Calcium ferrite catalyst loaded with nickel-iron alloy, and preparation method and application thereof

Abstract

This invention provides a calcium ferrite catalyst supported on a nickel-iron alloy, its preparation method, and its application. The calcium ferrite catalyst of this invention comprises calcium ferrite and a nickel-iron alloy supported on the calcium ferrite. This calcium ferrite catalyst is applied to the photothermal catalytic hydrogenation conversion of CO2. Supporting nickel-iron alloy nanoparticles on calcium ferrite can effectively reduce the energy barrier of CO2 hydrogenation conversion, promote the activation of CO2 and H2, and thus improve the catalyst's CO2 catalytic hydrogenation activity. Within a wide temperature range (250-500℃), the CO2 conversion rate continuously increases with increasing temperature. The main products are CH4 and CO. At 500℃, the CO2 conversion rate is 55.8%, and the CH4 and CO yields are 21.0 mmol·g. ‑ 1 h ‑1 and 53.7 mmol·g ‑1 h ‑1 .

Description

Technical Field

[0001] This invention relates to the field of carbon capture, utilization and storage technology, and in particular to a calcium ferrite catalyst supported on nickel-iron alloy, its preparation method and application. Background Technology

[0002] The increasingly severe problem of climate change caused by global warming has threatened global ecological balance and human well-being, and CO2, as the most significant greenhouse gas in the atmosphere, has received increasing attention. Efficiently converting CO2 into high-value-added fuels or chemicals can not only reduce CO2 concentration, effectively curb the greenhouse effect, and mitigate the environmental impact of global climate change; it can also provide humanity with sustainable, renewable, high-value-added fuels, reducing dependence on traditional fossil fuels and potentially alleviating the fossil fuel shortage; and by artificially promoting the carbon cycle and creating substantial economic benefits, it achieves the dual goals of environmental protection and the sustainable use of CO2 resources.

[0003] In recent years, photothermal catalysis has been proven to effectively promote the catalytic hydrogenation of CO2. Photothermal catalysis combines the high efficiency of thermocatalysis with the low energy consumption of photocatalysis, not only overcoming the high energy consumption of thermocatalysis but also avoiding the problems of low reaction rate and low solar energy utilization in photocatalysis, thus further improving catalytic efficiency and achieving the goals of increasing reaction rate and CO2 conversion while reducing reaction condition requirements. Based on this research background, developing efficient photothermal catalysts to achieve efficient CO2 conversion using photothermal catalysis technology has significant research and practical value. However, existing catalysts still have many problems: low quantum efficiency, high cost, low CO2 conversion rate, low yield of target products, and catalyst deactivation due to high-temperature sintering. Therefore, to achieve a breakthrough in this technology, it is necessary to synthesize inexpensive catalyst materials with high activity, high selectivity, and high stability. Summary of the Invention

[0004] This invention aims to at least partially address a problem in related technologies by providing a calcium ferrite catalyst supported on a nickel-iron alloy. Under photothermal synergistic conditions, this catalyst exhibits excellent catalytic performance in converting CO2 into high-value-added chemicals, with low preparation cost and high catalytic activity. This invention also provides a method for preparing the calcium ferrite catalyst supported on a nickel-iron alloy, resulting in a catalyst with good crystallinity and a considerable product yield.

[0005] In a first aspect, the present invention provides a calcium ferrite catalyst supported on a nickel-iron alloy, the catalyst comprising calcium ferrite and a nickel-iron alloy supported on the calcium ferrite.

[0006] Preferably, the calcium ferrite catalyst supported on nickel-iron alloy has a nickel mass fraction of 15-19% and an iron mass fraction of 1-5%.

[0007] Secondly, the present invention also provides a method for preparing the calcium ferrite catalyst supported on nickel-iron alloy, comprising the following steps:

[0008] The magnetic iron-rich components were separated from the fly ash by magnetic separation. The magnetic iron-rich components were then dissolved in acid and filtered to obtain the first mixture.

[0009] Add quicklime to the first mixture, filter, and obtain Fe(OH)3 precipitate;

[0010] After mixing quicklime and the Fe(OH)3 precipitate, water was added to obtain a precursor emulsion.

[0011] The precursor emulsion was heated and stirred to obtain a viscous substance;

[0012] After drying the viscous substance, it was calcined to obtain solid calcium ferrite.

[0013] The Fe(OH)3 precipitate was dissolved in acid, and then nickel salt was added to obtain a second mixture.

[0014] The calcium ferrite solid was added to the second mixture, impregnated, dried, and calcined.

[0015] The calcined product was reduced to obtain a calcium ferrite catalyst supported on nickel-iron alloy.

[0016] Preferably, the molar ratio of calcium to iron in the precursor emulsion is (1-1.3):1.

[0017] Preferably, in the step of heating and stirring the precursor emulsion to obtain a viscous substance, the heating temperature is 50-90°C and the stirring time is 2-5 hours.

[0018] Preferably, the viscous substance is dried and then calcined to obtain solid calcium ferrite; wherein the drying temperature is 90-120℃ and the time is 8-12h.

[0019] The calcination specifically includes:

[0020] The dried viscous material is heated to 300-400℃ at a rate of 5-20℃ / min and calcined for 1-2 hours.

[0021] Then raise the temperature to 600-900℃ at a rate of 5-20℃ / min and calcine for 3-6 hours.

[0022] Preferably, in the steps of adding the calcium ferrite solid to the second mixture, impregnating, drying, and calcining, the sum of the mass of nickel and iron elements in the second mixture is 20% to 30% of the mass of calcium ferrite.

[0023] The impregnation method is ultrasonic impregnation, with an impregnation temperature of 30-50℃ and a time of 1-3 hours;

[0024] The drying temperature is 90–120℃, and the time is 8–12 hours.

[0025] The calcination process specifically includes heating the dried product to 400-500℃ at a rate of 5-20℃ / min and calcining for 3-4 hours.

[0026] Preferably, the fly ash is coal-fired fly ash, and the iron content in the fly ash is 4-40% by mass.

[0027] And / or, in the step of adding quicklime to the first mixture, filtering, and obtaining Fe(OH)3 precipitate, adding excess quicklime allows the iron in the first mixture to be completely converted into Fe(OH)3 precipitate;

[0028] And / or, the nickel salt includes at least one of nickel nitrate, nickel chloride, nickel bromide, or nickel sulfate;

[0029] And / or, in the steps of dissolving the magnetic iron-rich component with acid and dissolving the Fe(OH)3 precipitate with acid, the acid includes at least one of hydrochloric acid, sulfuric acid, and nitric acid;

[0030] And / or, in the step of reducing the calcined product, the calcined product is reduced in a reducing atmosphere containing hydrogen.

[0031] The volume concentration of hydrogen in the reducing atmosphere is 10-100%, the reduction temperature is 400-700℃, and the reduction time is 1-5h.

[0032] And / or, after drying the viscous substance, calcining it, and then sieving it to obtain calcium ferrite solid with a particle size of 100-200 μm.

[0033] Thirdly, the present invention also provides the application of the calcium ferrite catalyst supported on nickel-iron alloy as described above or the calcium ferrite catalyst supported on nickel-iron alloy prepared by the preparation method described above in the photothermal catalytic hydrogenation conversion of CO2 to prepare CH4 and CO.

[0034] Preferably, in the aforementioned application, the temperature for the photothermal catalytic hydrogenation conversion of CO2 to prepare CH4 and CO is 250–500°C.

[0035] The present invention has the following advantages over the prior art:

[0036] 1. The present invention relates to a calcium ferrite catalyst supported on a nickel-iron alloy, comprising calcium ferrite and a nickel-iron alloy supported on the calcium ferrite. This calcium ferrite catalyst is applied to the photothermal catalytic hydrogenation conversion of CO2. Supporting nickel-iron alloy nanoparticles on calcium ferrite effectively lowers the energy barrier for CO2 hydrogenation conversion, promotes the activation of CO2 and H2, and thus improves the catalyst's CO2 catalytic hydrogenation activity. Within a wide temperature range (250-500℃), the CO2 conversion rate increases continuously with increasing temperature. The main products are CH4 and CO. At 500℃, the CO2 conversion rate is 55.8%, and the CH4 and CO yields are 21.0 mmol·g⁻¹. -1 h -1 and 53.7 mmol·g -1 h -1 ;

[0037] 2. The preparation method of the calcium ferrite catalyst supported on nickel-iron alloy of the present invention uses magnetic iron-rich fly ash components and quicklime as raw materials for the catalyst. The iron-rich fly ash components are mainly obtained from the magnetic separation of coal-fired fly ash. On the one hand, this promotes the resource utilization of fly ash by-products from coal-fired power plants, and on the other hand, it significantly reduces the production cost of the catalyst. The use of iron-rich fly ash components and quicklime as raw materials for the catalyst in this invention can not only recycle waste, but also reduce the demand for transition metal raw materials, which is in line with the concept of sustainable development. Moreover, this invention is applied to CO2 conversion, reduces the CO2 concentration in the atmosphere, and obtains high-value-added chemicals, which is environmentally friendly. Attached Figure Description

[0038] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0039] Figure 1 SEM image of the calcium ferrite catalyst supported on nickel-iron alloy prepared in Example 1;

[0040] Figure 2 The XRD pattern of the calcium ferrite catalyst supported on nickel-iron alloy prepared in Example 1;

[0041] Figure 3 CO2 conversion rate and product selectivity of the calcium ferrite catalyst supported on nickel-iron alloy prepared in Example 1 during photothermal catalytic CO2 hydrogenation at 250–500 °C;

[0042] Figure 4The product yield of the calcium ferrite catalyst supported on nickel-iron alloy prepared in Example 1 during photothermal catalytic hydrogenation conversion of CO2 at 250–500 °C. Detailed Implementation

[0043] The technical solutions of the embodiments of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0044] It should be noted that the order of description of the following embodiments is not intended to limit the preferred order of embodiments. Furthermore, in the description of this application, the term "comprising" means "including but not limited to". Various embodiments of the present invention may exist in the form of a range; it should be understood that the description in the form of a range is merely for convenience and brevity and should not be construed as a rigid limitation on the scope of the invention; therefore, it should be considered that the range description has specifically disclosed all possible sub-ranges and single numerical values ​​within that range. For example, it should be considered that the range description from 1 to 6 has specifically disclosed sub-ranges, such as from 1 to 3, from 1 to 4, from 1 to 5, from 2 to 4, from 2 to 6, from 3 to 6, etc., and single digits within the range, such as 1, 2, 3, 4, 5, and 6, regardless of the range. Additionally, whenever a numerical range is indicated herein, it means including any referenced number (fraction or integer) within the indicated range.

[0045] This application provides a calcium ferrite catalyst supported on a nickel-iron alloy. The catalyst includes calcium ferrite and a nickel-iron alloy supported on the calcium ferrite.

[0046] Specifically, the catalyst of this invention comprises calcium ferrite and nickel-iron alloy nanoparticles supported on calcium ferrite. The nickel-iron alloy-supported calcium ferrite catalyst of this invention is applied to the photothermal catalytic CO2 hydrogenation conversion. Supporting nickel-iron alloy nanoparticles on calcium ferrite can effectively reduce the energy barrier of CO2 hydrogenation conversion, promote the activation of CO2 and H2, and thus improve the catalyst's CO2 catalytic hydrogenation activity. Within a wide temperature range (250-500℃), the CO2 conversion rate continuously increases with increasing temperature. The main products are CH4 and CO. At 500℃, the CO2 conversion rate is 55.8%, and the CH4 and CO yields are 21.0 mmol·g⁻¹. -1 h -1 and 53.7 mmol·g -1 h -1 .

[0047] In some embodiments, the catalyst contains 15-19% nickel and 1-5% iron by mass.

[0048] Based on the same inventive concept, the present invention also provides a method for preparing the above-mentioned calcium ferrite catalyst supported on nickel-iron alloy, comprising the following steps:

[0049] S1. Using magnetic separation, the magnetic iron-rich components are separated from the fly ash. The magnetic iron-rich components are then dissolved in acid and filtered to obtain the first mixture.

[0050] S2. Add quicklime to the first mixture, filter, and obtain Fe(OH)3 precipitate;

[0051] S3. After mixing quicklime and Fe(OH)3 precipitate, water is added to obtain a precursor emulsion.

[0052] S4. Heat and stir the precursor emulsion to obtain a viscous substance;

[0053] S5. After drying the viscous substance, calcination is performed to obtain solid calcium ferrite.

[0054] S6. After dissolving the Fe(OH)3 precipitate with acid, add nickel salt to obtain the second mixture;

[0055] S7. Add the calcium ferrite solid to the second mixture, impregnate, dry, and calcine;

[0056] S8. The calcined product is reduced to obtain a calcium ferrite catalyst supported on nickel-iron alloy.

[0057] In some embodiments, the molar ratio of calcium to iron in the precursor emulsion is (1 to 1.3):1.

[0058] In some embodiments, in the step of heating and stirring the precursor emulsion to obtain a viscous substance, the heating temperature is 50-90°C and the stirring time is 2-5 hours.

[0059] In some embodiments, the viscous substance is dried and then calcined to obtain solid calcium ferrite; wherein the drying temperature is 90–120°C and the time is 8–12 h.

[0060] Calcination specifically includes:

[0061] The dried viscous material is heated to 300-400℃ at a rate of 5-20℃ / min and calcined for 1-2 hours.

[0062] Then raise the temperature to 600-900℃ at a rate of 5-20℃ / min and calcine for 3-6 hours.

[0063] In some embodiments, in the steps of adding solid calcium ferrite to the second mixture, impregnating, drying, and calcining, the sum of the mass of nickel and iron elements in the second mixture is 20-30% of the mass of calcium ferrite.

[0064] The impregnation method is ultrasonic impregnation, with an impregnation temperature of 30–50℃ and a time of 1–3 hours;

[0065] The drying temperature is 90–120℃, and the time is 8–12 hours.

[0066] The calcination process specifically includes heating the dried product to 400-500℃ at a rate of 5-20℃ / min and calcining for 3-4 hours.

[0067] In some embodiments, the fly ash is coal fly ash, and the iron component in the fly ash is mainly Fe2O3, with an iron content of 4-40% by mass.

[0068] In some embodiments, in the step of adding quicklime (i.e., calcium hydroxide) to the first mixture, filtering, and obtaining Fe(OH)3 precipitate, an excess of quicklime is added so that the iron in the first mixture is completely converted into Fe(OH)3 precipitate.

[0069] In some embodiments, the nickel salt includes at least one of nickel nitrate, nickel chloride, nickel bromide, or nickel sulfate.

[0070] In some embodiments, the acid used in the steps of dissolving the magnetic iron-rich component with acid and dissolving the Fe(OH)3 precipitate with acid includes at least one of hydrochloric acid, sulfuric acid, and nitric acid.

[0071] In some embodiments, in the step of reducing the calcined product, the calcined product is reduced in a reducing atmosphere containing hydrogen.

[0072] The volume concentration of hydrogen in the reducing atmosphere is 10-100%, the reduction temperature is 400-700℃, and the reduction time is 1-5h.

[0073] Specifically, the reducing atmosphere containing hydrogen includes hydrogen and other inert gases, such as nitrogen, helium, argon, neon, etc. Preferably, the reducing atmosphere containing hydrogen includes a mixture of nitrogen and hydrogen.

[0074] In some embodiments, the viscous substance is dried, calcined, and then sieved to obtain calcium ferrite solid with a particle size of 100-200 μm.

[0075] The present invention discloses a method for preparing a calcium ferrite catalyst supported on nickel-iron alloy, which uses magnetic iron-rich fly ash components and quicklime as raw materials for the catalyst. The iron-rich fly ash components are mainly obtained from the magnetic separation of coal-fired fly ash. This method promotes the resource utilization of fly ash by-products from coal-fired power plants and significantly reduces the production cost of the catalyst. The use of iron-rich fly ash components and quicklime as raw materials for the catalyst not only allows for the recycling of waste materials but also reduces the demand for transition metal raw materials, which is in line with the concept of sustainable development. Furthermore, the present invention is applied to CO2 conversion, reducing the concentration of CO2 in the atmosphere and obtaining high-value-added chemicals, which is environmentally friendly.

[0076] Based on the same inventive concept, the present invention also provides the application of the above-mentioned calcium ferrite catalyst supported on nickel-iron alloy or the calcium ferrite catalyst supported on nickel-iron alloy prepared by the above-mentioned preparation method in the photothermal catalytic hydrogenation conversion of CO2 to CH4 and CO.

[0077] In some embodiments, the temperature for photothermal catalytic CO2 hydrogenation to prepare CH4 and CO is 250–500 °C.

[0078] The following specific embodiments further illustrate the calcium ferrite catalyst supported on nickel-iron alloys of the present invention, its preparation method, and its application. This section further illustrates the content of the present invention in conjunction with specific embodiments, but should not be construed as limiting the present invention. Unless otherwise specified, the technical means used in the embodiments are conventional means well known to those skilled in the art. Unless otherwise specified, the reagents, methods, and equipment used in the present invention are conventional reagents, methods, and equipment in the art.

[0079] Example 1

[0080] This application provides a method for preparing a calcium ferrite catalyst supported on a nickel-iron alloy, comprising the following steps:

[0081] S1. Using magnetic separation, the magnetic iron-rich component is separated from the fly ash. Take 6.80g of the magnetic iron-rich component with an iron content of about 30wt%, dissolve it with sufficient hydrochloric acid, filter out the solid insoluble matter, and obtain the first mixture.

[0082] S2. Add excess quicklime to the first mixture, filter, obtain Fe(OH)3 precipitate, wash with water, and dry.

[0083] S3: Weigh 2.67g of Fe(OH)3 and 1.85g of quicklime from S2 and add sufficient water (specifically 200g of water) to obtain a precursor emulsion;

[0084] S4. Place the precursor emulsion from S3 in a water bath stirrer and stir at 80°C for 3 hours to obtain a viscous substance.

[0085] S5. The viscous material was placed in a drying oven and dried at 100℃ for 12 hours. Then it was placed in a muffle furnace and heated to 400℃ at a heating rate of 10℃ / min for 1 hour. Then it was heated to 700℃ at a heating rate of 10℃ / min for 4 hours. The product was then ground and sieved to obtain calcium ferrite solid with an average particle size of 150μm.

[0086] S6. Weigh 0.06g of Fe(OH)3 in S2 again, dissolve it in 10.11mL of 1% nitric acid solution, and add 2.82g of Ni(NO3)2·6H2O crystals to obtain the second mixture.

[0087] S7. Weigh 2.4g of calcium ferrite solid from S5 and add it to the second mixture in S6 for ultrasonic impregnation. The impregnation temperature is 30℃ and the time is 3h.

[0088] The impregnated solution was placed in a drying oven and dried at 100°C for 12 hours, and then placed in a muffle furnace and heated to 400°C at a heating rate of 10°C / min for 4 hours.

[0089] S8. The calcined product was placed in a tube furnace and reduced at 500°C for 2 hours in a reducing atmosphere containing hydrogen to prepare 3g of calcium ferrite catalyst supported on nickel-iron alloy (denoted as 19%Ni+1%Fe / CFO).

[0090] The reducing atmosphere containing hydrogen includes a mixture of nitrogen and hydrogen, with a hydrogen volume concentration of 50%.

[0091] Example 2

[0092] This application provides a method for preparing a calcium ferrite catalyst supported on a nickel-iron alloy, comprising the following steps:

[0093] S1. Using magnetic separation, the magnetic iron-rich component is separated from the fly ash. Take 5.20g of the magnetic iron-rich component with an iron content of about 40wt%, dissolve it with sufficient hydrochloric acid, filter out the solid insoluble matter, and obtain the first mixture.

[0094] S2. Add excess quicklime to the first mixture, filter, obtain Fe(OH)3 precipitate, wash with water, and dry.

[0095] S3: Weigh 2.67g of Fe(OH)3 and 1.85g of quicklime from S2 and add sufficient water (specifically 200g of water) to obtain a precursor emulsion;

[0096] S4. Place the precursor emulsion from S3 in a water bath stirrer and stir at 90°C for 2 hours to obtain a viscous substance.

[0097] S5. The viscous material was placed in a drying oven and dried at 90°C for 12 hours. Then it was placed in a muffle furnace and heated to 300°C at a heating rate of 15°C / min for 2 hours. Then it was heated to 600°C at a heating rate of 15°C / min for 6 hours. The product was then ground and sieved to obtain calcium ferrite solid with an average particle size of 150 μm.

[0098] S6. Weigh 0.11g of Fe(OH)3 in S2 again, dissolve it in 20.21mL of 1% nitric acid solution, and add 2.68g of Ni(NO3)2·6H2O crystals to obtain the second mixture.

[0099] S7. Weigh 2.4g of calcium ferrite solid from S5 and add it to the second mixture in S6 for ultrasonic impregnation. The impregnation temperature is 50℃ and the time is 1h.

[0100] The impregnated solution was placed in a drying oven and dried at 90°C for 12 hours, and then placed in a muffle furnace and heated to 500°C at a heating rate of 15°C / min for 3 hours.

[0101] S8. The calcined product was placed in a tube furnace and reduced at 400°C for 4 hours in a reducing atmosphere containing hydrogen to prepare 3g of calcium ferrite catalyst supported on nickel-iron alloy (denoted as 18%Ni+2%Fe / CFO).

[0102] The reducing atmosphere containing hydrogen includes a mixture of nitrogen and hydrogen, with a hydrogen volume concentration of 50%.

[0103] Example 3

[0104] This application provides a method for preparing a calcium ferrite catalyst supported on a nickel-iron alloy, comprising the following steps:

[0105] S1. Using magnetic separation, the magnetic iron-rich component is separated from the fly ash. Take 4.25g of the magnetic iron-rich component with an iron content of about 50wt%, dissolve it with sufficient hydrochloric acid, filter out the solid insoluble matter, and obtain the first mixture.

[0106] S2. Add excess quicklime to the first mixture, filter, obtain Fe(OH)3 precipitate, wash with water, and dry.

[0107] S3: Weigh 2.67g of Fe(OH)3 and 1.85g of quicklime from S2 and add sufficient water (specifically 200g of water) to obtain a precursor emulsion;

[0108] S4. Place the precursor emulsion from S3 in a water bath stirrer and stir at 70°C for 3 hours to obtain a viscous substance.

[0109] S5. The viscous material was placed in a drying oven and dried at 120℃ for 8 hours. Then it was placed in a muffle furnace and heated to 400℃ at a heating rate of 5℃ / min for 1 hour. Then it was heated to 800℃ at a heating rate of 5℃ / min for 4 hours. The product was ground and sieved to obtain calcium ferrite solid with an average particle size of 150μm.

[0110] S6. Weigh 0.17g of Fe(OH)3 in S2 again, dissolve it in 30.32mL of 1% nitric acid solution, and add 2.53g of Ni(NO3)2·6H2O crystals to obtain the second mixture.

[0111] S7. Weigh 2.4g of calcium ferrite solid from S5 and add it to the second mixture in S6 for ultrasonic impregnation. The impregnation temperature is 40℃ and the time is 2h.

[0112] The impregnated solution was placed in a drying oven and dried at 120°C for 8 hours, and then placed in a muffle furnace and heated to 400°C at a heating rate of 5°C / min for 4 hours.

[0113] S8. The calcined product was placed in a tube furnace and reduced at 600°C for 2 hours in a reducing atmosphere containing hydrogen to prepare 3g of calcium ferrite catalyst supported on nickel-iron alloy (denoted as 17%Ni+3%Fe / CFO).

[0114] The reducing atmosphere containing hydrogen includes a mixture of nitrogen and hydrogen, with a hydrogen volume concentration of 30%.

[0115] Example 4

[0116] This application provides a method for preparing a calcium ferrite catalyst supported on a nickel-iron alloy, comprising the following steps:

[0117] S1. Using magnetic separation, the magnetic iron-rich component is separated from the fly ash. Take 3.61g of the magnetic iron-rich component with an iron content of about 60wt%, dissolve it with sufficient hydrochloric acid, filter out the solid insoluble matter, and obtain the first mixture.

[0118] S2. Add excess quicklime to the first mixture, filter, obtain Fe(OH)3 precipitate, wash with water, and dry.

[0119] S3: Weigh 2.67g of Fe(OH)3 and 1.85g of quicklime from S2 and add sufficient water (specifically 200g of water) to obtain a precursor emulsion;

[0120] S4. Place the precursor emulsion from S3 in a water bath stirrer and stir at 60°C for 5 hours to obtain a viscous substance.

[0121] S5. The viscous material was placed in a drying oven and dried at 110℃ for 10h. Then it was placed in a muffle furnace and heated to 300℃ at a heating rate of 10℃ / min for 2h. Then it was heated to 800℃ at a heating rate of 10℃ / min for 4h. The product was ground and sieved to obtain calcium ferrite solid with an average particle size of 150μm.

[0122] S6. Weigh 0.23g of Fe(OH)3 in S2 again, dissolve it in 40.43mL of 1% nitric acid solution, and add 2.38g of Ni(NO3)2·6H2O crystals to obtain the second mixture.

[0123] S7. Weigh 2.4g of calcium ferrite solid from S5 and add it to the second mixture in S6 for ultrasonic impregnation. The impregnation temperature is 30℃ and the time is 3h.

[0124] The impregnated solution was placed in a drying oven and dried at 110°C for 10 hours, and then placed in a muffle furnace and heated to 500°C at a heating rate of 10°C / min for 3 hours.

[0125] S8. The calcined product was placed in a tube furnace and reduced at 700°C for 1 hour in a reducing atmosphere containing hydrogen to prepare 3g of calcium ferrite catalyst supported on nickel-iron alloy (denoted as 16%Ni+4%Fe / CFO).

[0126] The reducing atmosphere containing hydrogen includes a mixture of nitrogen and hydrogen, with a hydrogen volume concentration of 80%.

[0127] Example 5

[0128] This application provides a method for preparing a calcium ferrite catalyst supported on a nickel-iron alloy, comprising the following steps:

[0129] S1. Using magnetic separation, the magnetic iron-rich component is separated from the fly ash. Take 3.16g of the magnetic iron-rich component with an iron content of about 70wt%, dissolve it with sufficient hydrochloric acid, filter out the solid insoluble matter, and obtain the first mixture.

[0130] S2. Add excess quicklime to the first mixture, filter, obtain Fe(OH)3 precipitate, wash with water, and dry.

[0131] S3: Weigh 2.67g of Fe(OH)3 and 1.85g of quicklime from S2 and add sufficient water (specifically 200g of water) to obtain a precursor emulsion;

[0132] S4. Place the precursor emulsion from S3 in a water bath stirrer and stir at 50°C for 5 hours to obtain a viscous substance.

[0133] S5. The viscous material was placed in a drying oven and dried at 100℃ for 12 hours. Then it was placed in a muffle furnace and heated to 400℃ at a heating rate of 15℃ / min for 1 hour. Then it was heated to 900℃ at a heating rate of 15℃ / min for 3 hours. The product was then ground and sieved to obtain calcium ferrite solid with an average particle size of 150μm.

[0134] S6. Weigh 0.29g of Fe(OH)3 in S2 again, dissolve it in 50.53mL of 1% nitric acid solution, and add 2.23g of Ni(NO3)2·6H2O crystals to obtain the second mixture.

[0135] S7. Weigh 2.4g of calcium ferrite solid from S5 and add it to the second mixture in S6 for ultrasonic impregnation. The impregnation temperature is 50℃ and the time is 1h.

[0136] The impregnated solution was placed in a drying oven and dried at 100°C for 12 hours, and then placed in a muffle furnace and heated to 400°C at a heating rate of 15°C / min for 4 hours.

[0137] S8. The calcined product was placed in a tube furnace and reduced at 500°C for 5 hours in a reducing atmosphere containing hydrogen to prepare 3g of calcium ferrite catalyst supported on nickel-iron alloy (denoted as 15%Ni+5%Fe / CFO).

[0138] The reducing atmosphere containing hydrogen includes a mixture of nitrogen and hydrogen, with a hydrogen volume concentration of 20%.

[0139] Performance testing

[0140] Figure 1 The image shows a SEM image of the calcium ferrite catalyst supported on nickel-iron alloy prepared in Example 1.

[0141] from Figure 1 As can be seen from the above, the calcium ferrite catalyst supported on nickel-iron alloy prepared in Example 1 is composed of nanoparticles with irregular shapes.

[0142] Figure 2 The image shows the XRD pattern of the calcium ferrite catalyst supported on nickel-iron alloy prepared in Example 1.

[0143] from Figure 2 As can be seen from the above, in the catalyst sample prepared in Example 1, nickel and iron are supported on calcium ferrite.

[0144] The calcium ferrite catalysts supported on nickel-iron alloys prepared in Examples 1 to 5 above were subjected to photothermal catalytic CO2 hydrogenation conversion tests.

[0145] The test methods for the photothermal catalytic CO2 hydrogenation conversion of the calcium ferrite catalyst supported on nickel-iron alloy in Examples 1-5 above are the same, as described below:

[0146] The catalytic hydrogenation performance of the calcium ferrite catalysts supported on nickel-iron alloys in Examples 1-5 was tested in a fixed-bed reactor. 0.4 g of the calcium ferrite catalyst supported on nickel-iron alloys was weighed, uniformly mixed with 1.2 g of quartz sand, and then packed into the reactor. CO2 and H2 were mixed and introduced into the reactor for reaction. The molar ratio of CO2 to H2 in the reaction gas was 1:4, the reaction temperature range was 250–500 °C, and the reaction pressure was atmospheric pressure.

[0147] The CO2 conversion rate, product selectivity, and product yield in the following examples and comparative examples were calculated using the following methods:

[0148] CO2 conversion rate = (CO2 concentration at reactor inlet - CO2 concentration at reactor outlet) / CO2 concentration at reactor inlet × 100%;

[0149] Product selectivity = Concentration of product at reactor outlet / (CO2 concentration at reactor inlet - CO2 concentration at reactor outlet) × 100%.

[0150] Product yield = (Total inlet flow rate per unit time × Inlet gas CO2 concentration × CO2 conversion rate × Product selectivity) / (Ideal gas molar volume under standard conditions × Catalyst mass)

[0151] Comparative Example 1

[0152] Comparative Example 1: Photothermal catalytic CO2 hydrogenation conversion experiments were conducted using catalysts LaNiO3, LaCoO3, and LaFeO3. The reaction conditions were as follows: 0.35 g of catalyst was uniformly mixed with 1.2 g of quartz sand; the light source was a 300 W xenon lamp; the molar ratio of H2 to CO2 in the reaction gas was 4:1; and the reaction temperature was 200 °C. The catalysts LaNiO3, LaCoO3, and LaFeO3 used in Comparative Example 1 were prepared according to the following literature: ZHAO S, LUO Y, LI C, et al. High-performance photothermalcatalytic CO2 reduction to CH4 and CO by ABO3 (A=La,Ce;B=Ni,Co,Fe) perovskitenanomaterials. Ceramics International, 2023, 49(12):20907-19.

[0153] Comparative Example 2

[0154] Comparative Example 2 used NiO / Ni-G catalyst for photothermal catalytic CO2 hydrogenation conversion. The reaction conditions were as follows: 40 mg of catalyst was uniformly mixed with 1.2 g of quartz sand; the light source was a 300 W xenon lamp; the molar ratio of H2 to CO2 in the reaction gas was 4:1; and the reaction temperature was 200 °C. The NiO / Ni-G catalyst described in Comparative Example 2 was prepared according to the following literature: MATEO D, ALBERO J, GARCíA H. Graphene supported NiO / Ni nanoparticles as efficient photocatalyst for gas phase CO2 reduction with hydrogen. Applied Catalysis B: Environmental, 2018, 224: 563-71.

[0155] Comparative Example 3

[0156] Comparative Example 3 used Pd@Nb2O5 catalyst for photothermal catalytic CO2 hydrogenation conversion. The reaction conditions were as follows: 4 mg of catalyst was uniformly mixed with 1.2 g of quartz sand; the light source was a 300 W xenon lamp; the molar ratio of H2 to CO2 in the reaction gas was 4:1; and the reaction temperature was 160 °C. The Pd@Nb2O5 catalyst described in Comparative Example 3 was prepared according to the following literature: JIA J, O'BRIEN PG, HE L, et al. Visible and Near-Infrared Photothermal Catalyzed Hydrogenation of Gaseous CO2 over Nanostructured Pd@Nb2O5. Advanced Science, 2016, 3(10): 1600-189.

[0157] Comparative Example 4

[0158] Comparative Example 4 involved a thermocatalytic CO2 hydrogenation conversion experiment using a 20% Ni / MFFAC catalyst. The reaction conditions were as follows: 0.2 g of catalyst was uniformly mixed with 1.2 g of quartz sand; the molar ratio of H2 to CO2 in the reaction gas was 4:1; and the catalytic reaction temperature was 400℃. The 20% Ni / MFFAC catalyst described in Comparative Example 4 was prepared according to the following patent: CN202110956770.3, "A Highly Efficient Catalyst with Magnetic Iron-Rich Component Supported Nickel and Its Preparation Method and Application".

[0159] The catalysts prepared in Examples 1-5 (19% Ni + 1% Fe / CFO, 18% Ni + 2% Fe / CFO, 17% Ni + 3% Fe / CFO, 16% Ni + 4% Fe / CFO, and 15% Ni + 5% Fe / CFO) were used in photothermal catalytic CO2 hydrogenation conversion experiments and compared with Comparative Examples 1-4, including CH4 yield and CO yield. The reaction conditions for photothermal catalytic CO2 hydrogenation conversion in Examples 1-5 were: catalyst 0.4 g; light source 300 W xenon lamp; molar ratio of H2:CO2 in the reaction gas 4:1; reaction temperature 400 °C.

[0160] The performance of the catalysts prepared in Examples 1-5 and Comparative Examples 1-4 is shown in Table 1 below.

[0161] Table 1 - Catalyst performance of different embodiments and comparative examples

[0162]

[0163]

[0164] As shown in Table 1, the photothermal catalytic CO2 hydrogenation conversion effects of Comparative Examples 1-4 and Examples 1-5 show that the CH4 and CO yields of the catalyst in Comparative Example 1, the CH4 yield of the catalyst in Comparative Example 2, and the CO yield of the catalyst in Comparative Example 3 are much lower than those of the catalyst prepared in this invention. Under the same conditions, the CH4 and CO yields of Comparative Example 4 are about half that of Example 1. It can be seen that the catalyst prepared in this invention has a good photothermal catalytic reduction effect on CO2.

[0165] Figure 3 The CO2 conversion rate and product selectivity of the calcium ferrite catalyst supported on nickel-iron alloy prepared in Example 1 during photothermal catalytic CO2 hydrogenation at 250–500 °C.

[0166] Figure 4 The product yield of the calcium ferrite catalyst supported on nickel-iron alloy prepared in Example 1 during photothermal catalytic hydrogenation conversion of CO2 at 250–500 °C.

[0167] Depend on Figure 3 It can be seen that the calcium ferrite catalyst supported on nickel-iron alloy prepared in Example 1 exhibits a CO2 conversion rate that increases with increasing temperature over a wide temperature window (250–500 °C) without showing a decreasing trend. The main products are CH4 and CO. The CH4 selectivity shows a "Z"-shaped pattern with increasing temperature, and the highest yield of 32.54 mmol·g is obtained at 400 °C. -1 h -1 .

[0168] Depend on Figure 4It can be seen that the calcium ferrite catalyst supported on nickel-iron alloy prepared in Example 1 still maintains high CO2 conversion and product yield under high temperature conditions. At 500℃, the CO2 conversion is 55.8%, and the CH4 and CO yields are 21.0 and 53.7 mmol·g, respectively. -1 h -1 This indicates that the catalyst has excellent catalytic performance and good anti-sintering properties.

[0169] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A calcium ferrite catalyst supported on a nickel-iron alloy, characterized in that, The catalyst comprises calcium ferrite and a nickel-iron alloy supported on the calcium ferrite; The catalyst contains 15-19% nickel and 1-5% iron by mass.

2. A method for preparing a calcium ferrite catalyst supported on a nickel-iron alloy as described in claim 1, characterized in that, Includes the following steps: The magnetic iron-rich components were separated from the fly ash by magnetic separation. The magnetic iron-rich components were then dissolved in acid and filtered to obtain the first mixture. Add quicklime to the first mixture, filter, and obtain Fe(OH)3 precipitate; After mixing quicklime and the Fe(OH)3 precipitate, water was added to obtain a precursor emulsion. The precursor emulsion was heated and stirred to obtain a viscous substance; After drying the viscous substance, it was calcined to obtain solid calcium ferrite. The Fe(OH)3 precipitate was dissolved in acid, and then nickel salt was added to obtain a second mixture. The calcium ferrite solid was added to the second mixture, impregnated, dried, and calcined. The calcined product was reduced to obtain a calcium ferrite catalyst supported on nickel-iron alloy.

3. The method for preparing the calcium ferrite catalyst supported on nickel-iron alloy as described in claim 2, characterized in that, The molar ratio of calcium to iron in the precursor emulsion is (1~1.3):

1.

4. The method for preparing the calcium ferrite catalyst supported on nickel-iron alloy as described in claim 2, characterized in that, In the step of heating and stirring the precursor emulsion to obtain a viscous substance, the heating temperature is 50~90℃ and the stirring time is 2~5h.

5. The method for preparing the calcium ferrite catalyst supported on nickel-iron alloy as described in claim 2, characterized in that, The viscous substance was dried and then calcined to obtain solid calcium ferrite; the drying temperature was 90~120℃ and the time was 8~12h. The calcination specifically includes: The dried viscous material is heated to 300-400℃ at a rate of 5-20℃ / min and calcined for 1-2 hours. Then raise the temperature to 600-900℃ at a rate of 5-20℃ / min and calcine for 3-6 hours.

6. The method for preparing the calcium ferrite catalyst supported on nickel-iron alloy as described in claim 2, characterized in that, In the steps of adding the calcium ferrite solid to the second mixture, impregnating, drying, and calcining, the sum of the mass of nickel and iron elements in the second mixture is 20-30% of the mass of calcium ferrite. The impregnation method is ultrasonic impregnation, with an impregnation temperature of 30~50℃ and a time of 1~3h; The drying temperature is 90~120℃ and the time is 8~12h; The calcination process specifically includes heating the dried product to 400-500℃ at a rate of 5-20℃ / min and calcining for 3-4 hours.

7. The method for preparing the calcium ferrite catalyst supported on nickel-iron alloy as described in any one of claims 2 to 6, characterized in that, The fly ash is coal-fired fly ash, and the iron content in the fly ash is 4-40% by mass. And / or, in the step of adding quicklime to the first mixture, filtering, and obtaining Fe(OH)3 precipitate, adding excess quicklime allows the iron in the first mixture to be completely converted into Fe(OH)3 precipitate; And / or, the nickel salt includes at least one of nickel nitrate, nickel chloride, nickel bromide, or nickel sulfate; And / or, in the steps of dissolving the magnetic iron-rich component with acid and dissolving the Fe(OH)3 precipitate with acid, the acid includes at least one of hydrochloric acid, sulfuric acid, and nitric acid; And / or, in the step of reducing the calcined product, the calcined product is reduced in a reducing atmosphere containing hydrogen. The volume concentration of hydrogen in the reducing atmosphere is 10-100%, the reduction temperature is 400-700℃, and the reduction time is 1-5h. And / or, after drying the viscous substance, calcining it, and then sieving it to obtain calcium ferrite solid with a particle size of 100-200 μm.

8. The application of a calcium ferrite catalyst supported on nickel-iron alloy as described in claim 1 or a calcium ferrite catalyst supported on nickel-iron alloy prepared by any of the preparation methods described in claims 2 to 7 in the photothermal catalytic hydrogenation conversion of CO2 to CH4 and CO.

9. In the application as described in claim 8, the temperature for the photothermal catalytic CO2 hydrogenation conversion to prepare CH4 and CO is 250~500℃.

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