Single-phase Fe5C2 catalyst resistant to water vapor oxidation as well as preparation method and application of single-phase Fe5C2 catalyst

Abstract

The invention discloses a water vapor oxidation resistant single-phase Fe5C2 catalyst as well as a preparation method and application thereof, and belongs to the technical field of catalytic materials. The preparation method comprises the following steps: S1, dispersing iron oxide in a solvent I, adding potassium permanganate, stirring and reacting for 1-12 hours, separating out a solid product, and drying; s2, the solid product is subjected to high-temperature phase transformation in the atmosphere of hydrogen and synthesis gas in sequence, and single-phase Fe5C2-coated MnO is obtained; and S3, dispersing Fe5C2-coated MnO in a solvent II, adding a silanization reagent, and vacuumizing at 30-80 DEG C for gas-phase treatment to obtain the Fe5C2-coated MnO composite material. In the obtained catalyst, Fe5C2 can be directly used as a catalytic active site, and pretreatment activation operation is not needed when the catalyst is used for a synthesis gas conversion reaction; the novel MnO with excellent hydrophobic performance can reduce the adsorption of Fe5C2 to water vapor and enhance the adsorption of Fe5C2 to CO at the same time, so that the catalytic active site Fe5C2 can be protected from being oxidized into Fe3O4 by the water vapor generated in the reaction in the synthesis gas conversion reaction, and the catalytic reaction efficiency is improved.

Description

Technical Field

[0001] This invention belongs to the field of catalytic materials technology, specifically relating to a single-phase Fe5C2 catalyst resistant to water vapor oxidation, its preparation method, and its application. Background Technology

[0002] The Fischer-Tropsch synthesis (FTS) reaction can convert syngas obtained from the gasification and reforming of carbonaceous feedstocks such as coal, biomass, and natural gas into various hydrocarbon products through a catalyst, including low-carbon olefins, long-chain α-olefins, gasoline, diesel, and paraffin wax. After processing, these can yield high-purity, high-value-added fine chemicals. This production route not only effectively solves the problem of my country's petroleum resource shortage but also enables the clean and efficient utilization of coal resources.

[0003] Iron-based FTS catalysts are among the most commonly used catalysts for FTS reactions, attracting widespread attention in both basic research and industrial applications due to their low cost and easily tunable product distribution. Iron carbide provides the active sites for the formation of various hydrocarbon products in the FTS reaction. However, the water vapor generated during the reaction readily oxidizes iron carbide to Fe3O4, resulting in traditional iron-based FTS catalysts often being mixtures of iron carbide and Fe3O4. Fe3O4 exhibits high activity for water-vapor shift side reactions. The oxidation of iron carbide to Fe3O4 during the reaction reduces the exposed active sites of iron carbide, lowering the catalyst's reactivity; furthermore, it triggers severe water-vapor shift side reactions, leading to the generation of a large amount of useless byproduct CO2, thus reducing carbon atom utilization efficiency (high-value C). 2+ The yield of hydrocarbons was significantly reduced.

[0004] Therefore, there is an urgent need to develop novel iron carbide catalysts that can resist water vapor oxidation. Summary of the Invention

[0005] To address the shortcomings of the prior art, one objective of this invention is to provide a method for preparing a single-phase Fe5C2 catalyst resistant to water vapor oxidation. The resulting catalyst can protect the catalytically active Fe5C2 sites from being oxidized to Fe3O4 by the water vapor generated during the syngas conversion reaction, thereby improving the catalytic reaction efficiency.

[0006] To achieve the above objectives, the specific technical solution of the present invention is as follows:

[0007] A method for preparing a single-phase Fe5C2 catalyst resistant to water vapor oxidation includes the following steps:

[0008] S1. Disperse iron oxide in solvent one, add potassium permanganate and stir the reaction for 1-12 hours, separate the solid product and dry it;

[0009] S2. The solid product obtained in step S1 is subjected to high-temperature phase transformation in hydrogen and syngas atmospheres to obtain single-phase Fe5C2@MnO;

[0010] S3. Disperse the Fe5C2@MnO obtained in step S2 in solvent II, add silanizing reagent, and perform gas phase treatment under vacuum at 30~80℃ to obtain a single-phase Fe5C2@hydrophobic MnO catalyst.

[0011] This invention involves sequentially subjecting Fe and Mn oxides to high-temperature phase transformation in hydrogen and syngas atmospheres to obtain a single-phase Fe5C2@MnO catalyst with a single-phase Fe5C2 core and MnO shell. Then, the MnO is hydrophobically modified to obtain a single-phase Fe5C2@hydrophobic MnO catalyst. MnO has few silane-modified sites, making it difficult to achieve good hydrophobic properties. This invention proposes a high-temperature vacuum gas-phase treatment method, where silane reagents diffuse uniformly as gaseous molecules into the MnO surface and pores under vacuum to achieve deep silane modification, resulting in MnO with excellent hydrophobic properties, which serves as the shell. This novel MnO with excellent hydrophobic properties reduces the adsorption of water vapor by Fe5C2 while enhancing the adsorption of CO, thus protecting the catalytically active Fe5C2 sites from oxidation to Fe3O4 by the water vapor generated during the syngas conversion reaction, thereby improving the catalytic reaction efficiency.

[0012] Preferably, the solvent includes at least one of methanol, ethanol, and acetic acid.

[0013] Preferably, the volume-to-mass ratio of solvent one to iron oxide is 50-1000 mL: 1 g. More preferably, the volume-to-mass ratio of solvent one to iron oxide is 400-600 mL: 1 g.

[0014] Preferably, the mass ratio of iron oxide to potassium permanganate is (1.5~35):1.

[0015] Preferably, in step S2, the conditions for the high-temperature phase transformation are: first reacting in a hydrogen atmosphere at 250~450℃ for 5~24h, and then reacting in a syngas atmosphere at 220~500℃ for 12~48h.

[0016] Preferably, the solvent two includes at least one of hexane, heptane, and octane.

[0017] Preferably, the volume-to-mass ratio of solvent 2 to Fe5C2@MnO is 1~100mL:1g.

[0018] Preferably, the silanizing agent includes at least one of trimethylchlorosilane, triisopropylchlorosilane, and tributylchlorosilane.

[0019] Preferably, the volume-to-mass ratio of the silanizing agent to Fe5C2@MnO is 0.05~2mL:1g.

[0020] Preferably, the gas phase treatment time is 10~180 min.

[0021] Another object of the present invention is to provide a single-phase Fe5C2 catalyst prepared by the method, the catalyst comprising a single-phase Fe5C2 as the core layer and a hydrophobic MnO as the shell layer.

[0022] Compared with the prior art, the advantages of the present invention are:

[0023] (1) In the catalyst of the present invention, single-phase Fe5C2 can be directly used as the catalytic active site. When used for syngas conversion reaction, no pretreatment activation operation is required. In industry, this can simplify the production process and reduce the production cost.

[0024] (2) In view of the technical problem that there are few sites on the surface of MnO that can be modified by silane, it is difficult to have good hydrophobic properties. This invention proposes a method of gas phase treatment by vacuuming at high temperature. In the vacuum environment, the silane reagent is uniformly diffused into the surface and pores of MnO in gaseous form to carry out deep silane modification, thereby obtaining MnO with excellent hydrophobic properties and a catalyst with single-phase Fe5C2 as the core layer and MnO with excellent hydrophobic properties as the shell layer.

[0025] (3) In the catalyst of the present invention, hydrophobic MnO can reduce the adsorption of water vapor by Fe5C2 and enhance the adsorption of carbon monoxide by Fe5C2. This protects the catalytically active Fe5C2 from being oxidized to Fe3O4 by the water vapor generated during the syngas conversion reaction. Therefore, the single-phase Fe5C2@hydrophobic MnO catalyst prepared by the present invention exhibits higher FTS main reaction activity and lower water-vapor shift side reaction activity in the syngas conversion reaction, improving carbon atom utilization efficiency and showing good industrial application prospects. Attached Figure Description

[0026] Figure 1 The XRD patterns of the catalysts prepared in Example 2 and Comparative Examples 1-3 of this invention are shown below.

[0027] Figure 2 Transmission electron microscopy and elemental distribution diagram of the catalyst prepared in Example 2 of this invention;

[0028] Figure 3 Photographs of the water droplet contact angles of the catalysts prepared in Example 2 and Comparative Examples 3-4 of this invention;

[0029] Figure 4The amount of water vapor and CO adsorbed by the catalysts prepared in Example 2 and Comparative Examples 1-3 of this invention;

[0030] Figure 5 This is a comparison chart of the syngas conversion performance of the catalysts prepared in Examples 1-4 and Comparative Examples 1-4 of the present invention;

[0031] Figure 6 The XRD patterns of the catalysts of Examples 1-4 and Comparative Examples 1-4 of this invention during the syngas conversion process are shown. Detailed Implementation

[0032] The technical solution of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0033] This invention provides a method for preparing a single-phase Fe5C2 catalyst resistant to water vapor oxidation, comprising the following steps:

[0034] S1. Disperse iron oxide in solvent one, add potassium permanganate and stir the reaction for 1-12 hours, separate the solid product and dry it;

[0035] S2. The solid product obtained in step S1 is subjected to high-temperature phase transformation in hydrogen and syngas atmospheres to obtain single-phase Fe5C2@MnO;

[0036] S3. Disperse the Fe5C2@MnO obtained in step S2 in solvent two, add silanizing agent, and perform gas phase treatment under vacuum at 30~80℃ to obtain a single-phase Fe5C2@hydrophobic MnO catalyst.

[0037] In step S1, the solvent can be selected from at least one of methanol, ethanol, and acetic acid.

[0038] In step S2, the conditions for the high-temperature phase transformation are: first reacting in a hydrogen atmosphere at 250~450℃ for 5~24h, and then reacting in a syngas atmosphere at 220~500℃ for 12~48h.

[0039] In step S3, the solvent two includes at least one of hexane, heptane, and octane; the gas phase treatment time is 10~180 min.

[0040] The silanizing agent includes at least one of trimethylchlorosilane, triisopropylchlorosilane, and tributylchlorosilane; the volume-to-mass ratio of the silanizing agent to Fe5C2@MnO is 0.05~2mL:1g; the silanizing agent is selected from trimethylchlorosilane, triisopropylchlorosilane, or tributylchlorosilane, and MnO with excellent hydrophobic properties can be obtained within the above ratio range.

[0041] The iron oxide in this invention can be commercially available iron oxide or iron oxide prepared by the following method, the specific steps of which are as follows:

[0042] A 20-100 g / L aqueous solution of ferric chloride, ferric nitrate, or ferrous sulfate is uniformly mixed with sodium acetate at a solid-liquid ratio of 50-200 g / L. 2-15 g of hexadecyltrimethylammonium bromide is added, and the mixture is stirred for 10-60 min. 20-100 mL of ethylenediamine is added, and stirring continues for 0.5-6 h. The mixture is then subjected to hydrothermal reaction at 100-250 °C for 6-24 h. The mixture is collected by centrifugation, and the product is washed with water and ethanol. After drying at 60-120 °C, ferric oxide is obtained.

[0043] Example 1

[0044] This embodiment provides a method for preparing a single-phase Fe5C2 catalyst resistant to water vapor oxidation, comprising the following steps:

[0045] S1. Dissolve 5g of ferric chloride in 250mL of water, add 15g of sodium acetate and mix evenly, add 3g of hexadecyltrimethylammonium bromide and stir for 20min, then add 20mL of ethylenediamine and continue stirring for 0.5h; react the mixed solution hydrothermally at 180℃ for 12h, wash the precipitate with water and ethanol, and dry at 120℃ to obtain ferric oxide;

[0046] S2. Disperse 0.5g of iron oxide in 200mL of ethanol, add 0.015g of potassium permanganate, stir and react for 2h, then separate the solid product and dry it at 100℃.

[0047] S3. Weigh 0.5g of the obtained solid product and place it in a tube furnace. Pass hydrogen gas at atmospheric pressure through the furnace at a flow rate of 50mL / min and maintain the temperature at 300℃ for 8h. Then pass syngas at atmospheric pressure (H2 / CO volume ratio of 2) through the furnace at a flow rate of 50mL / min and maintain the temperature at 250℃ for 24h to obtain single-phase Fe5C2@MnO.

[0048] S4. Disperse 0.2 g of Fe5C2@MnO in 10 mL of n-hexane, add 0.2 mL of trimethylsilane chloride, and perform gas phase treatment under vacuum in a vacuum oven at 80 °C for 10 min to obtain a single-phase Fe5C2@hydrophobic MnO catalyst.

[0049] Example 2

[0050] This embodiment provides a method for preparing a single-phase Fe5C2 catalyst resistant to water vapor oxidation, comprising the following steps:

[0051] S1. Dissolve 15g of ferric chloride in 220mL of water, add 25g of sodium acetate and mix evenly, add 7.5g of hexadecyltrimethylammonium bromide and stir for 30min, then add 53mL of ethylenediamine and continue stirring for 1h; the mixed solution is hydrothermally reacted at 200℃ for 10h, the precipitate is washed with water and ethanol and dried at 100℃ to obtain ferric oxide;

[0052] S2. Disperse 1g of iron oxide in 600mL of ethanol, add 0.09g of potassium permanganate, stir and react for 2h, then separate the solid product and dry it at 100℃.

[0053] S3. Weigh 0.5g of the obtained solid product and place it in a tube furnace. Pass hydrogen gas at atmospheric pressure through the furnace at a flow rate of 50mL / min and maintain the temperature at 350℃ for 10h. Then pass syngas at atmospheric pressure (H2 / CO volume ratio of 2) through the furnace at a flow rate of 50mL / min and maintain the temperature at 320℃ for 12h to obtain single-phase Fe5C2@MnO.

[0054] S4. Disperse 0.2 g of Fe5C2@MnO in 10 mL of n-hexane, add 0.2 mL of trimethylsilane chloride, and perform gas phase treatment under vacuum in a vacuum oven at 80 °C for 10 min to obtain a single-phase Fe5C2@hydrophobic MnO catalyst.

[0055] Example 3

[0056] This embodiment provides a method for preparing a single-phase Fe5C2 catalyst resistant to water vapor oxidation, comprising the following steps:

[0057] S1. Dissolve 5g of ferric chloride in 100mL of water, add 10g of sodium acetate and mix evenly, add 3g of hexadecyltrimethylammonium bromide and stir for 20min, then add 20mL of ethylenediamine and continue stirring for 0.5h; react the mixed solution hydrothermally at 200℃ for 12h, wash the precipitate with water and ethanol, and dry at 100℃ to obtain ferric oxide;

[0058] S2. Disperse 0.5g of iron oxide in 200mL of ethanol, add 0.17g of potassium permanganate, stir and react for 2h, then separate the solid product and dry it at 100℃.

[0059] S3. Weigh 0.5g of the obtained solid product and place it in a tube furnace. Pass hydrogen gas at atmospheric pressure through the furnace at a flow rate of 50mL / min and maintain the temperature at 300℃ for 6h. Then pass syngas at atmospheric pressure (H2 / CO volume ratio of 2) through the furnace at a flow rate of 50mL / min and maintain the temperature at 350℃ for 20h to obtain single-phase Fe5C2@MnO.

[0060] S4. Disperse 0.2 g of Fe5C2@MnO in 10 mL of n-hexane, add 0.2 mL of trimethylsilane chloride, and perform gas phase treatment under vacuum in a vacuum oven at 50 °C for 60 min to obtain a single-phase Fe5C2@hydrophobic MnO catalyst.

[0061] Example 4

[0062] This embodiment provides a method for preparing a single-phase Fe5C2 catalyst resistant to water vapor oxidation, comprising the following steps:

[0063] S1. Dissolve 15g of ferric chloride in 220mL of water, add 25g of sodium acetate and mix evenly, add 7.5g of hexadecyltrimethylammonium bromide and stir for 30min, then add 53mL of ethylenediamine and continue stirring for 1h; the mixed solution is hydrothermally reacted at 200℃ for 10h, the precipitate is washed with water and ethanol and dried at 100℃ to obtain ferric oxide;

[0064] S2. Disperse 1.5g of iron oxide in 900mL of ethanol, add 0.85g of potassium permanganate, stir and react for 2h, then separate the solid product and dry it at 100℃.

[0065] S3. Weigh 0.5g of the obtained solid product and place it in a tube furnace. Pass hydrogen gas at atmospheric pressure through the furnace at a flow rate of 50mL / min and maintain the temperature at 350℃ for 10h. Then pass syngas at atmospheric pressure (H2 / CO volume ratio of 2) through the furnace at a flow rate of 50mL / min and maintain the temperature at 320℃ for 12h to obtain single-phase Fe5C2@MnO.

[0066] S4. Disperse 0.2 g of Fe5C2@MnO in 10 mL of n-hexane, add 0.2 mL of trimethylsilane chloride, and perform gas phase treatment under vacuum in a vacuum oven at 50 °C for 60 min to obtain a single-phase Fe5C2@hydrophobic MnO catalyst.

[0067] Comparative Example 1

[0068] This comparative example provides a method for preparing Fe2O3@MnO2 catalyst, including the following steps:

[0069] S1. Dissolve 15g of ferric chloride in 220mL of water, then add 25g of sodium acetate and mix thoroughly. Add 7.5g of hexadecyltrimethylammonium bromide and stir for 30min, then add 53mL of ethylenediamine and continue stirring for 1h. The mixture is then subjected to hydrothermal reaction at 200℃ for 10h. The precipitate is washed with water and ethanol and dried at 100℃ to obtain ferric oxide.

[0070] S2. Disperse 1g of iron oxide in 600mL of ethanol, add 0.09g of potassium permanganate, stir and react for 2h, then separate the solid product and dry it at 100℃ to obtain Fe2O3@MnO2.

[0071] Comparative Example 2

[0072] This comparative example provides a method for preparing an Fe5C2 catalyst, comprising the following steps:

[0073] S1. Dissolve 15g of ferric chloride in 220mL of water, add 25g of sodium acetate and mix evenly, add 7.5g of hexadecyltrimethylammonium bromide and stir for 30min, then add 53mL of ethylenediamine and continue stirring for 1h; react the mixed solution hydrothermally at 200℃ for 10h, wash the precipitate with water and ethanol, and dry at 100℃ to obtain ferric oxide.

[0074] S2. Weigh 0.5g of iron oxide and place it in a tube furnace. Pass hydrogen gas at atmospheric pressure through the furnace at a flow rate of 50mL / min and maintain the temperature at 350℃ for 10h. Then pass syngas at atmospheric pressure (H2 / CO volume ratio of 2) through the furnace at a flow rate of 50mL / min and maintain the temperature at 320℃ for 12h to obtain single-phase Fe5C2.

[0075] Comparative Example 3

[0076] This comparative example provides a method for preparing a Fe5C2@MnO catalyst. The steps are basically the same as those in Example 2, except that step S4 is omitted, resulting in a single-phase Fe5C2@MnO catalyst.

[0077] Comparative Example 4

[0078] The preparation method of the single-phase Fe5C2 catalyst in this comparative example is basically the same as that in Example 2, except that step S4 is as follows:

[0079] 0.2 g of Fe5C2@MnO was dispersed in 10 mL of n-hexane, and 0.2 mL of trimethylsilane chloride was added. The mixture was stirred at 30 °C for 12 h to carry out silanization treatment. The product was washed and dried at 80 °C to obtain the desired catalyst.

[0080] Figure 1The XRD patterns of the catalysts prepared in Example 2 and Comparative Examples 1-3 of this invention demonstrate that iron exists directly in the Fe5C2 phase in the single-phase Fe5C2@hydrophobic MnO catalyst synthesized by the preparation method of this invention.

[0081] Figure 2 The transmission electron microscope and elemental distribution diagram of the single-phase Fe5C2@hydrophobic MnO catalyst prepared in Example 2 of this invention show that the hydrophobic MnO is wrapped around Fe5C2.

[0082] Figure 3 The images show the water droplet contact angles of the catalysts prepared in Example 2 and Comparative Examples 3-4 of this invention. It can be seen that the contact angles of the catalysts in Comparative Examples 3 and 4 are 21° and 62°, respectively, while the contact angle of the catalyst in Example 2 is 127°. This proves that the single-phase Fe5C2@hydrophobic MnO catalyst synthesized by the preparation method of this invention has good hydrophobicity.

[0083] Figure 4 The adsorption amounts of water vapor and CO on the catalysts prepared in Example 2 and Comparative Examples 1-3 of this invention demonstrate that the hydrophobic MnO in the single-phase Fe5C2@hydrophobic MnO catalyst synthesized by the preparation method of this invention can significantly reduce the adsorption of water vapor by the catalyst, while enhancing the adsorption of CO by the catalyst.

[0084] MnO surfaces have few sites suitable for silane modification, making it difficult to achieve good hydrophobic properties. For example, in Comparative Example 4, the conventional liquid-phase silanization treatment resulted in a catalyst with a water droplet contact angle of only 62°. Figure 3 Although the contact angle is increased compared to the untreated catalyst, it is still hydrophilic. This invention proposes a method for gas-phase treatment by evacuating in a vacuum oven, which allows trimethylsilane chloride to diffuse uniformly as gaseous molecules into the surface and pores of MnO for deep silane modification. Figure 3 and Figure 4 This method has been shown to effectively inhibit the adsorption of liquid water droplets and gaseous water vapor by MnO, demonstrating excellent hydrophobic properties.

[0085] The syngas conversion performance of the catalysts prepared in the examples and comparative examples was tested separately. The specific method was as follows: 0.1 g of catalyst was weighed and loaded into a fixed-bed reactor, and syngas (containing 31.6% CO, 63.4% H2, and 5% N2 by volume fraction) was introduced at a flow rate of 15 mL / min. The reaction pressure was then increased to 2.0 MPa, and the temperature to 260 °C for syngas conversion performance evaluation. Specifically, the Fe2O3@MnO2 catalyst prepared in Comparative Example 1 required pretreatment activation with pure H2 at 350 °C for 10 hours before syngas conversion testing after being loaded into the fixed-bed reactor. However, in the catalyst synthesized by the method of this invention, iron exists directly in the Fe5C2 phase. This Fe5C2 can directly serve as the catalytic active site, eliminating the need for pretreatment activation when used in the syngas conversion reaction.

[0086] Figure 5 The results show a comparison of the syngas conversion performance of the catalysts prepared in the embodiments and comparative examples of this invention. It can be seen that the Fe2O3@MnO2 catalyst prepared in Comparative Example 1 has no reactivity without pretreatment activation. However, the catalyst synthesized through the preparation steps of this invention does not require pretreatment activation and exhibits excellent reactivity when directly used for syngas conversion. This simplifies the production process and reduces production costs in industrial applications.

[0087] Figure 6 The images show the XRD patterns of the catalysts prepared in the embodiments and comparative examples of this invention during the syngas reforming process. In the syngas reforming reaction, the iron species in the catalyst are subjected to carbonization by CO and oxidation by water vapor. Therefore, the catalyst in Comparative Example 1 becomes a mixture of Fe5C2 and Fe3O4. Although the iron in the catalysts synthesized in Comparative Examples 2 and 3 exists directly in the Fe5C2 phase (… Figure 1 However, the water vapor generated in the reaction can still easily oxidize Fe5C2 to Fe3O4, resulting in the catalyst in Comparative Example 2 and Comparative Example 3 also becoming a mixture of Fe5C2 and Fe3O4. Figure 6 In contrast, the hydrophobic MnO in the single-phase Fe5C2@hydrophobic MnO catalyst synthesized by the method of this invention can reduce the adsorption of water vapor by Fe5C2 and enhance the adsorption of CO by Fe5C2. Figure 4 This can inhibit the oxidation of iron by water vapor and promote the carbonization of iron by CO, thereby protecting the catalytically active site Fe5C2 from being oxidized to Fe3O4 by the water vapor generated in the reaction during the syngas conversion reaction. Therefore, the catalysts prepared in Examples 1-4 still only contain Fe5C2 and not Fe3O4 during the reaction. Figure 6 ).

[0088] Iron carbide provides the active sites for the Fischer-Tropsch (FTS) reaction, which produces various hydrocarbon products. Fe3O4 exhibits high activity in the water-gas shift side reaction. During the reaction, the oxidation of iron carbide to Fe3O4 reduces the exposed active sites, decreasing the catalyst's reactivity. Furthermore, it triggers severe water-gas shift side reactions, leading to the generation of a large amount of useless byproduct CO2. The catalysts in Comparative Examples 1-4 were mixtures of Fe5C2 and Fe3O4, while the catalysts in Examples 1-4 contained only Fe5C2. Therefore, the catalyst prepared in this invention exhibits higher activity in the Fischer-Tropsch main reaction and lower activity in the water-gas shift side reaction, thereby significantly improving the reactivity of high-value C4. 2+ Hydrocarbon yield ( Figure 5 ).

[0089] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A method for preparing a single-phase Fe5C2 catalyst resistant to water vapor oxidation, characterized in that, Includes the following steps: S1. Disperse iron oxide in solvent one, add potassium permanganate and stir the reaction for 1-12 hours, separate the solid product and dry it; S2. The solid product obtained in step S1 is subjected to high-temperature phase transformation in hydrogen and syngas atmospheres to obtain single-phase Fe5C2@MnO; S3. Disperse the Fe5C2@MnO obtained in step S2 in solvent II, add silanizing reagent, and perform gas phase treatment under vacuum at 30~80℃ to obtain a single-phase Fe5C2@hydrophobic MnO catalyst.

2. The method for preparing a single-phase Fe5C2 catalyst resistant to water vapor oxidation according to claim 1, characterized in that, The solvent includes at least one of methanol, ethanol, and acetic acid.

3. The method for preparing a single-phase Fe5C2 catalyst resistant to water vapor oxidation according to claim 1, characterized in that, The mass ratio of iron oxide to potassium permanganate is (1.5~35):

1.

4. The method for preparing a single-phase Fe5C2 catalyst resistant to water vapor oxidation according to claim 1, characterized in that, In step S2, the conditions for the high-temperature phase transformation are: first reacting in a hydrogen atmosphere at 250~450℃ for 5~24h, and then reacting in a syngas atmosphere at 220~500℃ for 12~48h.

5. The method for preparing a single-phase Fe5C2 catalyst resistant to water vapor oxidation according to claim 1, characterized in that, The solvent two includes at least one of hexane, heptane, and octane.

6. The method for preparing a single-phase Fe5C2 catalyst resistant to water vapor oxidation according to claim 1, characterized in that, The silanizing agent includes at least one of trimethylchlorosilane, triisopropylchlorosilane, and tributylchlorosilane.

7. The method for preparing a single-phase Fe5C2 catalyst resistant to water vapor oxidation according to claim 1, characterized in that, The gas phase treatment time is 10~180 min.

8. The method for preparing a single-phase Fe5C2 catalyst resistant to water vapor oxidation according to claim 1, characterized in that, The volume-to-mass ratio of the silanizing agent to Fe5C2@MnO is 0.05~2mL:1g.

9. The single-phase Fe5C2 catalyst prepared by the method according to any one of claims 1 to 8, characterized in that, The catalyst comprises a single-phase Fe5C2 as the core layer and a hydrophobic MnO as the shell layer.

10. The application of the single-phase Fe5C2 catalyst prepared by the method according to any one of claims 1 to 8 in the catalytic conversion of syngas.

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