surface cleaning, polishing, and quality inspection.

4. The method for preparing a catalyst for producing ethylene oxide from carbon dioxide according to claim 3, characterized in that: The copper precursor salt in step (1) is any one of copper sulfate, copper nitrate and copper chloride, and the silver precursor salt is silver nitrate.

5. The method for preparing a catalyst for producing ethylene oxide from carbon dioxide according to claim 3, characterized in that: The drying temperature in step (2) is 80°C-120°C.

6. The method for preparing a catalyst for producing ethylene oxide from carbon dioxide according to claim 3, characterized in that: The alkaline agent in step (3) is a sodium hydroxide solution with a concentration of 1.5 mol / L, which is added dropwise at a rate of 2 ml / min.

7. The method for preparing a catalyst for producing ethylene oxide from carbon dioxide according to claim 3, characterized in that: The aging temperature in step (4) is 70-90° C., and the aging time is 4-5 hours.

8. The method for preparing a catalyst for producing ethylene oxide from carbon dioxide according to claim 3, characterized in that: The calcination in step (4) is carried out in a nitrogen atmosphere at a temperature of 400-800°C and a calcination time of 4 hours.

9. The method for preparing a catalyst for producing ethylene oxide from carbon dioxide according to claim 3, characterized in that: In the step (5), the calcined sample is reduced and activated in a hydrogen atmosphere at 400° C. for 3 hours.

10. The method for preparing a catalyst for producing ethylene oxide from carbon dioxide according to claim 3, characterized in that: In step (6), the printed catalyst body is subjected to heat treatment under a reducing atmosphere by reducing and activating it in a hydrogen atmosphere at 400° C. for 3 hours.

Images