A catalyst for CO2 hydrogenation to produce low-carbon mixed alcohols and co-producing olefins, its preparation and application

Abstract

The application belongs to the technical field of catalysts, and particularly relates to a catalyst for preparing low-carbon mixed alcohols and coproducing olefins through CO2 hydrogenation as well as preparation and application thereof. x Fe y M-zB, wherein M is a metal additive, B is an alkali metal additive, x and y are molar ratios of Co and Fe compared to M, the value ranges of x and y are both 1-5, and z is a mass fraction of B in the catalyst, the value range of z is 0.3-5%. The catalyst for preparing low-carbon mixed alcohols and coproducing olefins through CO2 hydrogenation provided by the application has excellent CO2 conversion rate and low-carbon mixed alcohol selectivity, can coproduce olefins, has high product added value, is simple to operate, has mild reaction, and has cheap and easily obtained raw materials, and has great application prospect.

Description

Technical Field

[0001] This invention belongs to the field of catalyst technology, specifically relating to a catalyst for the co-production of low-carbon mixed alcohols and olefins by CO2 hydrogenation, and its preparation and application. Background Technology

[0002] Low-carbon mixed alcohols (C2-C6 mixed alcohols, C 2+ Olefins (OH) have a high octane number and can be used as clean fuels and gasoline additives, as well as solvents and industrial raw materials. Olefins are extremely important basic raw materials in the chemical industry, used to produce high-value-added chemicals and plastics, and are in high demand. The synthesis of low-carbon mixed alcohols and olefins by CO2 hydrogenation requires effective C / C coupling and appropriate hydrogenation; therefore, the rational design and construction of catalysts are extremely crucial.

[0003] Catalysts for synthesizing lower alcohols mainly contain active components such as Rh, Mo, Co, Cu, and Fe. However, the high cost of the noble metal Rh limits its large-scale application, while Mo requires harsh reaction conditions. For example, Chinese invention patent CN115999555A discloses a catalyst for the hydrogenation of CO2 to produce higher alcohols, its preparation method, and its application. The general molecular formula of the catalyst is Cu. x Co1M y -zA, where M is a metal additive, A is an alkali metal additive, x and y are the molar ratios of metal Cu and metal additive M relative to metal Co, respectively, with values ​​ranging from 0.5 to 2 and 0.5 to 1.5, and z is the mass fraction of alkali metal additive in the catalyst, with values ​​ranging from 0.5 to 5%. However, the CO2 conversion rate and selectivity of the target product of this invention are not ideal and are difficult to meet the needs of industrial production.

[0004] The active component of catalysts for olefin synthesis is mainly Fe, which is further modified by Mn, K, Co, and rare earth elements. For example, Chinese invention patent CN111185180A discloses a catalyst for the hydrogenation of carbon dioxide to produce high-carbon olefins, its preparation method, and its application. The catalyst of this invention uses serrated metal-type single-walled carbon nanotube bundles as a support, loaded with iron and potassium active components; iron accounts for 8-30% of the total mass of the catalyst, and potassium accounts for 0.2-5.0% of the total mass of the metal. It is used for the hydrogenation reaction of carbon dioxide. This catalyst can directly and efficiently convert carbon dioxide into high-value olefins with a selectivity of over 62%, of which high-carbon olefins account for over 60%. However, this invention has problems such as poor reproducibility of preparation, many by-products, and low carbon dioxide conversion rate.

[0005] Alkali metals are important electronic additives that can effectively regulate adsorption and desorption behavior during the reaction process and inhibit the formation of by-products. Given the advantages of Co and Fe in terms of strong chain growth ability, high hydrogenation activity, low cost, and relatively mild reaction conditions, effectively coupling Co, Fe and alkali metal components to construct multifunctional synergistic sites may be an effective way to promote the formation of high-value-added products and is also a key area for future research and development with great potential.

[0006] Therefore, developing highly active, highly selective, inexpensive, and readily available mild catalysts is an important breakthrough for the production of high-value-added products from CO2 hydrogenation. Summary of the Invention

[0007] This invention addresses the problems existing in the prior art by providing a catalyst for the co-production of low-carbon mixed alcohols and olefins via CO2 hydrogenation, as well as its preparation and application, which can effectively promote the resource utilization of CO2.

[0008] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0009] A catalyst for the co-production of low-carbon mixed alcohols and olefins by CO2 hydrogenation, wherein the catalyst has the general molecular formula Co. x Fe y M-zB, where M is a metal additive, B is an alkali metal additive, x and y are the molar ratios of Co and Fe relative to M, respectively, with values ​​ranging from 1 to 5, and z is the mass fraction of B in the catalyst, with values ​​ranging from 0.3 to 5%.

[0010] Preferably, the value of z is 2%.

[0011] Preferably, M is selected from one or more of the metallic elements Zn, Mn, Al, Zr and Ce.

[0012] More preferably, M is the metallic element Zn.

[0013] Preferably, B is selected from one or more of the metallic elements Li, Na, K, Rb, and Cs.

[0014] More preferably, B is selected from the metallic elements Na, K, or Cs.

[0015] The present invention also provides a method for preparing the above-mentioned catalyst, comprising the following steps:

[0016] (1) Mix Co salt, Fe salt and M salt in water to obtain solution 1;

[0017] (2) Dissolve the precipitant containing B in water to obtain solution 2;

[0018] (3) Mix solution 1 and solution 2 to obtain a suspension, and then age, dry and calcine to obtain the final product.

[0019] Preferably, the Co salt, Fe salt and M salt in step (1) are each independently selected from one or more of their respective nitrates, chlorides, sulfates and acetates.

[0020] More preferably, the Co salt, Fe salt, and M salt are each independently selected from their respective nitrates.

[0021] Preferably, the total molar concentration of metal ions in solution 1 is 0.5-2 mol / L.

[0022] More preferably, the total molar concentration of metal ions in solution 1 is 1.5 mol / L.

[0023] Preferably, the precipitant in step (2) is selected from one or more of Na2CO3, K2CO3, Rb2CO3, Cs2CO3, Na2HCO3, K2HCO3, LiOH, NaOH, KOH, RbOH and CsOH.

[0024] More preferably, the precipitant is Na2CO3, K2CO3 or Cs2CO3.

[0025] Preferably, the total molar concentration of metal ions in solution 2 is 0.5-2 mol / L.

[0026] More preferably, the total molar concentration of metal ions in solution 2 is 2 mol / L.

[0027] Preferably, the mixing temperature in step (3) is 20-80°C, the mixture is stirred during mixing, and the pH of the suspension is controlled to be 8-10. The stirring speed is 400-700 rpm.

[0028] More preferably, the mixing temperature is 25°C, the pH is 8, and the stirring speed is 500 rpm.

[0029] Preferably, the aging time in step (3) is 0.5-24 hours, and centrifugation and washing are performed after aging.

[0030] More preferably, the aging time is 2-8 hours.

[0031] The preferred aging time is 2 hours.

[0032] Preferably, the centrifugation and washing are performed 1-8 times each.

[0033] Preferably, the drying temperature is 80-120℃ and the drying time is 6-48h.

[0034] More preferably, the drying temperature is 100°C and the drying time is 12 hours.

[0035] Preferably, the roasting temperature is 350-450℃ and the roasting time is 2-10h.

[0036] More preferably, the roasting temperature is 400℃ and the roasting time is 3 hours.

[0037] Preferably, the drying and roasting atmosphere is air.

[0038] This invention also provides the application of the above-mentioned catalyst in the co-production of olefins from low-carbon mixed alcohols by CO2 hydrogenation, comprising the following steps:

[0039] (1) The catalyst is mixed with quartz sand and packed into a fixed bed constant temperature zone;

[0040] (2) The loaded catalyst is then reduced in an H2 atmosphere;

[0041] (3) Cool down, introduce raw material gas and carry out reaction.

[0042] Preferably, the catalyst and quartz sand in step (1) are both 40-60 mesh, and the mass ratio of the catalyst to the quartz sand is 1:2.

[0043] Preferably, the reduction temperature in step (2) is 300-400℃, the reduction time is 0.5-10h, and the reduction pressure is 0.1MPa.

[0044] More preferably, the reduction temperature is 350°C and the reduction time is 3 hours.

[0045] Preferably, the cooling temperature in step (3) is 250-280℃, the raw material gas is a mixture of H2, CO2 and N2 with a volume ratio of 72:24:4, the reaction temperature is 240-280℃, the reaction pressure is 3MPa, and the reaction space velocity is 3000mL·g. cat -1 ·h -1 .

[0046] More preferably, the cooling temperature is 280°C, and the reaction temperature is 280°C.

[0047] Compared with the prior art, the present invention has the following beneficial effects:

[0048] The catalyst provided by this invention for the co-production of olefins from CO2 hydrogenation to low-carbon mixed alcohols has excellent CO2 conversion and low-carbon mixed alcohol selectivity. It can co-produce olefins, has high added value, is simple to operate, has a mild reaction, and uses inexpensive and readily available raw materials. It has great application prospects and is suitable for industrial production. Detailed Implementation

[0049] It is worth noting that the raw materials used in this invention are all commercially available products.

[0050] Example 1

[0051] Based on the metal molar ratios x = Co / Zn = 5 and y = Fe / Zn = 1, 21.0 g of cobalt nitrate hexahydrate, 5.8 g of ferric nitrate nonahydrate, and 4.3 g of zinc nitrate hexahydrate were weighed and dissolved in deionized water to prepare a 1.5 mol / L solution 1. 29.9 g of anhydrous potassium carbonate was weighed and dissolved in deionized water to prepare a 2 mol / L solution 2. Solutions 1 and 2 were simultaneously added dropwise to a 300 mL beaker at 25 °C and a stirring speed of 500 r / min, maintaining the pH at 8. After the addition was complete, the mixture was aged at 25 °C for 2 h, then centrifuged and washed 5 times each, followed by drying in a 100 °C oven for 12 h, and then calcined in a muffle furnace at 400 °C for 3 h. The K content in the catalyst was determined to be 1.9% using inductively coupled plasma atomic emission spectrometry (ICP-OES, Optima 8000, PerkinElmer). The obtained catalyst was named Co5Fe1Zn1-2%K.

[0052] The performance of the above catalyst in a fixed-bed reactor for the hydrogenation of carbon dioxide to produce low-carbon mixed alcohols and co-production of olefins was evaluated. 1 g of the above catalyst (40-60 mesh) was weighed and mixed with 2 g of quartz sand particles (40-60 mesh) and packed into a fixed-bed isothermal zone. Pure H2 was then introduced at 0.1 MPa and maintained at 350 °C for 3 h. After reduction, the temperature was lowered to 280 °C, and a feed gas mixture of H2, CO2, and N2 (volume ratio 72:24:4) was introduced. The reaction temperature was 280 °C, the reaction pressure was 3 MPa, and the space velocity was 3000 mL·g⁻¹. cat -1 ·h -1 The performance results are shown in Table 1.

[0053] Example 2

[0054] The catalyst preparation method and evaluation process were the same as in Example 1, except that the metal molar ratios x = Co / Zn = 2 and y = Fe / Zn = 1 were changed. The masses of the raw materials were: 14.7 g cobalt nitrate hexahydrate, 10.2 g ferric nitrate nonahydrate, 7.5 g zinc nitrate hexahydrate, and 31.3 g anhydrous potassium carbonate. The K content in the catalyst was determined to be 2.0% using inductively coupled plasma atomic emission spectrometry (ICP-OES, Optima 8000, PerkinElmer). The obtained catalyst was named Co2Fe1Zn1-2%K. Its performance results are shown in Table 1.

[0055] Example 3

[0056] The catalyst preparation method and evaluation process were the same as in Example 1, except that the metal molar ratios x = Co / Zn = 1 and y = Fe / Zn = 1 were changed. The masses of the raw materials were: 9.8 g cobalt nitrate hexahydrate, 13.6 g ferric nitrate nonahydrate, 10.0 g zinc nitrate hexahydrate, and 32.5 g anhydrous potassium carbonate. The K content in the catalyst was determined to be 1.8% using inductively coupled plasma optical emission spectrometry (ICP-OES, Optima 8000, PerkinElmer). The obtained catalyst was named Co1Fe1Zn1-2%K. Its performance results are shown in Table 1.

[0057] Example 4

[0058] The catalyst preparation method and evaluation process were the same as in Example 1, except that the metal molar ratios x = Co / Zn = 1 and y = Fe / Zn = 2 were changed. The masses of the raw materials were: 7.3 g cobalt nitrate hexahydrate, 20.4 g ferric nitrate nonahydrate, 7.5 g zinc nitrate hexahydrate, and 34.8 g anhydrous potassium carbonate. The K content in the catalyst was determined to be 2.0% using inductively coupled plasma optical emission spectrometry (ICP-OES, Optima 8000, PerkinElmer). The obtained catalyst was named Co1Fe2Zn1-2%K. Its performance results are shown in Table 1.

[0059] Example 5

[0060] The catalyst preparation method and evaluation process were the same as in Example 1, except that the metal molar ratios x = Co / Zn = 1 and y = Fe / Zn = 5 were changed. The masses of the raw materials were: 4.2 g cobalt nitrate hexahydrate, 29.2 g ferric nitrate nonahydrate, 4.3 g zinc nitrate hexahydrate, and 37.9 g anhydrous potassium carbonate. The K content in the catalyst was determined to be 1.9% using inductively coupled plasma optical emission spectrometry (ICP-OES, Optima 8000, PerkinElmer). The obtained catalyst was named Co1Fe5Zn1-2%K. Its performance results are shown in Table 1.

[0061] Table 1 Effect of different metal ratios on catalytic performance

[0062]

[0063] Table 1 shows that after adjusting the Co / Zn and Fe / Zn molar ratios, the CO2 conversion rate was higher than 37%, while the methanol selectivity was lower than 5%. When x = Co / Zn = 2, the highest CO2 conversion rate was achieved. 2+ OH selectivity (30.3%), with the highest olefin selectivity (36.1%) when y = Fe / Zn = 5.

[0064] Example 6

[0065] The catalyst preparation method and evaluation process were the same as in Example 2, except that the number of washing cycles was changed to 8. The K content in the catalyst was measured to be 0.33% using inductively coupled plasma optical emission spectrometry (ICP-OES, Optima 8000, PerkinElmer), and the resulting catalyst was named Co2Fe1Zn1-0.3%K. Its performance results are shown in Table 2.

[0066] Example 7

[0067] The catalyst preparation method and evaluation process were the same as in Example 2, except that the number of washing cycles was changed to 4. The K content in the catalyst was determined to be 1.2% using inductively coupled plasma optical emission spectrometry (ICP-OES, Optima 8000, PerkinElmer), and the resulting catalyst was named Co2Fe1Zn1-1%K. Its performance results are shown in Table 2.

[0068] Example 8

[0069] The catalyst preparation method and evaluation process were the same as in Example 2, except that the number of washing cycles was changed to two. The K content in the catalyst was determined to be 2.9% using inductively coupled plasma optical emission spectrometry (ICP-OES, Optima 8000, PerkinElmer), and the resulting catalyst was named Co2Fe1Zn1-3%K. Its performance results are shown in Table 2.

[0070] Example 9

[0071] The catalyst preparation method and evaluation process were the same as in Example 2, except that the number of washing cycles was changed to one. The K content in the catalyst was determined to be 5.1% using inductively coupled plasma optical emission spectrometry (ICP-OES, Optima 8000, PerkinElmer), and the resulting catalyst was named Co5Fe1Zn1-5%K. Its performance results are shown in Table 2.

[0072] Table 2 Effect of different washing cycles on catalytic performance

[0073]

[0074] Table 2 shows that the K content can be controlled by changing the number of washing cycles during catalyst preparation. The CO2 conversion rate decreases with increasing K content, while the C content... 2+ OH selectivity increases with increasing K content, and olefin selectivity reaches its maximum value (22%) when the K content is 2.0%.

[0075] Example 10

[0076] The catalyst preparation method and evaluation process were the same as in Example 2, except that the reaction temperature in the performance evaluation was changed to 260℃. The performance results are shown in Table 3.

[0077] Example 11

[0078] The catalyst preparation method and evaluation process were the same as in Example 2, except that the reaction temperature in the performance evaluation was changed to 240℃. The performance results are shown in Table 3.

[0079] Table 3 Effect of different reaction temperatures on catalytic performance

[0080]

[0081]

[0082] Table 3 shows that reaction temperature has a significant impact on catalytic performance. Lowering the reaction temperature reduces CO2 conversion, olefin selectivity, and methanol selectivity, but... 2+ OH selectivity increases, reaching a maximum of 44.4%.

[0083] Example 12

[0084] The catalyst preparation method and evaluation process were the same as in Example 2, except that the precipitant was replaced with 24.0 g of anhydrous sodium carbonate. The K content in the catalyst was determined to be 2.1% using inductively coupled plasma optical emission spectrometry (ICP-OES, Optima 8000, PerkinElmer). The resulting catalyst was named Co2Fe1Zn1-2%Na. Its performance results are shown in Table 4.

[0085] Example 13

[0086] The catalyst preparation method and evaluation process were the same as in Example 2, except that the precipitant was changed to 73.9 g of anhydrous cesium carbonate. The K content in the catalyst was determined to be 2.0% using inductively coupled plasma atomic emission spectrometry (ICP-OES, Optima 8000, PerkinElmer). The resulting catalyst was named Co2Fe1Zn1-2%Cs. Its performance results are shown in Table 4.

[0087] Table 4. Effects of different alkali metal promoters on catalytic performance

[0088]

[0089] Table 4 shows that the type of alkali metal promoter has a significant impact on catalytic performance. When the alkali metal is K, C 2+ OH selectivity is the highest, reaching up to 30.3%.

[0090] Example 14

[0091] The catalyst preparation method and evaluation process were the same as in Example 2, except that the metal promoter Zn was replaced with Mn, and the metal molar ratios were x = Co / Mn = 2 and y = Fe / Mn = 1. The masses of each raw material were: 15.1 g cobalt nitrate hexahydrate, 10.5 g ferric nitrate nonahydrate, 6.5 g manganese nitrate tetrahydrate, and 32.3 g anhydrous potassium carbonate. The K content in the catalyst was measured to be 2.1% using inductively coupled plasma atomic emission spectrometry (ICP-OES, Optima 8000, PerkinElmer), and the obtained catalyst was named Co2Fe1Mn1-2%K. Its performance results are shown in Table 5.

[0092] Example 15

[0093] The catalyst preparation method and evaluation process were the same as in Example 2, except that the metal promoter Zn was replaced with Al, and the metal molar ratios were x = Co / Al = 2 and y = Fe / Al = 1. The masses of each raw material were: 13.8 g cobalt nitrate hexahydrate, 9.6 g ferric nitrate nonhydrate, and 8.9 g aluminum nitrate nonhydrate, and 19.9 g potassium hydroxide was used as the precipitant. The K content in the catalyst was measured to be 2.1% using inductively coupled plasma atomic emission spectrometry (ICP-OES, Optima 8000, PerkinElmer), and the obtained catalyst was named Co2Fe1Al1-2%K. Its performance results are shown in Table 5.

[0094] Example 16

[0095] The catalyst preparation method and evaluation process were the same as in Example 2, except that the metal promoter Zn was replaced with Zr, and the metal molar ratios were x = Co / Zr = 2 and y = Fe / Zr = 1. The masses of each raw material were: 15.6 g cobalt nitrate hexahydrate, 10.8 g ferric nitrate nonahydrate, 11.5 g zirconium nitrate pentahydrate, and 33.3 g anhydrous potassium carbonate. The K content in the catalyst was measured to be 1.9% using inductively coupled plasma optical emission spectrometry (ICP-OES, Optima 8000, PerkinElmer), and the obtained catalyst was named Co2Fe1Zr1-2%K. Its performance results are shown in Table 5.

[0096] Example 17

[0097] The catalyst preparation method and evaluation process were the same as in Example 2, except that the metal promoter Zn was replaced with Ce, and the metal molar ratios were x = Co / Ce = 2 and y = Fe / Ce = 1. The masses of each raw material were: 13.0 g cobalt nitrate hexahydrate, 9.0 g ferric nitrate nonahydrate, 9.7 g cerium nitrate hexahydrate, and 27.7 g anhydrous potassium carbonate. The K content in the catalyst was determined to be 2.0% using inductively coupled plasma atomic emission spectrometry (ICP-OES, Optima 8000, PerkinElmer), and the obtained catalyst was named Co2Fe1Ce1-2%K. Its performance results are shown in Table 5.

[0098] Table 5. Effects of different metal promoters on catalytic performance

[0099]

[0100] Table 5 shows that the type of metal promoter has a significant impact on catalytic performance. When the metal promoter is Zn, although the CO2 conversion rate is lower compared to other examples, it is beneficial to C. 2+ The formation of OH and alkenes.

[0101] Comparative Example 1

[0102] The catalyst preparation method and evaluation process were the same as in Example 2, except that the Fe component was removed, i.e., ferric nitrate nonahydrate was not added to the raw materials, resulting in the catalyst Co2Zn1-2%K. Its performance results are shown in Table 6.

[0103] Comparative Example 2

[0104] The catalyst preparation method and evaluation process were the same as in Example 2, except that the Zn component was removed, i.e., zinc nitrate hexahydrate was not added to the raw materials, resulting in the catalyst Co2Fe1-2%K. Its performance results are shown in Table 6.

[0105] Comparative Example 3

[0106] The catalyst preparation method and evaluation process were the same as in Example 2, except that the Co component was replaced with Cu, and the metal molar ratios were x = Cu / Zn = 2 and y = Fe / Zn = 1. The masses of each raw material were: 12.2 g copper nitrate trihydrate, 10.2 g ferric nitrate nonhydrate, 7.5 g zinc nitrate hexahydrate, and 31.3 g anhydrous potassium carbonate. The K content in the catalyst was determined to be 2.0% using inductively coupled plasma optical emission spectrometry (ICP-OES, Optima 8000, PerkinElmer). The obtained catalyst was named Cu2Fe1Zn1-2%K. Its performance results are shown in Table 6.

[0107] Comparative Example 4

[0108] The catalyst preparation method and evaluation process were the same as in Example 2, except that the Fe component was replaced with Cu, and the metal molar ratios were x = Co / Zn = 2 and y = Cu / Zn = 1. The masses of each raw material were: 16.5 g cobalt nitrate hexahydrate, 6.8 g copper nitrate trihydrate, 8.4 g zinc nitrate hexahydrate, and 31.3 g anhydrous potassium carbonate. The K content in the catalyst was determined to be 2.0% using inductively coupled plasma optical emission spectrometry (ICP-OES, Optima 8000, PerkinElmer). The obtained catalyst was named Co2Cu1Zn1-2%K. Its performance results are shown in Table 6.

[0109] Comparative Example 5

[0110] The catalyst preparation method and evaluation process were the same as in Example 2, except that the metal molar ratios x = Co / Zn = 7 and y = Fe / Zn = 6 were changed. The masses of each raw material were: 13.6 g cobalt nitrate hexahydrate, 16.1 g ferric nitrate nonahydrate, 2.0 g zinc nitrate hexahydrate, and 31.3 g anhydrous potassium carbonate. The K content in the catalyst was measured to be 2.0% using inductively coupled plasma optical emission spectrometry (ICP-OES, Optima 8000, PerkinElmer). The obtained catalyst was named Co7Fe6Zn1-2%K. Its performance results are shown in Table 6.

[0111] Comparative Example 6

[0112] The catalyst was prepared according to Example 1 of the invention patent CN115999555A, and the evaluation process was the same as that of Example 2 of this invention. The performance results are shown in Table 6.

[0113] Table 6. Catalytic performance results of Comparative Examples 1-6

[0114]

[0115] Based on the performance results analysis of Examples 1-17 and Comparative Examples 1-6 above, the metal promoter Zn and the alkali metal promoter K have significant promoting effects on the preparation of lower alcohols and olefins by Co-Fe based CO2 hydrogenation. Furthermore, the content of various components, the catalyst preparation method, and the reaction conditions all affect the catalytic performance. When the CO2 conversion rate is 16.5%, C... 2+ The highest selectivity was 44.4% for alcohols and 9.6% for olefins; when the CO2 conversion rate was 50.3%, the highest selectivity for olefins was 36.1%, and C... 2+ The alcohol selectivity was 22.6%. Furthermore, the catalysts in Examples 1-17 exhibited good stability.

[0116] Finally, it should be noted that the above content is only used to illustrate the technical solution of the present invention, and is not intended to limit the scope of protection of the present invention. Simple modifications or equivalent substitutions made by those skilled in the art to the technical solution of the present invention do not depart from the essence and scope of the technical solution of the present invention.

Claims

1. The application of a catalyst in the co-production of low-carbon mixed alcohols and olefins by CO2 hydrogenation, characterized in that, The catalyst has the general molecular formula Co. x Fe y M-zB, where M is a metal additive, specifically the metal element Zn, B is an alkali metal additive, x and y are the molar ratios of Co and Fe relative to M, respectively, with values ​​ranging from 1 to 5, and z is the mass fraction of B in the catalyst, with values ​​ranging from 1 to 5%.

2. The application according to claim 1, characterized in that, The B is selected from one or more of the metallic elements Li, Na, K, Rb, and Cs.

3. The application according to claim 1 or 2, characterized in that, Includes the following steps: (1) The catalyst is mixed with quartz sand and packed into a fixed bed constant temperature zone; (2) The loaded catalyst is then reduced in an H2 atmosphere; (3) Cool down, introduce raw material gas and carry out the reaction. In step (1), the catalyst and quartz sand are both 40-60 mesh, and the mass ratio of the catalyst to the quartz sand is 1:2; in step (2), the reduction temperature is 300-400℃, and the reduction time is 0.5-10 h; in step (3), the cooling temperature is 250-280℃, the raw material gas is a mixture of H2, CO2 and N2 with a volume ratio of 72:24:4, and the reaction temperature is 240-280℃.

4. A method for preparing a catalyst for any one of the applications described in claims 1-3, characterized in that, Includes the following steps: (1) Mix Co salt, Fe salt and M salt in water to obtain solution 1; (2) Dissolve the precipitant containing B in water to obtain solution 2; (3) Mix solution 1 and solution 2 to obtain a suspension, and then age, dry and calcine to obtain the final product.

5. The preparation method according to claim 4, characterized in that, The Co salt, Fe salt and M salt mentioned in step (1) are each independently selected from one or more of their respective nitrates, chlorides, sulfates and acetates, and the total molar concentration of metal ions in solution 1 is 0.5-2 mol / L.

6. The preparation method according to claim 4, characterized in that, The precipitant in step (2) is selected from one or more of Na2CO3, K2CO3, Rb2CO3, Cs2CO3, NaHCO3, KHCO3, LiOH, NaOH, KOH, RbOH and CsOH, and the total molar concentration of metal ions in solution 2 is 0.5-2 mol / L.

7. The preparation method according to claim 4, characterized in that, The mixing temperature in step (3) is 20-80℃, the mixture is stirred during mixing, and the pH of the suspension is controlled at 8-10. The stirring speed is 400-700 rpm.

8. The preparation method according to claim 4, characterized in that, The aging time in step (3) is 0.5-24h, the drying temperature is 80-120℃, the drying time is 6-48h, the roasting temperature is 350-450℃, the roasting time is 2-10h, and the atmosphere for both drying and roasting is air.

9. The preparation method according to claim 8, characterized in that, After aging, the material is centrifuged and washed 1-8 times.

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