Fe-Co micrometer alloy catalyst, preparation method and application thereof

Abstract

The present application relates to the field of catalytic conversion of carbon dioxide, in particular to a Fe-Co microalloy catalyst and its preparation method and application, the present application first reduces the metal salt solution under strong alkaline conditions by hydrazine hydrate treatment, adjusts the amount of cyclohexane dispersant and end-capping agent PEG-400 and reaction time to realize the preparation of Fe-Co microalloy. Drying in room temperature air makes the alloy particles surface oxidized, and then H2 reduction treatment is carried out to obtain Fe-Co microalloy with high dispersion oxygen vacancies on the surface, which can be directly used for CO2 hydrogenation reaction without subsequent treatment. The catalyst is easy to synthesize and has good stability, the catalyst prepared by the present application can realize more than 99% methane selectivity in CO2 hydrogenation reaction, and the CO2 conversion rate in high-pressure reaction kettle can reach 62.5% in 1h.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of catalytic conversion of carbon dioxide, in particular to a Fe-Co micro-alloy catalyst and its preparation method and application. BACKGROUND

[0002] Carbon dioxide is not only the main source of greenhouse gas emissions, but also plays a key role in the carbon cycle on Earth. However, due to its chemical stability, the conversion and utilization of carbon dioxide has always been a challenge. Among the numerous conversion pathways, the methanation of carbon dioxide has received particular attention because it can directly convert carbon dioxide into methane, a clean fuel. However, there are still many problems to be solved in CO2 methanation. First, the cleavage of the carbon-oxygen bond (C-O) in the carbon dioxide molecule is a major challenge, resulting in low efficiency of carbon dioxide methanation at low temperatures (≤ 350℃). Although the use of cost-effective nickel-based catalysts can improve the methanation performance at low temperatures (~ 300℃), there are still few reports on achieving high carbon dioxide conversion at lower temperatures (≤ 240℃), and the structure-catalytic performance correlation of the catalyst is not well understood. Second, the content and distribution of oxygen vacancies and hydroxyl groups in the catalyst support affect the methanation performance, but the exact potential mechanisms controlling these effects have not been consistently documented.

[0003] Transition metal nano-alloys have been widely used in the catalytic conversion of CO2, but the small size of the nanoparticles weakens the CO2 adsorption capacity, leading to the production of more byproduct CO. In addition, how to increase the active sites of the alloy catalyst, improve the stability and recovery ability of the catalyst, and achieve high selectivity and high conversion rate during the preparation process are the problems to be solved at present. SUMMARY

[0004] In view of the above technical problems of the prior art, the purpose of the present application is to provide a Fe-Co micro-alloy catalyst and its preparation method and application. The present application controls the size of the metal alloy by dispersing agent, end-capping agent and reaction time, and realizes the formation of high-dispersed oxygen vacancies in the H2 reduction step by using the difference in metal redox performance and the metal arrangement method in the alloy step.

[0005] To solve the above technical problems, the present application adopts the following technical scheme:

[0006] A preparation method of a Fe-Co micro-alloy catalyst, comprising the following steps:

[0007] The application discloses a preparation method of Fe-Co micron alloy particles.

[0008] The Fe-Co micron alloy particles are subjected to H2 reduction treatment after surface oxidation to obtain Fe-Co micron alloy catalysts with high-dispersed oxygen vacancies.

[0009] The application discloses a preparation method of Fe-Co micron alloy particles.

[0010] The application has the following advantages: ① simple process, low requirement on experimental equipment; ② easy to control the size and morphology of the micron particles; ③ easy to handle the reduction product; ④ other reduction agents have the problems of complex reduction process, insufficient reduction capacity, need to add complexing agents, and difficult to handle the reduction product.

[0011] In the preferred embodiment of the application, the molar ratio of cobalt to iron in the soluble cobalt salt and the soluble iron salt is 3-9:1.

[0012] In the preferred embodiment of the application, the ratio of the amount of cyclohexane to the amount of the soluble cobalt salt is 1 mL:0.6 mmol-14 mmol, the ratio of the amount of cyclohexane to the amount of polyethylene glycol 400 is 1 mL:3.4 g-21.5 g, and the ratio of the amount of water to the amount of polyethylene glycol 400 is 1 mL:0.05 g-0.34 g.

[0013] In the preferred embodiment of the present application, the ratio of the amount of the soluble cobalt salt to the amount of hydrazine hydrate is 1 mL:0.02 mmol~0.5 mmol, and the mass concentration of the hydrazine hydrate is 75%~85%.

[0014] In the preferred embodiment of the present application, the hydrothermal reaction temperature is 70℃~85℃, the hydrothermal reaction time is 6 h~10h, and the sodium hydroxide and the hydrazine hydrate are added at 70℃~85℃: ①The original solvent is mixed uniformly; ②The reaction speed is accelerated, and a part of N2 generated due to the reduction reaction is released, so as to avoid the gas pressure in the polytetrafluoroethylene reaction kettle being too high; ③The reaction temperature being too high is relatively dangerous.

[0015] In the preferred embodiment of the present application, the H2 reduction treatment temperature is 280℃~400℃, and the reduction treatment time is 1h~3 h.

[0016] In the preferred embodiment of the present application, the soluble cobalt salt is cobalt chloride hexahydrate, and the soluble iron salt is ferrous sulfate heptahydrate.

[0017] Another object of the present application is to provide a Fe-Co microalloy catalyst prepared by the above preparation method.

[0018] A third object of the present application is to provide an application of the Fe-Co microalloy catalyst in the CO2 hydrogenation reaction.

[0019] The application method is: passing the CO2 and H2 mixed gas into the Fe-Co microalloy catalyst for reaction, the reaction temperature is 160℃~280℃, the reaction pressure is 3 MPa~6 MPa, the reaction time is 60 min~70 min, and the volume ratio of CO2 to H2 in the mixed gas is 1:3~6.

[0020] Compared with the prior art, the present application has the beneficial effects that:

[0021] 0、The present application uses soluble cobalt salt and soluble iron salt as raw materials, cyclohexane as a dispersant, polyethylene glycol 400 as a capping agent, uses hydrazine hydrate to reduce the soluble metal salt, obtains Fe-Co micron alloy particles, and obtains the Fe-Co micron alloy catalyst with high dispersion oxygen vacancies after the surface oxidation of the Fe-Co micron alloy and H2 reduction treatment, the dispersant cyclohexane used in the present application can efficiently disperse the alloy particles, promote the ordered arrangement of the alloy particles, polyethylene glycol 400 changes the shape of the alloy particles by regulating the growth rate of different crystal faces, different molecular weight polyethylene glycols have different viscosities and high molecular chain lengths, thereby affecting the reaction in the solution, and the polyethylene glycol with higher molecular weight can excessively inhibit the growth of the alloy particles, finally, the high dispersion oxygen vacancies are formed in the H2 reduction step by utilizing the difference in the metal redox performance and the metal arrangement mode in the synthesis step, the active sites of the catalyst are increased, and efficient methanation of CO2 is realized.

[0022] 1、The Fe-Co micron alloy catalyst has a larger specific surface area and higher stability, the high-efficiency dispersed oxygen vacancies in the Fe-Co micron alloy are helpful to CO2 adsorption and methanation reaction, the metal active sites around the oxygen vacancies in the Fe-Co micron alloy structure can efficiently activate H2, the hydrogen overflow effect makes the C-O bond adsorbed on the Fe-Co micron alloy more easily broken, and the high-dispersion vacancies effectively inhibit C-C coupling, so that the selectivity of CH4 is significantly improved.

[0023] 2、The Fe-Co micron alloy with surface high-dispersion oxygen vacancies prepared in the present application can be directly used for CO2 hydrogenation reaction without subsequent treatment, the catalyst is easy to synthesize, has good stability, and low material price, the catalyst prepared in the present application can realize more than 99% of the selectivity of methane in the CO2 hydrogenation reaction, the CO2 conversion rate in a high-pressure reaction kettle can reach 62.5% in 1 h, and the catalyst has industrial development prospects. BRIEF DESCRIPTION OF DRAWINGS

[0024] Figure 1 The micro-morphology diagram of the catalyst prepared for the present application examples 1-2 and comparative example 1.

[0025] Figure 2 The X-ray diffraction diagram of the catalyst prepared for the present application examples 1-2 and comparative example 1.

[0026] Figure 3 The hydrogen temperature programmed reduction diagram of the catalyst prepared for the present application examples 1-2 and comparative example 1. DETAILED DESCRIPTION

[0027] The technical solutions in the embodiments of the present application will be clearly and completely described with the preferred embodiments and the accompanying drawings, and it is obvious that the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments of the present application, all the other embodiments obtained by those skilled in the art without creative work fall within the protection scope of the present application.

[0028] It should be noted that all the professional terms used in the present application are only for the purpose of describing the specific embodiments, and are not intended to limit the protection scope of the present application. Unless otherwise specified, the various raw materials, reagents, instruments and equipment used in the following embodiments of the present application can be purchased from the market or prepared by the existing method.

[0029] Embodiment 1

[0030] A preparation method of a Fe-Co micron alloy catalyst, comprising the following steps:

[0031] (1) Dissolve 5.36 g of cobalt chloride hexahydrate, 0.695 g of ferrous sulfate heptahydrate, 4 mL of cyclohexane and 34.4 g of polyethylene glycol 400 in 250 mL of deionized water, wherein the molar ratio of cobalt to iron is 9:1, and then add 12.35 g of sodium hydroxide and 106 mL of 80% hydrazine hydrate when heated to 80°C, to obtain a black-gray mixed solution.

[0032] (2) Place the black-gray mixed solution in a polytetrafluoroethylene reaction kettle, and reduce at 80°C for 6 h. After cooling, use a permanent magnet bar to preliminarily separate the solid product in the black-gray mixed solution, to obtain Fe-Co micron alloy particles.

[0033] (3) Wash the solid product with deionized water for 5 times and then with anhydrous ethanol for 3 times, and dry at room temperature under air condition to promote the oxidation of the surface of the micron alloy. Dry the Fe-Co micron alloy at 300°C for 1 h for H2 reduction treatment, to obtain a Fe-Co micron alloy catalyst.

[0034] Embodiment 2

[0035] A preparation method of a Fe-Co micron alloy catalyst, comprising the following steps:

[0036] (1) Dissolve cobalt chloride hexahydrate, ferrous sulfate heptahydrate, 4 mL of cyclohexane and 34.4 g of polyethylene glycol 400 in 250 mL of deionized water, wherein the molar ratio of cobalt to iron is 3:1, and then add 12.35 g of sodium hydroxide and 106 mL of 80% hydrazine hydrate when heated to 80°C, to obtain a black-gray mixed solution.

[0037] (2) The black-gray mixed solution is placed in a polytetrafluoroethylene reactor, and reduction treatment is performed at 80°C for 6 hours. After cooling, a permanent magnet rod is used to preliminarily separate the solid product in the black-gray mixed solution, to obtain Fe-Co micron alloy particles.

[0038] (3) The solid product is washed 5 times with deionized water and 3 times with anhydrous ethanol, and dried at room temperature under air conditions to promote the oxidation of the micron alloy surface. The dried Fe-Co micron alloy is subjected to H2 reduction treatment at 300°C for 1 hour, to obtain a Fe-Co micron alloy catalyst.

[0039] Example 3

[0040] A preparation method of a Fe-Co micron alloy catalyst, comprising the following steps:

[0041] (1) 5.36 g of cobalt chloride hexahydrate, 0.695 g of ferrous sulfate heptahydrate, 1.6 mL of cyclohexane, and 13.76 g of polyethylene glycol 400 are dissolved in 100 mL of deionized water, wherein the molar ratio of cobalt to iron is 9:1. When heated to 80°C, 12.35 g of sodium hydroxide and 42.4 mL of 80% hydrazine hydrate are added, to obtain a black-gray mixed solution.

[0042] (2) The black-gray mixed solution is placed in a polytetrafluoroethylene reactor, and reduction treatment is performed at 80°C for 6 hours. After cooling, a permanent magnet rod is used to preliminarily separate the solid product in the black-gray mixed solution, to obtain Fe-Co micron alloy particles.

[0043] (3) The solid product is washed 5 times with deionized water and 3 times with anhydrous ethanol, and dried at room temperature under air conditions to promote the oxidation of the micron alloy surface. The dried Fe-Co micron alloy is subjected to H2 reduction treatment at 300°C for 1 hour, to obtain a Fe-Co micron alloy catalyst.

[0044] Example 4

[0045] A preparation method of a Fe-Co micron alloy catalyst, comprising the following steps:

[0046] (1) 5.36 g of cobalt chloride hexahydrate, 0.695 g of ferrous sulfate heptahydrate, 1.6 mL of cyclohexane, and 13.76 g of polyethylene glycol 400 are dissolved in 100 mL of deionized water, wherein the molar ratio of cobalt to iron is 9:1. When heated to 80°C, 12.35 g of sodium hydroxide and 42.4 mL of 80% hydrazine hydrate are added, to obtain a black-gray mixed solution.

[0047] (2) The black-gray mixed solution is placed in a polytetrafluoroethylene reaction kettle, and reduction treatment is performed at 70°C for 10 h. After cooling, the solid product in the black-gray mixed solution is preliminarily separated using a permanent magnet bar to obtain Fe-Co micron alloy particles.

[0048] (3) The solid product is washed 5 times using deionized water and then washed 3 times using anhydrous ethanol. Drying is performed at room temperature under air conditions to promote surface oxidation of the micron alloy. The dried Fe-Co micron alloy is subjected to H2 reduction treatment at 280°C for 3 h to obtain a Fe-Co micron alloy catalyst.

[0049] Example 5

[0050] A preparation method of a Fe-Co micron alloy catalyst includes the following steps:

[0051] (1) 5.36 g of cobalt chloride hexahydrate, 0.695 g of ferrous sulfate heptahydrate, 2.4 mL of cyclohexane, and 24.4 g of polyethylene glycol 400 are dissolved in 180 mL of deionized water, wherein the molar ratio of cobalt to iron is 9:1. When heated to 80°C, 12.35 g of sodium hydroxide and 65 mL of 80% hydrazine hydrate are added to obtain a black-gray mixed solution.

[0052] (2) The black-gray mixed solution is placed in a polytetrafluoroethylene reaction kettle, and reduction treatment is performed at 85°C for 8 h. After cooling, the solid product in the black-gray mixed solution is preliminarily separated using a permanent magnet bar to obtain Fe-Co micron alloy particles.

[0053] (3) The solid product is washed 5 times using deionized water and then washed 3 times using anhydrous ethanol. Drying is performed at room temperature under air conditions to promote surface oxidation of the micron alloy. The dried Fe-Co micron alloy is subjected to H2 reduction treatment at 400°C for 2 h to obtain a Fe-Co micron alloy catalyst.

[0054] Comparative Example 1

[0055] A preparation method of a Fe-Co micron alloy catalyst includes the following steps:

[0056] (3) Cobalt chloride hexahydrate, ferrous sulfate heptahydrate, 4 mL of cyclohexane, and 34.4 g of polyethylene glycol 400 are dissolved in 250 mL of deionized water, wherein the molar ratio of cobalt to iron is 1:3. When heated to 80°C, 12.35 g of sodium hydroxide and 106 mL of 80% hydrazine hydrate are added to obtain a black-gray mixed solution.

[0057] (4) The black-gray mixed solution is placed in a polytetrafluoroethylene reaction kettle, and reduction treatment is performed at 80°C for 6 h. After cooling, the solid product in the black-gray mixed solution is preliminarily separated using a permanent magnet bar.

[0058] (5) The solid product was washed 5 times with deionized water and 3 times with anhydrous ethanol, and dried at room temperature under air condition to promote the oxidation of the surface of the micron alloy. The dried Fe-Co micron alloy was subjected to H2 reduction treatment at 300℃ for 1h to obtain a Fe-Co micron alloy catalyst.

[0059] In a high-pressure reaction kettle equipped with magnetic stirring, 100 mg of catalyst was added, and CO2 and H2 mixed gas was introduced. After reaching the reaction temperature, samples were taken every certain period of time to detect the content of each component in the gas phase by gas chromatography (GC-FID / TCD), and the CH4 selectivity and CO2 conversion rate were calculated:

[0060]

[0061]

[0062] Application Example 1

[0063] 100 mg of Fe-Co micron alloy (1:3) was placed in the reaction kettle, CO2:H2 (3:1) mixed gas was introduced, the reaction conditions were adjusted to 280℃, 6 MPa, and the reaction was carried out for 60 min. The CO2 and CH4 contents were measured and the CO2 conversion rate was calculated to be 30.9%, and the CH4 selectivity was 80.7%.

[0064] Application Example 2

[0065] 100 mg of Fe-Co micron alloy (1:3) was placed in the reaction kettle, CO2:H2 (1:3) mixed gas was introduced, the reaction conditions were adjusted to 280℃, 6 MPa, and the reaction was carried out for 60 min. The CO2 and CH4 contents were measured and the CO2 conversion rate was calculated to be 20.7%, and the CH4 selectivity was 96.1%.

[0066] Application Example 3

[0067] 100 mg of Fe-Co micron alloy (1:9) was placed in the reaction kettle, CO2:H2 (1:3) mixed gas was introduced, the reaction conditions were adjusted to 280℃, 6 MPa, and the reaction was carried out for 60 min. The CO2 and CH4 contents were measured and the CO2 conversion rate was calculated to be 35.8%, and the CH4 selectivity was 99%.

[0068] Application Example 4

[0069] 100 mg Fe-Co microalloy (1:9) was placed in a reaction kettle, CO2:H2(1:3) mixed gas was introduced, the reaction conditions were adjusted to 160℃, 6 MPa, and reacted for 60 min. The CO2 and CH4 contents were measured and the CO2 conversion rate was calculated to be 4.3%, and the CH4 selectivity was 98.7%.

[0070] Application Example 5

[0071] 100 mg Fe-Co microalloy (1:9) was placed in a reaction kettle, CO2:H2(1:3) mixed gas was introduced, the reaction conditions were adjusted to 200℃, 6 MPa, and reacted for 60 min. The CO2 and CH4 contents were measured and the CO2 conversion rate was calculated to be 9.1%, and the CH4 selectivity was 99.1%.

[0072] Application Example 6

[0073] 100 mg Fe-Co microalloy (1:9) was placed in a reaction kettle, CO2:H2(1:3) mixed gas was introduced, the reaction conditions were adjusted to 240℃, 6 MPa, and reacted for 60 min. The CO2 and CH4 contents were measured and the CO2 conversion rate was calculated to be 18.7%, and the CH4 selectivity was 98.9%.

[0074] Application Example 7

[0075] 100 mg Fe-Co microalloy (1:9) was placed in a reaction kettle, CO2:H2(1:3) mixed gas was introduced, the reaction conditions were adjusted to 280℃, 3 MPa, and reacted for 60 min. The CO2 and CH4 contents were measured and the CO2 conversion rate was calculated to be 53.1%, and the CH4 selectivity was 93.6%.

[0076] Application Example 8

[0077] 100 mg Fe-Co microalloy (1:9) was placed in a reaction kettle, CO2:H2(1:3) mixed gas was introduced, the reaction conditions were adjusted to 280℃, 4 MPa, and reacted for 60 min. The CO2 and CH4 contents were measured and the CO2 conversion rate was calculated to be 45.5%, and the CH4 selectivity was 94.8%.

[0078] Application Example 9

[0079] 100 mg Fe-Co microalloy (1:9) was placed in a reaction kettle, CO2:H2(1:3) mixed gas was introduced, the reaction conditions were adjusted to 280℃, 5 MPa, and reacted for 60 min. The CO2 and CH4 contents were measured and the CO2 conversion rate was calculated to be 38.6%, and the CH4 selectivity was 98.4%.

[0080] Application Example 10

[0081] 100 mg Fe-Co micron alloy (1:9) was placed in the reaction kettle, CO2:H2 (1:6) mixed gas was introduced, the reaction conditions were adjusted to 280℃, 6 MPa, and the reaction was carried out for 60 min. The CO2 and CH4 contents were measured and the CO2 conversion rate was calculated to be 62.5%, and the CH4 selectivity was 96%.

[0082] Result analysis

[0083] Table 1 Test results of application examples 1-10

[0084]

[0085] From Table 1, it can be seen that the CO2 conversion rate increases with the increase of the reaction temperature, and the influence on the methane selectivity is low; the CO2 conversion rate decreases with the increase of the reaction pressure, but the methane selectivity is significantly improved. The increase of the proportion of H2 in the mixed gas significantly improves the CO2 conversion rate, but the methane selectivity decreases slightly. The proportion of metals in the Fe-Co micron alloy also has a great influence on the CO2 conversion rate and the CH4 selectivity, and the CO2 methanation effect is best when the Fe:Co is 1:9. According to the analysis of the above application data, the Fe-Co micron alloy still has high CH4 selectivity and CO2 conversion rate under the condition of great changes in temperature, pressure and other related parameters.

[0086] Figure 1 The morphology of the Fe-Co micron alloy catalyst prepared in different Fe-Co proportions for the application examples 1-2 and the comparative example 1, from the figure, it can be seen that according to the amount of ferrous sulfate heptahydrate and cobalt chloride hexahydrate used, the morphology of the catalyst has changed significantly. It can be clearly seen that the size of the Fe-Co particles increases significantly with the increase of the Co content, and the structure changes from cubic to flower rod, and the crystal mainly grows along the rod direction. The results show that the size and morphology of the catalyst are successfully controlled.

[0087] Figure 2 The X-ray diffraction (XRD) pattern of the catalyst prepared in the application examples 1-2 and the comparative example 1, the XRD spectrum of the catalyst is consistent with the standard PDF card (PDF#48-1816 Co3Fe7, PDF#50-0795 Co7Fe3, PDF#15-0806 Co), which indicates the successful synthesis of the Fe-Co micron alloy catalyst. In addition, the characteristic peak position of the catalyst before and after the reaction is consistent, and the catalyst before and after the reaction is the same substance, and the change of the peak intensity is mainly due to the further reduction in the hydrogenation process, which leads to the increase of the oxygen vacancy of the catalyst.

[0088] Figure 3 The H2-TPR (hydrogen temperature programmed reduction) graphs of the catalysts prepared for Example 1-Example 2 and Comparative Example 1 of the present application can be seen that the hydrogen consumption is significantly lower when Fe:Co is 1:3 and 1:9 than 3:1. Because the Fe-Co microparticles with higher Co content are more difficult to be oxidized, the amount of hydrogen consumed in the reduction process is less, so that there are less surface oxygen vacancies after reduction, which effectively inhibits C-C coupling, and thus the CH4 selectivity is higher. When Fe:Co is 1:9, the reduction peak appears at a lower temperature in the reduction process than when Fe:Co is 1:3, indicating that the microparticle alloy is more easily reduced when Fe:Co is 1:9, and the advantage is obvious at a reaction temperature of 280℃, so that the CO2 conversion is higher when Fe:Co is 1:9.

[0089] In summary, the present application uses soluble cobalt salt and soluble iron salt as raw materials, cyclohexane as a dispersant, polyethylene glycol 400 as a capping agent, and hydrazine hydrate to reduce the soluble metal salt to obtain Fe-Co microparticle alloy, and then perform H2 reduction treatment to obtain Fe-Co microparticle alloy catalyst with high dispersion of oxygen vacancies. The dispersant cyclohexane used in the present application can efficiently disperse the alloy particles, promote the ordered arrangement of the alloy particles, and polyethylene glycol 400 can change the shape of the alloy particles by regulating the growth rate of different crystal planes. Different molecular weights of PEG have different viscosities and high molecular chain lengths, thereby affecting the reaction in the solution. Higher molecular weight polyethylene glycol can excessively inhibit the growth of alloy particles. Finally, the difference in metal redox performance and the metal arrangement mode in the synthesis step are used to realize the formation of high dispersion of oxygen vacancies in the H2 reduction step, increase the active sites of the catalyst, and realize efficient methanation of CO2. The Fe-Co microparticle alloy catalyst of the present application has a large specific surface area and high stability, with a specific surface area of 284 m 2 / g~1952 m 2 / g. Increasing the amount of cobalt salt during synthesis increases the size of the alloy particles, and the specific surface area decreases. The Fe-Co microparticle alloy catalyst still has 90% catalytic activity after 4 cycles. The high dispersion of oxygen vacancies in the Fe-Co microparticle alloy helps to adsorb CO2, which is beneficial to the methanation reaction. The metal active sites around the oxygen vacancies in the Fe-Co microparticle alloy structure can efficiently activate H2. The hydrogen overflow effect makes it easier for the C-O bond adsorbed on the Fe-Co microparticle alloy to break, and the high dispersion of vacancies effectively inhibits C-C coupling, significantly improving the selectivity of CH4.

[0090] It is to be understood that every range of values disclosed herein is to be understood to encompass any and every sub-range of values within the range. Although the preferred embodiments of the invention have been described above, it will be appreciated that those skilled in the art, on consideration of this disclosure, will be able to devise additional embodiments that, although not explicitly described or shown herein, embody the principles of the invention and, thus, are within the spirit and scope of the invention. Accordingly, while the preferred embodiments of the invention have been described above, it will be appreciated that those skilled in the art will be able to devise additional embodiments that, although not explicitly described or shown herein, embody the principles of the invention and, thus, are within the spirit and scope of the invention.

[0091] Obviously, numerous modifications and variations of the present application are possible in light of the above teachings. It is therefore to be understood that within the scope of the appended claims, the application can be practiced otherwise than as specifically described herein.

Claims

1. Use of a Fe-Co microalloy catalyst in the reaction of CO2 hydrogenation to methane, characterized in that, The preparation method of the Fe-Co microalloy catalyst comprises the following steps: The soluble cobalt salt and the soluble iron salt are mixed with cyclohexane as a dispersing agent and polyethylene glycol 400 as a capping agent, and then dissolved in water; after heating, hydrazine hydrate is added to reduce the soluble cobalt salt and the soluble iron salt under alkaline conditions to obtain a mixed solution; the solid product in the mixed solution is separated to obtain Fe-Co microalloy particles; The surface of the Fe-Co microalloy particles is oxidized and then subjected to H2 reduction treatment to obtain the Fe-Co microalloy catalyst with high-dispersed oxygen vacancies; The molar ratio of cobalt to iron in the soluble cobalt salt and the soluble iron salt is 3-9:

1.

2. Use according to claim 1, characterized in that, The ratio of the amount of cyclohexane to the amount of the soluble cobalt salt is 1 mL:0.6 mmol-14 mmol, the ratio of the amount of cyclohexane to the amount of polyethylene glycol 400 is 1 mL:3.4 g-21.5 g, and the ratio of the amount of water to the amount of polyethylene glycol 400 is 1 mL:0.05 g-0.34 g.

3. Use according to claim 1, characterized in that, The ratio of the amount of hydrazine hydrate to the amount of the soluble cobalt salt is 1 mL:0.02 mmol-0.5 mmol.

4. Use according to claim 1, characterized in that, The heating temperature is 70-85°C, and the reduction treatment time of hydrazine hydrate is 6-10 hours.

5. The use according to claim 1, characterized in that, The H2 reduction treatment temperature is 280-400°C, and the H2 reduction treatment time is 1-3 hours.

6. Use according to claim 1, characterized in that, The soluble cobalt salt is cobalt chloride hexahydrate, and the soluble iron salt is ferrous sulfate heptahydrate.

7. Use according to claim 1, characterized in that, The Fe-Co microalloy catalyst is subjected to reaction by introducing CO2 and H2 mixed gas, the reaction temperature is 160-280°C, the reaction pressure is 3-6 MPa, the reaction time is 60-70 minutes, and the volume ratio of CO2 to H2 in the mixed gas is 1:3-6.

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