Iron-cobalt catalyst suitable for catalyzing carbon dioxide hydrogenation reaction, and preparation method and application thereof

Abstract

The application discloses an iron-cobalt catalyst suitable for catalyzing carbon dioxide hydrogenation reaction and a preparation method and application thereof. The catalyst is prepared by taking iron salt and cobalt salt as raw materials, adopting a coprecipitation method to obtain a catalyst precursor, drying and calcining the catalyst precursor, and activating the catalyst precursor in an activation atmosphere to obtain an iron-cobalt bimetallic catalyst with controllable metal proportion. The addition of cobalt can increase the basic sites on the surface of the catalyst, significantly improve carbon dioxide adsorption, and promote carbonization of iron. Changing the activation atmosphere and introducing alkali metals can make the iron-cobalt oxide form a unique iron-cobalt alloy carbide (Fe 1‑ x Co x )5C2 with uniform distribution of iron and cobalt, which is beneficial to improving the "intimacy" between iron and cobalt, so as to obtain higher carbon dioxide conversion rate and high carbon hydrocarbon selectivity. When the catalyst is used for preparing high carbon hydrocarbons by carbon dioxide hydrogenation, the carbon dioxide conversion rate is greater than 50%, the high carbon hydrocarbon selectivity is greater than 68%, the selectivity of generated carbon monoxide and methane is low, the catalytic activity is good, and the time required to reach the highest reaction activity is obviously shortened.

Description

Technical Field

[0001] The present invention belongs to the technical field of catalysts, and in particular relates to an iron-cobalt bimetallic catalyst suitable for catalyzing the hydrogenation of carbon dioxide to produce higher carbon hydrocarbons, as well as a preparation method and application thereof. Background Art

[0002] Using chemical catalysis to convert carbon dioxide into high-value hydrocarbon products, fuels and polymers is one of the effective ways to solve the greenhouse effect problem.

[0003] Iron-based catalysts are widely used in the carbon dioxide hydrogenation reaction to produce hydrocarbons because of their low price, wide operating temperature range and rich carbon dioxide hydrogenation products. Carbon dioxide is a thermodynamically stable, fully oxidized, chemically inert molecule with relatively weak adsorption on the catalyst surface. Traditional iron-based catalysts are difficult to obtain high catalytic activity and high selectivity for high-carbon hydrocarbon products. Currently, there are many studies on carbon dioxide hydrogenation to produce light olefins (patents CN111111760B, CN111111763B, CN112174764B), but there are fewer reports on the development of catalysts for producing high-carbon hydrocarbon products. High-carbon hydrocarbons (carbon number ≥ 5) are one of the preferred alternatives to gasoline as liquid fuels due to their high added value and low aromatic content.

[0004] Patent CN114870886A provides a multifunctional catalyst (Na-Fe3O4 / ZSM-5) composed of a metal oxide and a molecular sieve. This catalyst has high selectivity for higher carbon hydrocarbons (68.5%) and low selectivity for methane (2.1%), but a low carbon dioxide conversion rate (22.4%). Patent CN114405537B provides a multifunctional catalyst composed of cesium-modified cobalt ferrite, which has high carbon dioxide conversion at 320°C and high selectivity for lower carbon hydrocarbons (~40%). However, its chain growth capacity is poor, and the cesium additive is expensive. Patent CN115155590A provides a nitrogen-doped carbon iron-based catalyst, which has high carbon dioxide conversion and selectivity for higher carbon hydrocarbons at a reaction temperature of 300°C. However, this catalyst is prepared via a hydrothermal synthesis method, which is complex and time-consuming, and requires a long time to reach peak hydrogenation activity. Therefore, it is crucial to develop a catalyst with a simple preparation process, high activity, high selectivity, and high stability for use in the hydrogenation of carbon dioxide to higher carbon hydrocarbons. Summary of the Invention

[0005] In response to the above-mentioned technical problems existing in the prior art, the purpose of the present invention is to provide an iron-cobalt bimetallic catalyst suitable for catalyzing the hydrogenation of carbon dioxide to produce higher carbon hydrocarbons, as well as its preparation method and application. The catalyst can form a unique iron-cobalt alloy carbide with controllable component content and a simple preparation process. At a reaction temperature of 300°C, the carbon dioxide conversion rate is greater than 50% and the higher carbon hydrocarbon selectivity is greater than 68%.

[0006] The technical solution adopted in the present invention is as follows:

[0007] The method for preparing the iron-cobalt bimetallic catalyst for catalyzing the hydrogenation of carbon dioxide to produce higher carbon hydrocarbons comprises the following steps:

[0008] 1) Dissolve the iron salt and cobalt salt in deionized water, add a precipitant until the pH reaches 8-10, and age the suspension at room temperature overnight;

[0009] 2) filtering the suspension obtained in step 1), washing with deionized water until neutral, drying, and then calcining in an air atmosphere to obtain an iron cobalt oxide material;

[0010] 3) dissolving a soluble metal salt of the metal M in deionized water, and adding the solution dropwise to the iron cobalt oxide material obtained in step 2) by an equal volume impregnation method, drying after sufficient impregnation, and calcining in an air atmosphere to obtain an iron cobalt oxide material doped with the metal element M;

[0011] 4) The iron-cobalt oxide material doped with the metal element M obtained in step 3) is heated to 300-500° C. in an activation atmosphere, and then maintained at a constant temperature for 1-4 hours for activation. After the activation is completed, the temperature is lowered to room temperature and then passivated in a passivation atmosphere for 1-4 hours to obtain an iron-cobalt bimetallic catalyst modified with the metal element M.

[0012] Furthermore, in step 1), the total metal ion concentration of the iron salt and the cobalt salt in deionized water is 0.1 to 1.0 mol·L -1 , preferably 0.3-0.6 mol·L -1 The molar ratio of iron salt to cobalt salt is 1:0.1-0.7, preferably 1:0.4-0.6; the concentration of the precipitant is 0.1-1.0 mol·L -1 The aqueous solution of ammonia, the iron salt and the cobalt salt are respectively their sulfate, nitrate or chloride salts.

[0013] Furthermore, the calcination temperature in step 2) or step 3) is 300-600°C, the calcination time is 4-6 hours, and the preferred calcination condition is 400-500°C.

[0014] Furthermore, the metal element M described in step 3) is a mixture of one or more elements of alkali metals, transition metals, and rare earth metals, and the soluble salt of metal M is its nitrate or carbonate; the mass of the metal element M is 1% to 10% of the mass of the iron cobalt oxide material, preferably 2 to 6%; the metal M is preferably one or both of Na and K.

[0015] Furthermore, the activation atmosphere described in step 4) is H2, CO, H2 / CO mixed gas or H2 / CH4 mixed gas; the volume fraction ratio of the H2 / CO mixed gas is H2 / CO = 1:0.4~1.5, preferably 1:0.7~1; the volume fraction ratio of the H2 / CH4 mixed gas is H2 / CH4 = 1:0.3~1.0, preferably 1:0.3~0.5.

[0016] Furthermore, in step 4), the passivation atmosphere is an O2 / N2 mixed gas with an O2 volume fraction of 0.5 to 2%.

[0017] The present invention provides use of any of the above catalysts in catalytic carbon dioxide hydrogenation reactions.

[0018] Furthermore, the catalytic reaction is carried out in a fixed bed reactor, and the target product of carbon dioxide hydrogenation is high-carbon hydrocarbons. The reaction temperature is 250-500°C, the reaction pressure is 1-5 MPa, and the reaction volume space velocity is 1500-6000 h -1 The volume fraction of H2 in the mixed gas H2 / CO2 / N2 is 65-75%, the volume fraction of CO2 is 20-25%, and the volume fraction of N2 is 5-10%.

[0019] Furthermore, the high-carbon hydrocarbons are hydrocarbon substances with a carbon number of ≥5.

[0020] Compared with the prior art, the present invention has the following beneficial effects:

[0021] 1) The present invention is an iron-cobalt bimetallic catalyst for the hydrogenation of carbon dioxide to produce higher carbon hydrocarbons. The iron-cobalt oxide material of the present invention is prepared by a coprecipitation method. The preparation process conditions are simple, the raw materials are easily available, and it is conducive to large-scale production. At the same time, the catalyst component content can be optimized by regulating the metal ratio of the precursor, which contributes to the synergistic effect of the bimetallic and the formation and stability of the active phase. In addition, the catalyst is doped with an auxiliary metal by adding an auxiliary agent to the iron-cobalt oxide material in an equal volume impregnation manner. The loading amount of the auxiliary metal can be well regulated, and the catalyst performance is stable.

[0022] 2) The iron-cobalt bimetallic catalyst of the present invention has a spinel structure. The addition of metallic cobalt can increase the basic sites on the catalyst surface, thereby significantly improving carbon dioxide adsorption and promoting iron carbonization. The introduction of cobalt promotes the reduction of iron, forming an Fe-rich 0The iron-cobalt alloy is conducive to the adsorption of carbon monoxide and the in-situ formation of active material iron carbide. The addition of alkali metals (sodium and potassium) as electron promoters increases the basicity of the catalyst surface, promotes the adsorption of carbon dioxide, weakens the adsorption of hydrogen, and is conducive to the conversion of carbon dioxide and the growth of the carbon chain.

[0023] 3) Compared with the existing carbon dioxide hydrogenation catalyst, the catalyst of the present invention can transform the iron cobalt oxide into a unique iron cobalt alloy carbide (Fe 1-x Co x )5C2, which helps improve the intimacy between metals and the tandem active sites, resulting in higher carbon dioxide conversion rates and higher selectivity for high-carbon hydrocarbons. At the same time, it significantly shortens the time it takes for the catalyst to reach peak hydrogenation activity. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 These are the XRD patterns of the mechanical mixture of iron oxide and cobalt oxide materials and iron cobalt oxide materials that have not been activated by the activation atmosphere.

[0025] Figure 2 This is the XRD pattern of the iron-cobalt bimetallic catalyst activated by activation atmosphere. DETAILED DESCRIPTION

[0026] The present invention will be further described below with reference to specific embodiments, but the protection scope of the present invention is not limited thereto.

[0027] Example 1

[0028] Weigh 5.25g of ferric nitrate nonahydrate (Fe(NO3)3·9H2O) and dissolve it in deionized water and stir at room temperature for 15min to obtain a mixed solution (total metal ion concentration is 0.5mol·L -1 ). Then it was mixed with 0.5 mol·L -1 An aqueous ammonia solution was added dropwise to the beaker at a rate of 2 ml / min until the suspension had a pH of 8.5. After precipitation, the suspension was aged overnight, filtered, and washed with distilled water until the pH reached 7.0. The resulting filter cake was dried at 110°C for 12 hours and then heated to 500°C in air at a rate of 5°C / min for 5 hours to produce the iron oxide material. The above steps were repeated with 2.04 g of cobalt nitrate hexahydrate (Co(NO3)2·6H2O) to produce the cobalt tetroxide material.

[0029] The obtained iron oxide and tricobalt tetroxide material were ground into powder together, and then were put into a tube furnace, and were activated at 400°C for 8h under H2atmosphere (H2flow rate was 40ml / min) with a heating rate of 5°C / min, and then were passivated by 1%O2-99%N2for 3h after the end of heating and cooling to room temperature, to obtain catalyst 65Fe+35Co(H2-400).

[0030] The XRD pattern of the mixture of the iron oxide and tricobalt tetroxide material obtained in Example 1 is shown in Figure 1 (a).

[0031] Example 2

[0032] 5.25g of iron nitrate nonahydrate (Fe(NO3)3·9H2O) and 2.04g of cobalt nitrate hexahydrate (Co(NO3)2·6H2O) were weighed and dissolved in 40ml of deionized water, and stirred at room temperature for 15min to obtain a mixed solution (the total concentration of metal ions was 0.5mol·L -1 ). Then, the mixed solution was added dropwise into a beaker with an ammonia solution of 0.5mol·L -1 at a speed of 2ml / min in a concurrent manner until the pH of the suspension was 8.5. After the precipitation was completed, the suspension was aged overnight, and then was filtered and washed with distilled water until the pH was 7.0. The obtained filter cake was dried at 110°C for 12h, and then was calcined at 500°C for 5h under air atmosphere with a heating rate of 5°C / min to obtain a cobalt-iron oxide material.

[0033] The obtained cobalt-iron oxide material was put into a tube furnace, and was activated at 400°C for 8h under H2atmosphere (H2flow rate was 40ml / min) with a heating rate of 5°C / min, and then was passivated by 1%O2-99%N2for 3h after the end of heating and cooling to room temperature, to obtain catalyst 65Fe35Co(H2-400).

[0034] The XRD pattern of the cobalt-iron oxide material obtained in Example 2 is shown in Figure 1 (b).

[0035] Example 3

[0036] The cobalt-iron oxide material obtained in Example 2 was put into a tube furnace, and was activated at 400°C for 2h under mixed gas (volume fraction ratio of H2 / CO was 1.5) atmosphere (mixed gas flow rate was 40ml / min) with a heating rate of 5°C / min, and then was passivated by 1%O2-99%N2for 3h after the end of heating and cooling to room temperature, to obtain catalyst 65Fe35Co(HC-400).

[0037] Comparative Example 1

[0038] Weigh 5.25g of ferric nitrate nonahydrate (Fe(NO3)3·9H2O) and dissolve it in deionized water and stir at room temperature for 15min to obtain a mixed solution (total metal ion concentration is 0.5mol·L -1 ). Then it was mixed with 0.5 mol·L -1 An aqueous ammonia solution was added dropwise to the beaker at a rate of 2 ml / min until the suspension had a pH of 8.5. After precipitation, the suspension was aged overnight, filtered, and washed with distilled water until the pH reached 7.0. The resulting filter cake was dried at 110°C for 12 hours and then calcined at 500°C in air at a rate of 5°C / min for 5 hours to produce the iron oxide material.

[0039] The obtained iron oxide was then placed in a tubular heating furnace and heated to 400°C at a heating rate of 5°C / min in a mixed gas (volume fraction ratio of H2 / CO = 1.5) atmosphere (mixed gas flow rate of 40 ml / min) for activation for 8 hours. After the heating was completed and the mixture was cooled to room temperature, 1% O2~99% N2 was introduced for passivation for 3 hours to obtain catalyst Fe (HC-400).

[0040] Comparative Example 2

[0041] The iron cobalt oxide material obtained in Example 2 was placed in a tubular heating furnace and heated to 400°C at a heating rate of 5°C / min under a CO atmosphere (CO flow rate of 40 ml / min) for activation for 2 h. After the heating was completed and the mixture was cooled to room temperature, 1% O2~99% N2 was introduced for passivation for 3 h to obtain catalyst 65Fe35Co (CO-400).

[0042] Comparative Example 3

[0043] The iron cobalt oxide material obtained in Example 2 was placed in a tubular heating furnace and activated for 2 hours at a heating rate of 5°C / min in a mixed gas atmosphere (volume fraction ratio of H2 / CO = 1.5) (mixed gas flow rate of 40 ml / min). After the heating was completed and the material was cooled to room temperature, 1% O2~99% N2 was not used for passivation to obtain catalyst 65Fe35Co (HC-400-N).

[0044] Example 4

[0045] Weigh 0.23 g of copper nitrate trihydrate (Cu(NO₃)₂·6H₂O) and dissolve it in 1.5 ml of deionized water. Weigh 3.0 g of the iron cobalt oxide material obtained in Example 2, evenly add 1.5 ml of the copper nitrate solution dropwise, and sonicate for 1 hour. Immerse the sample for 12 hours, dry it at 110°C for 12 hours, and then heat it to 500°C in air at a rate of 5°C / min for 5 hours to obtain the copper-modified iron cobalt oxide material.

[0046] The obtained copper-modified iron-cobalt oxide material was then placed in a tubular heating furnace and heated to 400°C at a heating rate of 5°C / min in a mixed gas atmosphere (volume fraction ratio of H2 / CO = 1.5) (mixed gas flow rate of 40 ml / min) for activation for 2 hours. After heating was completed and the mixture was cooled to room temperature, 1% O2~99% N2 was introduced for passivation for 3 hours to obtain the catalyst 2Cu-65Fe35Co (HC-400).

[0047] Example 5

[0048] Weigh 0.19 g of cerium nitrate hexahydrate (Ce(NO₃)₂·6H₂O) and dissolve it in 1.5 ml of deionized water. Add 1.5 ml of the cerium nitrate solution dropwise to 3.0 g of the iron cobalt oxide material obtained in Example 2, and ultrasonicate for 1 hour. Immerse the sample for 12 hours, dry it at 110°C for 12 hours, and then calcine it at 500°C in air at a heating rate of 5°C / min for 5 hours to obtain the cerium-modified iron cobalt oxide material.

[0049] The obtained cerium-modified iron cobalt oxide material was then placed in a tubular heating furnace and heated to 400°C at a heating rate of 5°C / min in a mixed gas atmosphere (volume fraction ratio of H2 / CO = 1.5) (mixed gas flow rate of 40 ml / min) for activation for 2 hours. After the heating was completed and the temperature was lowered to room temperature, 1% O2~99% N2 was introduced for passivation for 3 hours to obtain the catalyst 2Ce-65Fe35Co (HC-400).

[0050] Example 6

[0051] Weigh 0.16g of anhydrous potassium nitrate (KNO3) and dissolve it in 1.5ml of deionized water. Weigh 3.0g of the iron cobalt oxide material obtained in Example 2 and evenly add 1.5ml of the potassium nitrate solution dropwise to it. Ultrasonicate for 1 hour. Immerse the sample for 12 hours, dry it at 110°C for 12 hours, and then heat it to 500°C in air at a heating rate of 5°C / min for 5 hours to obtain the potassium-modified iron cobalt oxide material.

[0052] The obtained potassium-modified iron cobalt oxide material was then placed in a tubular heating furnace and heated to 400°C at a heating rate of 5°C / min in a mixed gas atmosphere (volume fraction ratio of H2 / CO = 1.5) (mixed gas flow rate of 40 ml / min) for activation for 2 hours. After the heating was completed and the temperature was lowered to room temperature, 1% O2~99% N2 was introduced for passivation for 3 hours to obtain the catalyst 2K-65Fe35Co (HC-400).

[0053] Example 7

[0054] Weigh 0.22g of anhydrous sodium nitrate (NaNO3) and dissolve it in 1.5ml of deionized water. Weigh 3.0g of the iron cobalt oxide material obtained in Example 2 and evenly add 1.5ml of the sodium nitrate solution dropwise to it. Ultrasonicate for 1h. Immerse the sample for 12h, dry it at 110°C for 12h, and then heat it to 500°C in air at a heating rate of 5°C / min for 5h to obtain the sodium-modified iron cobalt oxide material.

[0055] The obtained sodium-modified iron cobalt oxide material was then placed in a tubular heating furnace and heated to 400°C at a heating rate of 5°C / min in a mixed gas atmosphere (volume fraction ratio of H2 / CO = 1.5) (mixed gas flow rate of 40 ml / min) for activation for 2 hours. After the heating was completed and the temperature was lowered to room temperature, 1% O2~99% N2 was introduced for passivation for 3 hours to obtain the catalyst 2Na-65Fe35Co (HC-400).

[0056] Example 8

[0057] Weigh 0.44g of anhydrous sodium nitrate (NaNO3) and 0.16g of anhydrous potassium nitrate (KNO3) and dissolve them in 1.5ml of deionized water. Weigh 3.0g of the iron cobalt oxide material obtained in Example 2, evenly add 1.5ml of the mixed salt solution, and sonicate for 1h. Immerse the sample for 12h, dry it at 110°C for 12h, and then heat it to 500°C in air at a heating rate of 5°C / min for 5h to obtain the potassium-sodium modified iron cobalt oxide material.

[0058] The obtained potassium-sodium modified iron cobalt oxide material was then placed in a tubular heating furnace and heated to 400°C at a heating rate of 5°C / min in a mixed gas atmosphere (volume fraction ratio of H2 / CO = 1.5) (mixed gas flow rate of 40 ml / min) for activation for 2 hours. After heating was completed and cooled to room temperature, 1% O2~99% N2 was introduced for passivation for 3 hours to obtain the catalyst 4Na-2K-65Fe35Co (HC-400).

[0059] Performance Testing

[0060] Catalyst performance was tested in a fixed-bed reactor. 0.5 ml of 60-100 mesh catalyst and 5.5 ml of quartz sand of the same mesh size were mixed evenly and loaded into the isothermal zone of the fixed-bed reactor. The catalytic reaction conditions were a temperature of 300°C, a reaction pressure of 1 MPa, and a reaction volumetric space velocity of 3000 h / min. -1The mixed reaction gas volume ratio of H2 / CO2 / N2 was 69% / 23% / 8%, with N2 serving as the internal standard gas for gas chromatography analysis. Carbon dioxide, carbon monoxide, and methane in the gaseous products were quantitatively analyzed by online gas chromatography equipped with a TCD detector, while hydrocarbons in the gaseous products were quantitatively analyzed by online gas chromatography equipped with an FID detector. The carbon dioxide conversion and product selectivity were calculated. The CO2 hydrogenation performance test results are listed in Table 1.

[0061] Table 1 Carbon dioxide hydrogenation performance on different catalysts

[0062]

[0063] As can be seen from Table 1, the carbon dioxide conversion rate of the iron-cobalt bimetallic catalyst in Example 8 of the present invention reached 51.35%, the methane selectivity was relatively low at 14.16%, and the carbon monoxide selectivity was only 3.43%. 5+ The hydrocarbon selectivity reached 68.76%.

[0064] Comparing Example 1 with Example 2, it can be seen that when the catalyst particles have a poor metal intimacy, the carbon dioxide conversion is reduced from 19.84% to 17.75%, and the methane selectivity increases rapidly to 57.43%. 5+ The hydrocarbon selectivity decreased to 16.74%. Figure 1 Curve a is the XRD pattern of mechanical mixing of Fe2O3 and Co3O4, and curve b is the XRD pattern of iron cobalt oxide material. Figure 1 As shown in Table 1, Examples 1 and 2, the iron-cobalt oxide material formed by close contact between the iron phase and the cobalt phase is beneficial to improving C 5+ Hydrocarbon selectivity is due to the fact that the carbon monoxide intermediate easily overflows from the ferroferric oxide to the cobalt site, resulting in a higher carbon monoxide concentration at the cobalt site, which is beneficial for improving the catalyst's carbon chain growth ability. The increased distance between the iron and cobalt phases leads to a significant increase in methane selectivity. This is due to the lower carbon monoxide concentration at the cobalt site, which enhances the methanation reaction of carbon dioxide and reduces the chain growth possibility of the Fischer-Tropsch reaction.

[0065] It can be seen from Table 1 that after changing the activation atmosphere and adding the promoter, the carbon dioxide conversion rate of the catalyst is significantly improved from 19.84% to 51.35%, and the target product C 5+ The hydrocarbon selectivity is increased to 68.76% at most. Figure 2 It can be concluded that the use of an activating atmosphere to activate the catalyst can form a unique bimetallic carbide, which is beneficial to improve the intimacy between the iron phase and the cobalt phase and the series active sites to obtain higher carbon dioxide conversion and C 5+Hydrocarbon selectivity. Compared with other additives such as Cu and Ce, the introduction of alkali metals (sodium and potassium) significantly improves the catalyst activity. The addition of alkali metals (sodium and potassium) as an electronic promoter increases the basicity of the catalyst surface, promotes the adsorption of carbon dioxide and weakens the adsorption of hydrogen, thereby inhibiting the methanation of carbon dioxide and facilitating the conversion of carbon dioxide and the growth of carbon chains. At the same time, the introduction of alkali metals enhances the carburizing ability of iron, which is beneficial to the formation of double metal carbide.

[0066] In addition, the activation effect of the mixed gas is better than that of CO, because under the CO atmosphere, the catalyst surface is more prone to accumulate amorphous carbon, which covers the active sites of the catalyst and reduces the catalytic activity. This can be seen from the amorphous carbon diffraction peak at 20°-30° of the curve of 65Fe35Co(CO-400) in Figure 2. Figure 2 In addition, the activation effect of the mixed gas is better than that of CO, because under the CO atmosphere, the catalyst surface is more prone to accumulate amorphous carbon, which covers the active sites of the catalyst and reduces the catalytic activity. This can be seen from the amorphous carbon diffraction peak at 20°-30° of the curve of 65Fe35Co(CO-400) in Figure 2. Figure 2 It can be concluded that the passivation gas can eliminate the influence of air by forming an outermost oxidation layer, thereby preventing further oxidation of air-sensitive materials (transition metals, metal carbides, etc.), and thereby improving the catalytic activity.

[0067] The content described in the specification is only a list of forms of the inventive concept, and the protection scope of the present application should not be regarded as limited to the specific forms described in the examples.

Claims

1. A method for preparing an iron-cobalt bimetallic catalyst suitable for catalyzing carbon dioxide hydrogenation reaction, characterized in that The following steps are involved: 1) Dissolve the iron and cobalt salts in deionized water, add a precipitant until the pH reaches 8-10, and age the suspension at room temperature overnight; 2) filtering the suspension obtained in step 1), washing with deionized water until neutral, drying, and then calcining in an air atmosphere to obtain an iron cobalt oxide material; 3) dissolving a soluble metal salt of metal M in deionized water and adding the solution dropwise to the iron cobalt oxide material obtained in step 2) by an equal volume impregnation method, drying the solution after sufficient impregnation, and calcining the solution in an air atmosphere to obtain the iron cobalt oxide material doped with the metal element M; 4) heating the iron-cobalt oxide material doped with the metal element M obtained in step 3) to 300-500° C. in an activation atmosphere, then maintaining the temperature for 1-4 hours for activation, cooling the temperature to room temperature after activation, and then passivating the material in a passivation atmosphere for 1-4 hours to obtain an iron-cobalt bimetallic catalyst modified with the metal element M; In step 3), the mass of the metal element M is 2-6% of the mass of the iron cobalt oxide material; the metal M is one or both of Na and K; The activation atmosphere in step 4) is a H2 / CO mixed gas, and the volume fraction ratio of the H2 / CO mixed gas is H2 / CO=1:1.

5.

2. The method for preparing an iron-cobalt bimetallic catalyst suitable for catalyzing carbon dioxide hydrogenation reaction according to claim 1, characterized in that In step 1), the total metal ion concentration of iron salt and cobalt salt in deionized water is 0.3~0.6mol·L -1 The molar ratio of iron salt to cobalt salt is 1:0.4~0.6; the concentration of the precipitant is 0.1~1.0 mol·L -1 The aqueous solution of ammonia, the iron salt and the cobalt salt are respectively their sulfate, nitrate or chloride salts.

3. The method for preparing an iron-cobalt bimetallic catalyst suitable for catalyzing carbon dioxide hydrogenation reaction according to claim 1, characterized in that In step 2) or step 3), the calcination temperature is 300-600° C., and the calcination time is 4-6 hours.

4. The method for preparing an iron-cobalt bimetallic catalyst suitable for catalyzing carbon dioxide hydrogenation reaction according to claim 3, characterized in that In step 2) or step 3), the calcination temperature is 400-500°C.

5. The method for preparing an iron-cobalt bimetallic catalyst suitable for catalyzing carbon dioxide hydrogenation reaction according to claim 1, characterized in that Step 4) The passivation atmosphere is an O2 / N2 mixed gas with an O2 volume fraction of 0.5~2%.

6. An iron-cobalt bimetallic catalyst suitable for catalyzing carbon dioxide hydrogenation reaction prepared by the method according to any one of claims 1 to 5.

7. Use of the iron-cobalt bimetallic catalyst as claimed in claim 6 in catalytic carbon dioxide hydrogenation reaction.

8. The use according to claim 7, characterized in that The catalytic reaction is carried out in a fixed bed reactor. The catalyst is loaded in the fixed bed reactor and a mixed gas of H2 / CO2 / N2 is introduced for catalytic reaction. The target product of carbon dioxide hydrogenation is high-carbon hydrocarbons. The reaction temperature is 250~500℃, the reaction pressure is 1~5MPa, and the reaction volume space velocity is 1500~6000h -1 The volume fraction of H2 in the H2 / CO2 / N2 mixture is 65~75%, the volume fraction of CO2 is 20~25%, and the volume fraction of N2 is 5~10%.

9. The use according to claim 8, characterized in that The high-carbon hydrocarbons are hydrocarbon substances with carbon atoms ≥5.

Images