Composition containing supported epsilon / epsilon '-iron carbide and chi-iron carbide as well as preparation method and application of composition

Abstract

The invention relates to a composition containing supported epsilon / epsilon '-iron carbide and chi-iron carbide as well as a preparation method and application of the composition. The method comprises the following steps: preparing a supported epsilon / epsilon'-iron carbide compound; preparing a load type x-iron carbide compound; and mixing the supported epsilon / epsilon '-iron carbide compound with the supported chi-iron carbide compound to obtain a composition containing the supported epsilon / epsilon'-iron carbide and the chi-iron carbide, or providing a supported iron carbide mixture comprising supported epsilon / epsilon '-iron carbide and supported chi-iron carbide, and carrying out dipping treatment on the supported iron carbide mixture through a third halide solution to obtain the composition containing supported epsilon / epsilon'-iron carbide and chi-iron carbide. According to the composition disclosed by the invention, halide ions are introduced, so that the synthesis gas conversion reaction has relatively high CO conversion rate and extremely low total CO2 selectivity.

Description

Technical Field

[0001] The present invention relates to the conversion of syngas, and particularly to a composition containing supported iron carbide that can be used for the conversion of syngas. Background Art

[0002] The technology for syngas conversion has become an increasingly important energy conversion route in recent years. After carbon-containing substances such as coal, natural gas, and biomass are gasified to obtain syngas, they are then converted into liquid fuels and high-value chemicals under the action of a catalyst.

[0003] Among them, the reaction equations for syngas conversion are as follows:

[0004] (2n + 1)H2 + nCO → C n H 2n+2 + nH2O (a)

[0005] 2nH2 + nCO → C n H 2n + nH2O (b)

[0006] (n + 1)H2 + 2nCO → C n H 2n+2 + nCO2 (c)

[0007] nH2 + 2nCO → C n H 2n + nCO2 (d)

[0008] Iron-based catalysts are the most commonly used catalysts in the field of syngas conversion. They have high activity, a wide range of applicable conditions, strong sulfur tolerance, simple on-line catalyst replacement, and are suitable for industrial continuous production. However, there is also the problem of excessive CO2 selectivity.

[0009] The paper published by Professor Enrique Iglesia ("Pathways for CO2 Formation and Conversion During Fischer-Tropsch Synthesis on Iron-Based Catalysts" (Catalysis Letters volume 80, pages 77-86 (2002))) elaborates that in the reaction of syngas conversion achieved by the Fischer-Tropsch synthesis principle, the generation of CO2 has two sources: (1) primary CO2 directly from the primary Fischer-Tropsch synthesis reaction (see the above equations (c), (d)); and (2) secondary CO2 generated by the water-gas-shift reaction (WGS reaction, CO + H2O → CO2 + H2) of H2O and CO at a higher CO conversion rate.

[0010] The prior art discloses a high-purity iron carbide catalyst that can reduce the primary CO2 in the Fischer-Tropsch synthesis reaction to nearly zero, while achieving a high CO space-time conversion rate, thereby reducing the total CO2 selectivity to <5% at a low CO conversion rate (usually below 35%). However, when the CO conversion rate increases, as the H2O content in the reaction environment rises, the WGS reaction intensifies, resulting in an increase in secondary CO2, and ultimately causing the total CO2 selectivity to increase at a high CO conversion rate. Summary of the Invention

[0011] To overcome at least one defect of the above prior art, in a first aspect, an embodiment of the present invention provides a method for preparing a composition containing supported ε / ε'-iron carbide and χ-iron carbide, including:

[0012] Preparing a supported ε / ε'-iron carbide composite;

[0013] Preparing a supported χ-iron carbide composite; and

[0014] Mixing the supported ε / ε'-iron carbide composite with the supported χ-iron carbide composite to obtain a composition containing supported ε / ε'-iron carbide and χ-iron carbide; or,

[0015] Providing a supported iron carbide mixture including supported ε / ε'-iron carbide and supported χ-iron carbide, and impregnating the supported iron carbide mixture with a third halide solution to obtain a composition containing supported ε / ε'-iron carbide and χ-iron carbide;

[0016] Wherein, the preparation of the supported ε / ε'-iron carbide composite or the supported ε / ε'-iron carbide includes the following steps:

[0017] (10) Using an iron-containing carrier as a supported ε / ε'-precursor or using the iron-containing carrier after impregnation treatment with a first halide solution as a supported ε / ε'-precursor;

[0018] (11) At 320 - 540 °C, reducing and surface-purifying the supported ε / ε'-precursor with hydrogen;

[0019] (12) At 70 - 185 °C, treating the product of step (11) with a first gas; the first gas includes hydrogen and carbon monoxide, and the molar ratio of hydrogen to carbon monoxide is 1.2:1 to 2.8:1;

[0020] (13) At 190 - 290 °C, the product of step (12) is treated with a second gas; the second gas includes hydrogen and carbon monoxide, and the molar ratio of hydrogen to carbon monoxide is 1:1 to 3.2:1;

[0021] Wherein, the iron-containing carrier is used as the supported ε / ε'-precursor, and the product obtained in step (13) is the supported ε / ε'-iron carbide; or, the iron-containing carrier is used as the supported ε / ε'-precursor, the product obtained in step (13) is the supported ε / ε'-iron carbide, and then the supported ε / ε'-iron carbide is impregnated with the first halide solution to obtain the supported ε / ε'-iron carbide composite;

[0022] The preparation process of the supported χ-iron carbide composite or the supported χ-iron carbide includes the following steps:

[0023] (20) Use the iron-containing carrier as the supported χ-precursor or use the iron-containing carrier as the supported χ-precursor after impregnation with a second halide solution;

[0024] (21) At 350 - 600 °C, the supported χ-precursor is reduced and surface-purified with hydrogen;

[0025] (22) At 0 - 41 °C, the product of step (21) is surface-passivated with a third gas;

[0026] (23) At 260 - 430 °C, the product of step (22) is treated with a fourth gas;

[0027] Wherein, the iron-containing carrier is used as the supported χ-precursor, and the product obtained in step (23) is the supported χ-iron carbide; or, the iron-containing carrier is used as the supported χ-precursor and subjected to the treatments of steps (21) and (22), the product of step (22) is impregnated with the second halide solution, and then the treatment of step (23) is carried out to obtain the supported χ-iron carbide composite; or, the iron-containing carrier is used as the supported χ-precursor, the product obtained in step (23) is the supported χ-iron carbide, and then the supported χ-iron carbide is impregnated with the second halide solution to obtain the supported χ-iron carbide composite;

[0028] The third gas includes 1 - 3 vol% of oxygen and 97 - 99 vol% of inert gas; the fourth gas includes hydrogen and carbon monoxide, and the molar ratio of hydrogen to carbon monoxide is 7:1 to 110:1;

[0029] Among them, the preparation method of the siderophore includes: performing a first impregnation treatment on the carrier in an iron salt solution, followed by a drying treatment and a calcination treatment; the first halide solution contains bromide ions and / or iodide ions, the second halide solution contains bromide ions and / or iodide ions, the third halide solution contains iodide ions and / or bromide ions, and the iron salt solution contains iron ions.

[0030] In a second aspect, an embodiment of the present invention provides a composition prepared by the above-mentioned preparation method.

[0031] In a third aspect, an embodiment of the present invention provides a catalyst, which includes the composition prepared by the above-mentioned preparation method or the above-mentioned composition.

[0032] In a fourth aspect, an embodiment of the present invention provides the application of the composition prepared by the above-mentioned preparation method, the above-mentioned composition or the above-mentioned catalyst in the synthesis gas conversion reaction.

[0033] In a fifth aspect, an embodiment of the present invention provides the application of the composition prepared by the above-mentioned preparation method, the above-mentioned composition or the above-mentioned catalyst in the reaction of synthesizing C and H fuels and / or chemicals based on the Fischer-Tropsch synthesis principle.

[0034] In a sixth aspect, an embodiment of the present invention provides a synthesis gas conversion process, which includes contacting the above-mentioned catalyst with synthesis gas under reaction conditions for reaction.

[0035] The iron carbide composition of an embodiment of the present invention can be used as a catalyst for the synthesis gas conversion reaction, especially the Fischer-Tropsch synthesis 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, realizing the comprehensive optimization of the reaction results. Description of the Drawings

[0036] 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:

[0037] Figure 1 is the XRD pattern of the supported ε / ε'-iron carbide composite prepared in Example 5 of the present invention;

[0038] Figure 2 is the XRD pattern of the supported χ-iron carbide composite prepared in Example 5 of the present invention. Detailed Embodiments

[0039] 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 variations in different embodiments, all of which do not depart from the scope of the present invention, and the descriptions therein are for illustrative purposes in nature and not intended to limit the present invention.

[0040] An embodiment of the present invention provides a iron carbide composition, comprising supported ε / ε'-iron carbide, supported χ-iron carbide, halide ions and optional promoter cations; wherein, the molar ratio of iron carbide to halide ions and promoter cations is 100:(0.12 - 44):(0 - 25), and the molar number of iron carbide is based on the molar number of 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 halide ions, or may include iron carbide, halide ions and promoter cations.

[0041] In one embodiment, the iron carbide composition is formed by mixing a supported ε / ε'-iron carbide complex and a supported χ-iron carbide complex.

[0042] In one embodiment, 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 χ-iron carbide or the supported χ-iron carbide complex is 3 - 28 nm, and further can be 5 - 26 nm.

[0043] In one embodiment, the supported ε / ε'-iron carbide (or the supported ε / ε'-iron carbide complex) has a hexagonal, pseudo-hexagonal or trigonal crystal system structure, and the supported χ-iron carbide (or the supported χ-iron carbide complex) has a monoclinic crystal system structure.

[0044] In one embodiment, based on the number of moles of iron carbide (100%) in the iron carbide composition, the molar content of supported ε / ε'-iron carbide is a, and the molar content of supported χ-iron carbide is b, where 0 < a ≤ 85%, 0 < b ≤ 85%, preferably, 0 < a ≤ 70%, 0 < b ≤ 70%. For example, a or b can be 1%, 5%, 10%, 15%, 20%, 30%, 50%, 80%. Alternatively, in the iron carbide composition, the molar content of supported ε / ε'-iron carbide composition is a, and the molar content of supported χ-iron carbide composition is b, where 0 < a ≤ 85%, 0 < b ≤ 85%, preferably, 0 < a ≤ 70%, 0 < b ≤ 70%. For example, a or b can be 1%, 5%, 10%, 15%, 20%, 30%, 50%, 80%. Among them, the number of moles of supported ε / ε'-iron carbide, supported χ-iron carbide, supported ε / ε'-iron carbide complex, and supported χ-iron carbide complex are calculated based on the number of moles of iron element contained in each.

[0045] In one embodiment, the molar ratio of iron carbide to halide ion can be 100:(0.12 - 44), further can be 100:(0.3 - 32), 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.

[0046] In one embodiment, the molar ratio of iron carbide to promoter cation can be 100:(0.1 - 25), further can be 100:(0.1 - 21), and still further can be 100:(0.1 - 10). For example, 100:0.5, 100:1, 100:5, 100:10, 100:15, 100:20.

[0047] In one embodiment, the iron carbide composition includes halide cations, and the halide cations can maintain charge balance with halide ions, that is, the total negative charge (or the total valence shown) carried by halide ions is equal to the total positive charge carried by halide cations.

[0048] In one embodiment, the iron carbide composition includes promoter anions, and the promoter cations can maintain charge balance with the promoter anions.

[0049] 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 (such as divalent and trivalent iron ions), manganese ions (such as divalent manganese ions), copper ions (such as monovalent and divalent copper ions), cobalt ions (such as divalent cobalt ions), molybdenum ions (such as divalent, trivalent, and tetravalent molybdenum ions), lanthanum ions (such as trivalent and tetravalent lanthanum ions), cerium ions (such as trivalent and tetravalent cerium ions), neodymium ions (such as trivalent and tetravalent neodymium ions); the complex cation includes one or more of hexaammine manganese ions, hexaammine iron ions, and hexaammine copper ions.

[0050] 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 ions may be one or more of manganese ions (such as divalent, trivalent, and tetravalent manganese ions), copper ions (such as monovalent and divalent copper ions), cobalt ions (such as divalent cobalt ions), molybdenum ions (such as divalent, trivalent, and tetravalent molybdenum ions), chromium ions (such as trivalent chromium ions), lanthanum ions (such as trivalent and tetravalent lanthanum ions), cerium ions (such as trivalent and tetravalent cerium ions), neodymium ions (such as trivalent and tetravalent neodymium ions), sodium ions, potassium ions, calcium ions, and barium ions.

[0051] 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.

[0052] One embodiment of the present invention provides a preparation method of the above composition, including:

[0053] Separately preparing a supported ε / ε'-iron carbide composite and a supported χ-iron carbide composite; and

[0054] Mixing the supported ε / ε'-iron carbide composite with the supported χ-iron carbide composite to obtain a composition containing the supported ε / ε'-iron carbide and χ-iron carbide; or,

[0055] Providing a supported iron carbide mixture including supported ε / ε'-iron carbide and supported χ-iron carbide, and subjecting the supported iron carbide mixture to a fourth impregnation treatment with a third halide solution to obtain a composition containing the supported ε / ε'-iron carbide and χ-iron carbide;

[0056] Wherein, the preparation of the supported ε / ε'-iron carbide composite or the supported ε / ε'-iron carbide includes the following steps:

[0057] (11) At 320 - 540 °C, the supported ε / ε'-precursor is reduced and surface-purified with hydrogen;

[0058] (12) At 70 - 185 °C, the product of step (11) is treated with a first gas; the first gas includes hydrogen and carbon monoxide, and the molar ratio of hydrogen to carbon monoxide is 1.2:1 to 2.8:1;

[0059] (13) At 190 - 290 °C, the product of step (12) is treated with a second gas; the second gas includes hydrogen and carbon monoxide, and the molar ratio of hydrogen to carbon monoxide is 1:1 to 3.2:1;

[0060] Wherein, the supported ε / ε'-precursor is an iron-containing carrier subjected to a second impregnation treatment with a first halide solution, and the product obtained in step (13) is a supported ε / ε'-iron carbide composite; or, the supported ε / ε'-precursor is an iron-containing carrier, and the product obtained in step (13) is a supported ε / ε'-iron carbide; or, the iron-containing carrier is used as the supported ε / ε'-precursor, the product obtained in step (13) is a supported ε / ε'-iron carbide, and then the supported ε / ε'-iron carbide is impregnated with a first halide solution to obtain a supported ε / ε'-iron carbide composite;

[0061] The preparation process of the supported χ-iron carbide composite or the supported χ-iron carbide includes the following steps:

[0062] (21) At 350 - 600 °C, the supported χ-precursor is reduced and surface-purified with hydrogen;

[0063] (22) At 0 - 41 °C, the product of step (21) is surface-passivated with a third gas;

[0064] (23) At 260 - 430 °C, the product of step (22) is treated with a fourth gas;

[0065] Among them, the third gas includes 1-3 vol% of oxygen and 97-99 vol% of inert gas; the fourth gas includes hydrogen and carbon monoxide, and the molar ratio of hydrogen to carbon monoxide is 7:1 to 110:1; the supported χ-precursor is an iron-containing carrier subjected to a third impregnation treatment with a second halide solution, and the product obtained in step (23) is a supported χ-iron carbide composite; or, the supported χ-precursor is an iron-containing carrier, and the product obtained in step (23) is supported χ-iron carbide; or, the iron-containing carrier is used as the supported χ-precursor for the treatments in steps (21) and (22), the product of step (22) is impregnated with a second halide solution, and then the treatment in step (23) is carried out to obtain a supported χ-iron carbide composite; or, the iron-containing carrier is used as the supported χ-precursor, the product obtained in step (23) is supported χ-iron carbide, and the supported χ-iron carbide is impregnated with a second halide solution to obtain a supported χ-iron carbide composite.

[0066] Among them, the preparation method of the iron-containing carrier includes: subjecting the carrier to a first impregnation treatment in an iron salt solution, followed by drying treatment and calcination treatment; the first halide solution contains bromide ions and / or iodide ions, the second halide solution contains bromide ions and / or iodide ions, the third halide solution contains iodide ions and / or bromide ions, and the iron salt solution contains iron ions.

[0067] In one embodiment, the iron content in the supported ε / ε'-precursor or the supported χ-precursor is 10-30 wt%, such as 12 wt%, 15 wt%, 18 wt%, 20 wt%, 22 wt%, 25 wt%, 28 wt%.

[0068] In one embodiment, the carrier includes one or more of silica, alumina, titanium dioxide, niobium pentoxide, and zirconia. Further, the particle size of the carrier is 30-200 μm, such as 50 μm, 60 μm, 80 μm, 100 μm, 120 μm, 150 μm, 180 μm.

[0069] In one embodiment, the iron salt solution is prepared by dissolving at least one water-soluble compound in a first solvent, and the at least one water-soluble compound includes one or more of ferric nitrate, ferric chloride, ammonium ferrous sulfate, and ammonium ferric citrate.

[0070] In one embodiment, the first solvent includes water.

[0071] In one embodiment, the drying process performed on the carrier after the first impregnation treatment includes the following steps: drying the impregnated carrier at 20-30°C for 0.5-4 h, then drying it at 35-80°C under a vacuum of 250-1200 Pa for 6-12 h, and then drying the dried material at 110-150°C for 3-24 h.

[0072] In one embodiment, the temperature of the calcination treatment after the drying process is 220-530°C, such as 250°C, 300°C, 350°C, 400°C, 450°C, 500°C; and the time is 1-10 h, such as 2 h, 4 h, 5 h, 6 h, 8 h.

[0073] In one embodiment, the raw materials for preparing the first halide solution at least include a first halide and a second solvent, the raw materials for preparing the second halide solution at least include a second halide and a third solvent, and the raw materials for preparing the third halide solution at least include a third halide and a fourth solvent; the first halide, the second halide, and the third halide each include a water-soluble bromide and / or iodide.

[0074] In one embodiment, the first halide, the second halide, and the third halide each independently include one or more of bromides and iodides containing cobalt, rare earth metal elements, copper, iron, manganese, and molybdenum. Further, the first halide, the second halide, and the third halide each independently include one or more of manganese bromide, iron bromide, copper bromide, cobalt bromide, molybdenum bromide, manganese iodide, iron iodide, copper iodide, rare earth bromides, rare earth iodides, hexaammine manganese bromide, hexaammine iron bromide, hexaammine copper bromide, hexaammine manganese iodide, hexaammine iron iodide, and hexaammine copper iodide.

[0075] In one embodiment, the raw materials for preparing the first halide solution further include a first soluble compound, the raw materials for preparing the second halide solution further include a second soluble compound, and the raw materials for preparing the third halide solution further include a third soluble compound; the first soluble compound, the second soluble compound, and the third soluble compound may each include one or more of salts (organic salts and / or inorganic salts) of manganese, copper, cobalt, molybdenum, rare earth metals, alkali metals, and alkaline earth metals. For example, the first soluble compound, the second soluble compound, and the third soluble compound may each 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.

[0076] In one embodiment, no chemical reaction occurs between the solute components of the same solution. For example, the solute of the first halide solution does not simultaneously include potassium carbonate and calcium nitrate.

[0077] In one embodiment, the first solvent, the second solvent, the third solvent, and the fourth solvent each independently include water and / or ethanol. For example, the first solvent, the second solvent, the third solvent, and the fourth solvent can all be water or a mixture of ethanol and water.

[0078] In one embodiment, the dosages of the first halide, the second halide, the third halide, the first soluble compound, the second soluble compound, and the third soluble compound can be appropriately selected according to the content of each ion in the composite to be prepared. Further, the concentrations of the first halide, the second halide, the third halide, the first soluble compound, the second soluble compound, and the third soluble 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.

[0079] In one embodiment, the temperature of the first impregnation treatment, the second impregnation treatment, the third impregnation treatment, or the fourth 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, or the fourth 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.

[0080] 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.

[0081] In one embodiment, any of the above impregnation treatments can adopt one of slurry impregnation method, saturated impregnation method, supersaturated impregnation method, or other feasible impregnation methods.

[0082] 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 (11) can be 320 to 540 °C, such as 320 °C, 350 °C, 360 °C, 380 °C, 390 °C, 400 °C, 420 °C, 450 °C, 460 °C, 480 °C, 500 °C, 520 °C; the treatment pressure can be 0.1 to 12 atm, further can be 0.5 to 3.6 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 to 15 h, further can be 1 to 12 h, such as 2 h, 3 h, 5 h, 8 h, 10 h.

[0083] 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 (11) 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.

[0084] In one embodiment, in the preparation of the supported ε / ε'-iron carbide composite or supported ε / ε'-iron carbide, the first gas in step (12) 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 gas can be a mixture of hydrogen and carbon monoxide.

[0085] 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 (12) can be 70 to 185 °C, such as 80 °C, 90 °C, 100 °C, 110 °C, 120 °C, 130 °C, 150 °C, 160 °C, 180 °C; the treatment pressure can be 0.01 to 6 atm, further can be 0.08 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, 5 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.

[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 the first gas in step (13) 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.

[0087] 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 gas in step (13) can be 1.2:1, 1.5:1, 1.8:1, 2:1, 2.2:1, 2.5:1, 2.8:1, 3:1. The second 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 (13) can be 190 - 290 °C, such as 200 °C, 210 °C, 230 °C, 250 °C, 260 °C, 270 °C, 280 °C; the treatment pressure can be 0.13 - 12 atm, further can be 0.22 - 5.1 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, 10 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.

[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 second gas in step (13) 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.

[0090] In one embodiment, in the preparation of the supported ε / ε'-iron carbide composite or supported ε / ε'-iron carbide, in step (13), the temperature of the system is raised from 70 - 185 °C to 190 - 290 °C at a heating rate of 0.2 - 5 °C / min, further, the temperature of the system is raised from 70 - 185 °C to 210 - 290 °C at a heating rate of 0.2 - 2.5 °C / min; the heating rate in step (13) 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.

[0091] 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 (21) can be 350 to 600 °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 13 atm, further can be 0.3 to 2.5 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.

[0092] 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 (21) 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.

[0093] In one embodiment, in the preparation of the supported χ-iron carbide composite or supported χ-iron carbide, the third gas in step (22) includes 1 to 3 vol% of oxygen and 97 to 99 vol% of an inert gas, and 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 third gas can be, for example, 1.5 vol%, 2 vol%, 2.5 vol%, 3 vol%.

[0094] 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 (22) can be 0 to 41 °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 1.2 atm, further can be 0 to 0.11 atm, such as 0.01 atm, 0.02 atm, 0.05 atm, 0.06 atm, 0.08 atm, 1 atm; the treatment time can be 5 to 72 h, further can be 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.

[0095] In one embodiment, in the preparation of the supported χ-iron carbide composite or supported χ-iron carbide, the gas flow rate of the third gas in step (22) can be 400 to 12000 mL / h / g, further can be 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.

[0096] 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 gas in step (23) can be 8:1, 10:1, 20:1, 30:1, 36:1, 40:1, 50:1, 60:1, 80:1, 100:1. The fourth gas can be a mixture of hydrogen and carbon monoxide.

[0097] In one embodiment, in the preparation of the supported χ-iron carbide composite or supported χ-iron carbide, the treatment temperature in step (23) 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 13 atm, further can be 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 can be 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.

[0098] 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 gas in step (23) can be 250 to 21,000 mL / h / g, further can be 2,000 to 18,000 mL / h / g, such as 1,000 mL / h / g, 3,000 mL / h / g, 5,000 mL / h / g, 6,000 mL / h / g, 7,700 mL / h / g, 8,000 mL / h / g, 10,000 mL / h / g, 12,000 mL / h / g, 15,000 mL / h / g, 16,000 mL / h / g.

[0099] In one embodiment, in the preparation of the supported χ-iron carbide composite or supported χ-iron carbide, in step (23), the temperature of the system is raised from 0 to 41 °C to 260 to 430 °C at a heating rate of 0.2 to 6 °C / min, and further, the temperature of the system is raised from 0 to 41 °C to 260 to 400 °C at a heating rate of 0.3 to 3.5 °C / min; the heating rate of step (23) 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, preferably, the above steps and the above impregnation treatment are all carried out under light-shielded conditions.

[0101] In one embodiment, the preparation process of the supported ε / ε'-iron carbide composite includes the following steps:

[0102] (10) Perform the first impregnation treatment on the carrier in the iron salt solution, and dry and calcine the impregnated carrier to obtain an iron-containing carrier; perform the second impregnation treatment on the iron-containing carrier in the first halide solution to obtain a supported ε / ε'-precursor;

[0103] (11) At 320 to 540 °C, reduce and surface-purify the supported ε / ε'-precursor with hydrogen.

[0104] (12) At 70 to 185 °C, treat the product of step (11) with the first gas.

[0105] (13) At 190 to 290 °C, treat the product of step (12) with the second gas to obtain the supported ε / ε'-iron carbide composite.

[0106] In one embodiment, the preparation method of the supported ε / ε'-iron carbide includes the following steps:

[0107] (10) The carrier is subjected to a first impregnation treatment in an iron salt solution, and the impregnated carrier is dried and calcined to obtain an iron-containing carrier (i.e., a supported ε / ε'-precursor).

[0108] (11) At 320 - 540 °C, the supported ε / ε'-precursor is reduced and surface-purified by hydrogen.

[0109] (12) At 70 - 185 °C, the product of step (11) is treated with a first gas.

[0110] (13) At 190 - 290 °C, the product of step (12) is treated with a second gas to obtain ε / ε'-iron carbide.

[0111] In one embodiment, the preparation process of the supported χ-iron carbide composite includes the following steps:

[0112] (20) The carrier is subjected to a first impregnation treatment in an iron salt solution, and the impregnated carrier is dried and calcined to obtain an iron-containing carrier; the iron-containing carrier is subjected to a third impregnation treatment in a second halide solution to obtain a supported χ-precursor.

[0113] (21) At 350 - 600 °C, the supported χ-precursor is reduced and surface-purified by hydrogen.

[0114] (22) At 0 - 41 °C, the product of step (21) is surface-passivated with a third gas.

[0115] (23) At 260 - 430 °C, the product of step (22) is treated with a fourth gas to obtain a supported χ-iron carbide composite.

[0116] In one embodiment, the preparation process of the supported χ-iron carbide includes the following steps:

[0117] (20) The carrier is subjected to a first impregnation treatment in an iron salt solution, and the impregnated carrier is dried and calcined to obtain an iron-containing carrier (i.e., a supported χ-precursor).

[0118] (21) At 350 - 600 °C, the supported χ-precursor is reduced and surface-purified by hydrogen.

[0119] (22) At 0 - 41 °C, the product of step (21) is surface-passivated with a third gas.

[0120] (23) At 260 - 430 °C, the product of step (22) is treated with a fourth gas to obtain a supported χ-iron carbide.

[0121] An embodiment of the present invention provides a catalyst comprising the above-mentioned iron carbide composition.

[0122] An embodiment of the present invention provides the use of the above-mentioned iron carbide composition or catalyst in the synthesis gas conversion reaction.

[0123] In one embodiment, the synthesis gas 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 synthesis gas and having an alcohol as the final product.

[0124] In one embodiment, the synthesis gas comprises CO and H2.

[0125] An embodiment of the present invention provides the use of the above-mentioned iron carbide composition or catalyst in the reaction for synthesizing C, 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 synthesis gas (a mixture of CO and H2) is used as a raw material, and through CO hydrogenation and carbon chain growth reactions under the action of a catalyst and appropriate conditions, chain hydrocarbons and / or their oxygen-containing derivatives are generated.

[0126] In one embodiment, the above reaction is a Fischer-Tropsch synthesis reaction, the reaction temperature can be 255 - 305 °C, such as 260 °C, 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.

[0127] An embodiment of the present invention provides a synthesis gas conversion process, which includes contacting the above-mentioned catalyst with synthesis gas under synthesis gas conversion reaction conditions for reaction.

[0128] In one embodiment, the synthesis gas conversion can be carried out in a high-temperature and high-pressure continuous reactor.

[0129] The iron carbide composition of an embodiment of the present invention can be used as a catalyst for the synthesis gas 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.

[0130] A kind of iron carbide composition according to an embodiment of the present invention can be used as a catalyst for syngas conversion reaction, enabling the reaction to maintain extremely low CO₂ selectivity at high CO conversion rate, while maintaining low CH₄ selectivity and high reaction stability, greatly improving the utilization efficiency of carbon atoms and the selectivity of effective products, breaking through the key technical bottleneck, and promoting the high-end, diversification and low-carbon of clean syngas conversion, indicating new trends and directions for the development of modern syngas chemistry.

[0131] A kind of iron carbide composition according to an embodiment of the present invention, as a catalyst for Fischer-Tropsch synthesis reaction, can maintain continuous and stable reaction for more than 300 h using a high-pressure continuous reactor under industrial Fischer-Tropsch synthesis reaction conditions, 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 utilization efficiency of carbon atoms is maintained above 95%, further above 97%; the selectivity of effective products can reach above 86.5%, further above 92%.

[0132] In one embodiment, through the Fischer-Tropsch synthesis reaction catalyzed by the iron carbide composition, a CO₂ selectivity of <4%, a carbon atom utilization efficiency of >96%, and an effective product selectivity of >89% can be achieved at a CO conversion rate of above 65%.

[0133] In this article, 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 ionic bond - , and also Br atoms that interact with H atoms by covalent bond.

[0134] The pressure values involved in this article are all gauge pressures.

[0135] Hereinafter, in combination with the drawings and specific embodiments, a kind of iron carbide composition according to an embodiment of the present invention and its application will be further described. Among them, the test methods involved are as follows:

[0136] 1. During the reaction process of the example or comparative example, use in-situ XRD to detect the phase change of the material with an X-ray diffractometer (Rigaku Corporation, model D / max-2600 / PC), and the crystal system structure of each iron carbide complex is measured by the X-ray diffractometer.

[0137] 2. The average grain diameter of each iron carbide or its complex is obtained through XRD testing.

[0138] 3. Use a Mössbauer spectrometer (Transmission 57 Fe, 57The Mössbauer spectroscopy of the iron carbide composition was detected by a Co(Rh) source sine velocity spectrometer to obtain the corresponding composition.

[0139] 4. The elemental detection of the iron carbide composition was carried out by an Inductive Coupled Plasma Emission Spectrometer (ICP).

[0140] 5. During the conversion reaction of syngas, 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 end of the reactor, including the generated hydrocarbon compounds, alcohol compounds, CO2, etc.

[0141] 6. The CO conversion rate %, CO2 selectivity %, CH4 selectivity %, carbon atom utilization efficiency %, and effective product selectivity % were calculated by the following formulas:

[0142] CO conversion rate % = [(moles of CO in the feed - moles of CO in the product) / moles of CO in the feed] × 100%;

[0143] CO2 selectivity % = [moles of CO2 in the product / (moles of CO in the feed - moles of CO in the product)] × 100%;

[0144] CH4 selectivity % = [moles of CH4 in the product / (moles of CO in the feed - moles of CO in the product)] × 100%;

[0145] Carbon atom utilization efficiency % = (1 - CO2 selectivity %) × 100%;

[0146] Effective product selectivity % = (1 - CO2 selectivity % - CH4 selectivity %) × 100%.

[0147] Example 1

[0148] Preparation of supported ε / ε'-iron carbide

[0149] (10) 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 3 h, then dried in a vacuum drying oven at 32 °C and a vacuum degree of 100 Pa for 6 h, the dried material is dried in an oven at 110 °C for 12 h, and then the obtained material is calcined in a muffle furnace at 400 °C for 3 h to obtain an iron-containing support, which is used as a supported ε / ε'-precursor;

[0150] (11) At a pressure of 390 °C and 1.0 atm, the supported ε / ε'-precursor is maintained in H₂ with a flow rate of 7000 mL / h / g for 3 h for reduction and surface purification treatment.

[0151] (12) The product obtained in step (11) is cooled to 150 °C and pretreated by contacting with a first gas at this temperature; wherein, the pressure of the system is 1.1 atm, the flow rate of the first gas is 6000 mL / h / g, and the treatment time is 1 h; the first gas is a mixture of H₂ and CO, and the molar ratio of H₂ to CO is 2.3:1.

[0152] (13) The product obtained in step (12) is contacted with a second gas. The pressure of the system is 1.0 atm, and the total gas flow rate is 13500 mL / h / g. Under this condition, the system is heated from 150 °C to 250 °C at a heating rate of 1.0 °C / min for carbide preparation; wherein, the second gas is a mixture of H₂ and CO, and the molar ratio of the two is H₂:CO = 1.55:1. The treatment time of the material at 250 °C is 5 h; after the treatment is completed, supported ε / ε'-iron carbide is prepared.

[0153] Preparation of supported χ-iron carbide

[0154] (20) An iron-containing carrier is prepared using exactly the same raw materials and method as in step (10) as the supported χ-precursor.

[0155] (21) At a pressure of 350 °C and 1.0 atm, the supported χ-precursor is maintained in H₂ with a flow rate of 10000 mL / h / g for 5 h for reduction and surface purification treatment.

[0156] (22) The product of step (21) is cooled to 30 °C and surface passivated by contacting with a third gas at this temperature; wherein, 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 third gas includes 1 vol% oxygen and 99 vol% nitrogen.

[0157] (23) The product of step (22) is contacted with a fourth gas. The pressure of the system is 2.1 atm, and the total gas flow rate is 11000 mL / h / g. Under this condition, the system is heated from 30 °C to 350 °C at a heating rate of 2.0 °C / min for carbide preparation; wherein, the fourth gas is a mixture of H₂ and CO, and the molar ratio of H₂ to CO is 40:1. The treatment time of the material at 350 °C is 1.5 h; after the treatment is completed, supported χ-iron carbide is prepared.

[0158] Preparation of the composition

[0159] Mix the above-prepared supported ε / ε’-iron carbide and supported χ-iron carbide in a molar ratio of 1:2.5 (based on the molar amount of iron contained in each) to obtain an iron carbide mixture. Dissolve manganese bromide and potassium nitrate in 70 ml of water to prepare an impregnation solution; impregnate the iron carbide mixture with the impregnation solution, with an impregnation ratio (molar ratio) of Fe:Br:K = 100:7.0:2.0, an impregnation temperature of 31 °C, and an impregnation time of 5 h; dry the impregnated solid material in a vacuum oven at 35 °C and a pressure of 120 Pa for 13 h to obtain an iron carbide composition, labeled as CX1.

[0160] Examples 1-1 to 3-8 were 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 was different, and the prepared compositions were 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 was extremely small, the content of each substance in the obtained composition was basically the same as the amount of the corresponding raw material used. For specific content values, see Table 1.

[0161] Example 4

[0162] Preparation of supported ε / ε’-iron carbide

[0163] Prepare supported ε / ε’-iron carbide using the same raw materials and processes as in steps (10) to (13) of Example 1.

[0164] Preparation of supported χ-iron carbide

[0165] Prepare supported χ-iron carbide using the same raw materials and processes as in steps (20) to (23) of Example 1.

[0166] Preparation of the composition

[0167] Mix the above-prepared supported ε / ε’-iron carbide and supported χ-iron carbide in a molar ratio of 1:2.5 (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 70 ml of water to prepare an impregnation solution; impregnate the iron carbide mixture with the impregnation solution, with an impregnation ratio (molar ratio) of Fe:Br:K:Na = 100:15:3.0:2.0, an impregnation temperature of 35 °C, and an impregnation time of 4 h; dry the impregnated solid material in a vacuum oven at 35 °C and a pressure of 120 Pa for 13 h to obtain an iron carbide composition, labeled as CX4.

[0168] Example 4-1

[0169] This example uses substantially the same raw materials and processes as in Example 1 to prepare the supported iron carbide composite, with the only difference being that: in step (13), the carbonization temperature is 190 °C. The finally obtained supported iron carbide composite is labeled as CX4-1.

[0170] Example 4-2

[0171] This example uses substantially the same raw materials and processes as in Example 1 to prepare the supported iron carbide composite, with the only difference being that: in step (13), the carbonization temperature is 290 °C. The finally obtained supported iron carbide composite is labeled as CX4-2.

[0172] Example 4-3

[0173] This example uses substantially the same raw materials and processes as in Example 1 to prepare the supported iron carbide composite, with the only difference being that: in the second gas of step (13), the molar ratio of hydrogen to carbon monoxide is 1:1. The finally obtained supported iron carbide composite is labeled as CX4-3.

[0174] Example 4-4

[0175] This example uses substantially the same raw materials and processes as in Example 1 to prepare the supported iron carbide composite, with the only difference being that: in the second gas of step (13), the molar ratio of hydrogen to carbon monoxide is 3.2:1. The finally obtained supported iron carbide composite is labeled as CX4-4.

[0176] Example 4-5

[0177] This example uses substantially the same raw materials and processes as in Example 1 to prepare the supported iron carbide composite, with the only difference being that: in step (23), the carbonization temperature is 260 °C. The finally obtained supported iron carbide composite is labeled as CX4-5.

[0178] Example 4-6

[0179] This example uses substantially the same raw materials and processes as in Example 1 to prepare the supported iron carbide composite, with the only difference being that: in step (23), the carbonization temperature is 430 °C. The finally obtained supported iron carbide composite is labeled as CX4-6.

[0180] Example 4-7

[0181] This example uses substantially the same raw materials and processes as in Example 1 to prepare the supported iron carbide composite, with the only difference being that: in the fourth gas of step (23), the molar ratio of hydrogen to carbon monoxide is 7:1. The finally obtained supported iron carbide composite is labeled as CX4-7.

[0182] Example 4-8

[0183] This example uses substantially the same raw materials and processes as Example 1 to prepare the supported iron carbide composite, with the only difference being that the molar ratio of hydrogen to carbon monoxide in the fourth gas in step (23) is 100:1. The finally prepared supported iron carbide composite is labeled CX4-8.

[0184] Examples 4-9

[0185] This example uses substantially the same raw materials and processes as Example 1 to prepare the supported iron carbide composite, with the only difference being that the system pressure in step (12) is 1 atm and the treatment time is 0.5 h. The finally prepared supported iron carbide composite is labeled CX4-9.

[0186] Examples 4-10

[0187] This example uses substantially the same raw materials and processes as Example 1 to prepare the supported iron carbide composite, with the only difference being that the treatment temperature in step (12) is 185 °C and the treatment time is 1.5 h. The finally prepared supported iron carbide composite is labeled CX4-10.

[0188] Examples 4-11

[0189] This example uses substantially the same raw materials and processes as Example 1 to prepare the supported iron carbide composite, with the only difference being that the total gas flow rate in step (22) is 5000 mL / h / g. The finally prepared supported iron carbide composite is labeled CX4-11.

[0190] Example 5

[0191] Preparation of Supported ε / ε’-Iron Carbide Composite

[0192] (10) An iron-containing carrier is prepared using exactly the same raw materials and method as in step (10) of Example 1;

[0193] Manganese bromide and potassium citrate are dissolved in 100 ml of water to prepare an impregnation solution; the above-prepared iron-containing carrier is dispersed in the impregnation solution, and impregnation treatment is carried out by the slurry impregnation method. The impregnation ratio (molar ratio) is Fe:Br:K = 100:7:2.0, the impregnation temperature is 30 °C, and the impregnation time is 3 h; then it is dried in a vacuum drying oven at 35 °C and a vacuum degree of 300 Pa for 12 h to obtain a supported ε / ε’-precursor.

[0194] The supported ε / ε’-precursor is treated using exactly the same raw materials and processes as in steps (11) to (13) of Example 1 to prepare a supported ε / ε’-iron carbide composite.

[0195] Preparation of Supported χ-Iron Carbide Composite

[0196] (20) The supported χ-precursor is prepared using exactly the same raw materials and method as in step (10).

[0197] The supported χ-precursor is processed using exactly the same raw materials and process as in steps (21) to (23) of Example 1 to obtain a supported χ-iron carbide composite.

[0198] Preparation of the composition

[0199] The supported ε / ε'-iron carbide composite and the supported χ-iron carbide composite prepared above are mixed in a molar ratio of 1:2.5 (based on the number of moles of iron contained in each) to obtain an iron carbide composition, labeled as CX5.

[0200] Comparative Example 1

[0201] In this example, an iron carbide composition is prepared using substantially the same raw materials and process as in Example 1, except that: in the preparation of the composition, the impregnation ratio is Fe:Br:K = 100:50.0:2.0. The finally obtained iron carbide composition is labeled as DX1.

[0202] Comparative Example 2

[0203] In this example, an iron carbide composition is prepared using substantially the same raw materials and process as in Example 1, except that: in the preparation of the composition, manganese bromide is not added to the impregnation solution. The finally obtained iron carbide composition is labeled as D2.

[0204] Comparative Example 3

[0205] In this example, an iron carbide composition is prepared using substantially the same raw materials and process as in Example 1, except that: in the preparation of the composition, manganese chloride is used in an equimolar amount instead of manganese bromide to prepare the impregnation solution. The finally obtained iron carbide composition is labeled as DX3.

[0206] Comparative Example 4

[0207] In this example, supported ε / ε'-iron carbide and supported χ-iron carbide are prepared using the same raw materials and process as in Example 1. The supported ε / ε'-iron carbide and the supported χ-iron carbide are mixed in a molar ratio of 1:2.5 (based on the number of moles of iron contained in each) to obtain an iron carbide composition, labeled as D4.

[0208] Comparative Example 5

[0209] In this example, an iron carbide composition is prepared using substantially the same raw materials and process as in Example 1, except that: in steps (13) and (23), the molar ratios of H2 and CO in the second gas and the fourth gas are 7:1 and 130:1, respectively. The obtained iron carbide mixture is labeled as DX5.

[0210] The iron carbide composites, iron carbide, iron carbide compositions, etc. prepared in each example and comparative example were subjected to XRD, Mössbauer spectroscopy, and ICP measurements in the aforementioned manner. Among them, the total content of the target iron carbide (i.e., the total content of ε / ε'-iron carbide and χ-iron carbide) was calculated based on 100 mol, and the relevant contents all refer to the number of moles. The specific results are shown in Table 1.

[0211] The catalytic reaction performance of the iron carbide compositions prepared in each example and comparative example was evaluated separately in a slurry bed continuous reactor. The catalyst loading was 9.0 g. Evaluation conditions: T = 255 °C, P = 2.75 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.

[0212] Table 1

[0213]

[0214]

[0215] Table 2

[0216]

[0217]

[0218] Table 3

[0219]

[0220]

[0221] 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 synthesis gas 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 long-term experiments were carried out. From the data of the reaction at 300 h in Table 3, it can be seen that after the iron carbide composition of the examples of the present invention was continuously operated in a stirred tank for a long period as a catalyst, its CO conversion rate, product selectivity, carbon atom utilization efficiency, and effective product selectivity all remained 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 synthesis gas conversion reaction, the comprehensive optimization of the reaction results can be achieved.

[0222] Unless otherwise specified, the terms used in this invention have the meanings commonly understood by those skilled in the art.

[0223] The embodiments described in this invention are for illustrative purposes only and are not intended to limit the scope of protection of this invention. Those skilled in the art can make various other substitutions, changes, and improvements within the scope of this invention. Therefore, this invention is not limited to the above embodiments but is only defined by the claims.

Claims

1. A method for preparing a composition containing supported ε / ε’-iron carbide and χ-iron carbide, comprising: Preparation of supported ε / ε’-iron carbide composite; Preparation of supported χ-iron carbide composite; and mixing the supported ε / ε’-iron carbide composite with the supported χ-iron carbide composite to obtain a composition containing supported ε / ε’-iron carbide and χ-iron carbide; or, providing a supported iron carbide mixture including supported ε / ε’-iron carbide and supported χ-iron carbide, and impregnating the supported iron carbide mixture with a third halide solution to obtain a composition containing supported ε / ε’-iron carbide and χ-iron carbide; wherein the preparation of the supported ε / ε’-iron carbide composite or the supported ε / ε’-iron carbide includes the following steps: (10) Using an iron-containing carrier as the supported ε / ε’-precursor or using the iron-containing carrier as the supported ε / ε’-precursor after impregnating it with a first halide solution; (11) At 320 - 540 °C, reducing and surface-purifying the supported ε / ε’-precursor with hydrogen; (12) At 70 - 185 °C, treating the product of step (11) with a first gas; the first gas includes hydrogen and carbon monoxide, and the molar ratio of hydrogen to carbon monoxide is 1.2:1 to 2.8:1; (13) At 190 - 290 °C, treating the product of step (12) with a second gas; the second gas includes hydrogen and carbon monoxide, and the molar ratio of hydrogen to carbon monoxide is 1:1 to 3.2:1; wherein, when using the iron-containing carrier as the supported ε / ε’-precursor, the product obtained in step (13) is the supported ε / ε’-iron carbide; or, when using the iron-containing carrier as the supported ε / ε’-precursor, the product obtained in step (13) is the supported ε / ε’-iron carbide, and then impregnating the supported ε / ε’-iron carbide with the first halide solution to obtain the supported ε / ε’-iron carbide composite; The preparation process of the supported χ-iron carbide composite or the supported χ-iron carbide includes the following steps: (20) Using an iron-containing carrier as the supported χ-precursor or using the iron-containing carrier as the supported χ-precursor after impregnating it with a second halide solution; (21) At 350 - 600 °C, reducing and surface-purifying the supported χ-precursor with hydrogen; (22) At 0 - 41 °C, performing surface passivation treatment on the product of step (21) with a third gas; (23) At 260 - 430 °C, treating the product of step (22) with a fourth gas; Among them, the iron-containing carrier is used as the supported χ-precursor, and the product obtained in step (23) is the supported χ-iron carbide; or, the iron-containing carrier is used as the supported χ-precursor for the treatments of steps (21) and (22), the product of step (22) is impregnated with the second halide solution, and then the treatment of step (23) is carried out to obtain the supported χ-iron carbide composite; or, the iron-containing carrier is used as the supported χ-precursor, the product obtained in step (23) is the supported χ-iron carbide, and then the supported χ-iron carbide is impregnated with the second halide solution to obtain the supported χ-iron carbide composite; The third gas includes 1 to 3 vol% of oxygen and 97 to 99 vol% of inert gas; the fourth gas includes hydrogen and carbon monoxide, and the molar ratio of hydrogen to carbon monoxide is 7:1 to 110:1; Among them, the preparation method of the iron-containing carrier includes: carrying out a first impregnation treatment on the carrier in an iron salt solution, and then carrying out a drying treatment and a calcination treatment; the first halide solution contains bromide ions and / or iodide ions, the second halide solution contains bromide ions and / or iodide ions, the third halide solution contains iodide ions and / or bromide ions, and the iron salt solution contains iron ions.

2. The preparation method according to claim 1, wherein, The preparation raw materials of the iron salt solution include one or more of ammonium ferric citrate, ammonium ferrous sulfate, ferric chloride, and ferric nitrate; and / or, The preparation raw materials of the first halide solution include a first halide and an optional first soluble compound, the preparation raw materials of the second halide solution include a second halide and an optional second soluble compound, and the preparation raw materials of the third halide solution include a third halide and an optional third soluble compound; The first halide, the second halide, and the third halide each independently include one or more of bromides and iodides containing cobalt, rare earth metal elements, copper, iron, manganese, and molybdenum; The first soluble compound, the second soluble compound, and the third soluble compound each independently selected from one or more of salts of rare earth metals, alkali metals, manganese, copper, molybdenum, cobalt, and alkaline earth metals; 3. The preparation method according to claim 1, wherein, The carrier is selected from one or more of silicon dioxide, niobium pentoxide, zirconia, titanium dioxide, and alumina; and / or, The temperature of the calcination treatment is 220 to 530 °C; and / or, The particle size of the carrier is 30 to 200 μm; and / or, The treatment pressure of step (11) is 0.1 to 12 atm, and the treatment pressure of step (12) is 0.01 to 6 atm; the treatment pressure of step (13) is 0.13 to 12 atm; the treatment pressure of step (21) is 0.1 to 13 atm, the treatment pressure of step (22) is 0 to 1.2 atm, and the treatment pressure of step (23) is 0.08 to 13 atm.

4. A composition prepared by the preparation method according to any one of claims 1 to 3.

5. The composition according to claim 4, comprising supported ε / ε’-iron carbide, supported χ-iron carbide, halide ions and optionally promoter cations; wherein, The molar ratio of iron carbide to the halide ion and the promoter cation is 100:(0.12 - 44):(0 - 25). The molar number of iron carbide is based on the molar number of iron element contained in the composition. The halide ion is iodide ion and / or bromide ion.

6. The composition according to claim 5, wherein, The molar ratio of iron carbide to the halide ion is 100:(0.3 - 32), and the molar ratio of iron carbide to the promoter cation is 100:(0.1 - 21); and / or, The promoter cation includes one or more of the second metal ions. Further, the promoter cation includes one or more of copper ion, chromium ion, molybdenum ion, alkaline earth metal ion, alkali metal ion, rare earth ion, cobalt ion, and manganese ion.

7. A catalyst comprising the composition prepared by the preparation method according to any one of claims 1 to 3 or the composition according to any one of claims 4 to 6.

8. Use of the composition prepared by the preparation method according to any one of claims 1 to 3, the composition according to any one of claims 4 to 6, or the catalyst according to claim 7 in a syngas conversion reaction.

9. Use of the composition prepared by the preparation method according to any one of claims 1 to 3, the composition according to any one of claims 4 to 6, or the catalyst according to claim 7 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 7 with syngas under reaction conditions for reaction.

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