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

Abstract

The invention provides a composition containing epsilon / epsilon '-iron carbide and x-iron carbide as well as a preparation method and application thereof, the composition comprises epsilon / epsilon'-iron carbide, x-iron carbide and halogen elements, and the halogen elements are bromine elements and / or iodine elements; wherein the molar ratio of the iron element contained in the composition to the halogen element is 100: (0.12-47). The composition provided by one embodiment of the invention can be used as a catalyst for a synthesis gas conversion reaction, and halogen ions such as bromine or iodine are introduced into the components of the composition, 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 belongs to the field of syngas conversion, and relates to an iron carbide composition capable of being used for syngas conversion and a preparation method thereof. Background Art

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

[0003] To convert syngas into liquid fuels, a catalyst is required. Among them, iron-based catalysts are the cheapest and most readily available catalysts for syngas conversion. Iron-based catalysts have the advantages of high activity, a wide applicable condition window, strong sulfur tolerance, simple online catalyst replacement, and being suitable for industrial continuous production. However, one of the bottleneck problems in the traditional iron-based catalyst syngas conversion technology is the excessively high CO2 selectivity (usually accounting for 35 - 45% of the converted raw material CO).

[0004] The prior art discloses a high-purity iron carbide catalyst, which can reduce the primary CO2 in the Fischer-Tropsch synthesis reaction to nearly zero, and at the same time can achieve a high CO space-time conversion rate, thereby reducing the total CO2 selectivity to <5% at a low CO conversion rate (usually lower than 35%). However, when the CO conversion rate increases, as the H2O content in the reaction environment increases, the WGS reaction becomes intense, resulting in an increase in secondary CO2, and ultimately causing an increase in the total CO2 selectivity at a high CO conversion rate.

[0005] 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 prior art, on the one hand, an embodiment of the present invention provides a composition containing ε / ε'-iron carbide and χ-iron carbide, including ε / ε'-iron carbide, χ-iron carbide, and a halogen element, where the halogen element is bromine element and / or iodine element; wherein, the molar ratio of the iron element contained in the composition to the halogen element is 100:(0.12 - 47).

[0007] On the other hand, an embodiment of the present invention provides a preparation method of a metallic iron carbide composition containing ε / ε'-iron carbide and χ-iron carbide, including:

[0008] Providing a metallic ε / ε'-iron carbide composite and a metallic χ-iron carbide composite;

[0009] Mix the metallic ε / ε’-iron carbide composite and the metallic χ-iron carbide composite to obtain a metallic iron carbide composition containing ε / ε’-iron carbide and χ-iron carbide; or,

[0010] Impregnate the iron carbide mixture with a third halide solution to obtain a metallic iron carbide composition containing ε / ε’-iron carbide and χ-iron carbide; the iron carbide mixture includes a metallic ε / ε’-iron carbide and a metallic χ-iron carbide, and the third halide solution includes bromide ions and / or iodide ions;

[0011] Among them, the preparation process of the metallic ε / ε’-iron carbide composite or the metallic ε / ε’-iron carbide includes the following steps:

[0012] (11) Under the action of hydrogen at 250-490 °C, reduce the ε / ε’-precursor.

[0013] (12) At 75-175 °C, pretreat the reduction product of step (11) with a first mixed gas.

[0014] (13) At 175-280 °C, prepare a carbide from the pretreatment product of step (12) with a second mixed gas.

[0015] Among them, the first mixed gas includes H2 and CO with a molar ratio of (1.2-2.8):1, and the second mixed gas includes H2 and CO with a molar ratio of (1-3):1;

[0016] The ε / ε’-precursor is nano-iron and / or nano-iron compound impregnated with a first halide solution for the first time, and the product obtained in step (13) is the metallic ε / ε’-iron carbide composite; or, the ε / ε’-precursor is nano-iron and / or nano-iron compound, and the product obtained in step (13) is the metallic ε / ε’-iron carbide; or, the ε / ε’-precursor is nano-iron and / or nano-iron compound, the product obtained in step (13) is the metallic ε / ε’-iron carbide, and then the metallic ε / ε’-iron carbide is impregnated with the first halide solution for the first time to obtain the metallic ε / ε’-iron carbide composite; among them, the nano-iron compound can be reduced to obtain nano-iron, and the first halide solution includes bromide ions and / or iodide ions;

[0017] The preparation process of the metallic χ-iron carbide composite or the metallic χ-iron carbide includes the following steps:

[0018] (21) Under the action of hydrogen at 320-510 °C, reduce the χ-precursor.

[0019] (22) At 0 to 45 °C, the reduction treatment product of step (21) is treated with an oxygen-containing gas to obtain a surface passivation product; the oxygen-containing gas includes 1 vol% to 3 vol% of oxygen;

[0020] (23) At 250 to 430 °C, the surface passivation product of step (22) is subjected to a carbide preparation treatment with a third mixed gas; the third mixed gas includes hydrogen and carbon monoxide in a molar ratio of 8:1 to 100:1;

[0021] The χ-precursor is the nano-iron and / or the nano-iron compound subjected to a second impregnation treatment with a second halide solution, and the product obtained in step (23) is the metal-type χ-iron carbide composite; or, the χ-precursor is the nano-iron and / or the nano-iron compound, and the product obtained in step (23) is the metal-type χ-iron carbide; or, the χ-precursor is the nano-iron and / or the nano-iron compound, the surface passivation product is subjected to the second impregnation treatment with the second halide solution, and then the treatment of step (23) is carried out to obtain the metal-type χ-iron carbide composite; or, the χ-precursor is the nano-iron and / or the nano-iron compound, and the product obtained in step (23) is subjected to the second impregnation treatment with the second halide solution to obtain the metal-type χ-iron carbide composite; wherein, the second halide solution includes bromide ions and / or iodide ions.

[0022] In a third aspect, an embodiment of the present invention provides a catalyst, including the above composition or the composition prepared by the above preparation method.

[0023] In a fourth aspect, an embodiment of the present invention provides the application of the above composition, the composition prepared by the above preparation method, or the above catalyst in a syngas conversion reaction.

[0024] In a fifth aspect, an embodiment of the present invention provides the application of the above composition, the composition prepared by the above preparation method, or the above catalyst in a reaction for synthesizing C, H fuels and / or chemicals based on the Fischer-Tropsch synthesis principle.

[0025] In a sixth aspect, an embodiment of the present invention provides a syngas conversion process, including contacting the above catalyst with syngas under reaction conditions for reaction.

[0026] A ferric carbide composition according to an embodiment of the present invention can be used as a catalyst for syngas conversion reactions, especially Fischer-Tropsch synthesis reactions. By introducing halogen ions such as bromine or iodine into the ferric 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

[0027] The drawings are only for the purpose of illustrating specific embodiments and are not considered to be a limitation of the present invention. Among them:

[0028] Figure 1 is the XRD pattern of the ε / ε’-ferric carbide composite of Example 5 of the present invention;

[0029] Figure 2 is the XRD pattern of the χ-ferric carbide composite of Example 5 of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0030] 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.

[0031] An embodiment of the present invention provides a ferric carbide composition, comprising ε / ε’-ferric carbide, χ-ferric carbide, and a halogen element, wherein the halogen element is bromine element and / or iodine element; wherein, the molar ratio of the iron element to the halogen element contained in the composition is 100:(0.12 - 47).

[0032] In one embodiment, the halogen element exists in the form of halogen ions, which can be bromide ions and / or iodide ions. The molar ratio of the iron element to the halogen element (or halogen ions) in the ferric carbide composition can be 100:(0.12 - 47), further can be 100:(0.3 - 35), and still further can be 100:(7 - 20), such as 100:0.5, 100:1, 100:5, 100:10, 100:15, 100:20, 100:25, 100:30, 100:40.

[0033] In one embodiment, the ferric carbide composition further comprises a promoter metal element, and the promoter metal element exists in the form of metal ions (promoter metal ions). The molar ratio of the iron element to the promoter metal element (or promoter metal ions) in the ferric carbide composition can be 100:(0.1 - 22), further can be 100:(0.1 - 18), and still further can be 100:(3 - 10), such as 100:0.5, 100:1, 100:5, 100:10, 100:15, 100:20.

[0034] In one embodiment, the promoter metal element is selected from one or more of manganese, copper, cobalt, molybdenum, chromium, rare earth elements, alkali metal elements, and alkaline earth metal elements; preferably, the promoter metal element is selected from one or more of manganese, copper, cobalt, molybdenum, chromium, lanthanum, cerium, neodymium, sodium, potassium, calcium, and barium.

[0035] In one embodiment, the iron carbide composition includes an ε / ε’-iron carbide complex and a χ-iron carbide complex. The ε / ε’-iron carbide complex includes ε / ε’-iron carbide, a first halogen element, and an optional first promoter metal element; the χ-iron carbide complex includes χ-iron carbide, a second halogen element, and an optional second promoter metal element; the first halogen element and the second halogen element are each independently bromine and / or iodine;

[0036] The sum of the molar amounts of ε / ε’-iron carbide and χ-iron carbide is the same as the molar amount of iron element contained in the composition, and the molar amounts of ε / ε’-iron carbide and χ-iron carbide are based on the molar amount of iron element contained therein; the sum of the molar amounts of the first halogen element and the second halogen element is the same as the molar amount of the halogen element contained in the composition; the sum of the molar amounts of the first promoter metal element and the second promoter metal element is the same as the molar amount of the promoter metal element contained in the composition.

[0037] In one embodiment, the halogen element contained in the iron carbide composition consists of the first halogen element and the second halogen element, and the promoter metal element consists of the first promoter metal element and the second promoter metal element.

[0038] In one embodiment, the first promoter metal element and the second promoter metal exist in the form of metal ions (the first promoter metal ion and the second promoter metal ion) respectively; the first halogen element and the second halogen element exist in the form of halide ions (the first halide ion and the second halide ion) respectively, and both can be bromide ions and / or iodide ions.

[0039] In one embodiment, the first promoter metal element and the second promoter metal element can be of the same type as the promoter metal element.

[0040] In one embodiment, ε / ε’-iron carbide (or the ε / ε’-iron carbide complex) has a hexagonal, pseudo-hexagonal or trigonal crystal system structure, and χ-iron carbide (or the χ-iron carbide complex) has a monoclinic crystal system structure.

[0041] In one embodiment, the grain diameter of ε / ε’-iron carbide or the ε / ε’-iron carbide complex is 5 - 30 nm, and further can be 8 - 26 nm; the grain diameter of χ-iron carbide or the χ-iron carbide complex is 6 - 35 nm, and further can be 9 - 28 nm.

[0042] In one embodiment, the iron carbide composition includes halide cations, and the halide cations can maintain charge balance with halide anions, that is, the total number of negative charges carried by the halide anions (or the total number of displayed valences) is equal to the total number of positive charges carried by the halide cations.

[0043] In one embodiment, the iron carbide composition includes promoter anions, and promoter metal ions can maintain charge balance with the promoter anions.

[0044] In one embodiment, based on the number of moles of iron carbide (100%) in the iron carbide composition, the molar content of ε / ε'-iron carbide is a, and the molar content of 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 the ε / ε'-iron carbide composition is a, and the molar content of the 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 ε / ε'-iron carbide, metallic χ-iron carbide, metallic ε / ε'-iron carbide complex, and metallic χ-iron carbide complex are calculated based on the number of moles of iron element contained in each.

[0045] In one embodiment, the ε / ε'-iron carbide complex includes a first halide cation, and the first halide cation can maintain charge balance with a first halide anion, that is, the total number of negative charges carried by the first halide anion (or the total number of displayed valences) is equal to the total number of positive charges carried by the first halide cation.

[0046] In one embodiment, the ε / ε'-iron carbide complex further includes a first promoter anion, and the first promoter anion can maintain charge balance with a first promoter metal ion.

[0047] In one embodiment, the χ-iron carbide complex includes a second halide cation, and the second halide cation can maintain charge balance with a second halide anion, that is, the total number of negative charges carried by the second halide anion (or the total number of displayed valences) is equal to the total number of positive charges carried by the second halide cation.

[0048] In one embodiment, the χ-iron carbide complex further includes a second promoter anion, and the second promoter anion can maintain charge balance with a second promoter metal ion.

[0049] In one embodiment, the halide cations are composed of a first halide cation and a second halide cation, and the promoter anions are composed of a first promoter anion and a second promoter anion.

[0050] In one embodiment, each of the halide cations, the first halide cation, and the second halide cation may include one or more of metal ions and complex cations. Further, each of the halide cations, the first halide cation, and the second halide cation may include 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), hexaammine manganese ions, hexaammine iron ions, and hexaammine copper ions.

[0051] In one embodiment, each of the promoter metal ions, the first promoter metal ion, and the second promoter metal ion 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. Each of the promoter metal ions, the first promoter metal ion, and the second promoter metal ion may include 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.

[0052] In one embodiment, each of the promoter anions, the first promoter anion, and the second promoter anion may include one or more of oxygen ions, complex ions, and acid radical ions, such as nitrate, citrate, and gluconate.

[0053] One embodiment of the present invention provides a method for preparing the above-mentioned metal-type iron carbide composition, including:

[0054] Providing a metal-type ε / ε'-iron carbide complex and a metal-type χ-iron carbide complex respectively; and

[0055] Mixing the metal-type ε / ε'-iron carbide complex and the metal-type χ-iron carbide complex to obtain a metal-type iron carbide composition containing ε / ε'-iron carbide and χ-iron carbide; or,

[0056] Providing an iron carbide mixture, the iron carbide mixture including metal-type ε / ε'-iron carbide and metal-type χ-iron carbide; and

[0057] The iron carbide mixture is subjected to a third impregnation treatment with a third halide solution to obtain a metallic iron carbide composition containing ε / ε'-iron carbide and χ-iron carbide; the third halide solution includes bromide ions and / or iodide ions;

[0058] Among them, the preparation process of the metallic ε / ε'-iron carbide complex or metallic ε / ε'-iron carbide includes the following steps:

[0059] (11) Under the action of hydrogen at 250-490 °C, the ε / ε'-precursor is subjected to a reduction treatment;

[0060] (12) At 75-175 °C, the reduction treatment product of step (11) is pretreated with a first mixed gas;

[0061] (13) At 175-280 °C, the pretreatment product of step (12) is subjected to a carbide preparation treatment with a second mixed gas;

[0062] Among them, the first mixed gas includes hydrogen and carbon monoxide with a molar ratio of (1.2-2.8):1, and the second mixed gas includes hydrogen and carbon monoxide with a molar ratio of (1-3):1;

[0063] The ε / ε'-precursor is nano-iron and / or nano-iron compound impregnated with a first halide solution for the first time, and the product obtained in step (13) is a metallic ε / ε'-iron carbide complex; or, the ε / ε'-precursor is nano-iron and / or nano-iron compound, and the product obtained in step (13) is metallic ε / ε'-iron carbide; or, the ε / ε'-precursor is nano-iron and / or nano-iron compound, the product obtained in step (13) is metallic ε / ε'-iron carbide, and then the metallic ε / ε'-iron carbide is impregnated with a first halide solution for the first time to obtain a metallic ε / ε'-iron carbide complex; among them, the nano-iron compound can be reduced to obtain nano-iron, and the first halide solution includes bromide ions and / or iodide ions;

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

[0065] (21) Under the action of hydrogen at 320-510 °C, the χ-precursor is subjected to a reduction treatment;

[0066] (22) At 0-45 °C, the reduction treatment product of step (21) is treated with an oxygen-containing gas to obtain a surface passivation product; the oxygen-containing gas includes 1 vol% to 3 vol% of oxygen;

[0067] (23) At 250 - 430 °C, the surface passivation product of step (22) is subjected to carbide preparation treatment with a third mixed gas; the third mixed gas includes hydrogen and carbon monoxide with a molar ratio of 8:1 to 100:1;

[0068] The χ-precursor is nano-iron and / or nano-iron compound subjected to a second impregnation treatment with a second halide solution, and the product obtained in step (23) is a metallic χ-iron carbide composite; or, the χ-precursor is nano-iron and / or nano-iron compound, and the product obtained in step (23) is metallic χ-iron carbide; or, the χ-precursor is nano-iron and / or the nano-iron compound, the surface passivation product is subjected to a second impregnation treatment with a second halide solution, and then the treatment of step (23) is carried out to obtain a metallic χ-iron carbide composite; or, the χ-precursor is nano-iron and / or nano-iron compound, and the product obtained in step (23) is subjected to a second impregnation treatment with a second halide solution to obtain a metallic χ-iron carbide composite; wherein, the second halide solution includes bromide ions and / or iodide ions.

[0069] In one embodiment, the nano-iron compound includes one or more of nano-iron oxide, nano-magnetite, nano-goethite, and nano-iron hydroxide oxide.

[0070] In one embodiment, the nano-iron or nano-iron compound can be nano-iron powder and / or nano-iron particles.

[0071] In one embodiment, the average grain diameter of the nano-iron or nano-iron compound is 6 - 35 nm, further it can be 9 - 28 nm, such as 10 nm, 12 nm, 15 nm, 18 nm, 20 nm, 22 nm, 25 nm, 30 nm, 32 nm.

[0072] In one embodiment, the raw materials for preparing the first halide solution include a first halide and a first solvent, the raw materials for preparing the second halide solution include a second halide and a second solvent, and the raw materials for preparing the third halide solution include a third halide and a third solvent; the first halide, the second halide, and the third halide are all water-soluble halides, including bromides and / or iodides.

[0073] 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, iron, molybdenum, copper, manganese, rare earth metal elements. Further, the first halide, the second halide, and the third halide each independently include one or more of manganese bromide, ferrous bromide, copper bromide, cobalt bromide, molybdenum bromide, manganese iodide, ferrous iodide, copper iodide, rare earth bromides, rare earth iodides, hexaammine manganese bromide, hexaammine iron bromide, hexaammine copper bromide, hexaammine manganese iodide, hexaammine iron iodide, hexaammine copper iodide.

[0074] In one embodiment, the raw materials for preparing the first halide solution further include a first auxiliary compound, the raw materials for preparing the second halide solution further include a second auxiliary compound, and the raw materials for preparing the third halide solution further include a third auxiliary compound.

[0075] In one embodiment, the first auxiliary compound, the second auxiliary compound, and the third auxiliary compound are each independently selected from 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 auxiliary compound, the second auxiliary compound, and the third auxiliary compound are each independently selected from 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, and the third solvent each independently include water and / or ethanol. For example, the first solvent, the second solvent, and the third solvent can all be water or a mixture of ethanol and water.

[0078] In one embodiment, the amounts of the first halide, the second halide, the third halide, the first auxiliary compound, the second auxiliary compound, and the third auxiliary 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 auxiliary compound, the second auxiliary compound, and the third auxiliary compound can all be 0.7 - 7 mol / L, such as 1 mol / L, 2 mol / L, 3 mol / L, 5 mol / L, and 6 mol / L.

[0079] In one embodiment, the temperature of the first impregnation treatment, the second impregnation treatment, or the third impregnation treatment is 0 - 50 °C, further can be 20 - 30 °C, such as 10 °C, 15 °C, 20 °C, 25 °C, 30 °C, 35 °C, 40 °C, 45 °C; the time of the first impregnation treatment, the second impregnation treatment, or the third 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, any impregnated material can be dried at 15 - 40°C, and further dried under light - proof 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 process 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 metallic ε / ε’ - iron carbide composite or metallic ε / ε’ - iron carbide, the treatment temperature in step (11) can be 250 - 490°C, such as 280°C, 300°C, 310°C, 320°C, 350°C, 370°C, 400°C, 420°C, 450°C, 480°C; the treatment pressure can be 0.1 - 13 atm, further can be 0.2 - 2.7 atm, such as 0.15 atm, 0.2 atm, 0.5 atm, 0.8 atm, 1 atm, 1.5 atm, 2 atm, 5 atm, 8 atm, 10 atm; the treatment time can be 0.5 - 8 h, further can be 1 - 7 h, such as 2 h, 3 h, 4 h, 5 h, 6 h.

[0083] In one embodiment, in the preparation of the metallic ε / ε’ - iron carbide composite or metallic ε / ε’ - iron carbide, the gas flow rate of H2 in step (11) can be 500 - 20000 mL / h / g, further can be 2500 - 15000 mL / h / g, such as 800 mL / h / g, 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.

[0084] In one embodiment, in the preparation of the metallic ε / ε’ - iron carbide composite or metallic ε / ε’ - iron carbide, the first mixed gas in step (12) includes hydrogen and carbon monoxide, and the molar ratio of hydrogen to carbon monoxide can be 1.2:1 - 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.

[0085] In one embodiment, in the preparation of the metallic ε / ε'-iron carbide composite or metallic ε / ε'-iron carbide, the treatment temperature in step (12) can be 75 to 175 °C, such as 80 °C, 90 °C, 100 °C, 110 °C, 120 °C, 130 °C, 150 °C, 160 °C; the treatment pressure can be 0.05 to 5 atm, further can be 0.05 to 2.5 atm, such as 0.06 atm, 0.08 atm, 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, 5 atm; the treatment time can be 15 to 90 min, further can be 25 to 70 min, such as 30 min, 35 min, 40 min, 45 min, 50 min, 55 min, 60 min, 80 min.

[0086] In one embodiment, in the preparation of the metallic ε / ε'-iron carbide composite or metallic ε / ε'-iron carbide, the gas flow rate of the first mixed gas in step (12) can be 200 to 8000 mL / h / g, further can be 1000 to 6500 mL / h / g, such as 500 mL / h / g, 1200 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.

[0087] In one embodiment, in the preparation of the metallic ε / ε'-iron carbide composite or metallic ε / ε'-iron carbide, the molar ratio of hydrogen to carbon monoxide in the second mixed 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. The second mixed gas can be a mixture of hydrogen and carbon monoxide.

[0088] In one embodiment, in the preparation of the metallic ε / ε'-iron carbide composite or metallic ε / ε'-iron carbide, the treatment temperature in step (13) can be 175 to 280 °C, such as 200 °C, 210 °C, 230 °C, 250 °C, 260 °C, 270 °C; the treatment pressure can be 0.11 to 9 atm, further can be 0.15 to 3 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, 2.8 atm, 5 atm, 8 atm; the treatment time can be 0.5 to 10 h, further can be 1.5 to 8 h, such as 1 h, 1.8 h, 2 h, 2.5 h, 3 h, 4 h, 5 h, 6 h, 9 h.

[0089] In one embodiment, in the preparation of the metallic ε / ε'-iron carbide composite or metallic ε / ε'-iron carbide, the gas flow rate of the second mixed gas in step (13) can be 200 to 20000 mL / h / g, further can be 4000 to 15000 mL / h / g, such as 1000 mL / h / g, 3000 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.

[0090] In one embodiment, in the preparation of the metallic ε / ε'-iron carbide composite or metallic ε / ε'-iron carbide, in step (13), the temperature of the system is raised from 75 to 175 °C to 175 to 280 °C at a heating rate of 0.2 to 5 °C / min. Further, the temperature of the system is raised from 75 to 175 °C to 200 to 270 °C at a heating rate of 0.2 to 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 metallic χ-iron carbide composite or metallic χ-iron carbide, the temperature of the reduction and surface purification treatment in step (21) can be 320 to 510 °C, such as 350 °C, 360 °C, 380 °C, 390 °C, 400 °C, 420 °C, 450 °C, 480 °C, 500 °C; the treatment pressure can be 0.15 to 15 atm, further can be 0.22 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, 5 atm, 8 atm, 10 atm, 15 atm; the treatment time can be 1.2 to 30 h, further can be 2 to 12 h, such as 5 h, 8 h, 10 h, 15 h, 20 h, 25 h.

[0092] In one embodiment, in the preparation of the metallic χ-iron carbide composite or metallic χ-iron carbide, the gas flow rate of H2 in step (21) can be 600 to 25000 mL / h / g, further can be 1200 to 16000 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.

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

[0094] In one embodiment, in the preparation of the metal-type χ-iron carbide composite or the metal-type χ-iron carbide, the temperature of the surface passivation treatment in step (22) 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, or 45 °C; the treatment pressure can be 0 to 1.3 atm, further 0 to 0.09 atm, such as 0.01 atm, 0.02 atm, 0.05 atm, 0.06 atm, 0.08 atm, or 1 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, or 70 h.

[0095] In one embodiment, in the preparation of the metal-type χ-iron carbide composite or the metal-type χ-iron carbide, the gas flow rate of the first oxygen-containing gas in step (22) 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, or 10000 mL / h / g.

[0096] In one embodiment, in the preparation of the metal-type χ-iron carbide composite or the metal-type χ-iron carbide, the molar ratio of hydrogen to carbon monoxide in the third mixed gas in step (23) can be 10:1, 20:1, 30:1, 36:1, 40:1, 50:1, 60:1, or 80:1. The third mixed gas can be a mixture of hydrogen and carbon monoxide.

[0097] In one embodiment, in the preparation of the metal-type χ-iron carbide composite or the metal-type χ-iron carbide, the treatment temperature in step (23) can be 250 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 10 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 metal-type χ-iron carbide composite or the metal-type χ-iron carbide, the gas flow rate of the third mixed gas in step (23) 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.

[0099] In one embodiment, in the preparation of the metal-type χ-iron carbide composite or the metal-type χ-iron carbide, in step (23), the temperature of the system is raised from 0 to 45 °C to 250 to 430 °C at a heating rate of 0.2 to 5 °C / min, and further, the temperature of the system is raised from 0 to 45 °C to 260 to 400 °C at a heating rate of 0.2 to 2.5 °C / min; the heating rate in 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 metal-type ε / ε'-iron carbide composite includes the following steps:

[0102] (10) Performing a first impregnation treatment on the nano-iron and / or nano-iron compound with a first halide solution to obtain a to-be-treated ε / ε'-precursor;

[0103] (11) Under the action of hydrogen at 250 - 490 °C, the ε / ε'-precursor is subjected to a reduction treatment;

[0104] (12) At 75 - 175 °C, the reduction treatment product of step (11) is pretreated with a first mixed gas;

[0105] (13) At 175 - 280 °C, the pretreatment product of step (12) is subjected to a carbide preparation treatment with a second mixed gas to obtain a metallic ε / ε'-iron carbide composite.

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

[0107] (11) Under the action of hydrogen at 250 - 490 °C, the ε / ε'-precursor (nano-iron and / or nano-iron compound) is subjected to a reduction treatment;

[0108] (12) At 75 - 175 °C, the reduction treatment product of step (11) is pretreated with a first mixed gas;

[0109] (13) At 175 - 280 °C, the pretreatment product of step (12) is subjected to a carbide preparation treatment with a second mixed gas to obtain ε / ε'-iron carbide.

[0110] In one embodiment, the preparation process of the metallic χ-iron carbide composite includes the following steps:

[0111] (20) The nano-iron and / or nano-iron compound is subjected to a second impregnation treatment with a second halide solution to obtain a χ-precursor to be treated;

[0112] (21) Under the action of hydrogen at 320 - 510 °C, the χ-precursor is subjected to a reduction treatment;

[0113] (22) At 0 - 45 °C, the reduction treatment product of step (21) is treated with an oxygen-containing gas to obtain a surface passivation product;

[0114] (23) At 250 - 430 °C, the surface passivation product of step (22) is subjected to a carbide preparation treatment with a third mixed gas to form a metallic χ-iron carbide composite.

[0115] In one embodiment, the preparation process of the metallic χ-iron carbide includes the following steps:

[0116] (21) Under the action of hydrogen at 320 - 510 °C, the χ-precursor (nano-iron and / or nano-iron compound) is subjected to a reduction treatment;

[0117] (22) At 0 - 45 °C, the reduction treatment product from step (21) is treated with an oxygen-containing gas to obtain a surface passivation product;

[0118] (23) At 250 - 430 °C, the surface passivation product from step (22) is subjected to a carbide preparation treatment with a third mixed gas to form metallic χ-iron carbide.

[0119] An embodiment of the present invention provides a catalyst comprising the above-mentioned iron carbide composition.

[0120] An embodiment of the present invention provides the application of the above-mentioned iron carbide composition or catalyst in the synthesis gas conversion reaction.

[0121] 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 using synthesis gas as the starting material and the final product being an alcohol.

[0122] In one embodiment, the synthesis gas comprises CO and H2.

[0123] An embodiment of the present invention provides the application 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 using synthesis gas (a mixture of CO and H2) as the raw material, under the action of a catalyst and appropriate conditions, through CO hydrogenation and carbon chain growth reactions to generate chain hydrocarbons and / or their oxygen-containing derivatives.

[0124] In one embodiment, the above reaction is a Fischer-Tropsch synthesis reaction, the reaction temperature can be 240 - 285 °C, such as 250 °C, 260 °C, 270 °C, 280 °C; the reaction pressure can be 2 - 3.5 MPa, and the molar ratio of H2 / CO can be 1.7 - 2.15.

[0125] 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.

[0126] In one embodiment, the synthesis gas conversion can be carried out in a high-temperature and high-pressure continuous reactor.

[0127] 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 halogen 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.

[0128] 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 an extremely low CO₂ selectivity at a high CO conversion rate, while maintaining a low CH₄ selectivity and relatively 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, diversified and low-carbon clean conversion of syngas, indicating new trends and directions for the development of modern syngas chemical industry.

[0129] 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 in an industrial Fischer-Tropsch synthesis reaction condition using a high-pressure continuous reactor. Its CO₂ selectivity is below 5%, and further below 3%; the selectivity of by-product CH₄ can be maintained below 8.5%, and further below 5.5%; the utilization efficiency of carbon atoms is maintained above 95%, and further above 97%; the selectivity of effective products can reach above 86.5%, and further above 92%.

[0130] In one embodiment, through the Fischer-Tropsch synthesis reaction catalyzed by the iron carbide composition, a CO₂ selectivity of <5%, a carbon atom utilization efficiency of >95%, and an effective product selectivity of >90% can be achieved at a CO conversion rate of more than 70%.

[0131] 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 ionic bond + and Br atoms that interact with H atoms by covalent bond.

[0132] All pressure values involved herein are gauge pressures.

[0133] Hereinafter, in conjunction with the accompanying 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:

[0134] 1. During the reaction process of the examples or comparative examples, an in-situ XRD detector, an X-ray diffractometer (manufactured by Rigaku Corporation, model D / max-2600 / PC), was used to monitor the phase change of the materials, and the crystal system structure of each iron carbide complex was measured by the X-ray diffractometer.

[0135] 2. The average grain diameter of each iron carbide or its complex was obtained through XRD testing.

[0136] 3. A Mössbauer spectrometer (Transmission 57 Fe, 57The Mössbauer spectroscopy of the iron carbide composition was performed using a Co(Rh) source sinusoidal velocity spectrometer to obtain the corresponding composition.

[0137] 4. The elemental analysis of the iron carbide composition was carried out using an Inductive Coupled Plasma Emission Spectrometer (ICP).

[0138] 5. During the conversion reaction of syngas, the products obtained from the reaction were analyzed by gas chromatography (Agilent 7890 gas chromatography) to calculate 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.

[0139] 6. The CO conversion rate %, CO2 selectivity %, CH4 selectivity %, carbon atom utilization efficiency %, and effective product selectivity % were calculated using the following formulas:

[0140] CO conversion rate % = [(moles of CO in feed - moles of CO in product) / moles of CO in feed] × 100%;

[0141] CO2 selectivity % = [moles of CO2 in product / (moles of CO in feed - moles of CO in product)] × 100%;

[0142] CH4 selectivity % = [moles of CH4 in product / (moles of CO in feed - moles of CO in product)] × 100%;

[0143] Carbon atom utilization efficiency % = (1 - CO2 selectivity %) × 100%;

[0144] Effective product selectivity % = (1 - CO2 selectivity % - CH4 selectivity %) × 100%.

[0145] Example 1

[0146] Preparation of metallic ε / ε'-iron carbide

[0147] (11) 5.6 g of nano iron particles with an average grain diameter of 20 nm were taken as the ε / ε'-precursor; at a temperature of 390 °C and a pressure of 3.1 atm, the ε / ε'-precursor was maintained in H2 with a flow rate of 9000 mL / h / g for 3 h for reduction and surface purification treatment.

[0148] (12) Cool the product obtained in step (11) to 170 °C and contact it with the first mixed gas at this temperature for pretreatment; wherein, the pressure of the system is 2.0 atm, the flow rate of the first mixed gas is 5000 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.

[0149] (13) Contact the product obtained in step (12) with the second mixed gas. The pressure of the system is 3.0 atm, and the total gas flow rate is 10000 mL / h / g. Under this condition, the system is heated to 250 °C at a heating rate of 1 °C / min to prepare carbides; wherein, the second mixed gas is a mixed gas of H2 and CO, and the molar ratio of H2 to CO is 1.5:1. The treatment time of the material at 250 °C is 6 h. After the treatment is completed, metallic ε / ε'-iron carbide is prepared and labeled as ε / ε'-C1.

[0150] Preparation of metallic χ-iron carbide

[0151] (21) Take 5.6 g of nano-iron particles with an average grain diameter of 20 nm as the χ-precursor; at a pressure of 420 °C and 2.0 atm, keep the χ-precursor in H2 with a flow rate of 10000 mL / h / g for 2 h to carry out reduction and surface purification treatment.

[0152] (22) Cool the product obtained in step (21) to 30 °C and contact it with an oxygen-containing gas at this temperature for surface passivation treatment to obtain a surface passivated product; wherein, the pressure of the system is 0.1 atm, the gas flow rate is 7500 mL / h / g, and the treatment time is 12 h; the oxygen-containing gas includes 1 vol% oxygen and 99 vol% nitrogen.

[0153] (23) Contact the surface passivated product with the third 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, the system is heated from 30 °C to 350 °C at a heating rate of 2.0 °C / min to carry out carbide preparation; wherein, the third mixed gas is a mixed gas of H2 and CO, and the molar ratio of H2 to CO is 50:1. The treatment time of the material at 350 °C is 6 h; after the treatment is completed, metallic χ-iron carbide is prepared and labeled as χ-C1.

[0154] Preparation of the composition

[0155] The as-prepared metallic ε / ε’-iron carbide and metallic χ-iron carbide were mixed at a molar ratio of 1:3 (based on the number of moles of iron contained in each) to obtain an iron carbide mixture. Manganese bromide and potassium nitrate were dissolved in 50 ml of water to prepare a third halide solution. The iron carbide mixture was impregnated with the third halide solution, and the impregnation ratio (molar ratio) was Fe:Br:K = 100:7.0:2.0. The impregnation temperature was 32 °C and the impregnation time was 2 h. The impregnated solid material was dried at 25 °C and 0.05 atm for 5 h to obtain an iron carbide composition, labeled as CX1.

[0156] 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 metal ions in each impregnating solution was different, and the compositions obtained 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 dosage of the corresponding raw materials. For specific content values, see Table 1.

[0157] Example 4

[0158] Preparation of Metallic ε / ε’-Iron Carbide Composite

[0159] (10) Copper nitrate, potassium citrate and manganese bromide were dissolved in 50 ml of water to prepare a first halide solution. 8.0 g of nano-iron oxide particles with an average grain diameter of 17 nm were taken, and the first halide solution was mixed with the nano-iron oxide particles, and impregnation treatment was carried out by the slurry impregnation method. The impregnation ratio (molar ratio) was Fe:Br:K:Cu = 100:15.0:3.0:9.0. The impregnation temperature was 37 °C and the impregnation time was 3 h. The impregnated solid material was dried at 25 °C and 0.05 atm for 5 h to obtain an ε / ε’-precursor.

[0160] (11) At a temperature of 420 °C and a pressure of 3.0 atm, the ε / ε’-precursor prepared in step (10) was maintained in H2 with a flow rate of 10000 mL / h / g for 3 h for reduction and surface purification treatment.

[0161] (12) The product obtained in step (11) was cooled to 170 °C and contacted with a first mixed gas for pretreatment at this temperature. Among them, the pressure of the system was 2.0 atm, the flow rate of the first mixed gas was 8000 mL / h / g, and the treatment time was 1 h. The first mixed gas was a mixed gas of H2 and CO, and the molar ratio of H2 to CO was 2:1.

[0162] (13) The product obtained in step (12) is contacted with a second mixed gas phase. The pressure of the system is 3.0 atm, and the total gas flow rate is 12000 mL / h / g. Under this condition, the system is heated to 250 °C at a heating rate of 1 °C / min for the preparation of carbide; wherein, the second mixed gas is a mixture of H2 and CO, and the molar ratio of H2 to CO is 1.5:1. The treatment time of the material at 250 °C is 8 h. After the treatment is completed, an ε / ε'-iron carbide composite is prepared.

[0163] Preparation of metallic χ-iron carbide composite

[0164] (20) A χ-precursor is prepared using exactly the same raw materials and method as in step (10).

[0165] (21) At a temperature of 430 °C and a pressure of 3.0 atm, the χ-precursor prepared in step (20) is maintained in H2 with a flow rate of 12000 mL / h / g for 2 h for reduction and surface purification treatment.

[0166] (22) The product of step (21) is cooled to 30 °C and contacted with an oxygen-containing gas at this temperature for surface passivation treatment to obtain a surface passivated product; wherein, the pressure of the system is 0.1 atm, the gas flow rate is 7500 mL / h / g, and the treatment time is 12 h; the oxygen-containing gas includes 2 vol% oxygen and 98 vol% nitrogen.

[0167] (23) The surface passivated product is contacted with a third mixed gas phase. The pressure of the system is 2.1 atm, and the total gas flow rate is 13000 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 third mixed gas is a mixture of H2 and CO, and the molar ratio of H2 to CO is 30:1. The treatment time of the material at 350 °C is 6 h; after the treatment is completed, a χ-iron carbide composite is prepared.

[0168] Preparation of the composition

[0169] The above-prepared metallic ε / ε'-iron carbide composite and metallic χ-iron carbide composite are mixed in a molar ratio of 1:3 (based on the number of moles of iron contained in each) to prepare an iron carbide composition, labeled as CX4.

[0170] Example 4-1

[0171] In this example, an iron carbide composition is prepared using basically the same raw materials and process as in Example 1, except that: the H2 flow rate in step (11) is 2500 mL / h / g; the H2 flow rate in step (21) is 1200 mL / h / g. The finally prepared iron carbide composition is labeled as CX4-1.

[0172] Example 4-2

[0173] This example uses substantially the same raw materials and process as Example 1 to prepare the iron carbide composition, with the only differences being: in step (11), the H2 flow rate is 15000 mL / h / g; in step (21), the H2 flow rate is 15000 mL / h / g. The finally obtained iron carbide composition is labeled as CX4-2.

[0174] Example 4-3

[0175] This example uses substantially the same raw materials and process as Example 1 to prepare the iron carbide composition, with the only differences being: in step (11), the H2 flow rate is 10000 mL / h / g; in step (21), the H2 flow rate is 10000 mL / h / g. The finally obtained iron carbide composition is labeled as CX4-3.

[0176] Example 4-4

[0177] This example uses substantially the same raw materials and process as Example 1 to prepare the iron carbide composition, with the only differences being: in step (13), the carbonization temperature is 280 °C; in step (23), the carbonization temperature is 430 °C. The finally obtained iron carbide composition is labeled as CX4-4.

[0178] Example 4-5

[0179] This example uses substantially the same raw materials and process as Example 1 to prepare the iron carbide composition, with the only differences being: in step (13), the carbonization temperature is 175 °C; in step (23), the carbonization temperature is 250 °C. The finally obtained iron carbide composition is labeled as CX4-5.

[0180] Example 4-6

[0181] This example uses substantially the same raw materials and process as Example 1 to prepare the iron carbide composition, with the only differences being: in step (13), the carbonization temperature is 245 °C; in step (23), the carbonization temperature is 360 °C. The finally obtained iron carbide composition is labeled as CX4-6.

[0182] Example 4-7

[0183] This example uses substantially the same raw materials and process as Example 1 to prepare the iron carbide composition, with the only differences being: in step (11), the reduction temperature is 250 °C; in step (21), the reduction temperature is 320 °C. The finally obtained iron carbide composition is labeled as CX4-7.

[0184] Example 4-8

[0185] This example uses substantially the same raw materials and process as Example 1 to prepare an iron carbide composition, with the only differences being that: in step (13), the carbonization pressure is 3 atm; in step (23), the carbonization pressure is 2.5 atm. The finally prepared iron carbide composition is labeled as CX4-8.

[0186] Examples 4-9

[0187] This example uses substantially the same raw materials and process as Example 1 to prepare an iron carbide composition, with the only differences being that: in step (11), the reduction time is 7 h; in step (21), the reduction time is 12 h. The finally prepared iron carbide composition is labeled as CX4-9.

[0188] Examples 4-10

[0189] This example uses substantially the same raw materials and process as Example 1 to prepare an iron carbide composition, with the only differences being that: in step (13), the carbonization time is 8 h; in step (23), the reduction time is 0.5 h. The finally prepared iron carbide composition is labeled as CX4-10.

[0190] Examples 4-11

[0191] This example uses substantially the same raw materials and process as Example 1 to prepare an iron carbide composition, with the only differences being that: in step (11), the reduction pressure is 2.7 atm; in step (21), the reduction pressure is 2.5 atm. The finally prepared iron carbide composition is labeled as CX4-11.

[0192] Examples 4-12

[0193] This example uses substantially the same raw materials and process as Example 1 to prepare an iron carbide composition, with the only difference being that: in step (12), the carbonization time is 70 min. The finally prepared iron carbide composition is labeled as CX4-12.

[0194] Example 5

[0195] Preparation of metallic ε / ε'-iron carbide composite

[0196] (10) Take manganese bromide and potassium gluconate and dissolve them in 50 ml of water to prepare a first halide solution; take 5.6 g of nano iron particles with an average grain diameter of 20 nm, mix the first halide solution with the nano iron particles, and perform an 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 40 °C, and the impregnation time is 6 h; dry the impregnated solid material at 25 °C and a pressure of 0.05 atm for 5 h to obtain an ε / ε'-precursor.

[0197] The ε / ε’-precursor was processed using the same process as steps (11) to (13) of Example 1 to obtain a metallic ε / ε’-iron carbide composite.

[0198] Preparation of metallic χ-iron carbide composite

[0199] (20) A χ-precursor was obtained using exactly the same raw materials and method as in step (10).

[0200] The χ-precursor was processed using the same process as steps (21) to (23) of Example 1 to obtain a metallic χ-iron carbide composite.

[0201] Preparation of the composition

[0202] The metallic ε / ε’-iron carbide composite and the metallic χ-iron carbide composite obtained above were mixed in a molar ratio of 1:3 (based on the number of moles of iron contained in each) to obtain an iron carbide composition, labeled CX 5.

[0203] Comparative Example 1

[0204] 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 (molar ratio) was Fe:Br:K = 100:50:2. The finally obtained iron carbide composition was labeled DX1.

[0205] Comparative Example 2

[0206] 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, manganese bromide was not added to the third halide solution of the impregnating solution, and only potassium nitrate was added. The finally obtained iron carbide composition was labeled D2.

[0207] Comparative Example 3

[0208] 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, manganese chloride in an equimolar amount was used instead of manganese bromide to prepare the third halide solution of the impregnating solution. The finally obtained iron carbide composition was labeled DX3.

[0209] Comparative Example 4

[0210] In this example, metallic ε / ε’-iron carbide and metallic χ-iron carbide were prepared using the same raw materials and process as in Example 1. The metallic ε / ε’-iron carbide and the metallic χ-iron carbide were mixed in a molar ratio of 1:3 (based on the number of moles of iron contained in each) to obtain an iron carbide composition, labeled D4.

[0211] Comparative Example 5

[0212] In this example, metal-type ε / ε'-iron carbide composite and metal-type χ-iron carbide composite were prepared using substantially the same raw materials and process as in Example 1, with the only difference being that in step (13), the temperature was lowered to 150 °C for operation. The finally obtained iron carbide composition was labeled DX5.

[0213] 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 were all in terms of moles. The specific results are shown in Table 1.

[0214] 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 = 260 °C, P = 2.80 MPa, H2:CO = 2.1:1, (H2 + CO) total amount = 14500 mL / h / g- Fe (standard state flow rate, relative to Fe element), and the circulation ratio was 1.19. 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.

[0215] Table 1

[0216]

[0217]

[0218]

[0219] Table 2

[0220]

[0221]

[0222] Table 3

[0223]

[0224]

[0225] Based on the above results, when the iron carbide composition containing halogen ions such as bromine or iodine prepared in the embodiments 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 selectivity of the effective product while maintaining a high CO conversion rate (>60%). Further, a long-term experiment was carried out. From the data of the reaction for 300 h in Table 3, it can be seen that after the long-term continuous operation of the iron carbide composition of the embodiments 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 embodiments of the present invention as a catalyst for the syngas conversion reaction, comprehensive optimization of the reaction results can be achieved.

[0226] Unless otherwise specified, the terms used in the present invention have the meanings commonly understood by those skilled in the art.

[0227] The embodiments described in the present invention are only for illustrative purposes 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 and is only defined by the claims.

Claims

1. A composition containing ε / ε'-iron carbide and χ-iron carbide, comprising ε / ε'-iron carbide, χ-iron carbide and a halogen element, wherein the halogen element is bromine element and / or iodine element; wherein, The molar ratio of the iron element contained in the composition to the halogen element is 100:(0.12 - 47).

2. The composition according to claim 1, further comprising a promoter metal element, wherein the promoter metal element is selected from one or more of copper, chromium, alkali metal elements, molybdenum, manganese, alkaline earth metal elements, cobalt, and rare earth elements; the molar ratio of the iron element to the promoter metal element is 100:(0.1 - 22); and / or, The molar ratio of the iron element to the halogen element is 100:(0.3 - 35).

3. The composition according to claim 2, comprising an ε / ε'-iron carbide complex and a χ-iron carbide complex, wherein the ε / ε'-iron carbide complex comprises the ε / ε'-iron carbide, a first halogen element and an optional first promoter metal element; the χ-iron carbide complex comprises the χ-iron carbide, a second halogen element and an optional second promoter metal element; the first halogen element and the second halogen element are each independently bromine element and / or iodine element; The sum of the molar numbers of the ε / ε'-iron carbide and the χ-iron carbide is the same as the molar number of the iron element contained in the composition, and the molar numbers of the ε / ε'-iron carbide and the χ-iron carbide are based on the molar number of the iron element contained therein; the sum of the molar numbers of the first halogen element and the second halogen element is the same as the molar number of the halogen element contained in the composition; the sum of the molar numbers of the first promoter metal element and the second promoter element is the same as the molar number of the promoter metal element contained in the composition.

4. The iron carbide composition according to claim 3, wherein, The types of the first promoter metal element, the second promoter metal element and the promoter metal element are the same; The sum of the molar amounts of the ε / ε'-iron carbide and the χ-iron carbide is 100 mol%, wherein the content of the ε / ε'-iron carbide is at most 85 mol%, and further at most 70 mol%; the content of the χ-iron carbide is at most 85 mol%, and further at most 70 mol%.

5. A preparation method of a metallic iron carbide composition containing ε / ε'-iron carbide and χ-iron carbide, comprising: Provide a metallic ε / ε'-iron carbide composite and a metallic χ-iron carbide composite; Mix the metallic ε / ε'-iron carbide composite and the metallic χ-iron carbide composite to obtain a metallic iron carbide composition containing ε / ε'-iron carbide and χ-iron carbide; or, Impregnate the iron carbide mixture with a third halide solution to obtain a metallic iron carbide composition containing ε / ε'-iron carbide and χ-iron carbide; the iron carbide mixture includes a metallic ε / ε'-iron carbide and a metallic χ-iron carbide, and the third halide solution includes bromide ions and / or iodide ions; Among them, the preparation process of the metallic ε / ε'-iron carbide composite or the metallic ε / ε'-iron carbide includes the following steps: (11) Under the action of hydrogen at 250 - 490 °C, reduce the ε / ε'-precursor; (12) At 75 - 175 °C, pretreat the reduction product of step (11) with a first mixed gas; (13) At 175 - 280 °C, prepare the carbide of the pretreatment product of step (12) with a second mixed gas; Among them, the first mixed gas includes H2 and CO with a molar ratio of (1.2 - 2.8):1, and the second mixed gas includes H2 and CO with a molar ratio of (1 - 3):1; The ε / ε'-precursor is nano-iron and / or nano-iron compound impregnated with a first halide solution for the first time, and the product obtained in step (13) is the metallic ε / ε'-iron carbide composite; or, the ε / ε'-precursor is nano-iron and / or nano-iron compound, and the product obtained in step (13) is the metallic ε / ε'-iron carbide; or, the ε / ε'-precursor is nano-iron and / or nano-iron compound, the product obtained in step (13) is the metallic ε / ε'-iron carbide, and then the metallic ε / ε'-iron carbide is impregnated with the first halide solution for the first time to obtain the metallic ε / ε'-iron carbide composite; among them, the nano-iron compound can be reduced to obtain nano-iron, and the first halide solution includes bromide ions and / or iodide ions; The preparation process of the metallic χ-iron carbide composite or the metallic χ-iron carbide includes the following steps: (21) Under the action of hydrogen at 320 - 510 °C, reduce the χ-precursor; (22) The reduction product obtained in step (21) is treated with an oxygen-containing gas at 0 to 45 °C to obtain a surface passivation product; the oxygen-containing gas includes 1 vol% to 3 vol% of oxygen; (23) The surface passivation product obtained in step (22) is subjected to carbide preparation treatment with a third mixed gas at 250 to 430 °C; the third mixed gas includes hydrogen and carbon monoxide with a molar ratio of 8:1 to 100:1; The χ-precursor is the nano-iron and / or the nano-iron compound that has been subjected to the second impregnation treatment with the second halide solution, and the product obtained in step (23) is the metallic χ-iron carbide composite; or, the χ-precursor is the nano-iron and / or the nano-iron compound, and the product obtained in step (23) is the metallic χ-iron carbide; or, the χ-precursor is the nano-iron and / or the nano-iron compound, the surface passivation product is subjected to the second impregnation treatment with the second halide solution, and then the treatment of step (23) is carried out to obtain the metallic χ-iron carbide composite; or, the χ-precursor is the nano-iron and / or the nano-iron compound, and the product obtained in step (23) is subjected to the second impregnation treatment with the second halide solution to obtain the metallic χ-iron carbide composite; wherein, the second halide solution includes bromide ions and / or iodide ions.

6. The preparation method according to claim 5, wherein The nano-iron compound includes one or more of nano-iron oxide, nano-magnetite, nano-goethite, and nano-iron hydroxide oxide; and / or, The treatment pressure in step (11) is 0.1 to 13 atm, the treatment pressure in step (12) is 0.05 to 5 atm, and the treatment pressure in step (13) is 0.11 to 9 atm; and / or, The treatment pressure in step (21) is 0.15 to 15 atm, the treatment pressure in step (22) is 0 to 1.3 atm, and the treatment pressure in step (23) is 0.08 to 10 atm; and / or, The average grain diameter of the nano-iron or the nano-iron compound is 6 to 35 nm.

7. The preparation method according to claim 5, wherein The preparation raw materials of the first halide solution include a first halide and a first solvent, the preparation raw materials of the second halide solution include a second halide and a second solvent, and the preparation raw materials of the third halide solution include a third halide and a third solvent; the first halide, the second halide, and the third halide all include bromine-containing compounds and / or iodine-containing compounds.

8. The preparation method according to claim 7, wherein The first halide, the second halide, and the third halide each independently include one or more of bromides and iodides containing cobalt, iron, molybdenum, copper, manganese, and rare earth metal elements; and / or, The raw materials for preparing the first halide solution further include a first auxiliary compound, the raw materials for preparing the second halide solution further include a second auxiliary compound, and the raw materials for preparing the third halide solution further include a third auxiliary compound; the first auxiliary compound, the second auxiliary compound, and the third auxiliary compound are each independently selected from one or more of salts of manganese, copper, cobalt, alkaline earth metals, alkali metals, molybdenum, and rare earth metals.

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

10. Use of the composition according to any one of claims 1 to 4, the composition prepared by the preparation method according to any one of claims 5 to 8, or the catalyst according to claim 9 in the synthesis gas conversion reaction.

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

12. A synthesis gas conversion process comprising contacting the catalyst according to claim 9 with synthesis gas under reaction conditions for reaction.

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