Supported iron carbide composition as well as preparation method and application thereof

Abstract

The invention relates to a supported iron carbide composition and a preparation method and application thereof, and the method comprises the following steps: providing an iron carbide composition which comprises a first iron carbide compound, a second iron carbide compound and a third iron carbide compound; or, providing an iron carbide mixture, the iron carbide mixture comprising a first iron carbide, a second iron carbide, and a third iron carbide; and carrying out dipping treatment on the iron carbide mixture to enable the iron carbide mixture to contain iodide ions and / or bromide ions, so as to prepare the iron carbide composition. The composition disclosed by the invention can be used as a catalyst for a synthesis gas conversion reaction, so that the reaction has relatively high CO conversion rate, extremely low total CO2 selectivity and low CH4 selectivity.

Description

Technical Field

[0001] The present invention relates to a catalyst for syngas conversion, and particularly to a supported iron carbide composition capable of being used for syngas conversion and a preparation method thereof. Background Art

[0002] The characteristics of China's primary energy structure are rich in coal, short of oil, and scarce in gas. Converting syngas (H2 + CO) produced from non-petroleum carbon resources (such as coal, natural gas, biomass, etc.) into liquid fuels can effectively alleviate problems such as the increasingly depleted and uneven distribution of petroleum resources.

[0003] Iron-based catalysts are the most common catalysts used for syngas conversion. They have advantages such as high activity and a wide applicable condition window, but there is also a problem of too high CO2 selectivity.

[0004] The generation of CO2 has two sources: (1) primary CO2 directly from the primary Fischer-Tropsch synthesis reaction; and (2) secondary CO2 generated by the water-gas-shift reaction (WGS reaction, CO + H2O → CO2 + H2) between H2O and CO at a relatively high CO conversion rate.

[0005] Reducing CO2 selectivity will significantly improve the carbon atom utilization efficiency and enhance the economic efficiency and environmental friendliness of the syngas conversion technology. Therefore, how to suppress the water-gas-shift side reaction at a high CO conversion rate, reduce CO2 selectivity, and improve the carbon atom utilization efficiency has become one of the common key problems in the field of syngas conversion. On the other hand, in addition to CO2, another main by-product in the field of syngas conversion is methane. In the reaction, a high CH4 selectivity and a high CO2 selectivity will jointly reduce the selectivity of the effective products of the reaction. Summary of the Invention

[0006] To overcome at least one defect of the above-mentioned prior art, in a first aspect, an embodiment of the present invention provides a preparation method of a supported iron carbide composition, including:

[0007] Providing an iron carbide composition, the iron carbide composition including a first iron carbide complex, a second iron carbide complex, and a third iron carbide complex; or,

[0008] Providing an iron carbide mixture, the iron carbide mixture including a first iron carbide, a second iron carbide, and a third iron carbide; and subjecting the iron carbide mixture to an impregnation treatment to make it contain iodide ions and / or bromide ions, thereby obtaining the iron carbide composition;

[0009] Wherein, the preparation of the first iron carbide complex or the first iron carbide includes the following steps:

[0010] S11: Reduce the first supported precursor with hydrogen at 330 - 560 °C;

[0011] S12: Under the action of the first mixed gas, treat the product obtained in step S11 at 80 - 175 °C; the first mixed gas includes hydrogen and carbon monoxide with a molar ratio of 1.2:1 - 2.8:1;

[0012] S13: Under the action of the second mixed gas, carry out the preparation treatment of carbide on the product obtained in step S12 at 195 - 300 °C; the second mixed gas includes hydrogen and carbon monoxide with a molar ratio of (1 - 3.2):1;

[0013] Among them, the first supported precursor is the first iron-based carrier subjected to the second impregnation treatment with the first impregnating solution, the first impregnating solution contains bromide ions and / or iodide ions, and the product obtained in step S13 is the first iron carbide complex; or, the first supported precursor is the first iron-based carrier, and the product obtained in step S13 is the first iron carbide; or, the first supported precursor is the first iron-based carrier, the product obtained in step S13 is the first iron carbide, and further carry out the second impregnation treatment on the first iron carbide with the first impregnating solution to obtain the first iron carbide complex;

[0014] The preparation process of the first iron-based carrier includes: carrying out the first impregnation treatment on the carrier in an aqueous solution containing iron ions, and drying and calcining the impregnated carrier;

[0015] The preparation process of the second iron carbide complex or the second iron carbide includes the following steps:

[0016] S21: Reduce the second supported precursor with hydrogen at 360 - 570 °C;

[0017] S22: Under the action of the third mixed gas, carry out the preparation treatment of carbide on the product obtained in step S21 at 300 - 440 °C; the third mixed gas includes hydrogen and carbon monoxide with a molar ratio of (4.5 - 100):1;

[0018] Among them, the second supported precursor is a second iron-based carrier subjected to a third impregnation treatment with a second impregnating solution, the second impregnating solution contains bromide ions and / or iodide ions, and the product obtained in step S22 is the second iron carbide complex; or, the second supported precursor is a second iron-based carrier, and the product obtained in step S22 is the second iron carbide; or, the second supported precursor is a second iron-based carrier, the product obtained in step S22 is the second iron carbide, and further, the second iron carbide is subjected to the third impregnation treatment with the second impregnating solution to obtain the second iron carbide complex;

[0019] The preparation process of the second iron-based carrier includes: subjecting the carrier to a first impregnation treatment in an aqueous solution containing iron ions, and drying and calcining the impregnated carrier;

[0020] The preparation process of the third iron carbide complex or the third iron carbide includes the following steps:

[0021] S31: Reducing the third supported precursor with hydrogen at 350°C to 620°C;

[0022] S32: Under the action of an oxygen-containing gas, subjecting the product obtained in step S31 to surface passivation treatment at 0°C to 45°C; the oxygen-containing gas includes 1 to 3 vol% of oxygen;

[0023] S33: Under the action of a fourth mixed gas, subjecting the product obtained in step S32 to carbide preparation treatment at 260°C to 430°C; the fourth mixed gas includes hydrogen and carbon monoxide with a molar ratio of (7 to 110):1;

[0024] Among them, the third supported precursor is a third iron-based carrier subjected to a fourth impregnation treatment with a third impregnating solution, the third impregnating solution contains bromide ions and / or iodide ions, and the product obtained in step S33 is the third iron carbide complex; or, the third supported precursor is a third iron-based carrier, and the product obtained in step S33 is the third iron carbide; or, the third supported precursor is a third iron-based carrier, the product of step S32 is subjected to the fourth impregnation treatment with the third impregnating solution, and then the treatment of step S33 is carried out to obtain the third iron carbide complex; or, the third supported precursor is a third iron-based carrier, the product obtained in step S33 is the third iron carbide, and the third iron carbide is subjected to the fourth impregnation treatment with the third impregnating solution to obtain the third iron carbide complex;

[0025] The preparation process of the third iron-based carrier includes: subjecting the carrier to a first impregnation treatment in an aqueous solution containing iron ions, and drying and calcining the impregnated carrier.

[0026] In a second aspect, an embodiment of the present invention provides a supported iron carbide composition prepared by the above-mentioned preparation method.

[0027] In a third aspect, an embodiment of the present invention provides a catalyst comprising the supported iron carbide composition prepared by the above-mentioned preparation method or the above-mentioned supported iron carbide composition.

[0028] In a fourth aspect, an embodiment of the present invention provides the application of the supported iron carbide composition prepared by the above-mentioned preparation method, the above-mentioned supported iron carbide composition or the above-mentioned catalyst in the reaction of synthesizing C, H fuels and / or chemicals based on the Fischer-Tropsch synthesis principle.

[0029] In a fifth aspect, an embodiment of the present invention provides a syngas conversion process, which includes contacting the above-mentioned catalyst with syngas under reaction conditions for reaction.

[0030] The iron carbide composition of an embodiment of the present invention can be used as a catalyst for syngas conversion reactions, especially Fischer-Tropsch synthesis reactions. By introducing halide ions into the iron carbide, the reaction has a high CO conversion rate, an extremely low total CO2 selectivity, and a low CH4 selectivity, achieving an overall optimization of the reaction results. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] The drawings are only for the purpose of showing specific embodiments and are not considered to be a limitation of the present invention. Among them:

[0032] Figure 1 is the XRD pattern of the supported χ-iron carbide composite prepared in Example 5 of the present invention;

[0033] Figure 2 is the XRD pattern of the supported ε / ε’-iron carbide composite prepared in Example 5 of the present invention;

[0034] Figure 3 is the XRD pattern of the supported θ-iron carbide composite prepared in Example 5 of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0035] Typical embodiments embodying the features and advantages of the present invention will be described in detail in the following description. It should be understood that the present invention can have various changes in different embodiments, all of which do not depart from the scope of the present invention, and the descriptions therein are essentially for illustrative purposes and not intended to limit the present invention.

[0036] An embodiment of the present invention provides an iron carbide composition, comprising a first iron carbide (or supported ε / ε'-iron carbide), a second iron carbide (or supported θ-iron carbide), a third iron carbide (or supported χ-iron carbide), a halide ion, and an optional promoter cation; wherein, the molar ratio of the iron carbide to the halide ion and the promoter cation is 100:(0.12 - 45):(0 - 22), and the molar number of the iron carbide is based on the molar number of the iron element contained in the supported iron carbide composition. Herein, "optional" means that it may or may not be included; for example, according to the above description, the iron carbide composition may include iron carbide and a halide ion, or may include iron carbide, a halide ion, and a promoter cation.

[0037] In one embodiment, the iron carbide composition is formed by mixing a first iron carbide complex (or supported ε / ε'-iron carbide complex), a second iron carbide complex (or supported θ-iron carbide complex), and a third iron carbide complex (or supported χ-iron carbide complex).

[0038] In one embodiment, the grain diameter of the supported χ-iron carbide or the supported χ-iron carbide complex is 3 - 28 nm, and further can be 5 - 26 nm; the grain diameter of the supported ε / ε'-iron carbide or the supported ε / ε'-iron carbide complex is 4 - 32 nm, and further can be 5 - 27 nm; the grain diameter of the supported θ-iron carbide or the supported θ-iron carbide complex is 4 - 37 nm, and further can be 6 - 32 nm.

[0039] In one embodiment, the supported χ-iron carbide or the supported χ-iron carbide complex has a monoclinic crystal structure, the supported ε / ε'-iron carbide or the supported ε / ε'-iron carbide complex has a hexagonal, pseudo-hexagonal or trigonal crystal structure, and the supported θ-iron carbide or the supported θ-iron carbide complex has an orthorhombic crystal structure.

[0040] In one embodiment, based on the number of moles of iron carbide (100 mol%) in the iron carbide composition, the molar content of supported θ-iron carbide is a, the molar content of supported χ-iron carbide is b, and the molar content of supported ε / ε'-iron carbide is c, where 0 < a ≤ 80%, 0 < b ≤ 80%, 0 < c ≤ 80%. Preferably, 0 < a ≤ 45%, 0 < b ≤ 45%, 0 < c ≤ 45%. For example, a, b, or c can be 1%, 5%, 10%, 15%, 20%, 30%, 35%, 40%, 50%, 80%. Alternatively, in the iron carbide composition, the molar content of supported θ-iron carbide complex is a, the molar content of supported χ-iron carbide complex is b, and the molar content of supported ε / ε'-iron carbide complex is c, where 0 < a ≤ 80%, 0 < b ≤ 80%, 0 < c ≤ 80%. Preferably, 0 < a ≤ 45%, 0 < b ≤ 45%, 0 < c ≤ 45%. For example, a, b, or c can be 1%, 5%, 10%, 15%, 20%, 30%, 35%, 40%, 50%, 80%. Among them, the number of moles of supported χ-iron carbide, supported ε / ε'-iron carbide, supported θ-iron carbide, supported χ-iron carbide complex, supported ε / ε'-iron carbide complex, and supported θ-iron carbide complex are calculated based on the number of moles of iron element contained in each.

[0041] In one embodiment, the molar ratio of iron carbide to halide ions can be 100:(0.12 - 45), further can be 100:(0.35 - 33), and still further can be 100:(7 - 20). For example, 100:0.5, 100:1, 100:5, 100:10, 100:15, 100:20, 100:25, 100:30, 100:40. The number of moles of iron carbide is the sum of the number of moles of the first iron carbide, the second iron carbide, and the third iron carbide.

[0042] In one embodiment, the molar ratio of iron carbide to promoter cations can be 100:(0.1 - 22), further can be 100:(0.1 - 18), and still further can be 100:(3 - 10). For example, 100:0.5, 100:1, 100:5, 100:10, 100:15, 100:20.

[0043] In one embodiment, the iron carbide composition includes halide cations, and the halide cations can maintain charge balance with the halide ions, that is, the total negative charge (or the total valence shown) of the halide ions is equal to the total positive charge of the halide cations.

[0044] In one embodiment, the iron carbide composition includes promoter anions, and the promoter cations can maintain charge balance with the promoter anions.

[0045] In one embodiment, the halide cations include one or more of a first metal ion and a complex cation. Further, the first metal ion includes one or more of iron ions (e.g., divalent and trivalent iron ions), manganese ions (e.g., divalent manganese ions), copper ions (e.g., monovalent and divalent copper ions), cobalt ions (e.g., divalent cobalt ions), molybdenum ions (e.g., divalent, trivalent, and tetravalent molybdenum ions), lanthanum ions (e.g., trivalent and tetravalent lanthanum ions), cerium ions (e.g., trivalent and tetravalent cerium ions), neodymium ions (e.g., trivalent and tetravalent neodymium ions); the complex cation includes one or more of hexaammine manganese ions, hexaammine iron ions, and hexaammine copper ions.

[0046] In one embodiment, the promoter cations include one or more of second metal ions. The second metal ions may include one or more of manganese ions, copper ions, cobalt ions, molybdenum ions, chromium ions, rare earth ions, alkali metal ions, and alkaline earth metal ions; for example, the second metal ion may be one or more of manganese ions (e.g., divalent, trivalent, and tetravalent manganese ions), copper ions (e.g., monovalent and divalent copper ions), cobalt ions (e.g., divalent cobalt ions), molybdenum ions (e.g., divalent, trivalent, and tetravalent molybdenum ions), chromium ions (e.g., trivalent chromium ions), lanthanum ions (e.g., trivalent and tetravalent lanthanum ions), cerium ions (e.g., trivalent and tetravalent cerium ions), neodymium ions (e.g., trivalent and tetravalent neodymium ions), sodium ions, potassium ions, calcium ions, and barium ions.

[0047] In one embodiment, the promoter anions include one or more of oxygen ions, complex ions, and acid radical ions, such as nitrate, citrate, and gluconate.

[0048] One embodiment of the present invention provides a method for preparing the above iron carbide composition, comprising:

[0049] Providing a first iron carbide complex (or supported ε / ε'-iron carbide complex), a second iron carbide complex (or supported θ-iron carbide complex), and a third iron carbide complex (or supported χ-iron carbide complex); and

[0050] Mixing the supported χ-iron carbide complex, the supported ε / ε'-iron carbide complex, and the supported θ-iron carbide complex to obtain an iron carbide composition; or,

[0051] Providing an iron carbide mixture, the iron carbide mixture including a first iron carbide (or supported ε / ε'-iron carbide), a second iron carbide (or supported θ-iron carbide), and a third iron carbide (or supported χ-iron carbide); and

[0052] Subjecting the iron carbide mixture to a fifth impregnation treatment with a fourth impregnating solution to obtain an iron carbide composition;

[0053] Among them, the preparation of the supported ε / ε'-iron carbide composite or supported ε / ε'-iron carbide comprises the following steps:

[0054] S11: Reducing the first supported precursor with hydrogen at 330 - 560 °C;

[0055] S12: Treating the product obtained in step S11 at 80 - 175 °C under the action of a first mixed gas; the first mixed gas comprises hydrogen and carbon monoxide with a molar ratio of 1.2:1 - 2.8:1;

[0056] S13: Preparing carbide for the product obtained in step S12 at 195 - 300 °C under the action of a second mixed gas; the second mixed gas comprises hydrogen and carbon monoxide with a molar ratio of (1 - 3.2):1;

[0057] Among them, the first supported precursor is a first iron-based carrier subjected to a second impregnation treatment with a first impregnating solution, the first impregnating solution contains bromide ions and / or iodide ions, and the product obtained in step S13 is a supported ε / ε'-iron carbide composite; or, the first supported precursor is a first iron-based carrier, and the product obtained in step S13 is supported ε / ε'-iron carbide; or, the first supported precursor is a first iron-based carrier, the product obtained in step S13 is supported ε / ε'-iron carbide, and further subjecting the supported ε / ε'-iron carbide to a second impregnation treatment with the first impregnating solution to obtain a supported ε / ε'-iron carbide composite;

[0058] The preparation process of the first iron-based carrier includes: subjecting the carrier to a first impregnation treatment in an aqueous solution containing iron ions, and drying and calcining the impregnated carrier;

[0059] The preparation process of the supported θ-iron carbide composite or supported θ-iron carbide comprises the following steps:

[0060] S21: Reducing the second supported precursor with hydrogen at 360 - 570 °C;

[0061] S22: Preparing carbide for the product obtained in step S21 at 300 - 440 °C under the action of a third mixed gas; the third mixed gas comprises hydrogen and carbon monoxide with a molar ratio of (4.5 - 100):1;

[0062] Among them, the second supported precursor is a second iron-based carrier that has undergone a third impregnation treatment with a second impregnating solution. The second impregnating solution contains bromide ions and / or iodide ions, and the product obtained in step S22 is a supported θ-iron carbide composite; or, the second supported precursor is a second iron-based carrier, and the product obtained in step S22 is supported θ-iron carbide; or, the second supported precursor is a second iron-based carrier, the product obtained in step S22 is supported θ-iron carbide, and further, the supported θ-iron carbide is subjected to a third impregnation treatment with the second impregnating solution to obtain a supported θ-iron carbide composite;

[0063] The preparation process of the second iron-based carrier includes: subjecting the carrier to a first impregnation treatment in an aqueous solution containing iron ions, and drying and calcining the impregnated carrier;

[0064] The preparation process of the supported χ-iron carbide composite or supported χ-iron carbide includes the following steps:

[0065] S31: Reducing the third supported precursor with hydrogen at 350 - 620 °C;

[0066] S32: Subjecting the product obtained in step S31 to a surface passivation treatment at 0 - 45 °C under the action of an oxygen-containing gas; the oxygen-containing gas includes 1 - 3 vol% oxygen;

[0067] S33: Preparing a carbide from the product obtained in step S32 at 260 - 430 °C under the action of a fourth mixed gas; the fourth mixed gas includes hydrogen and carbon monoxide with a molar ratio of (7 - 110):1;

[0068] Among them, the third supported precursor is a third iron-based carrier that has undergone a fourth impregnation treatment with a third impregnating solution. The third impregnating solution contains bromide ions and / or iodide ions, and the product obtained in step S33 is a supported χ-iron carbide composite; or, the third supported precursor is a third iron-based carrier, and the product obtained in step S33 is supported χ-iron carbide; or, the third supported precursor is a third iron-based carrier, the product of step S32 is subjected to a fourth impregnation treatment with the third impregnating solution, and then the treatment of step S33 is carried out to obtain a supported χ-iron carbide composite; or, the third supported precursor is a third iron-based carrier, the product obtained in step S33 is supported χ-iron carbide, and the supported χ-iron carbide is subjected to a fourth impregnation treatment with the third impregnating solution to obtain a supported χ-iron carbide composite;

[0069] The preparation process of the third iron-based carrier includes: subjecting the carrier to a first impregnation treatment in an aqueous solution containing iron ions, and drying and calcining the impregnated carrier.

[0070] In one embodiment, the iron content in the first, second or third supported precursor is 10 to 30 wt%, such as 12 wt%, 15 wt%, 18 wt%, 20 wt%, 22 wt%, 25 wt%, 28 wt%.

[0071] In one embodiment, the carrier comprises one or more of silica, alumina, titanium dioxide, niobium pentoxide and zirconia. Further, the particle size of the carrier is 30 to 200 μm, such as 50 μm, 60 μm, 80 μm, 100 μm, 120 μm, 150 μm, 180 μm.

[0072] In one embodiment, an aqueous solution containing iron ions is prepared by dissolving at least one water-soluble compound in a first solvent. The at least one water-soluble compound includes an iron salt, and the iron salt includes one or more of iron nitrate, iron chloride, ammonium ferrous sulfate and ammonium ferric citrate.

[0073] In one embodiment, the first solvent includes water.

[0074] In one embodiment, the drying treatment performed on the carrier after the first impregnation treatment includes the following process: drying the impregnated carrier at 20 to 30 °C for 0.5 to 4 h, then drying it at 35 to 80 °C under a vacuum of 250 to 1200 Pa for 6 to 12 h, and then drying the dried material at 110 to 150 °C for 3 to 24 h.

[0075] In one embodiment, the temperature of the calcination treatment after the drying treatment is 230 to 520 °C, such as 250 °C, 280 °C, 300 °C, 350 °C, 400 °C, 450 °C, 500 °C; the time is 1 to 10 h, such as 2 h, 4 h, 5 h, 6 h, 8 h.

[0076] In one embodiment, the raw materials for preparing the first impregnation solution at least include a first halide and a second solvent, the raw materials for preparing the second impregnation solution at least include a second halide and a third solvent, the raw materials for preparing the third impregnation solution at least include a third halide and a fourth solvent, and the raw materials for preparing the fourth impregnation solution at least include a fourth halide and a fifth solvent; the first halide, the second halide, the third halide, and the fourth halide each include a water-soluble bromide and / or iodide.

[0077] In one embodiment, the first halide, the second halide, the third halide, and the fourth halide each independently include one or more of bromides and iodides containing molybdenum, manganese, copper, rare earth metal elements, iron, and cobalt. Further, the first halide, the second halide, the third halide, and the fourth halide each independently include one or more of manganese bromide, iron(II) bromide, copper bromide, cobalt bromide, molybdenum bromide, manganese iodide, iron(II) iodide, copper iodide, rare earth bromides, rare earth iodides, manganese hexammine bromide, iron hexammine bromide, copper hexammine bromide, manganese hexammine iodide, iron hexammine iodide, and copper hexammine iodide.

[0078] In one embodiment, the raw materials for preparing the first impregnating solution further include a first auxiliary agent compound, the raw materials for preparing the second impregnating solution further include a second auxiliary agent compound, the raw materials for preparing the third impregnating solution further include a third auxiliary agent compound, and the raw materials for preparing the fourth impregnating solution further include a fourth auxiliary agent compound; the first auxiliary agent compound, the second auxiliary agent compound, the third auxiliary agent compound, and the fourth auxiliary agent compound may each independently include one or more of salts (inorganic salts or organic salts) of manganese, copper, cobalt, molybdenum, chromium, rare earth metals, alkali metals, and alkaline earth metals. For example, the first auxiliary agent compound, the second auxiliary agent compound, the third auxiliary agent compound, and the fourth auxiliary agent compound may each independently be one or more of potassium nitrate, sodium nitrate, manganese nitrate, copper nitrate, cobalt nitrate, molybdenum nitrate, calcium nitrate, barium nitrate, rare earth nitrates, potassium carbonate, sodium carbonate, potassium citrate, sodium citrate, manganese citrate, copper citrate, cobalt citrate, molybdenum citrate, calcium citrate, barium citrate, potassium gluconate, sodium gluconate, lithium gluconate, rubidium gluconate, cesium gluconate, manganese gluconate, copper gluconate, and calcium gluconate.

[0079] In one embodiment, no chemical reaction occurs between the solute components of the same solution. For example, the solute of the first impregnating solution does not simultaneously include potassium carbonate and calcium nitrate.

[0080] In one embodiment, the first solvent, the second solvent, the third solvent, the fourth solvent, and the fifth solvent each independently include water and / or ethanol. For example, the first solvent, the second solvent, the third solvent, the fourth solvent, and the fifth solvent may all be water or a mixture of ethanol and water.

[0081] In one embodiment, the dosages of the first halide, the second halide, the third halide, the fourth halide, the first auxiliary compound, the second auxiliary compound, the third auxiliary compound, and the fourth auxiliary compound can be appropriately selected according to the contents of the respective ions in the composite to be prepared. Further, the concentrations of the first halide, the second halide, the third halide, the fourth halide, the first auxiliary compound, the second auxiliary compound, the third auxiliary compound, and the fourth auxiliary compound can all be 0.7 - 7 mol / L, such as 1 mol / L, 2 mol / L, 3 mol / L, 5 mol / L, 6 mol / L.

[0082] In one embodiment, the temperature of the first impregnation treatment, the second impregnation treatment, the third impregnation treatment, the fourth impregnation treatment, or the fifth impregnation treatment can be 0 - 50 °C, further can be 20 - 30 °C, such as 10 °C, 15 °C, 20 °C, 30 °C, 35 °C, 40 °C, 45 °C; the time of the first impregnation treatment, the second impregnation treatment, the third impregnation treatment, the fourth impregnation treatment, or the fifth impregnation treatment can be 0.1 - 12 h, further can be 0.2 - 10 h, still further can be 0.3 - 9 h, such as 0.5 h, 1 h, 2 h, 3 h, 4 h, 5 h, 6 h, 7 h, 8 h.

[0083] In one embodiment, the material after any impregnation treatment can be dried at 15 - 40 °C, and further dried under light - shielding conditions. The drying temperature can be, for example, 20 °C, 25 °C, 30 °C, 35 °C; the drying time can be 0.5 - 12 h. The drying treatment can be carried out under normal pressure or reduced pressure conditions.

[0084] In one embodiment, any of the above impregnation treatments can adopt one of the slurry impregnation method, the saturated impregnation method, the supersaturated impregnation method, or other feasible impregnation methods.

[0085] In one embodiment, in the preparation of the supported ε / ε’ - iron carbide composite or the supported ε / ε’ - iron carbide, the treatment temperature in step S11 can be 330 - 560 °C, such as 350 °C, 360 °C, 380 °C, 390 °C, 400 °C, 420 °C, 450 °C, 460 °C, 480 °C, 500 °C, 520 °C, 550 °C; the treatment pressure can be 0.1 - 12 atm, further can be 0.3 - 2.9 atm, such as 0.2 atm, 0.5 atm, 0.8 atm, 1 atm, 1.5 atm, 2 atm, 2.5 atm, 5 atm, 8 atm, 10 atm; the treatment time can be 0.7 - 15 h, further can be 1 - 12 h, such as 2 h, 3 h, 5 h, 8 h, 10 h.

[0086] In one embodiment, in the preparation of the supported ε / ε'-iron carbide composite or supported ε / ε'-iron carbide, the gas flow rate of H2 in step S11 can be 600 to 25000 mL / h / g, further can be 2800 to 22000 mL / h / g, such as 1000 mL / h / g, 1500 mL / h / g, 2000 mL / h / g, 3000 mL / h / g, 5000 mL / h / g, 6000 mL / h / g, 8000 mL / h / g, 10000 mL / h / g, 12000 mL / h / g, 15000 mL / h / g, 18000 mL / h / g, 20000 mL / h / g.

[0087] In one embodiment, in the preparation of the supported ε / ε'-iron carbide composite or supported ε / ε'-iron carbide, the first mixed gas in step S12 includes hydrogen and carbon monoxide, and the molar ratio of hydrogen to carbon monoxide can be 1.2:1 to 2.8:1, such as 1.5:1, 1.8:1, 2:1, 2.2:1, 2.5:1. The first mixed gas can be a mixture of hydrogen and carbon monoxide.

[0088] In one embodiment, in the preparation of the supported ε / ε'-iron carbide composite or supported ε / ε'-iron carbide, the treatment temperature in step S12 can be 80 to 175 °C, such as 90 °C, 100 °C, 110 °C, 120 °C, 130 °C, 150 °C, 160 °C, 170 °C; the treatment pressure can be 0.01 to 5 atm, further can be 0.03 to 2.5 atm, such as 0.1 atm, 0.2 atm, 0.5 atm, 0.8 atm, 1 atm, 1.2 atm, 1.5 atm, 1.8 atm, 2 atm, 3 atm, 4 atm; the treatment time can be 15 to 120 min, further can be 20 to 90 min, such as 30 min, 35 min, 40 min, 45 min, 50 min, 55 min, 60 min, 80 min, 100 min.

[0089] In one embodiment, in the preparation of the supported ε / ε'-iron carbide composite or supported ε / ε'-iron carbide, the gas flow rate of the first mixed gas in step S12 can be 300 to 12000 mL / h / g, further can be 1500 to 9000 mL / h / g, such as 500 mL / h / g, 1000 mL / h / g, 1800 mL / h / g, 2000 mL / h / g, 3000 mL / h / g, 4000 mL / h / g, 5000 mL / h / g, 6000 mL / h / g, 7000 mL / h / g, 10000 mL / h / g.

[0090] In one embodiment, in the preparation of the supported ε / ε'-iron carbide composite or supported ε / ε'-iron carbide, the molar ratio of hydrogen to carbon monoxide in the second mixed gas in step S13 can be 1.2:1, 1.5:1, 1.8:1, 2:1, 2.2:1, 2.5:1, 2.8:1. The second mixed gas can be a mixture of hydrogen and carbon monoxide.

[0091] In one embodiment, in the preparation of the supported ε / ε'-iron carbide composite or supported ε / ε'-iron carbide, the treatment temperature in step S13 can be 195 - 300 °C, such as 200 °C, 210 °C, 230 °C, 250 °C, 260 °C, 270 °C, 280 °C; the treatment pressure can be 0.1 - 9 atm, further can be 0.25 - 4 atm, such as 0.5 atm, 0.8 atm, 1 atm, 1.2 atm, 1.5 atm, 1.8 atm, 2 atm, 2.2 atm, 2.8 atm, 3 atm, 3.5 atm, 4 atm, 5 atm, 8 atm; the treatment time can be 1.5 - 15 h, further can be 2.5 - 12 h, such as 2 h, 3 h, 4 h, 5 h, 6 h, 9 h, 10 h.

[0092] In one embodiment, in the preparation of the supported ε / ε'-iron carbide composite or supported ε / ε'-iron carbide, the gas flow rate of the second mixed gas in step S13 can be 500 - 30000 mL / h / g, further can be 3000 - 25000 mL / h / g, such as 1000 mL / h / g, 4000 mL / h / g, 5000 mL / h / g, 6000 mL / h / g, 7000 mL / h / g, 8000 mL / h / g, 10000 mL / h / g, 12000 mL / h / g, 15000 mL / h / g, 18000 mL / h / g, 20000 mL / h / g, 22000 mL / h / g.

[0093] In one embodiment, in the preparation of the supported ε / ε'-iron carbide composite or supported ε / ε'-iron carbide, in step S13, the temperature of the system is raised from 80 - 175 °C to 195 - 300 °C at a heating rate of 0.2 - 5 °C / min, further, the temperature of the system is raised from 90 - 185 °C to 210 - 290 °C at a heating rate of 0.2 - 2.5 °C / min; the heating rate in step S13 can be, for example, 0.5 °C / min, 0.8 °C / min, 1 °C / min, 1.2 °C / min, 1.5 °C / min, 1.8 °C / min, 2 °C / min, 2.2 °C / min, 3 °C / min, 4 °C / min.

[0094] In one embodiment, in the preparation of the supported θ-iron carbide composite or supported θ-iron carbide, the temperature of the reduction treatment in step S21 can be 360 to 570 °C, such as 360 °C, 380 °C, 400 °C, 420 °C, 450 °C, 460 °C, 480 °C, 500 °C, 520 °C, 550 °C, 560 °C; the treatment pressure can be 0.12 to 13 atm, further can be 0.3 to 2.8 atm, such as 0.15 atm, 0.2 atm, 0.5 atm, 0.8 atm, 1 atm, 1.5 atm, 2 atm, 2.5 atm, 5 atm, 8 atm, 10 atm; the treatment time can be 0.7 to 15 h, further can be 1 to 12 h, such as 2 h, 3 h, 5 h, 8 h, 10 h, 13 h.

[0095] In one embodiment, in the preparation of the supported θ-iron carbide composite or supported θ-iron carbide, the gas flow rate of H2 in step S21 can be 600 to 25000 mL / h / g, further can be 2800 to 22000 mL / h / g, such as 1000 mL / h / g, 1500 mL / h / g, 2000 mL / h / g, 2500 mL / h / g, 3000 mL / h / g, 5000 mL / h / g, 6000 mL / h / g, 8000 mL / h / g, 10000 mL / h / g, 12000 mL / h / g, 15000 mL / h / g, 18000 mL / h / g, 20000 mL / h / g.

[0096] In one embodiment, in the preparation of the supported θ-iron carbide composite or supported θ-iron carbide, the third mixed gas in step S22 includes hydrogen and carbon monoxide, and the molar ratio of hydrogen to carbon monoxide can be 4.5:1 to 100:1, such as 5:1, 10:1, 20:1, 30:1, 36:1, 40:1, 50:1, 60:1, 80:1, 100:1. The third mixed gas can be a mixture of hydrogen and carbon monoxide.

[0097] In one embodiment, in the preparation of the supported θ-iron carbide composite or supported θ-iron carbide, the treatment temperature in step S22 can be 300 to 440 °C, such as 300 °C, 320 °C, 330 °C, 350 °C, 380 °C, 400 °C, 420 °C; the treatment pressure can be 0 to 15 atm, further 0.01 to 8 atm, such as 0.1 atm, 0.2 atm, 0.5 atm, 0.8 atm, 1 atm, 1.5 atm, 2 atm, 3 atm, 5 atm, 8 atm, 10 atm, 12 atm; the treatment time can be 3 to 72 h, further 5 to 48 h, such as 10 h, 15 h, 20 h, 25 h, 30 h, 40 h, 45 h, 50 h, 55 h, 60 h, 70 h.

[0098] In one embodiment, in the preparation of the supported θ-iron carbide composite or supported θ-iron carbide, the gas flow rate of the third mixed gas in step S22 can be 200 to 35000 mL / h / g, further 1200 to 20000 mL / h / g, such as 500 mL / h / g, 1000 mL / h / g, 1800 mL / h / g, 2000 mL / h / g, 3000 mL / h / g, 4000 mL / h / g, 5000 mL / h / g, 6000 mL / h / g, 7000 mL / h / g, 10000 mL / h / g, 12000 mL / h / g, 15000 mL / h / g, 18000 mL / h / g, 25000 mL / h / g, 30000 mL / h / g.

[0099] In one embodiment, in the preparation of the supported θ-iron carbide composite or supported θ-iron carbide, in step S22, the temperature of the system is raised or lowered from the temperature of step S21 to the temperature of step S22 at a variable temperature rate (heating rate or cooling rate) of 0.2 to 5 °C / min. Further, the temperature of the system is raised or lowered to 300 to 400 °C at a variable temperature rate of 0.2 to 2.5 °C / min; the heating or cooling rate in step S22 can be, for example, 0.5 °C / min, 0.8 °C / min, 1 °C / min, 1.2 °C / min, 1.5 °C / min, 1.8 °C / min, 2 °C / min, 2.2 °C / min, 3 °C / min, 4 °C / min.

[0100] In one embodiment, in the preparation of the supported χ-iron carbide composite or supported χ-iron carbide, the temperature of the reduction treatment in step S31 can be 350 to 620 °C, such as 360 °C, 380 °C, 400 °C, 420 °C, 450 °C, 460 °C, 480 °C, 500 °C, 520 °C, 550 °C, 560 °C, 580 °C, 600 °C; the treatment pressure can be 0.1 to 11 atm, further can be 0.3 to 2.9 atm, such as 0.15 atm, 0.2 atm, 0.5 atm, 0.8 atm, 1 atm, 1.5 atm, 2 atm, 2.5 atm, 5 atm, 8 atm, 10 atm; the treatment time can be 0.7 to 15 h, further can be 1 to 12 h, such as 2 h, 3 h, 5 h, 8 h, 10 h, 13 h.

[0101] In one embodiment, in the preparation of the supported χ-iron carbide composite or supported χ-iron carbide, the gas flow rate of H2 in step S31 can be 600 to 25000 mL / h / g, further can be 2800 to 22000 mL / h / g, such as 1000 mL / h / g, 1500 mL / h / g, 2000 mL / h / g, 2500 mL / h / g, 3000 mL / h / g, 5000 mL / h / g, 6000 mL / h / g, 8000 mL / h / g, 10000 mL / h / g, 12000 mL / h / g, 15000 mL / h / g, 18000 mL / h / g, 20000 mL / h / g.

[0102] In one embodiment, in the preparation of the supported χ-iron carbide composite or supported χ-iron carbide, the oxygen-containing gas in step S32 includes 1 to 3 vol% of oxygen and 97 to 99 vol% of inert gas. The inert gas refers to a gas that does not participate in the reactions of the above steps. For example, the inert gas can be nitrogen. The content of oxygen in the first oxygen-containing gas can be, for example, 1.5 vol%, 2 vol%, 2.5 vol%, 3 vol%.

[0103] In one embodiment, in the preparation of the supported χ-iron carbide composite or supported χ-iron carbide, the temperature of the surface passivation treatment in step S32 can be 0 to 45 °C, such as 1 °C, 5 °C, 10 °C, 15 °C, 20 °C, 25 °C, 30 °C, 35 °C, 40 °C, 45 °C; the treatment pressure can be 0 to 1.5 atm, further 0 to 0.09 atm, such as 0.01 atm, 0.02 atm, 0.05 atm, 0.06 atm, 0.08 atm, 1 atm, 1.5 atm; the treatment time can be 5 to 72 h, further 10 to 56 h, such as 8 h, 12 h, 15 h, 20 h, 25 h, 30 h, 35 h, 40 h, 45 h, 50 h, 55 h, 60 h, 70 h.

[0104] In one embodiment, in the preparation of the supported χ-iron carbide composite or supported χ-iron carbide, the gas flow rate of the oxygen-containing gas in step S32 can be 400 to 12000 mL / h / g, further 1400 to 8500 mL / h / g, such as 500 mL / h / g, 1000 mL / h / g, 1500 mL / h / g, 2000 mL / h / g, 3000 mL / h / g, 4000 mL / h / g, 5000 mL / h / g, 6000 mL / h / g, 7000 mL / h / g, 10000 mL / h / g.

[0105] In one embodiment, in the preparation of the supported χ-iron carbide composite or supported χ-iron carbide, the molar ratio of hydrogen to carbon monoxide in the fourth mixed gas in step S33 can be 8:1, 10:1, 20:1, 30:1, 36:1, 40:1, 50:1, 60:1, 80:1, 100:1. The fourth mixed gas can be a mixture of hydrogen and carbon monoxide.

[0106] In one embodiment, in the preparation of the supported χ-iron carbide composite or supported χ-iron carbide, the treatment temperature in step S33 can be 260 to 430 °C, such as 280 °C, 300 °C, 320 °C, 330 °C, 350 °C, 380 °C, 400 °C; the treatment pressure can be 0.08 to 15 atm, further 0.15 to 2.5 atm, such as 0.1 atm, 0.2 atm, 0.5 atm, 0.8 atm, 1 atm, 1.2 atm, 1.5 atm, 1.8 atm, 2 atm, 2.2 atm, 5 atm, 8 atm, 10 atm; the treatment time can be 0.3 to 30 h, further 0.5 to 2.4 h, such as 1 h, 1.5 h, 1.8 h, 2 h, 2.2 h, 5 h, 10 h, 15 h, 20 h, 25 h.

[0107] In one embodiment, in the preparation of the supported χ-iron carbide composite or supported χ-iron carbide, the gas flow rate of the fourth mixed gas in step S33 can be 250 to 21000 mL / h / g, further can be 2000 to 18000 mL / h / g, such as 1000 mL / h / g, 3000 mL / h / g, 5000 mL / h / g, 6000 mL / h / g, 7700 mL / h / g, 8000 mL / h / g, 10000 mL / h / g, 12000 mL / h / g, 15000 mL / h / g, 16000 mL / h / g.

[0108] In one embodiment, in the preparation of the supported χ-iron carbide composite or supported χ-iron carbide, in step S33, the temperature of the system is raised from 0 to 45 °C to 260 to 430 °C at a heating rate of 0.1 to 5.5 °C / min. Further, the temperature of the system is raised from 0 to 45 °C to 260 to 400 °C at a heating rate of 0.15 to 2 °C / min; the heating rate in step S33 can be, for example, 0.5 °C / min, 0.8 °C / min, 1 °C / min, 1.2 °C / min, 1.5 °C / min, 1.8 °C / min, 2 °C / min, 2.2 °C / min, 3 °C / min, 4 °C / min.

[0109] In one embodiment, preferably, the above steps and the above impregnation treatment are all carried out under light-shielded conditions.

[0110] In one embodiment, the preparation process of the supported ε / ε'-iron carbide composite includes the following steps:

[0111] S10: The carrier is subjected to a first impregnation treatment in an aqueous solution containing iron ions, and the impregnated carrier is dried and calcined to obtain a first iron-based carrier; the first iron-based carrier is subjected to a second impregnation treatment in a first impregnating solution to obtain a first supported precursor;

[0112] S11: The first supported precursor is reduced at 330 to 560 °C by hydrogen.

[0113] S12: Under the action of a first mixed gas, the product obtained in step S11 is treated at 80 to 175 °C.

[0114] S13: Under the action of a second mixed gas, the product obtained in step S12 is subjected to a carbide preparation treatment at 195 to 300 °C to prepare a supported ε / ε'-iron carbide composite.

[0115] In one embodiment, the preparation method of the supported ε / ε'-iron carbide includes the following steps:

[0116] S10: Perform a first impregnation treatment on the support in an aqueous solution containing iron ions, and then dry and calcine the impregnated support to obtain a first iron-based support (i.e., a first supported precursor).

[0117] S11: Reduce the first supported precursor with hydrogen at 330 - 560 °C.

[0118] S12: Under the action of a first mixed gas, treat the product obtained in step S11 at 80 - 175 °C.

[0119] S13: Under the action of a second mixed gas, perform a carbide preparation treatment on the product obtained in step S12 at 195 - 300 °C to obtain ε / ε'-iron carbide.

[0120] In one embodiment, the preparation method of the supported θ-iron carbide composite includes the following steps:

[0121] S20: Perform a first impregnation treatment on the support in an aqueous solution containing iron ions, and then dry and calcine the impregnated support to obtain a second iron-based support; perform a third impregnation treatment on the second iron-based support in a second impregnation solution to obtain a second supported precursor.

[0122] S21: Reduce the second supported precursor with hydrogen at 360 - 570 °C.

[0123] S22: Under the action of a third mixed gas, perform a carbide preparation treatment on the product obtained in step S21 at 300 - 440 °C to obtain a θ-iron carbide composite.

[0124] In one embodiment, the preparation method of the supported θ-iron carbide includes the following steps:

[0125] S20: Perform a first impregnation treatment on the support in an aqueous solution containing iron ions, and then dry and calcine the impregnated support to obtain a second iron-based support (i.e., a second supported precursor).

[0126] S21: Reduce the second supported precursor with hydrogen at 360 - 570 °C.

[0127] S22: Under the action of a third mixed gas, perform a carbide preparation treatment on the product obtained in step S21 at 300 - 440 °C to obtain θ-iron carbide.

[0128] In one embodiment, the preparation process of the supported χ-iron carbide composite includes the following steps:

[0129] S30: Perform a first impregnation treatment on the carrier in an aqueous solution containing iron ions, and then dry and calcine the impregnated carrier to obtain a third iron-based carrier; perform a fourth impregnation treatment on the third iron-based carrier in a third impregnation solution to obtain a third supported precursor;

[0130] S31: Reduce the third supported precursor with hydrogen at 350 - 620 °C;

[0131] S32: Under the action of an oxygen-containing gas, perform a surface passivation treatment on the product obtained in step S31 at 0 - 45 °C;

[0132] S33: Under the action of a fourth mixed gas, perform a carbide preparation treatment on the product obtained in step S32 at 260 - 430 °C to obtain a supported χ-iron carbide composite.

[0133] In one embodiment, the preparation process of the supported χ-iron carbide includes the following steps:

[0134] S30: Perform a first impregnation treatment on the carrier in an aqueous solution containing iron ions, and then dry and calcine the impregnated carrier to obtain a third iron-based carrier (i.e., the third supported precursor);

[0135] S31: Reduce the third supported precursor with hydrogen at 350 - 620 °C;

[0136] S32: Under the action of an oxygen-containing gas, perform a surface passivation treatment on the product obtained in step S31 at 0 - 45 °C;

[0137] S33: Under the action of a fourth mixed gas, perform a carbide preparation treatment on the product obtained in step S32 at 260 - 430 °C to obtain a supported χ-iron carbide.

[0138] One embodiment of the present invention provides a catalyst comprising the above iron carbide composition.

[0139] One embodiment of the present invention provides the application of the above iron carbide composition or catalyst in a syngas conversion reaction.

[0140] In one embodiment, the syngas conversion reaction can be a Fischer-Tropsch synthesis reaction or other reactions based on the Fischer-Tropsch synthesis principle, such as a reaction starting from syngas and with the final product being alcohol.

[0141] In one embodiment, the syngas comprises CO and H2.

[0142] One embodiment of the present invention provides an application of the above iron carbide composition or catalyst in a reaction for synthesizing C and H fuels and / or chemicals based on the Fischer-Tropsch synthesis principle. Among them, the reaction based on the Fischer-Tropsch synthesis principle refers to a reaction in which syngas (a mixture of CO and H2) is used as a raw material, and through CO hydrogenation and carbon chain growth reactions under a catalyst and appropriate conditions, to generate chain hydrocarbons and / or their oxygen-containing derivatives.

[0143] In one embodiment, the above reaction is a Fischer-Tropsch synthesis reaction, the reaction temperature can be 260 - 310 °C, such as 270 °C, 280 °C, 290 °C, 300 °C; the reaction pressure can be 2 - 3.5 MPa, and the molar ratio of H2 / CO can be 1.7 - 2.15.

[0144] One embodiment of the present invention provides a syngas conversion process, including contacting the above catalyst with syngas to react under syngas conversion reaction conditions.

[0145] In one embodiment, the syngas conversion can be carried out in a high-temperature and high-pressure continuous reactor.

[0146] The iron carbide composition of one embodiment of the present invention can be used as a catalyst for syngas conversion reaction. By introducing halide ions into the iron carbide, the reaction has a high CO conversion rate, an extremely low total CO2 selectivity, and a low CH4 selectivity. At the same time, benefiting from the very high CO space-time conversion rate of the iron carbide composition catalyst, it shows considerable activity.

[0147] The iron carbide composition of one embodiment of the present invention can be used as a catalyst for syngas conversion reaction, enabling the reaction to maintain an extremely low CO2 selectivity at a high CO conversion rate, while maintaining a low CH4 selectivity and a high reaction stability, greatly improving the utilization efficiency of carbon atoms and the selectivity of effective products, breaking through the key technical bottleneck, and being able to promote the high-end, diversification, and low-carbonization of clean syngas conversion, indicating a new trend and direction for the development of modern syngas chemical industry.

[0148] The iron carbide composition of one embodiment of the present invention, as a catalyst for Fischer-Tropsch synthesis reaction, under industrial Fischer-Tropsch synthesis reaction conditions, can maintain continuous and stable reaction for more than 300 h using a high-pressure continuous reactor, with its CO2 selectivity below 5%, further below 3%; the selectivity of its by-product CH4 can be maintained below 8.5%, further below 5.5%; the carbon atom utilization efficiency is maintained above 95%, further above 97%; the selectivity of effective products can reach above 86.5%, further above 92%.

[0149] In one embodiment, through the Fischer-Tropsch synthesis reaction catalyzed by an iron carbide composition, a CO2 selectivity of <4.5%, a carbon atom utilization efficiency of >95%, and an effective product selectivity of >89% can be achieved at a CO conversion rate of over 74%.

[0150] As used herein, the "ions" contained in the complex include all particles that are combined with other particles by covalent bonds and / or ionic bonds. For example, the bromide ions in the complex include both Br that interacts with K by an ionic bond + interacting with - and Br atoms that interact with H atoms by a covalent bond.

[0151] All pressure values involved herein are gauge pressures.

[0152] Hereinafter, an iron carbide composition and its application in one embodiment of the present invention will be further described in conjunction with the accompanying drawings and specific examples. Among them, the test methods involved are as follows:

[0153] 1. During the reaction process of the examples or comparative examples, an in-situ XRD detector was used to monitor the phase changes of the materials with an X-ray diffractometer (Rigaku Corporation, model D / max-2600 / PC), and the crystal system structures of the iron carbide complexes were measured by the X-ray diffractometer.

[0154] 2. The average grain diameter of each iron carbide or its complex was obtained through XRD testing.

[0155] 3. A Mössbauer spectrometer (Transmission 57 Fe, 57 Co(Rh) source sinusoidal velocity spectrometer) was used to perform Mössbauer spectroscopy detection on the iron carbide composition to obtain the corresponding composition.

[0156] 4. An inductively coupled plasma emission spectrometer (ICP) was used to perform elemental detection on the iron carbide composition.

[0157] 5. During the synthesis gas conversion reaction process, the products obtained from the reaction were subjected to gas chromatography analysis (Agilent 7890 gas chromatography) for calculating the conversion rate, selectivity, etc. The products refer to the tail gas collected from the reactor end, including the generated hydrocarbon compounds, alcohol compounds, CO2, etc.

[0158] 6. The CO conversion rate %, CO2 selectivity %, CH4 selectivity %, carbon atom utilization efficiency %, and effective product selectivity % were calculated through the following formulas:

[0159] CO conversion rate % = [(moles of CO in feed - moles of CO in product) / moles of CO in feed] × 100%;

[0160] CO2 selectivity % = [moles of CO2 in product / (moles of CO in feed - moles of CO in product)] × 100%;

[0161] CH4 selectivity % = [moles of CH4 in product / (moles of CO in feed - moles of CO in product)] × 100%;

[0162] Carbon atom utilization efficiency % = (1 - CO2 selectivity %) × 100%;

[0163] Effective product selectivity % = (1 - CO2 selectivity % - CH4 selectivity %) × 100%.

[0164] Example 1

[0165] Preparation of supported ε / ε’-iron carbide

[0166] S10: Weigh 20 g of silica as the support, and impregnate the support in an aqueous solution of ammonium ferric citrate, where the ammonium ferric citrate solution is weighed and prepared according to the content of 30 wt% of elemental iron in the final support; the impregnated support is dried at 30 °C for 2 h, then dried in a vacuum drying oven at 40 °C and a vacuum degree of 300 Pa for 8 h, the dried material is dried in an oven at 120 °C for 24 h, and then the obtained material is calcined in a muffle furnace at 500 °C for 5 h to obtain the first iron-based support (supported precursor);

[0167] S11: At a temperature of 500 °C and a pressure of 2.0 atm, the first supported precursor is maintained in H2 with a flow rate of 20000 mL / h / g for 5 h for reduction and surface purification treatment.

[0168] S12: Cool the product obtained in step S11 to 150 °C, and contact it with the first mixed gas at this temperature for pretreatment; where the pressure of the system is 2.0 atm, the flow rate of the first mixed gas is 6000 mL / h / g, and the treatment time is 1 h; the first mixed gas is a mixed gas of H2 and CO, and the molar ratio of H2 to CO is 2:1.

[0169] S13: Contact the product obtained in step S12 with a second mixed gas phase. The pressure of the system is 2.0 atm, and the total gas flow rate is 15000 mL / h / g. Under these conditions, heat the system from 150 °C to 250 °C at a heating rate of 2.0 °C / min to prepare carbides. Among them, the second mixed gas is a mixture of H2 and CO, and the molar ratio of the two is H2:CO = 1.5:1. The treatment time of the material at 250 °C is 3 h. After the treatment is completed, supported ε / ε'-iron carbide is prepared.

[0170] Preparation of supported θ-iron carbide

[0171] S20: Use exactly the same raw materials and methods as in step S10 to obtain a second supported precursor.

[0172] S21: At a pressure of 450 °C and 2.5 atm, keep the second supported precursor in H2 with a flow rate of 15000 mL / h / g for 8 h to carry out reduction and surface purification treatment.

[0173] S22: Contact the product of step S21 with a third mixed gas phase. The pressure of the system is 15 atm, and the total gas flow rate is 10000 mL / h / g. Under these conditions, cool the system from 450 °C to 400 °C at a cooling rate of 1.5 °C / min to prepare carbides. Among them, the third mixed gas is a mixture of H2 and CO, and the molar ratio of the two is H2:CO = 50:1. The treatment time of the material at 400 °C is 12 h. After the treatment is completed, supported θ-iron carbide is prepared.

[0174] Preparation of supported χ-iron carbide

[0175] S30: Use exactly the same raw materials and methods as in step S10 to obtain a third supported precursor.

[0176] S31: At a pressure of 450 °C and 2.0 atm, keep the third supported precursor in H2 with a flow rate of 12000 mL / h / g for 6 h to carry out reduction and surface purification treatment.

[0177] S32: Cool the product of step S31 to 30 °C and contact it with an oxygen-containing gas at this temperature for surface passivation treatment. Among them, the pressure of the system is 0.08 atm, the gas flow rate is 7500 mL / h / g, and the treatment time is 24 h. The oxygen-containing gas includes 2 vol% oxygen and 98 vol% nitrogen.

[0178] S33: Contact the product of step S32 with a fourth mixed gas. The pressure of the system is 2.1 atm, and the total gas flow rate is 11000 mL / h / g. Under this condition, heat the system from 30 °C to 350 °C at a heating rate of 2.0 °C / min to prepare carbides; wherein, the fourth mixed gas is a mixture of H2 and CO, and the molar ratio of H2 to CO is 80:1. The treatment time of the material at 350 °C is 2.2 h; after the treatment is completed, supported χ-iron carbide is prepared.

[0179] Preparation of the composition

[0180] Mix the above-prepared supported χ-iron carbide, supported ε / ε’-iron carbide, and supported θ-iron carbide in a molar ratio of 5:3:4 (based on the number of moles of iron contained in each) to obtain an iron carbide mixture. Dissolve manganese bromide and potassium nitrate in 150 ml of water to obtain an impregnation solution; disperse the iron carbide mixture in the impregnation solution and perform impregnation treatment by the slurry impregnation method. The impregnation ratio (molar ratio) is Fe:Br:K = 100:7:2.0; the impregnation temperature is 35 °C, and the impregnation time is 2 h; then dry in a vacuum drying oven at 35 °C and a vacuum degree of 300 Pa for 12 h to obtain an iron carbide composition, labeled as CX1.

[0181] Examples 1-1 to 3-8 are all prepared with substantially the same raw materials and processes as in Example 1, except that: the content or type of halide ions or promoter cations in each impregnation solution is different, and the prepared compositions are sequentially labeled as CX1-1 to CX3-8 using the same numbering as in Example 1. Since the loss of materials during the preparation process is extremely small, the content of each substance in the obtained composition is basically the same as the dosage of the corresponding raw materials. For specific content values, see Table 1.

[0182] Example 4

[0183] Preparation of supported ε / ε’-iron carbide

[0184] Use the same raw materials and processes as in steps S10 to S13 of Example 1 to prepare supported ε / ε’-iron carbide.

[0185] Preparation of supported θ-iron carbide

[0186] Use the same raw materials and processes as in steps S20 to S22 of Example 1 to prepare supported θ-iron carbide.

[0187] Preparation of supported χ-iron carbide

[0188] Use the same raw materials and processes as in steps S30 to S33 of Example 1 to prepare supported χ-iron carbide.

[0189] Preparation of the composition

[0190] Mix the above-prepared supported ε / ε'-iron carbide, supported χ-iron carbide, and supported θ-iron carbide in a molar ratio of 5:3:4 (based on the molar amount of iron contained in each) to obtain an iron carbide mixture. Dissolve manganese bromide, potassium citrate, and sodium nitrate in 50 ml of water to prepare an impregnating solution. Impregnate the iron carbide mixture with the impregnating solution, with an impregnation ratio (molar ratio) of Fe:Br:K:Na = 100:15:3:2, an impregnation temperature of 32 °C, and an impregnation time of 2.7 h; then dry it in a vacuum drying oven at 33 °C and a vacuum degree of 200 Pa for 10 h to obtain an iron carbide composition, labeled as CX4.

[0191] Example 4-1

[0192] This example uses substantially the same raw materials and process as in Example 1 to prepare a supported iron carbide complex, with the only difference being that: in step S13, the carbonization temperature is 195 °C. The finally obtained supported iron carbide complex is labeled as CX4-1.

[0193] Example 4-2

[0194] This example uses substantially the same raw materials and process as in Example 1 to prepare a supported iron carbide complex, with the only difference being that: in step S13, the carbonization temperature is 300 °C. The finally obtained supported iron carbide complex is labeled as CX4-2.

[0195] Example 4-3

[0196] This example uses substantially the same raw materials and process as in Example 1 to prepare a supported iron carbide complex, with the only difference being that: in the second mixed gas in step S13, the molar ratio of hydrogen to carbon monoxide is 1:1. The finally obtained supported iron carbide complex is labeled as CX4-3.

[0197] Example 4-4

[0198] This example uses substantially the same raw materials and process as in Example 1 to prepare a supported iron carbide complex, with the only difference being that: in the second mixed gas in step S13, the molar ratio of hydrogen to carbon monoxide is 3.2:1. The finally obtained supported iron carbide complex is labeled as CX4-4.

[0199] Example 4-5

[0200] This example uses substantially the same raw materials and process as in Example 1 to prepare a supported iron carbide complex, with the only difference being that: in step S22, the carbonization temperature is 300 °C. The finally obtained supported iron carbide complex is labeled as CX4-5.

[0201] Example 4-6

[0202] In this example, a supported iron carbide composite is prepared using substantially the same raw materials and process as in Example 1, with the only difference being that the carbonization temperature in step S22 is 440 °C. The finally obtained supported iron carbide composite is labeled as CX4-6.

[0203] Examples 4-7

[0204] In this example, a supported iron carbide composite is prepared using substantially the same raw materials and process as in Example 1, with the only difference being that the molar ratio of hydrogen to carbon monoxide in the third mixed gas in step S22 is 4.5:1. The finally obtained supported iron carbide composite is labeled as CX4-7.

[0205] Examples 4-8

[0206] In this example, a supported iron carbide composite is prepared using substantially the same raw materials and process as in Example 1, with the only difference being that the molar ratio of hydrogen to carbon monoxide in the third mixed gas in step S22 is 100:1. The finally obtained supported iron carbide composite is labeled as CX4-8.

[0207] Examples 4-9

[0208] In this example, a supported iron carbide composite is prepared using substantially the same raw materials and process as in Example 1, with the only difference being that the carbonization temperature in step S33 is 260 °C. The finally obtained supported iron carbide composite is labeled as CX4-9.

[0209] Examples 4-10

[0210] In this example, a supported iron carbide composite is prepared using substantially the same raw materials and process as in Example 1, with the only difference being that the carbonization temperature in step S33 is 430 °C. The finally obtained supported iron carbide composite is labeled as CX4-10.

[0211] Examples 4-11

[0212] In this example, a supported iron carbide composite is prepared using substantially the same raw materials and process as in Example 1, with the only difference being that the molar ratio of hydrogen to carbon monoxide in the fourth mixed gas in step S33 is 100:1. The finally obtained supported iron carbide composite is labeled as CX4-11.

[0213] Example 5

[0214] Preparation of Supported ε / ε’-Iron Carbide Composite

[0215] S10: The first iron-based carrier is prepared using exactly the same raw materials and method as in step S10 of Example 1;

[0216] Dissolve manganese bromide and potassium gluconate in 100 ml of water to obtain an impregnation solution; weigh 28 g of the first iron-based carrier prepared above, disperse it in the impregnation solution, and perform impregnation treatment by the slurry impregnation method. The impregnation ratio (molar ratio) is Fe:Br:K = 100:7.0:2.0, the impregnation temperature is 30 °C, and the impregnation time is 3 h; then dry it in a vacuum drying oven at 35 °C and a vacuum degree of 300 Pa for 12 h to obtain the first supported precursor.

[0217] Treat the first supported precursor with exactly the same raw materials and process as in steps S11 to S13 of Example 1 to obtain a supported ε / ε'-iron carbide composite.

[0218] Preparation of supported θ-iron carbide composite

[0219] S20: Use exactly the same raw materials and method as in step S10 to obtain a second supported precursor.

[0220] Treat the second supported precursor with exactly the same raw materials and process as in steps S21 to S22 of Example 1 to obtain a supported θ-iron carbide composite.

[0221] Preparation of supported χ-iron carbide composite

[0222] S30: Use exactly the same raw materials and method as in step S10 to obtain a third supported precursor.

[0223] Treat the third supported precursor with exactly the same raw materials and process as in steps S31 to S32 of Example 1 to obtain a supported χ-iron carbide composite.

[0224] Preparation of composition

[0225] Mix the supported χ-iron carbide composite, supported ε / ε'-iron carbide composite, and supported θ-iron carbide composite prepared above in a molar ratio of 5:3:4 (based on the molar number of iron contained in each) to obtain an iron carbide composition, labeled as CX5.

[0226] Comparative Example 1

[0227] In this example, an iron carbide composition was prepared using substantially the same raw materials and process as in Example 1, except that: in the preparation of the composition, the impregnation ratio was Fe:Br:K = 100:50.0:2.0. The finally obtained iron carbide composition was labeled as DX1.

[0228] Comparative Example 2

[0229] In this example, an iron carbide composition was prepared using substantially the same raw materials and process as in Example 1, with the only difference being that in the preparation of the composition, manganese bromide was not added when preparing the impregnating solution, and only potassium nitrate was added. The finally prepared iron carbide composition was labeled D2.

[0230] Comparative Example 3

[0231] In this example, an iron carbide composition was prepared using substantially the same raw materials and process as in Example 1, with the only difference being that in the preparation of the composition, manganese chloride was used to replace manganese bromide in an equimolar amount when preparing the impregnating solution. The finally prepared iron carbide composition was labeled DX3.

[0232] Comparative Example 4

[0233] ε / ε’-iron carbide, χ-iron carbide, and θ-iron carbide were prepared using exactly the same raw materials and steps as in Example 1. The χ-iron carbide, ε / ε’-iron carbide, and θ-iron carbide were mixed in a molar ratio of 5:3:4 (based on the molar number of iron contained in each) to obtain an iron carbide mixture, which was labeled D4.

[0234] Comparative Example 5

[0235] In this example, an iron carbide composite was prepared using substantially the same raw materials and process as in Example 1, with the only difference being that in steps S13, S22, and S33, the molar ratios of H2 and CO in the second, third, and fourth mixed gases for carbide preparation were 2:1, 120:1, and 120:1, respectively. The finally prepared iron carbide composite was labeled DX5.

[0236] The iron carbide composites, iron carbides, iron carbide compositions, etc. prepared in each example and comparative example were measured by XRD, Mössbauer spectroscopy, and ICP in the aforementioned manner. Among them, the total content of iron carbide (i.e., the total content of ε / ε’-iron carbide, χ-iron carbide, and θ-iron carbide) was calculated based on 100 mol, and the relevant contents all refer to the molar number. The specific results are shown in Table 1.

[0237] The catalytic reaction performance of the iron carbide compositions prepared in each example and comparative example was evaluated in a slurry bed continuous reactor. The catalyst loading was 9.0 g. Evaluation conditions: T = 262 °C, P = 2.95 MPa, H2:CO = 2.1:1, (H2 + CO) total amount = 15000 mL / h / g- Fe (standard state flow rate, relative to the Fe element), and the circulation ratio was 1.2. The reaction was carried out, and the reaction products were analyzed by gas chromatography. The reaction performance evaluation data at 24 h and 300 h of the reaction are shown in Tables 2 and 3.

[0238] Table 1

[0239]

[0240]

[0241] Table 2

[0242]

[0243]

[0244] Table 3

[0245]

[0246]

[0247] Based on the above results, when the iron carbide composition containing halide ions such as bromine or iodine prepared in the examples of the present invention is used as a catalyst for the syngas conversion reaction under industrial conditions, it can exhibit ultra-low CO2 selectivity, relatively low CH4 selectivity, extremely high carbon atom utilization efficiency, and effective product selectivity while maintaining a high CO conversion rate (>60%). Further, through long-term experiments, it can be seen from the data of the reaction for 300 h in Table 3 that after the long-term continuous operation of the iron carbide composition of the examples of the present invention as a catalyst in a stirred tank, its CO conversion rate, product selectivity, carbon atom utilization efficiency, and effective product selectivity all remain stable without obvious changes, showing good operation stability. Therefore, by using the iron carbide composition of the examples of the present invention as a catalyst for the syngas conversion reaction, comprehensive optimization of the reaction results can be achieved.

[0248] Unless otherwise specified, the terms used in the present invention have the meanings commonly understood by those skilled in the art.

[0249] The embodiments described in the present invention are for illustrative purposes only and are not intended to limit the protection scope of the present invention. Those skilled in the art can make various other substitutions, changes, and improvements within the scope of the present invention. Therefore, the present invention is not limited to the above embodiments but is only defined by the claims.

Claims

1. A method for preparing a supported iron carbide composition, comprising: Provided is an iron carbide composition, which comprises a first iron carbide complex, a second iron carbide complex and a third iron carbide complex; Alternatively, provided is an iron carbide mixture, which comprises a first iron carbide, a second iron carbide and a third iron carbide; and the iron carbide mixture is subjected to an impregnation treatment to make it contain iodide ions and / or bromide ions, thereby obtaining the iron carbide composition; wherein, the preparation of the first iron carbide complex or the first iron carbide comprises the following steps: S11: Reducing a first supported precursor with hydrogen at 330-560 °C; S12: Treating the product obtained in step S11 at 80-175 °C under the action of a first mixed gas; the first mixed gas comprises hydrogen and carbon monoxide with a molar ratio of 1.2:1-2.8:1; S13: Preparing a carbide by treating the product obtained in step S12 at 195-300 °C under the action of a second mixed gas; the second mixed gas comprises hydrogen and carbon monoxide with a molar ratio of (1-3.2):1; wherein, the first supported precursor is a first iron-based carrier subjected to a second impregnation treatment with a first impregnating solution, the first impregnating solution contains bromide ions and / or iodide ions, and the product obtained in step S13 is the first iron carbide complex; alternatively, the first supported precursor is a first iron-based carrier, and the product obtained in step S13 is the first iron carbide; alternatively, the first supported precursor is a first iron-based carrier, the product obtained in step S13 is the first iron carbide, and the first iron carbide is further subjected to a second impregnation treatment with the first impregnating solution to obtain the first iron carbide complex; The preparation process of the first iron-based carrier comprises: subjecting the carrier to a first impregnation treatment in an aqueous solution containing iron ions, and drying and calcining the impregnated carrier; The preparation process of the second iron carbide complex or the second iron carbide comprises the following steps: S21: Reducing a second supported precursor with hydrogen at 360-570 °C; S22: Preparing a carbide by treating the product obtained in step S21 at 300-440 °C under the action of a third mixed gas; the third mixed gas comprises hydrogen and carbon monoxide with a molar ratio of (4.5-100):1; wherein, the second supported precursor is a second iron-based carrier subjected to a third impregnation treatment with a second impregnating solution, the second impregnating solution contains bromide ions and / or iodide ions, and the product obtained in step S22 is the second iron carbide complex; alternatively, the second supported precursor is a second iron-based carrier, and the product obtained in step S22 is the second iron carbide; alternatively, the second supported precursor is a second iron-based carrier, the product obtained in step S22 is the second iron carbide, and the second iron carbide is further subjected to the third impregnation treatment with the second impregnating solution to obtain the second iron carbide complex; The preparation process of the second iron-based support includes: performing a first impregnation treatment on the support in an aqueous solution containing iron ions, and drying and calcining the impregnated support; The preparation process of the third iron carbide complex or the third iron carbide includes the following steps: S31: Reducing the third supported precursor with hydrogen at 350°C to 620°C; S32: Under the action of an oxygen-containing gas, subjecting the product obtained in step S31 to surface passivation treatment at 0°C to 45°C; the oxygen-containing gas includes 1 to 3 vol% of oxygen; S33: Under the action of a fourth mixed gas, subjecting the product obtained in step S32 to carbide preparation treatment at 260°C to 430°C; the fourth mixed gas includes hydrogen and carbon monoxide with a molar ratio of (7 to 110):1; Wherein, the third supported precursor is a third iron-based support subjected to a fourth impregnation treatment with a third impregnating solution, the third impregnating solution contains bromide ions and / or iodide ions, and the product obtained in step S33 is the third iron carbide complex; or, the third supported precursor is a third iron-based support, and the product obtained in step S33 is the third iron carbide; or, the third supported precursor is a third iron-based support, subjecting the product of step S32 to the fourth impregnation treatment with the third impregnating solution, and then performing the treatment of step S33 to obtain the third iron carbide complex; or, the third supported precursor is a third iron-based support, the product obtained in step S33 is the third iron carbide, and the third iron carbide is subjected to the fourth impregnation treatment with the third impregnating solution to obtain the third iron carbide complex; The preparation process of the third iron-based support includes: performing a first impregnation treatment on the support in an aqueous solution containing iron ions, and drying and calcining the impregnated support.

2. The preparation method according to claim 1, wherein, The treatment pressure in step S11 is 0.1 to 12 atm, and the time is 0.7 to 15 h; the treatment pressure in step S12 is 0.01 to 5 atm, and the time is 15 to 120 min; the treatment pressure in step S13 is 0.1 to 9 atm, and the time is 1.5 to 15 h; or, The aqueous solution containing iron ions is prepared by dissolving at least one water-soluble compound in a first solvent, the at least one water-soluble compound includes an iron salt, and the iron salt includes one or more of ferric nitrate, ammonium ferric citrate, ferric chloride, and ammonium ferrous sulfate; or, The particle size of the support is 30 to 200 μm; or, The preparation raw materials of the first impregnating solution at least include a first halide and a second solvent, the preparation raw materials of the second impregnating solution at least include a second halide and a second solvent, and the preparation raw materials of the third impregnating solution at least include a third halide and a third solvent; the first halide, the second halide, and the third halide each include a water-soluble bromide and / or iodide.

3. The preparation method according to claim 2, wherein, The first halide, the second halide, and the third halide each independently include one or more of bromides and iodides containing molybdenum, manganese, copper, rare earth metal elements, iron, and cobalt; and / or, The raw materials for preparing the first impregnating solution further include a first auxiliary agent compound, the raw materials for preparing the second impregnating solution further include a second auxiliary agent compound, and the raw materials for preparing the third impregnating solution further include a third auxiliary agent compound; the first auxiliary agent compound, the second auxiliary agent compound, and the third auxiliary agent compound each independently selected from one or more of salts of rare earth metals, alkaline earth metals, manganese, copper, alkali metals, molybdenum, and cobalt; and / or, The treatment pressure in step S21 is 0.12 - 13 atm, and the treatment pressure in step S22 is 0 - 15 atm.

4. The preparation method according to claim 1, wherein, The carrier is selected from one or more of niobium pentoxide, silica, zirconia, titanium dioxide, and alumina; and / or, The temperature of the calcination treatment is 230 - 520 °C; and / or, The material after the fourth impregnation treatment is dried at 15 - 40 °C; and / or, The treatment pressure in step S31 is 0.1 - 11 atm, the treatment pressure in step S32 is 0 - 1.5 atm, and the treatment pressure in step S33 is 0.08 - 15 atm.

5. A supported iron carbide composition prepared by the preparation method according to any one of claims 1 to 4.

6. The composition according to claim 5, comprising a first iron carbide, a second iron carbide, a third iron carbide, a halide ion, and an optional promoter cation; wherein, The first iron carbide has a hexagonal, pseudo - hexagonal or trigonal crystal system structure, the second iron carbide has an orthorhombic crystal system structure, and the third iron carbide has a monoclinic crystal system structure; The molar ratio of iron carbide to the halide ion and the auxiliary cation is 100:(0.12 - 45):(0 - 22). The number of moles of iron carbide is the sum of the number of moles of the first iron carbide, the second iron carbide, and the third iron carbide. The number of moles of iron carbide is calculated based on the number of moles of iron element contained in the supported iron carbide composition. The halide ion is an iodide ion and / or a bromide ion.

7. The composition according to claim 6, wherein, The molar ratio of iron carbide to the halide ion is 100:(0.35 - 33), and the molar ratio of iron carbide to the auxiliary cation is 100:(0.1 - 18); and / or, In the iron carbide, the molar content of the first iron carbide is a, the molar content of the second iron carbide is b, and the molar content of the third iron carbide is c, where 0 < a ≤ 80%, 0 < b ≤ 80%, and 0 < c ≤ 80%; and / or, The auxiliary cation includes one or more of alkaline earth metal ions, chromium ions, cobalt ions, manganese ions, copper ions, alkali metal ions, molybdenum ions, and rare earth ions.

8. A catalyst comprising the supported iron carbide composition prepared by the preparation method according to any one of claims 1 to 4 or the supported iron carbide composition according to any one of claims 5 to 7.

9. Use of the supported iron carbide composition prepared by the preparation method according to any one of claims 1 to 4, the supported iron carbide composition according to any one of claims 5 to 7 or the catalyst according to claim 8 in a reaction for synthesizing C, H fuels and / or chemicals based on the Fischer-Tropsch synthesis principle.

10. A syngas conversion process comprising contacting the catalyst according to claim 8 with syngas under reaction conditions for reaction.

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