An alkali metal supported cobalt-based catalyst, its preparation method and use

Abstract

The application provides a kind of alkali metal loaded cobalt-based catalyst and its preparation method and application, it is related to carbon dioxide hydrogenation preparation ethanol catalyst preparation technical field.The active center of catalyst of the application is cobalt metal in cobalt aluminum spinel structure, simultaneously contains Co 0 And CoAl2O4 Dual-catalytic active site, and further introduces alkali metal, can significantly improve the conversion rate of carbon dioxide and the selectivity of ethanol.In carbon dioxide hydrogenation reaction, the conversion rate of carbon dioxide is higher, and the selectivity of ethanol is higher.

Description

Technical Field

[0001] This invention relates to the field of catalyst preparation technology for carbon dioxide hydrogenation to ethanol, and particularly to an alkali metal supported cobalt-based catalyst, its preparation method, and its application. Background Technology

[0002] The utilization of CO2 coupled with "green hydrogen" through catalytic hydrogenation to convert it into high-value-added chemical products is of great practical significance for reducing CO2 emissions and improving the ecosystem.

[0003] In recent years, numerous studies have been reported on the synthesis of methanol from CO2 hydrogenation, and preliminary industrial-scale production has been achieved. However, reports on the direct conversion of methanol from CO2 hydrogenation to ethanol are relatively few. Ethanol, as one of the most basic chemical products, has wide applications in various fields, serving as a gasoline additive, a solvent in material synthesis, and an industrial intermediate. Compared to methanol, ethanol has a higher energy density and a higher calorific value; therefore, the CO2 hydrogenation to ethanol synthesis reaction is a more industrially valuable process route.

[0004] The reaction mechanism of CO2 hydrogenation to ethanol shows that the formyl (·CHO) intermediate generated during the reaction is difficult to break the CO bond and couple the C-C bond in a timely manner. Therefore, the formation of products such as methane (CH4), carbon monoxide (CO), and methanol is inevitable. Based on this, achieving high ethanol selectivity and yield in the CO2 hydrogenation to ethanol reaction requires simultaneously coordinating the adsorption, activation, C-C bond formation, and selective hydrogenation of CO2. Currently, based on the active component, catalysts for CO2 hydrogenation to ethanol mainly include noble metal-based catalysts, Co-based catalysts, Cu-based catalysts, and Mo-based catalysts. Among them, Co-based catalysts have been widely studied due to their strong hydrogenation capacity, C-C bond coupling ability, and low cost. Chinese patent CN106311281A uses basic nickel carbonate as a template, introduces transition metal molybdenum through ion exchange, impregnates it with alkali metal potassium, and finally sulfides it to obtain a ternary metal sulfide catalyst with a layered structure. The catalytic evaluation results of this catalyst show that the molar fraction of ethanol in the total alcohol is 43%, indicating significant room for improvement. According to current research, the key to the catalytic hydrogenation of CO2 to ethanol by Co-based catalysts lies in reducing the hydrogenation performance of metallic Co, so that CO2 can be converted into a CO intermediate, which is then converted into ethanol through a CC coupling reaction.

[0005] In summary, Co-based catalysts still have drawbacks in current carbon dioxide hydrogenation reactions, such as excessively strong Co catalytic hydrogenation, the main products being CH4 and CO, and low selectivity for ethanol. Summary of the Invention

[0006] To address the shortcomings of existing technologies, this invention provides a catalyst for the hydrogenation of carbon dioxide to ethanol and a method for its preparation. The catalyst of this invention exhibits high carbon dioxide conversion and high ethanol selectivity in the carbon dioxide hydrogenation reaction.

[0007] One of the objectives of this invention is to provide an alkali metal-supported cobalt-based catalyst.

[0008] The second objective of this invention is to provide a method for preparing the alkali metal-supported cobalt-based catalyst.

[0009] A third objective of this invention is to provide an application of the alkali metal-supported cobalt-based catalyst.

[0010] In order to achieve the above-mentioned objectives of the present invention, the following technical solution is adopted:

[0011] In a first aspect, the present invention provides an alkali metal-supported cobalt-based catalyst, comprising cobalt aluminum spinel and an alkali metal supported on the cobalt aluminum spinel, wherein the active center of the cobalt aluminum spinel exists partly in the form of a CoAl2O4 spinel-type structure and partly in the form of zero-valent Co. 0 It exists in form.

[0012] The active center of the catalyst of this invention is cobalt metal in a cobalt-aluminum spinel structure, and also contains Co. 0 The presence of both CoAl2O4 and alkali metals as dual catalytic active sites, along with the further introduction of alkali metals, can significantly improve the conversion rate of carbon dioxide and the selectivity of ethanol.

[0013] In some implementations, the alkali metal loading is 5 wt% to 15 wt% based on the mass of the cobalt aluminum spinel.

[0014] In some embodiments, the alkali metal includes one of lithium, sodium, and potassium.

[0015] In some embodiments, cobalt existing in the form of a CoAl2O4 spinel structure and Co in the form of zero-valent cobalt... 0 The molar ratio of cobalt in its various forms is 15:1 to 2:1.

[0016] Secondly, the present invention provides a method for preparing the above-mentioned alkali metal-supported cobalt-based catalyst, comprising the following steps:

[0017] S1. Dissolve cobalt salt and aluminum isopropoxide in ethylene glycol, stir under heating conditions, wash with ethanol by centrifugation, and dry in a vacuum drying oven; place the dried powder in a muffle furnace for high-temperature calcination to obtain cobalt aluminum spinel.

[0018] S2. Cobalt aluminum spinel and alkali metal chloride are dissolved in deionized water and stirred evenly. The mixture is stirred under heating conditions to ensure that the deionized water evaporates completely. Then, it is placed in a vacuum drying oven for drying. The dried powder is placed in a muffle furnace for high-temperature calcination and then subjected to hydrogen reduction treatment to obtain alkali metal supported cobalt-based catalyst.

[0019] Step S1:

[0020] In some embodiments, in step S1, the cobalt salt includes one or more of cobalt nitrate or its hydrate, cobalt carbonate or its hydrate, and cobalt sulfate or its hydrate.

[0021] In some embodiments, in step S1, the molar ratio of cobalt in the cobalt salt to aluminum in aluminum isopropoxide is 1:2 to 1:8.

[0022] In some embodiments, in step S1, the stirring and heating temperature is 30°C to 90°C, the stirring speed is 200 rpm to 600 rpm, and the stirring time is 2 to 6 hours.

[0023] In some embodiments, in step S1, the centrifugation speed is 2000 rpm to 6000 rpm, and the number of centrifugal washing cycles is 2 to 5.

[0024] In some embodiments, in step S1, the drying temperature is 30°C to 100°C and the drying time is 3h to 15h.

[0025] In some embodiments, in step S1, the high-temperature calcination temperature is 400℃~800℃, the calcination time is 1h~8h, and the heating rate is 1℃ / min~10℃ / min.

[0026] Step S2:

[0027] In some embodiments, in step S2, the alkali metal chloride includes one or more of lithium chloride, sodium chloride, and potassium chloride.

[0028] In some embodiments, in step S2, the amount of alkali metal added is 5wt%-15wt% based on the mass of cobalt aluminum spinel.

[0029] In some embodiments, in step S2, the heating and stirring temperature is 50°C to 100°C, and the stirring speed is 200 rpm to 600 rpm.

[0030] In some embodiments, in step S2, the drying temperature is 30°C to 100°C, and the drying time is 3 hours to 15 hours.

[0031] In some embodiments, in step S2, the high-temperature calcination temperature is 200℃~800℃, the calcination time is 1h~8h, and the heating rate is 1℃ / min~10℃ / min.

[0032] In some embodiments, the conditions for hydrogen reduction treatment in step S2 are: space velocity of 3000 mL / g / h to 10000 mL / g / h, reduction temperature of 250℃ to 800℃, and reduction time of 1h to 6h.

[0033] Thirdly, the present invention provides an application of the above-mentioned alkali metal-supported cobalt-based catalyst in the catalytic reaction of carbon dioxide hydrogenation to produce ethanol.

[0034] The catalyst is loaded into a fixed-bed reactor for carbon dioxide hydrogenation reaction after being tableted, crushed, and sieved, wherein the particle size of the sieved particles is 10-60 mesh.

[0035] Preferably, the conditions for the catalytic reaction are: a reaction temperature of 200–400°C, a reaction pressure of 2–4 MPa, a total space velocity of 3000–8000 mL / g / h, and the gas used is a mixture of CO2 and H2, wherein the volume ratio of CO2 to H2 is 1:1–4.

[0036] The catalyst was subjected to hydrogen pre-reduction treatment before the reaction test. The reduction conditions were: hydrogen space velocity of 3000 mL / g / h to 10000 mL / g / h, reduction temperature of 250℃ to 400℃, and reduction time of 1h to 6h.

[0037] Technical effects:

[0038] (1) The present invention provides a simple preparation method, convenient operation process, low price and cost, and the prepared catalyst has a high conversion rate of carbon dioxide and a high selectivity of ethanol in the carbon dioxide hydrogenation reaction.

[0039] (2) The alkali metal modified cobalt-based catalyst prepared in this invention increases the reduction temperature of cobalt by pre-forming a cobalt-aluminum spinel structure, thereby avoiding the formation of Co under a reducing atmosphere. 0 Simultaneously, by controlling the reduction temperature, unreduced CoAl2O4 and cobalt are present during the reaction, meaning Co is formed in situ. 0 -CoAl2O4 dual catalytic sites.

[0040] (3) The alkali metal modified cobalt-based catalyst prepared in this invention can flexibly modulate the Co content by adjusting the pre-reduction temperature and the cobalt-aluminum ratio. 0 The number of -CoAl2O4 dual catalytic sites can effectively suppress excessive hydrogenation while promoting carbon-carbon coupling reactions, thereby significantly improving the selectivity of ethanol.

[0041] (4) The alkali metal modified cobalt-based catalyst prepared in this invention improves the selectivity of ethanol and further enhances the adsorption capacity of the catalyst for carbon dioxide by introducing alkali metal elements, thereby improving the conversion rate of carbon dioxide.

[0042] The present invention has been described in detail above; however, the above embodiments are merely illustrative in nature and are not intended to limit the invention. Furthermore, this document is not limited to the foregoing prior art or the invention itself, or to any theory described in the following embodiments. Attached Figure Description

[0043] Figure 1 The X-ray diffraction (XRD) pattern of the catalyst prepared in Example 1. Detailed Implementation

[0044] The present invention will be further described below with reference to the embodiments. It should be noted that the following embodiments are provided for illustrative purposes only and do not constitute a limitation on the scope of protection of the present invention.

[0045] Unless otherwise specified, the raw materials, reagents, and methods used in the embodiments are all conventional raw materials, reagents, and methods in the art.

[0046] Example 1

[0047] (1) Dissolve 1g of cobalt nitrate hexahydrate (0.0034mol) and 3.5g of aluminum isopropoxide (0.017mol) in 50mL of ethylene glycol. Stir at 80℃ and 500rpm for 4h, then wash 4 times with ethanol by centrifugation, and dry in a vacuum drying oven at 110℃ for 12h.

[0048] (2) The powder was placed in a muffle furnace and calcined at 700℃ for 4 hours with a heating rate of 2℃ / min to prepare cobalt aluminum spinel;

[0049] (3) Dissolve 500 mg of cobalt aluminum spinel and lithium chloride obtained by calculating the mass fraction in deionized water, stir evenly, stir at 80℃ and 500 rpm to make the deionized water evaporate completely, and then place it in a vacuum drying oven at 80℃ for 12 h; the lithium loading is 5%.

[0050] (4) The powder was placed in a muffle furnace and calcined at 400°C for 4 hours at a heating rate of 2°C / min to prepare the catalyst.

[0051] The X-ray diffraction (XRD) pattern of the catalyst is as follows: Figure 1 As shown in the figure, the catalyst contains a spinel structure. After appropriate reduction, CoAl2O4 and Co species can coexist, forming a dual catalytic active site with a molar ratio of 10:1.

[0052] The catalyst underwent hydrogen pre-reduction treatment before reaction testing at a space velocity of 8000 mL / g / h at 400℃ for 4 h. After cooling to room temperature, the reaction performance was evaluated in a fixed-bed reactor at a reaction temperature of 260℃, a reaction pressure of 3 MPa, a total space velocity of 6000 mL / g / h, and a CO2 / H2 volume ratio of 24:72. The reaction performance test results are shown in Table 1.

[0053] Example 2: The H2 pre-reduction temperature was changed to 600℃.

[0054] (1) Dissolve 1g of cobalt nitrate hexahydrate (0.0034mol) and 3.5g of aluminum isopropoxide (0.017mol) in 50mL of ethylene glycol. Stir at 80℃ and 500rpm for 4h, then wash 4 times with ethanol by centrifugation, and dry in a vacuum drying oven at 110℃ for 12h.

[0055] (2) The powder was placed in a muffle furnace and calcined at 700℃ for 4 hours with a heating rate of 2℃ / min to prepare cobalt aluminum spinel;

[0056] (3) Dissolve 500 mg of cobalt aluminum spinel and lithium chloride obtained by calculating the mass fraction in deionized water, stir evenly, stir at 80℃ and 500 rpm to make the deionized water evaporate completely, and then place it in a vacuum drying oven at 80℃ for 12 h; the lithium loading is 5%.

[0057] (4) The powder was placed in a muffle furnace and calcined at 400°C for 4 hours at a heating rate of 2°C / min to prepare the catalyst.

[0058] The catalyst underwent hydrogen pre-reduction treatment before reaction testing at a space velocity of 8000 mL / g / h at 600℃ for 4 h. After cooling to room temperature, the reaction performance was evaluated in a fixed-bed reactor at a reaction temperature of 260℃, a reaction pressure of 3 MPa, a total space velocity of 6000 mL / g / h, and a CO2 / H2 volume ratio of 24:72. The reaction performance test results are shown in Table 1.

[0059] Example 3: The type of alkali metal was changed to sodium.

[0060] (1) Dissolve 1g of cobalt nitrate hexahydrate (0.0034mol) and 3.5g of aluminum isopropoxide (0.017mol) in 50mL of ethylene glycol. Stir at 80℃ and 500rpm for 4h, then wash 4 times with ethanol by centrifugation, and dry in a vacuum drying oven at 110℃ for 12h.

[0061] (2) The powder was placed in a muffle furnace and calcined at 700℃ for 4 hours with a heating rate of 2℃ / min to prepare cobalt aluminum spinel;

[0062] (3) Dissolve 500 mg of cobalt aluminum spinel and sodium chloride (calculated by mass fraction) in deionized water, stir evenly, stir at 80°C and 500 rpm until the deionized water evaporates completely, and then place in a vacuum drying oven at 80°C for 12 h; the sodium loading is 5%.

[0063] (4) The powder was placed in a muffle furnace and calcined at 400°C for 4 hours at a heating rate of 2°C / min to prepare the catalyst.

[0064] The catalyst underwent hydrogen pre-reduction treatment before reaction testing at a space velocity of 8000 mL / g / h at 600℃ for 4 h. After cooling to room temperature, the reaction performance was evaluated in a fixed-bed reactor at a reaction temperature of 260℃, a reaction pressure of 3 MPa, a total space velocity of 6000 mL / g / h, and a CO2 / H2 volume ratio of 24:72. The reaction performance test results are shown in Table 1.

[0065] Example 4: The type of alkali metal was changed to potassium.

[0066] (1) Dissolve 1g of cobalt nitrate hexahydrate (0.0034mol) and 3.5g of aluminum isopropoxide (0.017mol) in 50mL of ethylene glycol. Stir at 80℃ and 500rpm for 4h, then wash 4 times with ethanol by centrifugation, and dry in a vacuum drying oven at 110℃ for 12h.

[0067] (2) The powder was placed in a muffle furnace and calcined at 700℃ for 4 hours with a heating rate of 2℃ / min to prepare cobalt aluminum spinel;

[0068] (3) Dissolve 500 mg of cobalt aluminum spinel and potassium chloride (calculated by mass fraction) in deionized water, stir evenly, stir at 80°C and 500 rpm until the deionized water evaporates completely, and then place in a vacuum drying oven at 80°C for 12 h; the potassium loading is 5%.

[0069] (4) The powder was placed in a muffle furnace and calcined at 400°C for 4 hours at a heating rate of 2°C / min to prepare the catalyst.

[0070] The catalyst underwent hydrogen pre-reduction treatment before reaction testing at a space velocity of 8000 mL / g / h at 600℃ for 4 h. After cooling to room temperature, the reaction performance was evaluated in a fixed-bed reactor at a reaction temperature of 260℃, a reaction pressure of 3 MPa, a total space velocity of 6000 mL / g / h, and a CO2 / H2 volume ratio of 24:72. The reaction performance test results are shown in Table 1.

[0071] Example 5: The molar ratio of cobalt to aluminum was changed to 1:2.

[0072] (1) Dissolve 1g of cobalt nitrate hexahydrate (0.0034mol) and 1.4g of aluminum isopropoxide (0.0068mol) in 50mL of ethylene glycol. Stir at 80℃ and 500rpm for 4h, then wash 4 times with ethanol by centrifugation, and dry in a vacuum drying oven at 110℃ for 12h.

[0073] (2) The powder was placed in a muffle furnace and calcined at 700℃ for 4 hours with a heating rate of 2℃ / min to prepare cobalt aluminum spinel;

[0074] (3) Dissolve 500 mg of cobalt aluminum spinel and potassium chloride (calculated by mass fraction) in deionized water, stir evenly, stir at 80°C and 500 rpm until the deionized water evaporates completely, and then place in a vacuum drying oven at 80°C for 12 h; the potassium loading is 5%.

[0075] (4) The powder was placed in a muffle furnace and calcined at 400°C for 4 hours at a heating rate of 2°C / min to prepare the catalyst.

[0076] The catalyst underwent hydrogen pre-reduction treatment before reaction testing at a space velocity of 8000 mL / g / h at 600℃ for 4 h. After cooling to room temperature, the reaction performance was evaluated in a fixed-bed reactor at a reaction temperature of 260℃, a reaction pressure of 3 MPa, a total space velocity of 6000 mL / g / h, and a CO2 / H2 volume ratio of 24:72. The reaction performance test results are shown in Table 1.

[0077] Comparative Example 1: The molar ratio of cobalt to aluminum was changed to 1:1.

[0078] (1) Dissolve 1g of cobalt nitrate hexahydrate (0.0034mol) and 0.7g of aluminum isopropoxide (0.0034mol) in 50mL of ethylene glycol. Stir at 80℃ and 500rpm for 4h, then wash 4 times with ethanol by centrifugation, and dry in a vacuum drying oven at 110℃ for 12h.

[0079] (2) The powder was placed in a muffle furnace and calcined at 700℃ for 4 hours with a heating rate of 2℃ / min to prepare cobalt aluminum spinel;

[0080] (3) Dissolve 500 mg of carrier and potassium chloride (calculated by mass fraction) in deionized water, stir evenly, stir at 80°C and 500 rpm until the deionized water evaporates completely, and then place in a vacuum drying oven at 80°C for 12 h; the potassium loading is 5%.

[0081] (4) The powder was placed in a muffle furnace and calcined at 400°C for 4 hours at a heating rate of 2°C / min to prepare the catalyst.

[0082] The catalyst underwent hydrogen pre-reduction treatment before reaction testing at a space velocity of 8000 mL / g / h at 600℃ for 4 h. After cooling to room temperature, the reaction performance was evaluated in a fixed-bed reactor at a reaction temperature of 260℃, a reaction pressure of 3 MPa, a total space velocity of 6000 mL / g / h, and a CO2 / H2 volume ratio of 24:72. The reaction performance test results are shown in Table 1.

[0083] Comparative Example 2: Changing the pre-reduction temperature of hydrogen

[0084] (1) Dissolve 1g of cobalt nitrate hexahydrate (0.0034mol) and 3.5g of aluminum isopropoxide (0.017mol) in 50mL of ethylene glycol. Stir at 80℃ and 500rpm for 4h, then wash 4 times with ethanol by centrifugation, and dry in a vacuum drying oven at 110℃ for 12h.

[0085] (2) The powder was placed in a muffle furnace and calcined at 700℃ for 4 hours with a heating rate of 2℃ / min to prepare cobalt aluminum spinel;

[0086] (3) Dissolve 500 mg of carrier and potassium chloride (calculated by mass fraction) in deionized water, stir evenly, stir at 80°C and 500 rpm until the deionized water evaporates completely, and then place in a vacuum drying oven at 80°C for 12 h; the potassium loading is 5%.

[0087] (4) The powder was placed in a muffle furnace and calcined at 400°C for 4 hours at a heating rate of 2°C / min to prepare the catalyst.

[0088] The catalyst underwent hydrogen pre-reduction treatment before reaction testing at a space velocity of 8000 mL / g / h at 200℃ for 4 h. After cooling to room temperature, the reaction performance was evaluated in a fixed-bed reactor at a reaction temperature of 260℃, a reaction pressure of 3 MPa, a total space velocity of 6000 mL / g / h, and a CO2 / H2 volume ratio of 24:72. The reaction performance test results are shown in Table 1.

[0089] Comparative Example 3: Aluminum isopropoxide was replaced with aluminum oxide.

[0090] (1) Dissolve 1g of cobalt nitrate hexahydrate (0.0034mol) and 1.73g of aluminum oxide (0.017mol) in 50mL of ethylene glycol. Stir at 80℃ and 500rpm for 4h, then wash 4 times with ethanol by centrifugation, and dry in a vacuum drying oven at 110℃ for 12h.

[0091] (2) The powder was placed in a muffle furnace and calcined at 700°C for 4 hours with a heating rate of 2°C / min to prepare a cobalt catalyst supported on alumina.

[0092] (3) Dissolve 500 mg of carrier and potassium chloride (calculated by mass fraction) in deionized water, stir evenly, stir at 80°C and 500 rpm until the deionized water evaporates completely, and then place in a vacuum drying oven at 80°C for 12 h; the potassium loading is 5%.

[0093] (4) The powder was placed in a muffle furnace and calcined at 400°C for 4 hours at a heating rate of 2°C / min to prepare the catalyst.

[0094] The catalyst underwent hydrogen pre-reduction treatment before reaction testing at a space velocity of 8000 mL / g / h at 600℃ for 4 h. After cooling to room temperature, the reaction performance was evaluated in a fixed-bed reactor at a reaction temperature of 260℃, a reaction pressure of 3 MPa, a total space velocity of 6000 mL / g / h, and a CO2 / H2 volume ratio of 24:72. The reaction performance test results are shown in Table 1.

[0095] Comparative Example 4: No Alkali Metal Modification

[0096] (1) Dissolve 1g of cobalt nitrate hexahydrate (0.0034mol) and 3.5g of aluminum isopropoxide (0.017mol) in 50mL of ethylene glycol. Stir at 80℃ and 500rpm for 4h, then wash 4 times with ethanol by centrifugation, and dry in a vacuum drying oven at 110℃ for 12h.

[0097] (2) The powder was placed in a muffle furnace and calcined at 700℃ for 4 hours with a heating rate of 2℃ / min to prepare cobalt aluminum spinel;

[0098] The catalyst underwent hydrogen pre-reduction treatment before the reaction test. The total space velocity of the feed gas was 8000 mL / g / h, and the pretreatment conditions were 600℃ for 4 h. After the temperature dropped to room temperature, the reaction performance was evaluated in a fixed-bed reactor with a reaction temperature of 260℃, a reaction pressure of 3 MPa, a space velocity of 6000 mL / g / h, and a CO2 / H2 volume ratio of 24:72. The reaction performance test results are shown in Table 1.

[0099] Table 1

[0100]

[0101]

[0102] As shown in Table 1, the catalyst prepared in this invention can effectively achieve the technical effect of carbon dioxide hydrogenation to ethanol. Compared with the comparative catalyst, the conversion rate of carbon dioxide and the selectivity of ethanol can be significantly improved by controlling the ratio of cobalt and aluminum, the hydrogen pre-reduction temperature, and the introduction of alkali metals, based on the construction of the cobalt-aluminum spinel structure. Taking Example 4 as an example, the conversion rate of carbon dioxide is 41%, the selectivity of total alcohols can reach 78%, and the selectivity of ethanol reaches 64%. This also shows that the preparation method of the catalyst of this invention can effectively improve the catalytic performance of selective hydrogenation of carbon dioxide to ethanol.

[0103] The above embodiments are merely illustrative of the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein, without departing from the spirit and substance defined by the claims of the present invention; and such modifications or substitutions are still within the scope defined by the claims of the present invention.

Claims

1. The application of an alkali metal-supported cobalt-based catalyst in the catalytic hydrogenation of carbon dioxide to ethanol, characterized in that, The alkali metal-supported cobalt-based catalyst comprises cobalt aluminum spinel and an alkali metal supported on the cobalt aluminum spinel. The cobalt active center of the cobalt aluminum spinel exists partly in a CoAl₂O₄ spinel-type structure and partly in zero-valent Co. 0 Form exists; Based on the mass of cobalt aluminum spinel, the alkali metal loading is 5wt%-15wt%; Cobalt existing in the form of CoAl2O4 spinel structure and Co in the form of zero-valent co 0 The molar ratio of cobalt in its various forms is 15:1 to 2:1; The preparation method of the alkali metal supported cobalt-based catalyst includes the following steps: S1. Dissolve cobalt salt and aluminum isopropoxide in ethylene glycol, stir under heating conditions, wash with ethanol by centrifugation, and dry in a vacuum drying oven; place the dried powder in a muffle furnace for high-temperature calcination to obtain cobalt aluminum spinel; the molar ratio of cobalt in the cobalt salt to aluminum in the aluminum isopropoxide is 1:2~1:

8. S2. Cobalt aluminum spinel and alkali metal chlorides are dissolved in deionized water and stirred evenly. The mixture is stirred under heating conditions until the deionized water is completely evaporated, and then dried in a vacuum drying oven. The dried powder is calcined at high temperature in a muffle furnace and then subjected to hydrogen reduction treatment to obtain alkali metal supported cobalt-based catalyst. The conditions for hydrogen reduction treatment are: space velocity of 8000 mL / g / h, reduction temperature of 250℃~800℃, and reduction time of 1h~6h.

2. The application according to claim 1, characterized in that, In step S1, the cobalt salt includes one or more of cobalt nitrate or its hydrate, cobalt carbonate or its hydrate, and cobalt sulfate or its hydrate.

3. The application according to claim 1, characterized in that, In step S1, the stirring and heating temperature is 30℃~90℃, the stirring speed is 200rpm~600rpm, and the stirring time is 2~6h; In step S1, the high-temperature calcination temperature is 400℃~800℃, the calcination time is 1h~8h, and the heating rate is 1℃ / min~10℃ / min.

4. The application according to claim 1, characterized in that, In step S2, the alkali metal chloride includes one or more of lithium chloride, sodium chloride, and potassium chloride.

5. The application according to claim 1, characterized in that, In step S2, the heating and stirring temperature is 50℃~100℃, and the stirring speed is 200rpm~600rpm; In step S2, the high-temperature calcination temperature is 200℃~800℃, the calcination time is 1h~8h, and the heating rate is 1℃ / min~10℃ / min.

6. The application according to claim 1, characterized in that, The conditions for preparing ethanol by the catalytic reaction of carbon dioxide hydrogenation are as follows: reaction temperature is 200~400℃, reaction pressure is 2~4MPa, total space velocity of the feed gas is 3000~8000mL / g / h, and the gas used is a mixture of CO2 and H2, wherein the volume ratio of CO2 to H2 is 1:1~1:4.

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