CN112569980A - Composition containing precipitate type epsilon/epsilon' iron carbide and chi iron carbide, preparation method, catalyst and application thereof, and Fischer-Tropsch synthesis method - Google Patents

Composition containing precipitate type epsilon/epsilon' iron carbide and chi iron carbide, preparation method, catalyst and application thereof, and Fischer-Tropsch synthesis method Download PDF

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CN112569980A
CN112569980A CN202011059127.2A CN202011059127A CN112569980A CN 112569980 A CN112569980 A CN 112569980A CN 202011059127 A CN202011059127 A CN 202011059127A CN 112569980 A CN112569980 A CN 112569980A
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epsilon
iron carbide
iron
carbide
chi
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CN112569980B (en
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门卓武
王鹏
吕毅军
程萌
常海
李为真
张雪冰
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China Energy Investment Corp Ltd
National Institute of Clean and Low Carbon Energy
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China Energy Investment Corp Ltd
National Institute of Clean and Low Carbon Energy
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    • BPERFORMING OPERATIONS; TRANSPORTING
    • B01PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01JCHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J27/00Catalysts comprising the elements or compounds of halogens, sulfur, selenium, tellurium, phosphorus or nitrogen; Catalysts comprising carbon compounds
    • B01J27/20Carbon compounds
    • B01J27/22Carbides
    • BPERFORMING OPERATIONS; TRANSPORTING
    • B01PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01JCHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J35/00Catalysts, in general, characterised by their form or physical properties
    • B01J35/60Catalysts, in general, characterised by their form or physical properties characterised by their surface properties or porosity
    • B01J35/61Surface area
    • B01J35/61310-100 m2/g
    • BPERFORMING OPERATIONS; TRANSPORTING
    • B01PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01JCHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J35/00Catalysts, in general, characterised by their form or physical properties
    • B01J35/60Catalysts, in general, characterised by their form or physical properties characterised by their surface properties or porosity
    • B01J35/61Surface area
    • B01J35/615100-500 m2/g
    • CCHEMISTRY; METALLURGY
    • C10PETROLEUM, GAS OR COKE INDUSTRIES; TECHNICAL GASES CONTAINING CARBON MONOXIDE; FUELS; LUBRICANTS; PEAT
    • C10GCRACKING HYDROCARBON OILS; PRODUCTION OF LIQUID HYDROCARBON MIXTURES, e.g. BY DESTRUCTIVE HYDROGENATION, OLIGOMERISATION, POLYMERISATION; RECOVERY OF HYDROCARBON OILS FROM OIL-SHALE, OIL-SAND, OR GASES; REFINING MIXTURES MAINLY CONSISTING OF HYDROCARBONS; REFORMING OF NAPHTHA; MINERAL WAXES
    • C10G2/00Production of liquid hydrocarbon mixtures of undefined composition from oxides of carbon
    • C10G2/30Production of liquid hydrocarbon mixtures of undefined composition from oxides of carbon from carbon monoxide with hydrogen
    • C10G2/32Production of liquid hydrocarbon mixtures of undefined composition from oxides of carbon from carbon monoxide with hydrogen with the use of catalysts
    • C10G2/33Production of liquid hydrocarbon mixtures of undefined composition from oxides of carbon from carbon monoxide with hydrogen with the use of catalysts characterised by the catalyst used
    • C10G2/331Production of liquid hydrocarbon mixtures of undefined composition from oxides of carbon from carbon monoxide with hydrogen with the use of catalysts characterised by the catalyst used containing group VIII-metals
    • C10G2/332Production of liquid hydrocarbon mixtures of undefined composition from oxides of carbon from carbon monoxide with hydrogen with the use of catalysts characterised by the catalyst used containing group VIII-metals of the iron-group

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Abstract

The invention relates to the field of Fischer-Tropsch synthesis reaction, and discloses a composition containing precipitated epsilon/epsilon' iron carbide and chi iron carbide, a preparation method thereof, a catalyst and application thereof, and a Fischer-Tropsch synthesis method. The composition comprises 95-100 mol% of precipitated epsilon/epsilon 'iron carbide and chi iron carbide and 0-5 mol% of Fe-containing impurities, wherein the Fe-containing impurities are substances containing iron elements except the epsilon/epsilon' iron carbide and the chi iron carbide; wherein the specific surface area of the composition is 40-320m2(ii) in terms of/g. Can simply prepare epsilon/epsilon' iron carbide and chi iron carbide, can be used as active components to obtain continuous and stable Fischer-Tropsch synthesis reaction, and has high selectivity of effective products.

Description

Composition containing precipitate type epsilon/epsilon' iron carbide and chi iron carbide, preparation method, catalyst and application thereof, and Fischer-Tropsch synthesis method
Technical Field
The invention relates to the field of Fischer-Tropsch synthesis reaction, in particular to a composition containing precipitated epsilon/epsilon' iron carbide and chi iron carbide, a preparation method, a catalyst and application thereof, and a Fischer-Tropsch synthesis method.
Background
The primary energy structure of China is characterized by rich coal, lack of oil and little gas. With the development of economy in China, the dependence of petroleum on the outside is continuously rising.
Fischer-Tropsch synthesis is an increasingly important energy conversion way in recent years, and can convert carbon monoxide and H2The syngas is converted into liquid fuels and chemicals.
The reaction equation for fischer-tropsch synthesis is as follows:
(2n+1)H2+nCO→CnH2n+2+nH2O (1),
2nH2+nCO→CnH2n+nH2O (2)。
in addition to alkanes and alkenes, industrial fischer-tropsch synthesis can also produce carbon dioxide (CO) as a by-product2) And methane (CH)4). The Fischer-Tropsch synthesis reaction has complex mechanism and multiple steps, such as CO dissociation, carbon (C) hydrogenation and CHxChain growth, and hydrogenation and dehydrogenation reactions that result in hydrocarbon product desorption and oxygen (O) removal.
Iron is the cheapest transition metal used in making fischer-tropsch synthesis catalysts. The traditional iron-based catalyst has high water gas shift (CO + H)2O→CO2+H2) Active, therefore, conventional iron-based catalysts typically have a higher CO by-product2Selectivity, typically 25% to 45% of the carbon monoxide of the conversion feedstock. This is one of the major disadvantages of iron-based fischer-tropsch catalysts.
The active phase of the iron-based catalyst is very complicated to change, which causes considerable debate between the nature of the active phase and the Fischer-Tropsch synthesis reaction mechanism of the iron-based catalyst.
CN104399501A discloses epsilon-Fe suitable for low-temperature Fischer-Tropsch synthesis reaction2C, a preparation method of the nano-particles. The initial precursor is skeleton iron, and the reaction system is intermittent discontinuous reaction of polyethylene glycol solvent. CO of this catalyst2Selectivity 18.9%, CH4The selectivity of (2) is 17.3%. The disadvantage is that the method can only be applied to low temperature below 200 ℃, and the reaction can not be continuously completed. This means that such catalysts are not suitable for continuous production under modern Fischer-Tropsch synthesis industrial conditions. However, since the skeleton iron cannot be completely carbonized, epsilon-Fe described in the above document2The nanoparticles of C contain a considerable amount of iron impurity components of the non-iron carbide type, and in fact, the prior art cannot obtain pure phase materials of iron carbide free of iron impurities, which are various Fe (element) -containing phase components of non-iron carbide.
Accordingly, there is a need for an improved iron-based catalyst for use in fischer-tropsch synthesis reactions.
Disclosure of Invention
The purpose of the invention is toSolves the problem of how to obtain a pure-phase iron carbide substance without Fe impurities by the iron-based catalyst, improves the stability of Fischer-Tropsch synthesis reaction, and simultaneously reduces CO2Or CH4The problem of overhigh selectivity of byproducts, provides a composition containing precipitated epsilon/epsilon' iron carbide and chi iron carbide, a preparation method thereof, a catalyst and application thereof, and a Fischer-Tropsch synthesis method.
In order to achieve the above object, the first aspect of the present invention provides a composition containing precipitated epsilon/epsilon ' iron carbide and chi iron carbide, which comprises 95 to 100 mol% of precipitated epsilon/epsilon ' iron carbide and chi iron carbide, and 0 to 5 mol% of Fe-containing impurities, which are substances containing iron elements other than epsilon/epsilon ' iron carbide and chi iron carbide, based on the total amount of the composition; wherein the specific surface area of the composition is 40-320m2/g。
In a second aspect, the present invention provides a process for preparing a composition comprising precipitated epsilon/epsilon' iron carbide and chi iron carbide, comprising:
mixing and coprecipitating an aqueous solution containing ferric salt and an alkaline precipitator, washing and separating the obtained precipitate to obtain a solid, and drying and roasting the solid to obtain a precursor;
(1) preparing precipitated epsilon/epsilon' iron carbide, comprising:
(1-1) reacting the precursor with H2Carrying out a first reduction at a temperature of 450-580 ℃;
(1-2) mixing the material obtained in the step (1-1) with H2Pre-treating CO at 90-185 deg.C, and H2The molar ratio to CO is 1.2-2.8: 1;
(1-3) mixing the material obtained in the step (1-2) with H2CO at a temperature of 200-2The molar ratio to CO is 1-3.2: 1; obtaining sediment type epsilon/epsilon' iron carbide;
(2) preparing precipitated X-type iron carbide, which comprises the following steps:
(2-1) reacting the precursor with H2Performing a second reduction at a temperature of 450-610 ℃;
(2-2) mixing the material obtained in the step (2-1) with O2Gas at a temperature of 0-Surface passivation treatment is carried out at 50 ℃, and the O-containing2O in gas2The volume concentration of (A) is 1-5%;
(2-3) mixing the material obtained in the step (2-2) with H2CO at a temperature of 260-2The molar ratio to CO is 7-110: 1; obtaining the precipitated X-shaped iron carbide;
(3) mixing 95-100 molar parts of precipitate epsilon/epsilon' iron carbide and chi iron carbide and 0-5 molar parts of Fe-containing impurities under the condition of inert gas;
wherein the Fe-containing impurities are iron-containing substances except epsilon/epsilon' iron carbide and chi iron carbide.
In a third aspect, the invention provides a composition containing precipitated epsilon/epsilon' iron carbide and chi iron carbide prepared by the method provided by the invention.
In a fourth aspect, the invention provides a catalyst comprising a composition comprising precipitated epsilon/epsilon' iron carbide and chi iron carbide as provided by the invention.
In a fifth aspect, the invention provides an application of the composition or the catalyst containing the precipitated epsilon/epsilon' iron carbide and the chi iron carbide in Fischer-Tropsch synthesis reaction.
In a sixth aspect, the invention provides a composition or catalyst containing precipitated epsilon/epsilon' iron carbide and chi iron carbide, and application of the composition or catalyst in synthesis reaction of C, H fuel and/or chemicals based on the Fischer-Tropsch principle.
In a seventh aspect, the invention provides a fischer-tropsch synthesis process comprising: under the condition of Fischer-Tropsch synthesis reaction, the synthetic gas is contacted with the composition or the catalyst containing the sediment type epsilon/epsilon' iron carbide and the chi iron carbide provided by the invention.
An eighth aspect of the present invention provides a fischer-tropsch synthesis method, comprising: the synthesis gas is contacted with a Fischer-Tropsch catalyst under the Fischer-Tropsch synthesis reaction condition, wherein the Fischer-Tropsch catalyst comprises a Mn component and the composition containing precipitated epsilon/epsilon' iron carbide and chi iron carbide.
Through the technical scheme, the invention has the following technical effects:
(1) the required raw materials are simple and easy to obtain, and the cost is low: the iron source of the main raw material for synthesizing the precursor can be commercial iron salt, and when active phase carbide is synthesized, only original reaction gas (carbon monoxide and hydrogen) of a Fischer-Tropsch synthesis reaction system is used, so that no inorganic or organic reaction raw material is involved, and the method is greatly simplified compared with the prior art;
(2) the operation steps are simple, and in a preferred embodiment, the whole process of preparing each crystal phase iron carbide can be realized in the same reactor, and then the crystal phase iron carbide and the active phase iron carbide are mixed to form the composition.
(3) The invention can prepare 100% purity epsilon/epsilon 'iron carbide and chi iron carbide by a precipitation method respectively through the steps provided by the method, and then the epsilon/epsilon' iron carbide and the chi iron carbide form a composition with Fe-containing impurities to further prepare the catalyst. The above iron carbide or composition or catalyst can be used at high temperatures and pressures (e.g., temperatures of 235 ℃.;, pressures of 2.0-2.5MPa, H)21.5-2.0) continuous reactor, the reaction stability is extremely high, the theoretical technical barrier of the traditional literature theory that pure iron carbide can not stably exist under the reaction condition is broken through, the stable temperature can reach 260 ℃, and CO can be realized2Very low selectivity: under the condition of industrial Fischer-Tropsch synthesis reaction, a high-pressure continuous reactor can be used for keeping continuous and stable reaction for more than 400h, and CO is generated2The selectivity is below 8% (preferably, 4% or below can be achieved); at the same time, its by-product CH4The selectivity is kept below 12 percent (preferably below 7 percent), the selectivity of the effective product can reach above 81 percent (preferably above 89 percent), and the method is very suitable for the high-efficiency production of oil wax products in the Fischer-Tropsch synthesis industry of the modern coal chemical industry.
Drawings
FIG. 1 is an XRD spectrum of precipitated ε/ε' iron carbide prepared in preparation example 1 provided in the present invention;
fig. 2 is an XRD spectrum of the precipitated type χ iron carbide prepared in preparation example 2 provided in the present invention.
Detailed Description
The following detailed description of embodiments of the invention refers to the accompanying drawings. It should be understood that the detailed description and specific examples, while indicating the present invention, are given by way of illustration and explanation only, not limitation.
The invention provides a composition containing precipitated epsilon/epsilon ' iron carbide and chi iron carbide, which comprises 95-100 mol% of precipitated epsilon/epsilon ' iron carbide and chi iron carbide and 0-5 mol% of Fe-containing impurities, wherein the Fe-containing impurities are substances containing iron elements except epsilon/epsilon ' iron carbide and chi iron carbide; wherein the specific surface area of the composition is 40-320m2/g。
The invention provides a composition, wherein the precipitated epsilon/epsilon 'iron carbide comprises 100% of epsilon-iron carbide and/or 100% of epsilon' -iron carbide and 100% of chi-iron carbide. Further, precipitated epsilon/epsilon' iron carbide and chi iron carbide may constitute the composition with other Fe-containing impurities. Under the limitation of the composition content of the composition, the composition containing the precipitate epsilon/epsilon' iron carbide and the precipitate chi iron carbide can be used alone or combined with other components when being applied to a Fischer-Tropsch synthesis catalyst, so that the stability of the Fischer-Tropsch synthesis reaction of the Fischer-Tropsch synthesis catalyst is improved, and CO is reduced2Or CH4Selectivity of by-products.
In some embodiments of the invention, the composition comprises precipitated epsilon/epsilon 'iron carbide and chi iron carbide of high purity, and Mossbauer spectroscopy is performed to observe that the crystalline phase comprises pure epsilon/epsilon' iron carbide and chi iron carbide on the obtained Mossbauer spectroscopy results. Preferably, the specific surface area of the composition is from 50 to 270m2(ii) in terms of/g. The specific surface area may be represented by N2The BET adsorption and desorption method (2). The composition comprises epsilon/epsilon' iron carbide of hexagonal, pseudo-hexagonal or trigonal system and chi iron carbide of monoclinic system.
In some embodiments of the invention, it is further preferred that the composition comprises 97 to 100 mol% precipitated epsilon/epsilon' iron carbide and chi iron carbide and 0 to 3 mol% Fe-containing impurities, based on the total amount of the composition. Can be determined by XRD and Mossbauer spectrometry analysis, and can also be determined according to the preparation charge of the composition.
In some embodiments of the present invention, preferably, the Fe-containing impurities are at least one of e/e' iron carbide and iron carbide other than x iron carbide, iron oxide, iron hydroxide, iron sulfide, and iron salt. The Fe-containing impurities may be introduced by solution impregnation, sputtering, atomic deposition or mixing.
In the specific embodiment provided by the invention, the molar ratio of the precipitated epsilon/epsilon' iron carbide to the chi iron carbide is a: b, wherein a is more than 0 and less than 100, b is more than 0 and less than 100, preferably, a is more than 0 and less than or equal to 75, and b is more than 0 and less than or equal to 75. The molar ratio of the iron carbides of the two phases in the above range can produce a synergistic effect, optimizing the dissociation path of CO and the hydrogenation path of the C species and CHxIncrease the catalytic activity and decrease CH4With CO2And adjusting the product distribution.
In a second aspect, the present invention provides a process for preparing a composition comprising precipitated epsilon/epsilon' iron carbide and chi iron carbide, comprising:
mixing and coprecipitating an aqueous solution containing ferric salt and an alkaline precipitator, washing and separating the obtained precipitate to obtain a solid, and drying and roasting the solid to obtain a precursor;
(1) preparing precipitated epsilon/epsilon' iron carbide, comprising:
(1-1) reacting the precursor with H2Carrying out a first reduction at a temperature of 450-580 ℃;
(1-2) mixing the material obtained in the step (1-1) with H2Pre-treating CO at 90-185 deg.C, and H2The molar ratio to CO is 1.2-2.8: 1;
(1-3) mixing the material obtained in the step (1-2) with H2CO at a temperature of 200-2The molar ratio to CO is 1-3.2: 1; obtaining sediment type epsilon/epsilon' iron carbide;
(2) preparing precipitated X-type iron carbide, which comprises the following steps:
(2-1) reacting the precursor with H2Performing a second reduction at a temperature of 450-610 ℃;
(2-2) mixing the material obtained in the step (2-1) with O2The gas is heated at a temperature of 0-50 deg.CSurface passivation treatment is carried out at the temperature of DEG C, and the O-containing2O in gas2The volume concentration of (A) is 1-5%;
(2-3) mixing the material obtained in the step (2-2) with H2CO at a temperature of 260-2The molar ratio to CO is 7-110: 1; obtaining the precipitated X-shaped iron carbide;
(3) mixing 95-100 molar parts of precipitate epsilon/epsilon' iron carbide and chi iron carbide and 0-5 molar parts of Fe-containing impurities under the condition of inert gas;
wherein the Fe-containing impurities are iron-containing substances except epsilon/epsilon' iron carbide and chi iron carbide.
One embodiment provided by the present invention first prepares the precursor. In the preparation process, preferably, the iron salt may be a water-soluble iron salt commonly used in the art, and the iron salt is selected from water-soluble iron salts, which may be commercially available products, for example, at least one of ferric nitrate, ferric chloride, ferrous ammonium sulfate and ferric ammonium citrate. The alkaline precipitator is at least one of sodium carbonate, sodium bicarbonate, potassium carbonate, potassium bicarbonate, sodium hydroxide, potassium hydroxide and ammonia water.
In the preparation process of the precursor, preferably, the precipitation conditions include: the pH value is 6-9 and the temperature is 45-90 ℃.
In the preparation process of the precursor, the precipitate is washed, namely deionized water is washed for multiple times until the conductivity of the washing filtrate is lower than 290 mu S/cm, and the solid is obtained along with multiple solid-liquid separation in the washing process. Preferably, the solid is dried for 6 to 10 hours at the temperature of between 35 and 80 ℃ and the vacuum degree of between 250 and 1200 Pa; drying the dried material at 75-180 ℃ for 3-24h, and roasting the obtained material at the temperature of 250-580 ℃ for 1-10 h. Obtaining the precursor.
The present invention provides an embodiment for preparing precipitated epsilon/epsilon' iron carbide.
In some embodiments of the present invention, step (1-1) may simultaneously perform in-situ generation of nano iron powder from iron element in the precursor and reduction of the generated nano iron powder.
In some embodiments of the invention, H in step (1-1)2Can be represented by H2Introducing the mixture into the reaction system in the form of a flow, and simultaneously controlling H2The pressure of the stream is controlled to control the pressure of the first reduction, preferably, the pressure of the first reduction is 0.1 to 15atm, preferably 0.3 to 2.6atm, and the time is 0.7 to 15 hours, preferably 1 to 12 hours in step (1-1).
In some embodiments of the invention, H2The amount of H to be used may be selected depending on the amount of the precursor to be treated, and preferably, in step (1-1), H2The gas flow rate of (b) is 600-25000mL/h/g, more preferably 2800-22000 mL/h/g.
In step (1-2) of the process provided by the present invention, H2And CO may be (H)2+ CO) mixed gas flow to participate in the pretreatment process; at the same time, by controlling (H)2+ CO) mixed gas stream pressure to control the pressure of the pretreatment process. Preferably, in the step (1-2), the pressure of the pretreatment is 0.05-7atm, preferably 0.08-4.5atm, and the time is 15-120min, preferably 20-90 min.
In some embodiments of the present invention, preferably, in step (1-2), H2The total gas flow rate with CO is 300-12000mL/h/g, more preferably 1500-9000 mL/h/g.
In the step (1-3) of the method provided by the present invention, conditions for achieving the production of the first carbide are provided so as to obtain precipitated epsilon/epsilon' iron carbide. H2And CO may be (H)2+ CO) in the form of a mixed gas stream into the first carbide production process; at the same time, by controlling (H)2+ CO) mixed gas stream pressure to control the pressure of the first carbide making process. Preferably, in the step (1-3), the first carbide is prepared at a pressure of 0.1-10atm, preferably 0.2-4.5atm, for a time of 1.5-15h, preferably 2.5-12 h;
in some embodiments of the present invention, preferably, in step (1-3), H2The total gas flow rate with CO is 500-30000mL/h/g, more preferably 3000-25000 mL/h/g.
In a preferred embodiment of the present invention, the first carbide manufacturing method further includes: in the step (1-3), the temperature is simultaneously raised from the pretreatment temperature to 200-300 ℃ at a temperature raising rate of 0.2-5 ℃/min. In this preferred embodiment, the resulting precipitated epsilon/epsilon' iron carbide may have better effective product selectivity in the fischer-tropsch synthesis reaction. Further preferably, the temperature is raised from the temperature of the pretreatment to 210-290 ℃ at a temperature raising rate of 0.2-2.5 ℃/min. In the temperature raising operation, the temperature of the pretreatment is 90-185 ℃ in the step (1-2). Namely, the temperature raising operation is: raising the temperature from 90-185 ℃ to 200-300 ℃ at a temperature raising rate of 0.2-5 ℃/min, preferably from 90-185 ℃ to 210-290 ℃ at a temperature raising rate of 0.2-2.5 ℃/min.
The invention provides an embodiment for preparing precipitated X-shaped iron carbide.
In some embodiments of the present invention, step (2-1) may simultaneously perform in-situ generation of nano iron powder from iron element in the precursor and reduction of the generated nano iron powder.
In some embodiments of the present invention, it is preferred that H in step (2-1)2Can be represented by H2Introducing the mixture into the reaction system in the form of a flow, and simultaneously controlling H2The pressure of the stream to control the pressure of the second reduction, preferably, in step (2-1), the pressure of the second reduction is 0.1 to 15atm, preferably 0.3 to 2.6 atm; the time is 0.7-15h, preferably 1-12 h.
In some embodiments of the invention, H2The amount of the precursor to be used can be selected according to the amount of the precursor to be treated, preferably, H2The gas flow rate of (b) is 600-25000mL/h/g, more preferably 2800-22000 mL/h/g.
In the step (2-2) of the process of the present invention, O is contained2The gas being O2Mixed gas with inert gas. The inert gas may be at least one of nitrogen, helium, argon, krypton, and xenon. Said oxygen-containing group2Introducing gas to participate in the surface passivation treatment process; at the same time, by controlling the content of O2The pressure of the gas controls the pressure of the surface passivation treatment. Preferably, in the step (2-2), the pressure of the surface passivation treatment is 0 to 1.6atm, preferablyIs selected from 0-0.09atm, and the time is 5-72h, preferably 10-56 h.
In some embodiments of the present invention, preferably, in the step (2-2), the O-containing compound is2The gas flow rate of the gas is 400-12000mL/h/g, and more preferably 1400-8500 mL/h/g.
In the step (2-3) of the method provided by the invention, conditions for realizing the preparation of the second carbide are provided so as to obtain pure x-shaped iron carbide. H2And CO may be (H)2+ CO) in the form of a mixed gas stream into the second carbide production process; at the same time, by controlling (H)2+ CO) mixed gas stream to control the pressure of the second carbide making process. Preferably, in the step (2-3), the second carbide is prepared at a pressure of 0.08 to 12atm, preferably 0.15 to 2.5atm, for a time of 0.3 to 30 hours, preferably 0.5 to 2.4 hours.
In some embodiments of the present invention, preferably, in step (2-3), H2The total gas flow rate with CO is 250-21000mL/h/g, more preferably 2000-18000 mL/h/g.
In a preferred embodiment of the present invention, the second carbide preparation further comprises: and (4) simultaneously performing temperature rise operation in the step (2-3), wherein the temperature is raised from the surface passivation treatment temperature to 250-430 ℃ at the temperature rise rate of 0.2-5 ℃/min. In the preferred embodiment, the obtained precipitated chi-type iron carbide can have better effective product selectivity in the Fischer-Tropsch synthesis reaction. Further preferably, the temperature is raised from the temperature of the surface passivation treatment to 260-400 ℃ at a temperature raising rate of 0.2-2.5 ℃/min. In the heating operation, the temperature of the surface passivation treatment is 0-50 ℃ in the step (2-2). Namely, the temperature raising operation is: raising the temperature from 0-50 ℃ to the temperature in step (2-3) of 250 ℃ to 430 ℃ at a temperature raising rate of 0.2-5 ℃/min, preferably from 0-50 ℃ to 260 ℃ to 400 ℃ at a temperature raising rate of 0.2-2.5 ℃/min.
In the present invention, "mL/h/g" in the iron carbide production process means the volume of gas introduced per gram of the material per hour, unless otherwise specified.
In another preferred embodiment of the present invention, the first reduction, pretreatment and first carbide preparation may be performed in the same fischer-tropsch synthesis reactor during the preparation of precipitated epsilon/epsilon' iron carbide. In the process of preparing the precipitated chi-type iron carbide, the second reduction, the surface passivation treatment and the second carbide preparation can be carried out in the same Fischer-Tropsch synthesis reactor. In-situ characterization equipment can be used to track the crystal phase transition of the material during the preparation process.
In the invention, the steps (1) and (2) in the method provided by the invention can realize the obtainment of the precipitate epsilon/epsilon' iron carbide and the precipitate chi iron carbide.
In the step (3) of the method provided by the invention, the sediment type epsilon/epsilon' iron carbide and the chi iron carbide are mixed into sediment type iron carbide. The mixing result satisfies that preferably, the molar ratio of the precipitated epsilon/epsilon' iron carbide to the chi iron carbide is a: b, wherein a is more than 0 and less than 100, b is more than 0 and less than 100, preferably, a is more than 0 and less than or equal to 75, and b is more than 0 and less than or equal to 75.
In some embodiments of the invention, the precipitated epsilon/epsilon' iron carbide and chi iron carbide-containing compositions may contain Fe-containing impurities that are incorporated by external means. Preferably, in the step (3), 97 to 100 parts by mole of the precipitated ε/ε' iron carbide and the χ iron carbide are mixed with 0 to 3 parts by mole of the Fe-containing impurities.
In the step (3) of the method provided by the invention, the mixing is carried out under the protection of inert gas, and the powders of the precipitation type epsilon/epsilon' iron carbide and the chi iron carbide and the Fe-containing impurity powder are mixed in a glove box according to the dosage requirement.
In a third aspect, the present invention provides a composition comprising precipitated epsilon/epsilon' iron carbide and chi iron carbide made by the process of the present invention. The composition comprises 95-100 mol% of precipitation type epsilon/epsilon 'iron carbide and chi iron carbide and 0-5 mol% of Fe-containing impurities, wherein the Fe-containing impurities are substances containing iron elements except the epsilon/epsilon' iron carbide and the chi iron carbide, and the total amount of the composition is calculated by the formula.
Preferably, the composition comprises 97 to 100 mol% of precipitated epsilon/epsilon' iron carbide and chi iron carbide, and 0 to 3 mol% of Fe-containing impurities, based on the total amount of the composition.
Preferably, the specific surface area of the composition is from 40 to 320m2Per g, preferably from 50 to 270m2/g。
Preferably, the mole ratio of epsilon/epsilon' iron carbide to chi iron carbide is a: b, wherein a is more than 0 and less than 100, b is more than 0 and less than 100, preferably, a is more than 0 and less than or equal to 75, and b is more than 0 and less than or equal to 75.
In a fourth aspect, the invention provides a catalyst comprising a composition comprising precipitated epsilon/epsilon' iron carbide and chi iron carbide as provided by the invention. Preferably, the catalyst may also comprise other components, such as promoters.
In the embodiment provided by the present invention, preferably, the composition containing precipitated epsilon/epsilon' iron carbide and chi iron carbide is contained in an amount of 75 wt% or more and less than 100 wt%, and the content of the auxiliary is contained in an amount of more than 0 wt% and 25 wt% or less, based on the total amount of the catalyst.
In the embodiment provided by the invention, preferably, the catalyst can be prepared by introducing the auxiliary agent by a method of impregnation, atomic deposition, sputtering or chemical deposition.
In a fifth aspect, the invention provides an application of the composition or the catalyst containing the precipitated epsilon/epsilon' iron carbide and the chi iron carbide in Fischer-Tropsch synthesis reaction.
The invention provides an application of the composition or the catalyst containing the precipitated epsilon/epsilon' iron carbide and the chi iron carbide in C, H fuel and/or chemical synthesis based on the Fischer-Tropsch synthesis principle.
In a seventh aspect, the present invention provides a fischer-tropsch synthesis reaction process, comprising: under the condition of Fischer-Tropsch synthesis reaction, the synthetic gas is contacted with the composition or the catalyst containing the sediment type epsilon/epsilon' iron carbide and the chi iron carbide provided by the invention.
The composition or the catalyst containing the precipitated epsilon/epsilon' iron carbide and the chi iron carbide is used for carrying out the Fischer-Tropsch synthesis reaction, and the Fischer-Tropsch synthesis reaction can be carried out at high temperature and high pressure, for example, the conditions of the Fischer-Tropsch synthesis reaction comprise: the temperature is 235 ℃ and 250 ℃, and the pressure is 2.3-2.5 MPa. But also can be used for realizing better effective product selectivity; the effective product is prepared from CO and H2Produced by the reaction, except for CH4With CO2Products containing carbon other than, or in bagsIncluding but not limited to C2And C2The above hydrocarbons, alcohols, aldehydes, ketones, esters, and the like.
In the present invention, the pressure refers to gauge pressure unless otherwise specified.
In some embodiments of the invention, preferably, the fischer-tropsch synthesis reaction is carried out in a high temperature, high pressure continuous reactor. The composition or the catalyst containing the sediment type epsilon/epsilon' iron carbide and the chi iron carbide can realize that the Fischer-Tropsch synthesis reaction can be continuously and stably carried out for more than 400 hours in a high-temperature high-pressure continuous reactor.
An eighth aspect of the present invention provides a fischer-tropsch synthesis method, comprising: the synthesis gas is contacted with a Fischer-Tropsch catalyst under the Fischer-Tropsch synthesis reaction condition, wherein the Fischer-Tropsch catalyst comprises a Mn component and the composition containing precipitated epsilon/epsilon' iron carbide and chi iron carbide.
In the specific embodiment provided by the invention, the composition of the fischer-tropsch catalyst can further comprise, based on the total amount of the fischer-tropsch catalyst, the content of the composition containing precipitated epsilon/epsilon' iron carbide and chi iron carbide is more than 75 wt% and less than 100 wt%, and the content of Mn is more than 0 wt% and less than 25 wt%. In the fischer-tropsch catalyst, Mn may be present as an oxide and may be incorporated into the fischer-tropsch catalyst by methods including, but not limited to, impregnation, chemical deposition, sputtering, atomic deposition.
The present invention will be described in detail below by way of examples. In the following examples and comparative examples,
in-situ XRD detection in the process of preparing the iron carbide, an X-ray diffractometer (Rigaku company, model D/max-2600/PC) is used for monitoring the crystal phase change of the material;
the obtained iron carbide and iron carbide composition were subjected to Mossbauer spectrometer (Transmission)57Fe,57A Co (Rh) source sinusoidal velocity spectrometer) to perform Mossbauer spectrum detection;
the BET specific surface area of the iron carbide composition was measured by a nitrogen adsorption method;
carrying out Fischer-Tropsch synthesis reaction:
carrying out gas chromatography (Agilent 6890 gas chromatography) on the product obtained by the reaction;
the effect of the reaction is calculated by the following formula:
CO2selectivity%2Mole number/(moles of CO in feed-moles of CO in discharge)]×100%;
CH4Selectivity%4Mole/(mole of CO in the feed x CO conversion% (1-CO)2Selectivity%))]×100%;
Effective product selectivity ═ 1-CO2Selective% CH4Selectivity%]×100%
The space-time conversion rate of raw material CO (mmol/h/g-Fe) (mole number of CO in feeding-mole number of CO in discharging)/reaction time/weight of Fe element;
efficient product formation space-time yield (mmol/h/g-Fe) ═ C of the reaction2And C2The above number of moles of hydrocarbon/reaction time/weight of Fe element.
Preparation example 1
(1) Mixing ferric nitrate with the concentration of 1.0mol/L and ammonium carbonate solution with the concentration of 0.8 mol/L of 1/L at the temperature of 60 ℃ and under the condition that the pH value is 7.2 to obtain precipitation slurry, washing the precipitation slurry by deionized water, filtering the precipitation slurry to obtain a filter cake, drying the filter cake at the temperature of 120 ℃ for 24 hours, and roasting the filter cake at the temperature of 350 ℃ for 5 hours to obtain a precursor.
(2) Mixing the precursor with H2At a pressure of 2.0atm, H2The flow rate of 20000mL/h/g, the temperature is 460 ℃ for the first reduction for 1 h;
(3) cooling the product obtained in the step (2) to 160 ℃, and reacting the product with H at 160 DEG C2Mixed gas with CO (pressure 4.5atm, total gas flow 9000mL/H/g, H2Contacting with CO at a molar ratio of 2:1) for pretreatment for 20 min;
(4) h is to be2The conditions of the mixed gas with CO are firstly changed as follows: pressure 3.5atm, total gas flow 12000mL/H/g, H2And (3) heating the mixture to the CO at a molar ratio of 1.5:1 from 160 ℃ to 270 ℃ at a heating rate of 2.5 ℃/min under the condition, and then carrying out first carbide preparation on the mixture and the material obtained in the step (3) for 2.5h to obtain precipitated iron carbide, wherein the precipitated iron carbide is pure epsilon/epsilon' iron carbide determined by Mossbauer spectroscopy and is marked as iron carbide 1.
The preparation method of the precipitated epsilon/epsilon ' iron carbide provided by the invention is not limited to the preparation example 1, and the specific implementation method for preparing the precipitated epsilon/epsilon ' iron carbide is described in the embodiment of Chinese patent application ' precipitated epsilon/epsilon ' iron carbide composition, the preparation method, the catalyst and the application thereof and the Fischer-Tropsch synthesis method ', and the whole content of the method is introduced into the invention.
Preparation example 2
(a) Mixing ferric nitrate with the concentration of 1.2mol/L and sodium carbonate solution with the concentration of 0.9 mol/L of 1 at the temperature of 55 ℃ and under the condition of pH value of 6.5 to obtain precipitation slurry, washing by deionized water, filtering to obtain a filter cake, drying at the temperature of 110 ℃ for 24 hours, and roasting at the temperature of 400 ℃ for 10 hours to obtain a precursor.
(b) Mixing the precursor with H2At a pressure of 1.8atm, H2The flow rate of 18000mL/h/g, the temperature is 460 ℃ for the second reduction for 1 h;
(c) cooling the product obtained in step (b) to 35 ℃ and reacting the product with O at the temperature2Performing surface passivation treatment by contact of inert gas, wherein O is contained in the gas2The volume concentration of the catalyst is 1 percent, the pressure is 0.08atm, the gas flow is 7500mL/h/g, and the treatment time is 20 h;
(d) will contain O2The mixed gas is changed into H2And CO, with the conditions: pressure 2.0atm, total gas flow 18000mL/H/g, H2And (3) the molar ratio of the carbon to CO is 35:1, the temperature is raised from 35 ℃ to 360 ℃ at the temperature raising rate of 2.0 ℃/min under the condition, then the product obtained in the step (c) is subjected to second carbide preparation, the carbonization time is 2.5h, and precipitated iron carbide is obtained and is pure chi iron carbide determined by Mossbauer spectroscopy and is marked as iron carbide 2.
The preparation method of the precipitated x iron carbide provided by the invention is not limited to preparation example 2, and the specific implementation method for preparing the precipitated x iron carbide is described in the embodiment of the Chinese patent application 'composition containing the precipitated x iron carbide, preparation method thereof, catalyst and application thereof, and Fischer-Tropsch synthesis method', and the entire content of the method is introduced into the invention.
Example 1
72 parts by mole (in terms of iron element, the same applies hereinafter) of iron carbide 1, 27 parts by mole of iron carbide 2 and 1 part by mole of ferrous oxide (i.e., Fe-containing impurities) were mixed under protection of Ar gas. After mixing, it is designated as iron carbide composition 1.
Example 2
Under the protection of Ar gas, 26 molar parts of iron carbide 1, 72 molar parts of iron carbide 2 and 2 molar parts of ferrous oxide (namely Fe-containing impurities) are mixed. After mixing, it is designated as iron carbide composition 2.
Example 3
Under the protection of Ar gas, 79 mol parts of iron carbide 1, 20 mol parts of iron carbide 2 and 1 mol part of ferrous oxide (namely Fe-containing impurities) are mixed. After mixing, it was designated as iron carbide composition 3.
Example 4
Under the protection of Ar gas, 20 molar parts of iron carbide 1, 77 molar parts of iron carbide 2 and 3 molar parts of ferrous oxide (namely Fe-containing impurities) are mixed. After mixing, it was designated as iron carbide composition 4.
Comparative example 1
Under the protection of Ar gas, 79 mol parts of iron carbide 1, 14 mol parts of iron carbide 2 and 7 mol parts of ferrous oxide (namely Fe-containing impurities) are mixed. After mixing, it was designated as iron carbide composition D1.
Comparative example 2
Under the protection of Ar gas, 14 molar parts of iron carbide 1, 80 molar parts of iron carbide 2 and 6 molar parts of ferrous oxide (namely Fe-containing impurities) are mixed. After mixing, it was designated as iron carbide composition D2.
Examples 5 to 8
Respectively taking 1-4 parts of iron carbide composition in N2Adding manganese citrate solution by immersion method under protection, and adding N at 25 deg.C2And drying the gas flow for 24 hours to obtain the Fischer-Tropsch catalyst 1-4 correspondingly. Wherein the amount of the added manganese citrate solution is impregnated, so that the obtained Fischer-Tropsch catalysts 1-4 respectively and correspondingly contain 85 wt% of iron carbide composition 1-6 and 15 wt% of MnO2
Comparative examples 3 to 4
Respectively taking iron carbide compositions D1-D2 as the balance of N2Adding manganese citrate solution by immersion method under protection, and adding N at 25 deg.C2And drying the gas flow for 24h to obtain the Fischer-Tropsch catalysts D1-D2. Wherein the manganese citrate is added by dippingThe liquid amount is that the obtained Fischer-Tropsch catalysts D1-D2 respectively contain 85 wt% of iron carbide composition D1-D2 and 15 wt% of MnO2
Test example
Mossbauer spectroscopy was performed on iron carbide 1-2, and the results of the determination of the Fe compound content are shown in Table 1. Wherein the content of the Fe compound is expressed in mol percent.
TABLE 1
Figure BDA0002711719170000161
In the preparation examples 1 and 2, in-situ XRD detection technology is adopted, and an X-ray diffractometer (Rigaku company, model D/max-2600/PC) is used for monitoring the crystal phase change of the material. The XRD test result of preparation example 1 is shown in FIG. 1, in which the curve is such that carbide 1 having a crystal phase of ε -Fe with a purity of 100% is obtained after all the carbonization steps are completed2C and epsilon-Fe2.2C, i.e. epsilon/epsilon' iron carbide, and together with an XRD standard card PDF-89-2005, the curves show that 2 θ is 37.7 °, 41.4 °, 43.2 °, 57.2 °, 68.0 °, 76.8 °, and 82.9 ° exactly in accordance with the standard card. The crystallinity of the generated target product epsilon/epsilon 'iron carbide is good, all characteristic peaks of the epsilon/epsilon' iron carbide are well corresponded, the purity is extremely high, and no other impurities exist.
The XRD test result of preparation example 2 is shown in FIG. 2, in which the curve is that carbide 2 obtained after all the carbonization steps is completed and the crystal phase is X-Fe with a purity of 100%5C2That is, χ iron carbide, all characteristic peaks and χ -Fe of the curve showing 2 θ main peaks of 35.7 °, 39.3 °, 40.8 °, 41.1 °, 42.7 °, 43.4 °, 44.0 °, 44.6 °, 45.0 °, 45.6 °, 47.2 °, and 50.2 °5C2The standard card PDF-89-8968 is completely identical. The crystallinity of the generated target product chi-iron carbide is good, the target product chi-iron carbide well corresponds to all characteristic peaks of the chi-iron carbide, the purity is extremely high, and no other impurities exist.
Mossbauer spectra and BET specific surface area measurements were performed for iron carbide compositions 1-4 and D1-D2, respectively, and the results are shown in Table 2.
TABLE 2
Figure BDA0002711719170000162
Figure BDA0002711719170000171
Evaluation example
In a fixed bed continuous reactor, the performance evaluation of the catalytic reaction is respectively carried out on Fischer-Tropsch catalysts 1-4, D1-D2 and iron carbide compositions 1-2. The catalyst loading was 10.0 g.
Evaluation conditions were as follows: t240 deg.C, P2.3 MPa, H2:CO=1.8:1,(H2+ CO) in a total amount of 40000mL/h/g-Fe(standard state flux, relative to Fe element). The reaction products were analyzed by gas chromatography, and the evaluation data of the reaction performance for the reactions of 24 hours and 400 hours are shown in tables 3 and 4.
TABLE 3
Figure BDA0002711719170000172
TABLE 4
Figure BDA0002711719170000173
Figure BDA0002711719170000181
As can be seen from the above examples, comparative examples and data in tables 1 to 4, the composition or catalyst containing precipitated epsilon/epsilon' iron carbide and chi iron carbide prepared by the invention has high space-time conversion rate of raw material CO, better reaction performance and ultralow CO in limited condition range when the Fischer-Tropsch synthesis reaction is carried out under industrial conditions2And (4) selectivity. At the same time, CH4Low selectivity and high selectivity of effective products.
Further long-period experiments are carried out, and the data of the reaction for 400h in the table 4 show that after the composition or the catalyst containing the precipitated epsilon/epsilon' iron carbide and the chi iron carbide prepared under the limited conditions provided by the invention runs for a long time, the CO conversion rate and the product selectivity are stable and have no obvious change, and the stability is greatly superior to that of the iron carbide in the prior art.
The composition or the catalyst containing the precipitate epsilon/epsilon' iron carbide and the chi iron carbide prepared by the invention can be suitable for a high-temperature high-pressure continuous reactor, has high reaction stability, and CO2Very low selectivity: under the condition of industrial Fischer-Tropsch synthesis reaction, a high-pressure continuous reactor can be used for keeping continuous and stable reaction for more than 400h, and CO is generated2The selectivity is below 8% (preferably, 4% or below can be achieved); at the same time, its by-product CH4The selectivity is also kept below 12 percent (preferably below 7 percent), and the selectivity of the effective product can reach above 81 percent (preferably above 89 percent). Wherein the catalyst effective product formation space-time yield of the preferred conditions (catalyst 1-2) can reach 160mmol/h/g-FeThe method is very suitable for the high-efficiency production of products such as gasoline and diesel oil in the large modern chemical Fischer-Tropsch synthesis industry.
The preferred embodiments of the present invention have been described in detail above with reference to the accompanying drawings, but the present invention is not limited thereto. Within the scope of the technical idea of the invention, numerous simple modifications can be made to the technical solution of the invention, including combinations of the individual specific technical features in any suitable way. The invention is not described in detail in order to avoid unnecessary repetition. Such simple modifications and combinations should be considered within the scope of the present disclosure as well.

Claims (23)

1. A composition containing precipitate type epsilon/epsilon ' iron carbide and chi iron carbide, which comprises 95 to 100mol percent of precipitate type epsilon/epsilon ' iron carbide and chi iron carbide and 0 to 5mol percent of Fe-containing impurities, wherein the Fe-containing impurities are substances containing iron elements except the epsilon/epsilon ' iron carbide and the chi iron carbide;
wherein the specific surface area of the composition is 40-320m2/g。
2. The composition according to claim 1, wherein the composition has a specific surface area of 50-270m2/g。
3. The composition according to claim 1 or 2, wherein the composition comprises 97-100 mol% of precipitated epsilon/epsilon' iron carbide and chi iron carbide, and 0-3 mol% of Fe-containing impurities, based on the total amount of the composition.
4. The composition of any one of claims 1-3, wherein the Fe-containing impurities are at least one of iron carbides other than ε/ε' and χ iron carbides, iron oxides, iron hydroxides, iron sulfides, iron salts.
5. The composition according to any one of claims 1 to 4, wherein the molar ratio of precipitated epsilon/epsilon' iron carbide to chi iron carbide is a: b, wherein a is more than 0 and less than 100, b is more than 0 and less than 100, preferably, a is more than 0 and less than or equal to 75, and b is more than 0 and less than or equal to 75.
6. A method of preparing a composition comprising precipitated epsilon/epsilon' iron carbide and chi iron carbide comprising:
mixing and coprecipitating an aqueous solution containing ferric salt and an alkaline precipitator, washing and separating the obtained precipitate to obtain a solid, and drying and roasting the solid to obtain a precursor;
(1) preparing precipitated epsilon/epsilon' iron carbide, comprising:
(1-1) reacting the precursor with H2Carrying out a first reduction at a temperature of 450-580 ℃;
(1-2) mixing the material obtained in the step (1-1) with H2Pre-treating CO at 90-185 deg.C, and H2The molar ratio to CO is 1.2-2.8: 1;
(1-3) mixing the material obtained in the step (1-2) with H2CO is carried out at the temperature of 200-300 DEG CMonocarbide preparation H2The molar ratio to CO is 1-3.2: 1; obtaining sediment type epsilon/epsilon' iron carbide;
(2) preparing precipitated X-type iron carbide, which comprises the following steps:
(2-1) reacting the precursor with H2Performing a second reduction at a temperature of 450-610 ℃;
(2-2) mixing the material obtained in the step (2-1) with O2The gas is subjected to surface passivation treatment at a temperature of 0-50 ℃, and the gas contains O2O in gas2The volume concentration of (A) is 1-5%;
(2-3) mixing the material obtained in the step (2-2) with H2CO at a temperature of 260-2The molar ratio to CO is 7-110: 1; obtaining the precipitated X-shaped iron carbide;
(3) mixing 95-100 molar parts of precipitate epsilon/epsilon' iron carbide and chi iron carbide and 0-5 molar parts of Fe-containing impurities under the condition of inert gas;
wherein the Fe-containing impurities are iron-containing substances except epsilon/epsilon' iron carbide and chi iron carbide.
7. The method according to claim 6, wherein in the step (3), the molar ratio of the precipitated epsilon/epsilon' iron carbide to the chi iron carbide is a: b, wherein a is more than 0 and less than 100, b is more than 0 and less than 100, preferably, a is more than 0 and less than or equal to 75, and b is more than 0 and less than or equal to 75.
8. The method according to claim 6 or 7, wherein the iron salt is selected from water soluble iron salts, preferably at least one of ferric nitrate, ferric chloride, ferrous ammonium sulfate and ferric ammonium citrate;
the alkaline precipitator is at least one of sodium carbonate, sodium bicarbonate, potassium carbonate, potassium bicarbonate, sodium hydroxide, potassium hydroxide and ammonia water;
preferably, the solid is dried for 6 to 10 hours at the temperature of between 35 and 80 ℃ and the vacuum degree of between 250 and 1200 Pa; drying the dried material at 75-180 ℃ for 3-24h, and roasting the obtained material at the temperature of 250-580 ℃ for 1-10 h.
9. The process according to any one of claims 6 to 8, wherein in step (1-1), the pressure of the first reduction is 0.1 to 15atm, preferably 0.3 to 2.6atm, and the time is 0.7 to 15h, preferably 1 to 12 h;
further preferably, in step (1-1), H2The gas flow rate of (b) is 600-25000mL/h/g, more preferably 2800-22000 mL/h/g.
10. The method according to any one of claims 6 to 8, wherein in step (1-2), the pressure of the pretreatment is 0.05 to 7atm, preferably 0.08 to 4.5atm, and the time is 15 to 120min, preferably 20 to 90 min;
further preferably, in step (1-2), H2The total gas flow rate with CO is 300-12000mL/h/g, more preferably 1500-9000 mL/h/g.
11. The method according to any one of claims 6 to 8, wherein, in step (1-3), the first carbide is prepared at a pressure of 0.1 to 10atm, preferably 0.2 to 4.5atm, for a time of 1.5 to 15h, preferably 2.5 to 12 h;
further preferably, in step (1-3), H2The total gas flow rate with CO is 500-30000mL/h/g, more preferably 3000-25000 mL/h/g.
12. The method of any of claims 6-8, wherein the first carbide preparation method further comprises: simultaneously performing temperature rise operation in the step (1-3), wherein the temperature is raised from the pretreatment temperature to 200-300 ℃ at the temperature rise rate of 0.2-5 ℃/min;
preferably, the temperature is raised from the temperature of the pretreatment to 210-290 ℃ at a temperature raising rate of 0.2-2.5 ℃/min.
13. The process according to any one of claims 6 to 8, wherein in step (2-1), the pressure of the second reduction is 0.1 to 15atm, preferably 0.3 to 2.6 atm; the time is 0.7 to 15 hours, preferably 1 to 12 hours;
further preferably, in step (2-1), H2The gas flow rate of (b) is 600-25000mL/h/g,more preferably 2800 and 22000 mL/h/g.
14. The method according to any one of claims 6 to 8, wherein in the step (2-2), the pressure of the surface passivation treatment is 0 to 1.6atm, preferably 0 to 0.09atm, and the time is 5 to 72h, preferably 10 to 56 h;
further preferably, in the step (2-2), the O-containing compound2The gas flow rate of the gas is 400-12000mL/h/g, and more preferably 1400-8500 mL/h/g.
15. The method according to any one of claims 6 to 8, wherein in step (2-3), the second carbide is prepared at a pressure of 0.08 to 12atm, preferably 0.15 to 2.5atm, for a time of 0.3 to 30h, preferably 0.5 to 2.4 h;
further preferably, in step (2-3), H2The total gas flow rate with CO is 250-21000mL/h/g, more preferably 2000-18000 mL/h/g.
16. The method of any of claims 6-8, wherein the second carbide preparation further comprises: in the step (2-3), the temperature is simultaneously raised from the temperature of the surface passivation treatment to 250-430 ℃ at a temperature raising rate of 0.2-5 ℃/min;
preferably, the temperature is raised from the temperature of the surface passivation treatment to 260-400 ℃ at a temperature raising rate of 0.2-2.5 ℃/min.
17. The method according to any one of claims 6 to 16, wherein 97 to 100 molar parts of the precipitated epsilon/epsilon' iron carbide and the chi iron carbide, 0 to 3 molar parts of the Fe-containing impurities are mixed in step (3).
18. A composition comprising precipitated epsilon/epsilon' iron carbide and chi iron carbide made by the method of any one of claims 6-17.
19. A catalyst comprising the precipitated epsilon/epsilon' iron carbide and chi iron carbide-containing composition of any one of claims 1-5 and 18.
20. Use of a composition comprising precipitated epsilon/epsilon' iron carbide and chi iron carbide according to any one of claims 1 to 5 and 18 or a catalyst according to claim 19 in a fischer-tropsch synthesis reaction.
21. Use of a composition comprising precipitated epsilon/epsilon' iron carbide and chi iron carbide according to any one of claims 1 to 5 and 18 or a catalyst according to claim 19 in the synthesis of C, H fuels and/or chemicals based on the fischer-tropsch principle.
22. A process for fischer-tropsch synthesis comprising: contacting synthesis gas with a composition comprising precipitated epsilon/epsilon' iron carbide and chi iron carbide according to any one of claims 1 to 5 and 18 or a catalyst according to claim 19 under fischer-tropsch synthesis reaction conditions;
preferably, the fischer-tropsch synthesis is carried out in a high temperature high pressure continuous reactor.
23. A process for fischer-tropsch synthesis comprising: contacting synthesis gas with a fischer-tropsch catalyst under fischer-tropsch synthesis reaction conditions, wherein the fischer-tropsch catalyst comprises a Mn component and a composition comprising precipitated iron epsilon/epsilon' and chi carbides according to any one of claims 1 to 5 and 18.
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