CN112569994B - Composition containing multi-phase iron carbide, preparation method, catalyst, application and Fischer-Tropsch synthesis method - Google Patents

Composition containing multi-phase iron carbide, preparation method, catalyst, application and Fischer-Tropsch synthesis method Download PDF

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CN112569994B
CN112569994B CN202011068854.5A CN202011068854A CN112569994B CN 112569994 B CN112569994 B CN 112569994B CN 202011068854 A CN202011068854 A CN 202011068854A CN 112569994 B CN112569994 B CN 112569994B
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iron carbide
carbide
epsilon
iron
temperature
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CN112569994A (en
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王鹏
赵华博
李为真
武鹏
门卓武
杨如意
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China Energy Investment Corp Ltd
National Institute of Clean and Low Carbon Energy
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National Institute of Clean and Low Carbon Energy
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    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
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    • B01J27/00—Catalysts comprising the elements or compounds of halogens, sulfur, selenium, tellurium, phosphorus or nitrogen; Catalysts comprising carbon compounds
    • B01J27/20—Carbon compounds
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    • B—PERFORMING OPERATIONS; TRANSPORTING
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    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J35/00—Catalysts, in general, characterised by their form or physical properties
    • B01J35/60—Catalysts, in general, characterised by their form or physical properties characterised by their surface properties or porosity
    • B01J35/61—Surface area
    • B01J35/612—Surface area less than 10 m2/g
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J35/00—Catalysts, in general, characterised by their form or physical properties
    • B01J35/60—Catalysts, in general, characterised by their form or physical properties characterised by their surface properties or porosity
    • B01J35/61—Surface area
    • B01J35/613—10-100 m2/g
    • C—CHEMISTRY; METALLURGY
    • C10—PETROLEUM, GAS OR COKE INDUSTRIES; TECHNICAL GASES CONTAINING CARBON MONOXIDE; FUELS; LUBRICANTS; PEAT
    • C10G—CRACKING 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
    • C10G2/00—Production of liquid hydrocarbon mixtures of undefined composition from oxides of carbon
    • C10G2/30—Production of liquid hydrocarbon mixtures of undefined composition from oxides of carbon from carbon monoxide with hydrogen
    • C10G2/32—Production of liquid hydrocarbon mixtures of undefined composition from oxides of carbon from carbon monoxide with hydrogen with the use of catalysts
    • C10G2/33—Production 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
    • C10G2/331—Production 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
    • C10G2/332—Production 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 epsilon/epsilon' iron carbide, chi iron carbide and theta iron carbide, a preparation method thereof, a catalyst and application thereof, and a Fischer-Tropsch synthesis method. A composition comprising epsilon/epsilon ' iron carbide, chi iron carbide and theta iron carbide, said composition comprising 95 to 100 mole percent epsilon/epsilon ' iron carbide, chi iron carbide and theta iron carbide, and 0 to 5 mole percent Fe-containing impurities, based on the total amount of said composition, of an elemental iron-containing material other than epsilon/epsilon ' iron carbide, chi iron carbide and theta iron carbide. The epsilon/epsilon' iron carbide, the chi iron carbide and the theta iron carbide can be simply prepared, and are used as active components to obtain continuous and stable Fischer-Tropsch synthesis reaction, and the effective product has high selectivity.

Description

Composition containing multi-phase iron carbide, preparation method, catalyst, application and Fischer-Tropsch synthesis method
Technical Field
The invention relates to the field of Fischer-Tropsch synthesis reaction, in particular to a composition containing epsilon/epsilon' iron carbide, chi iron carbide and theta iron carbide, a preparation method, a catalyst, application and a Fischer-Tropsch synthesis method.
Background
The primary energy structure of China is characterized by rich coal, oil deficiency and less gas. With the development of the economy in China, the dependence of petroleum on the outside is continuously increased.
Fischer-Tropsch synthesis is an increasingly important energy conversion pathway in recent years, which can convert carbon monoxide and H 2 Is converted into liquid fuel and chemicals.
The reaction equation for Fischer-Tropsch synthesis is as follows:
(2n+1)H 2 +nCO→C n H 2n+2 +nH 2 O (1)，
2nH 2 +nCO→C n H 2n +nH 2 O (2)。
in addition to alkanes and alkenes, industrial Fischer-Tropsch synthesis can also produce carbon dioxide (CO) 2 ) And methane (CH) 4 ). The Fischer-Tropsch synthesis reaction is complicated in mechanism and numerous in steps, such as CO dissociation, carbon (C) hydrogenation, CH x Chain growth, and hydrogenation and dehydrogenation reactions that result in desorption and oxygen (O) removal of hydrocarbon products.
Iron is the cheapest transition metal for making fischer-tropsch catalysts. Conventional iron-based catalysts have a very high water gas shift (co+h) 2 O→CO 2 +H 2 ) The activity is high, so that the traditional iron-based catalyst usually has higher byproduct CO 2 The selectivity is typically 25% -45% of the carbon monoxide of the conversion feedstock. This is one of the major disadvantages of iron-based catalysts for fischer-tropsch synthesis reactions.
The change of the active phase of the iron-based catalyst is very complex, which results in considerable controversy over the nature of the active phase and the fischer-tropsch reaction mechanism of the iron-based catalyst.
CN104399501A discloses epsilon-Fe suitable for low temperature Fischer-Tropsch synthesis reaction 2 C, a nanoparticle preparation method. The initial precursor is skeleton iron, and the reaction system is intermittent polyethylene glycol solventDiscontinuous reaction. CO of such a catalyst 2 Selectivity is 18.9%, CH 4 The selectivity bit of (2) 17.3%. The disadvantage is that the reaction can not be continuously completed only when the reaction is applied to low temperatures below 200 ℃. This means that such catalysts are not suitable for continuous production under modern fischer-tropsch synthesis industry conditions. However, since the skeleton iron cannot be completely carbonized, epsilon-Fe described in the publication 2 C nanoparticles contain a significant amount of iron impurity components other than iron carbide type, and in fact, the prior art has failed to obtain epsilon-Fe free of iron impurities 2 C pure phase material, wherein the Fe impurity is non- ε -Fe 2 C contains various Fe (element) phase components.
Therefore, improvements in iron-based catalysts used in fischer-tropsch synthesis reactions are needed.
Disclosure of Invention
The invention aims to solve the problem of how to obtain pure-phase iron carbide substances without Fe impurities by an iron-based catalyst, improve the stability of Fischer-Tropsch synthesis reaction and reduce CO at the same time 2 Or CH (CH) 4 The problem of too high selectivity of byproducts provides a composition containing epsilon/epsilon' iron carbide, chi iron carbide and theta iron carbide, a preparation method thereof, a catalyst and application thereof, and a Fischer-Tropsch synthesis method.
In order to achieve the above object, a first aspect of the present invention provides a composition containing epsilon/epsilon ' iron carbide, chi iron carbide and theta iron carbide, which comprises 95 to 100mol% epsilon/epsilon ' iron carbide, chi iron carbide and theta iron carbide, and 0 to 5mol% of Fe-containing impurities, which are iron-containing substances other than epsilon/epsilon ' iron carbide, chi iron carbide and theta iron carbide, based on the total amount of the composition.
In a second aspect, the invention provides a method of preparing a composition comprising epsilon/epsilon' iron carbide, chi iron carbide and theta iron carbide, comprising:
(1) Preparing epsilon/epsilon' iron carbide, comprising:
(1-1) mixing a nano-iron powder or a nano-powder iron compound capable of obtaining a nano-iron powder by reduction with H 2 Performing a first surface cleaning treatment at a temperature of 250-510 ℃;
(1-2) mixing the material obtained in the step (1-1) withH 2 Pretreating CO at 80-180deg.C, H 2 The molar ratio of the catalyst to CO is 1.2-2.8:1, a step of;
(1-3) mixing the material obtained in the step (1-2) with H 2 Preparing first carbide by CO at 180-280 deg.C, H 2 The molar ratio of CO to CO is 1-3:1, obtaining pure epsilon/epsilon' iron carbide;
(2) Preparing theta iron carbide, comprising:
(2-1) mixing a nano-iron powder or a nano-powder iron compound capable of obtaining a nano-iron powder by reduction with H 2 At temperature T 1 Performing a second surface cleaning treatment at 380-520 ℃;
(2-2) mixing the material obtained in the step (2-1) with H 2 CO at temperature T 2 Preparing a second carbide at 280-430 ℃ for 20-120H, wherein H 2 The mol ratio of CO to CO is 5-120:1, obtaining pure theta iron carbide;
(3) Preparing χ iron carbide, comprising:
(3-1) mixing a nano-iron powder or a nano-powder iron compound capable of obtaining a nano-iron powder by reduction with H 2 Performing a third surface cleaning treatment at a temperature of 350-510 ℃;
(3-2) mixing the material obtained in the step (3-1) with an O-containing material 2 Surface passivation treatment is carried out on the gas at the temperature of 0-50 ℃, and the gas contains O 2 O in gas 2 The volume concentration of (2) is 1-5%;
(3-3) mixing the material obtained in the step (3-2) with H 2 Preparing a third carbide by CO at 250-430 ℃ and H 2 The mol ratio of CO to CO is 8-100:1, obtaining pure χ iron carbide;
(4) Mixing 95-100 mol parts of pure epsilon/epsilon' iron carbide, chi iron carbide and theta iron carbide and 0-5 mol parts of Fe-containing impurities under the protection of inert gas;
wherein the Fe-containing impurities are iron-containing substances except epsilon/epsilon' iron carbide, chi iron carbide and theta iron carbide.
In a third aspect, the invention provides a composition comprising epsilon/epsilon' iron carbide, chi iron carbide and theta iron carbide produced by the method of the invention.
In a fourth aspect, the invention provides a catalyst comprising a composition comprising epsilon/epsilon' iron carbide, chi iron carbide, and theta iron carbide as provided herein.
In a fifth aspect, the invention provides the use of a composition or catalyst comprising epsilon/epsilon' iron carbide, chi iron carbide and theta iron carbide as provided herein in a Fischer-Tropsch synthesis reaction.
In a sixth aspect, the invention provides the use of a composition or catalyst comprising epsilon/epsilon' iron carbide, chi iron carbide and theta iron carbide as provided herein for the synthesis of C, H fuels and/or chemicals based on the fischer-tropsch synthesis principle.
In a seventh aspect the invention provides a method of fischer-tropsch synthesis comprising: under Fischer-Tropsch reaction conditions, the synthesis gas is contacted with a composition or catalyst comprising epsilon/epsilon' iron carbide, chi iron carbide and theta iron carbide as provided by the invention.
In an eighth aspect the invention provides a method of fischer-tropsch synthesis comprising: the synthesis gas is contacted with a Fischer-Tropsch catalyst under Fischer-Tropsch reaction conditions, wherein the Fischer-Tropsch catalyst comprises a Mn component and a composition comprising epsilon/epsilon' iron carbide, chi iron carbide and theta iron carbide provided by the invention.
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 main raw material iron source is only common commercial nanometer iron powder, and can also be common commercial nanometer iron oxide (Fe) which can be reduced in a Fischer-Tropsch synthesis reactor to generate nanometer iron 2 O 3 ) Powder, nano magnetite (Fe) 3 O 4 ) Nano powder iron compounds such as powder, nano goethite powder, nano iron hydrate powder and the like; when synthesizing active phase carbide, only the original reaction gas (carbon monoxide and H) of the reaction system is utilized 2 ) The preparation method is finished; does not involve any inorganic or organic matter reaction raw materials, and is greatly simplified compared with the prior art;
(2) The preparation method has simple operation steps, and in a preferred embodiment, the whole preparation process of each crystal phase iron carbide can realize the preparation of the active phase in the same reactor, and then the active phase is mixed to form the composition.
(3) The method comprises the steps of preparing active phases epsilon/epsilon' iron carbide, theta iron carbide and chi iron carbide with 100% purity respectively, forming a composition with Fe-containing impurities, and preparing a catalyst with an auxiliary agent. The above iron carbide or composition or catalyst can be used for high temperature and high pressure (e.g., 235-260 ℃ C., 1.5-2.5MPa, H) 2 The reaction stability of the continuous reactor with/CO=1.5-2.0) is extremely high, the theoretical technical barrier of the traditional literature theory that under the reaction condition, pure-phase iron carbide cannot exist stably is broken, the stable temperature can reach 260 ℃, and CO can be realized 2 The selectivity is extremely low, so that under the condition of industrial Fischer-Tropsch synthesis reaction, a high-pressure continuous reactor can be used for continuous stable reaction for more than 400 hours, and CO 2 The selectivity is below 8% (preferably 4% or below); at the same time, by-product of the reaction CH 4 The selectivity is kept below 12% (preferably below 8%) and the selectivity of the effective product is above 80% (preferably above 88%). Is very suitable for the high-efficiency production of oil wax products in the large industry of modern coal industry and Fischer-Tropsch synthesis.
Drawings
FIG. 1 is an XRD pattern of epsilon/epsilon' iron carbide of preparation 1 as provided in the present invention;
FIG. 2 is an XRD pattern of the χ -iron carbide produced in preparation example 2 provided in the present invention;
fig. 3 is an XRD pattern of iron theta carbide produced in preparation example 3 provided in the present invention.
Detailed Description
The following describes specific embodiments of the present invention in detail with reference to the drawings. It should be understood that the detailed description and specific examples, while indicating and illustrating the invention, are not intended to limit the invention.
In a first aspect, the present invention provides a composition comprising epsilon/epsilon ' iron carbide, chi iron carbide and theta iron carbide, said composition comprising 95 to 100 mole% epsilon/epsilon ' iron carbide, chi iron carbide and theta iron carbide, and 0 to 5 mole% of an Fe-containing impurity, said Fe-containing impurity being an elemental iron-containing material other than epsilon/epsilon ' iron carbide, chi iron carbide and theta iron carbide, based on the total amount of said composition.
The composition provided by the invention comprises epsilon/epsilon' -ferric carbide with the purity of 100%, chi ferric carbide with the purity of 100% and theta ferric carbide with the purity of 100%. Further, epsilon/epsilon' iron carbide, chi iron carbide and theta iron carbide are combined with other Fe-containing impurities to form the composition. Under the limitation of the composition content of the composition, when the composition containing epsilon/epsilon' ferric carbide, chi ferric carbide and theta ferric carbide provided by the invention can be applied to a Fischer-Tropsch synthesis catalyst, the composition can be singly used or combined with other components, so that the stability of the Fischer-Tropsch synthesis catalyst in Fischer-Tropsch synthesis reaction is improved, and CO is reduced 2 Or CH (CH) 4 By-product selectivity.
In some embodiments of the invention, the compositions contain high purity epsilon/epsilon 'iron carbide, chi iron carbide, and theta iron carbide, and musburger analysis can be performed to observe that the crystalline phase contains pure epsilon/epsilon' iron carbide, chi iron carbide, and theta iron carbide on the musburger results obtained. Preferably, the specific surface area of the composition is 4-60m 2 Preferably 5-40m 2 And/g. The specific surface area can be determined by N 2 Is determined by BET adsorption and desorption methods. The composition comprises hexagonal, pseudo-hexagonal or trigonal epsilon/epsilon' iron carbide, monoclinic chi iron carbide and orthorhombic theta iron carbide.
In some embodiments of the invention, it is further preferred that the composition comprises 97-100 mole% epsilon/epsilon' iron carbide, chi iron carbide and theta iron carbide, and 0-3 mole% Fe-containing impurities, based on the total amount of the composition. Can be determined by XRD and Mossburg spectrometry analysis, and can also be determined according to the preparation feeding amount of the composition.
In some embodiments of the invention, the Fe-containing impurity is at least one of epsilon/epsilon' iron carbide, chi iron carbide, and theta iron carbide other than iron carbide, iron oxide, iron hydroxide, iron sulfide, 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, epsilon/epsilon' iron carbide and chiThe molar ratio of iron carbide to theta iron carbide is a: b: c, wherein a is more than 0 and less than 100, b is more than 0 and less than 100, c is more than 0 and less than 100, and preferably a is more than 0 and less than or equal to 90,0, b is more than or equal to 75,0, and c is more than or equal to 90. The molar ratio of the three phases of iron carbide can produce a coordinated effect in the above range, optimize the dissociation path of CO and the hydrogenation path of C species and CH x Improving catalytic activity and reducing CH 4 With CO 2 And the selectivity of the product distribution is regulated.
In a second aspect, the invention provides a method of preparing a composition comprising epsilon/epsilon' iron carbide, chi iron carbide and theta iron carbide, comprising:
(1) Preparing epsilon/epsilon' iron carbide, comprising:
(1-1) mixing a nano-iron powder or a nano-powder iron compound capable of obtaining a nano-iron powder by reduction with H 2 Performing a first surface cleaning treatment at a temperature of 250-510 ℃;
(1-2) mixing the material obtained in the step (1-1) with H 2 Pretreating CO at 80-180deg.C, H 2 The molar ratio of the catalyst to CO is 1.2-2.8:1, a step of;
(1-3) mixing the material obtained in the step (1-2) with H 2 Preparing first carbide by CO at 180-280 deg.C, H 2 The molar ratio of CO to CO is 1-3:1, obtaining pure epsilon/epsilon' iron carbide;
(2) Preparing theta iron carbide, comprising:
(2-1) mixing a nano-iron powder or a nano-powder iron compound capable of obtaining a nano-iron powder by reduction with H 2 At temperature T 1 Performing a second surface cleaning treatment at 380-520 ℃;
(2-2) mixing the material obtained in the step (2-1) with H 2 CO at temperature T 2 Preparing a second carbide at 280-430 ℃ for 20-120H, wherein H 2 The mol ratio of CO to CO is 5-120:1, obtaining pure theta iron carbide;
(3) Preparing χ iron carbide, comprising:
(3-1) mixing a nano-iron powder or a nano-powder iron compound capable of obtaining a nano-iron powder by reduction with H 2 Performing a third surface cleaning treatment at a temperature of 350-510 ℃;
(3-2) mixing the material obtained in the step (3-1) with an O-containing material 2 Surface passivation treatment is carried out on the gas at the temperature of 0-50 ℃, and the gas contains O 2 O in gas 2 The volume concentration of (2) is 1-5%;
(3-3) mixing the material obtained in the step (3-2) with H 2 Preparing a third carbide by CO at 250-430 ℃ and H 2 The mol ratio of CO to CO is 8-100:1, obtaining pure χ iron carbide;
(4) Mixing 95-100 mol parts of pure epsilon/epsilon' iron carbide, chi iron carbide and theta iron carbide and 0-5 mol parts of Fe-containing impurities under the protection of inert gas;
wherein the Fe-containing impurities are iron-containing substances except epsilon/epsilon' iron carbide, chi iron carbide and theta iron carbide.
In the preparation method provided by the invention, the steps (1), (2) and (3) are used for preparing iron carbide with different crystal forms. The raw materials are selected from nano iron powder, and the average particle diameter of the nano iron powder can be measured by an X-ray diffraction method. Preferably, the average grain diameter of the nano-iron powder is 4-35nm, and more preferably 10-27nm. The nano-powder iron compound may be a compound containing an iron element, and preferably, the nano-powder iron compound is selected from at least one of nano-iron oxide powder, nano-magnetite powder, nano-goethite powder and nano-iron oxyhydroxide powder. The nano iron powder and the nano powder iron compound are used as raw materials for preparing epsilon/epsilon' iron carbide, chi iron carbide and theta iron carbide.
In some embodiments of the present invention, if the raw materials in the steps (1-1), (2-1) and (3-1) are nano iron powder, the steps (1-1), (2-1) and (3-1) may function to perform a surface purification treatment on the nano iron powder; if the raw materials in the steps (1-1), (2-1) and (3-1) are nano-powder iron compounds capable of obtaining nano-iron powder through in-situ reduction, the steps (1-1), (2-1) and (3-1) can simultaneously play roles of reducing the nano-powder iron compounds to produce nano-iron powder and performing surface purification treatment on the produced nano-iron powder.
One embodiment provided by the invention prepares pure epsilon/epsilon' iron carbide.
Preferably, H in step (1-1) 2 Can be H 2 The flow is introduced into the reaction system and at the same time, H is controlled 2 The pressure of the stream controls the pressure of the first surface cleaning treatment, preferably, in step (1-1), the pressure of the first surface cleaning treatment is 0.1 to 15atm, preferably 0.2 to 2.5atm, for 0.5 to 8 hours, preferably 1 to 7 hours.
In some embodiments of the invention, H 2 The amount of (C) may be selected depending on the amount of the raw material to be treated, and preferably, in the step (1-1), H 2 The gas flow rate of (2) is 500-20000mL/h/g, more preferably 2500-15000mL/h/g.
In the step (1-2) of the method provided by the invention, H 2 And CO can be (H) 2 +CO) mixed gas flow is introduced to participate in the pretreatment process; at the same time, by controlling (H 2 +co) pressure of the mixed gas stream to control the pressure of the pretreatment process. Preferably, in step (1-2), the pretreatment is carried out at a pressure of 0.05-7atm, preferably 0.05-2.5atm, for a period of 15-90min, preferably 25-75min.
In some embodiments of the present invention, preferably, in step (1-2), H 2 The total gas flow with CO is 200-8000mL/h/g, more preferably 1000-6500mL/h/g.
In step (1-3) of the method provided by the present invention, conditions are provided to achieve the preparation of the first carbide to obtain pure ε/ε' iron carbide. H 2 And CO can be (H) 2 +co) in the form of a mixed gas stream into the process of the first carbide preparation; at the same time, by controlling (H 2 +co) to control the pressure of the first carbide manufacturing process. Preferably, in step (3), the first carbide is prepared at a pressure of 0.09 to 10atm, preferably 0.15 to 3atm, for a time of 0.5 to 10 hours, preferably 1.5 to 8 hours;
in some embodiments of the present invention, preferably, in step (1-3), H 2 The total gas flow rate with CO is 200-20000mL/h/g, more preferably 4000-15000mL/h/g.
In some embodiments of the present invention, preferably, H in step (1-2) 2 Molar ratio to CO is greater than H in step (1-3) 2 Molar ratio to CO.
According to a preferred embodiment of the present invention, the first carbide preparation further comprises: : and (3) simultaneously carrying out temperature rising operation in the step (1-3), and rising the temperature from the temperature of the pretreatment to 180-280 ℃ at a temperature rising rate of 0.2-5 ℃/min. In this preferred embodiment, the resulting pure phase epsilon/epsilon' iron carbide can have better effective product selectivity in the Fischer-Tropsch reaction. Further preferably, the temperature from the pretreatment is raised to 200-270 ℃ at a temperature raising rate of 0.2-2.5 ℃/min. In the temperature raising operation, the temperature of the pretreatment is 80-180 ℃ in the step (1-2). Namely, the temperature raising operation is: the temperature is raised from 80 to 180℃to 180℃in step (1-3) at a temperature-raising rate of 0.2 to 5℃per minute, preferably from 80 to 180℃to 200 to 270℃at a temperature-raising rate of 0.2 to 2.5℃per minute.
In some embodiments of the invention, steps (1-2) and (1-3) are set to the temperature, H, at which the pretreatment and carbide preparation are performed, respectively 2 Molar ratio to CO. The temperatures H set in the respective steps (1-2) and (1-3) are the same 2 The molar ratio to CO is not the same. During the temperature increasing operation, the temperature settings in steps (1-2) and (1-3) are different.
In another embodiment provided by the invention, pure theta iron carbide is prepared.
Preferably, H in step (2-1) 2 Can be H 2 The flow is introduced into the reaction system and at the same time, H is controlled 2 The pressure of the stream controls the pressure of the second surface cleaning treatment, preferably, in step (2-1), the pressure of the second surface cleaning treatment is 0 to 25atm, preferably, 0.01 to 3atm; the time is 1-40h, preferably 2-18h.
In the step (2-1) provided by the invention, H 2 The amount of (C) may be selected depending on the amount of the raw material to be treated, and preferably, in the step (2-1), H 2 The gas flow rate of (2) is 400-22000mL/h/g, more preferably 1000-18000mL/h/g.
In step (2-2) provided by the present invention, conditions are provided to achieve the preparation of the second carbide to obtain pure θ iron carbide. H 2 And CO can be (H) 2 +CO) mixingIntroducing the mixed gas flow into the process of preparing the second carbide; at the same time, by controlling (H 2 +co) to control the pressure of the second carbide manufacturing process. Preferably, in step (2-3), the second carbide is prepared at a pressure of 0-28atm, preferably 0.01-20atm, for a time of 20-120h, preferably 24-80h.
In some embodiments of the present invention, preferably, in step (2-2), H 2 The total gas flow rate with CO is 200-35000mL/h/g, more preferably 1200-20000mL/h/g.
In step (2-2) provided by the present invention, according to a preferred embodiment of the present invention, the second carbide preparation further includes: in the step (2-2), the temperature change operation is carried out simultaneously, and the temperature is changed from the temperature T 1 Cooling or heating to temperature T at a variable temperature rate of 0.2-5deg.C/min 2 . In this preferred embodiment, the resulting pure phase θ iron carbide can have better effective product selectivity in the Fischer-Tropsch reaction. Further preferably, from temperature T 1 The temperature is reduced or increased to 300-400 ℃ at a variable temperature rate of 0.2-2.5 ℃/min.
One embodiment provided herein prepares pure χ iron carbide.
Preferably, H in step (3-1) 2 Can be H 2 The flow is introduced into the reaction system and at the same time, H is controlled 2 The pressure of the stream controls the pressure of the third surface cleaning treatment, preferably, in step (3-1), the pressure of the third surface cleaning treatment is 0.12 to 18atm, preferably, 0.22 to 2.5atm; the time is 1.2-30 hours, preferably 2-12 hours.
In some embodiments of the invention, H 2 The amount of (C) may be selected according to the amount of the raw material to be treated, preferably H 2 The gas flow rate of (C) is 600-25000mL/h/g, more preferably 1200-16000mL/h/g.
In the step (3-2) of the method provided by the invention, O is contained 2 The gas being O 2 And inert gas. The inert gas may be at least one of nitrogen, helium, argon, krypton, and xenon. The O contains 2 The gas is introduced to participate in the surface passivation treatment process; at the same time, by controlling the content of O 2 The pressure of the gas controls the pressure of the surface passivation process. Preferably, in step (3-2), the surface passivation treatment is performed at a pressure of 0 to 1.6atm, preferably 0 to 0.09atm, for a time of 5 to 72 hours, preferably 10 to 56 hours.
In some embodiments of the present invention, preferably, in step (3-2), the O-containing 2 The gas flow rate of the gas is 400-12000mL/h/g, more preferably 1400-8500mL/h/g.
In step (3-3) of the method provided by the present invention, conditions are provided to achieve the preparation of the third carbide to obtain pure χ iron carbide. H 2 And CO can be (H) 2 +co) in the form of a mixed gas stream into the process for the preparation of said carbide; at the same time, by controlling (H 2 +co) to control the pressure of the third carbide manufacturing process. Preferably, in step (3-3), the third carbide is prepared at a pressure of 0.08-12atm, preferably 0.15-2.5atm, for a time of 0.3-30h, preferably 0.5-2.4h.
In some embodiments of the present invention, preferably, in step (3-3), H 2 The total gas flow with CO is 250-21000mL/h/g, more preferably 2000-18000mL/h/g.
In a preferred embodiment of the present invention, the third carbide preparation further comprises: and (3-3) simultaneously carrying out temperature rising operation, wherein the temperature of the surface passivation treatment is raised to 250-430 ℃ at a temperature rising rate of 0.2-5 ℃/min. In this preferred embodiment, the resulting pure phase χ iron carbide provides better effective product selectivity in the Fischer-Tropsch reaction. Further preferably, the temperature from the surface passivation treatment is raised to 260-400 ℃ at a temperature raising rate of 0.2-2.5 ℃/min. In the temperature raising operation, the temperature of the surface passivation treatment refers to the temperature of 0-50 ℃ in the step (3-2). Namely, the temperature raising operation is: the temperature is raised from 0 to 50℃to 250 to 430℃in step (3-3) at a temperature-raising rate of 0.2 to 5℃per minute, preferably from 0 to 50℃to 260 to 400℃at a temperature-raising rate of 0.2 to 2.5℃per minute.
In the present invention, "mL/h/g" refers to the volume of air intake per gram of material per hour during the iron carbide production process, unless otherwise specified.
In one embodiment of the method provided by the invention, the first surface purification treatment, the pretreatment and the first carbide preparation may be performed in the same Fischer-Tropsch synthesis reactor during the preparation of epsilon/epsilon' iron carbide. In the process of preparing theta iron carbide, the second surface purification treatment and the second carbide preparation may be performed in the same fischer-tropsch synthesis reactor. In the process of preparing the χ -iron carbide, the third surface purification treatment, the surface passivation treatment and the third carbide preparation can be performed in the same Fischer-Tropsch synthesis reactor. In-situ characterization equipment can be used for tracking the crystal phase transition of materials in the preparation process.
In the invention, the pure-phase epsilon/epsilon' iron carbide, the pure-phase theta iron carbide and the pure-phase chi iron carbide can be obtained through the steps (1), (2) and (3) in the method provided by the invention.
The method provided by the invention is used for realizing the composition containing epsilon/epsilon' iron carbide, chi iron carbide and theta iron carbide in the step (4). Wherein, the pure-phase epsilon/epsilon' iron carbide, chi iron carbide and theta iron carbide are mixed into the pure-phase iron carbide. Preferably, the mole ratio of ε/ε' iron carbide, χ iron carbide, and θ iron carbide is a: b: c, wherein a is more than 0 and less than 100, b is more than 0 and less than 100, c is more than 0 and less than 100, and preferably a is more than 0 and less than or equal to 90,0, b is more than or equal to 75,0, and c is more than or equal to 90.
In some embodiments of the invention, the composition comprising epsilon/epsilon' iron carbide, chi iron carbide, and theta iron carbide may comprise Fe-containing impurities that are incorporated by way of external addition. Preferably, in step (4), 97 to 100 mole parts of pure ε/ε' iron carbide, χ iron carbide and θ iron carbide are mixed with 0 to 3 mole parts of Fe-containing impurities.
In the step (4) of the method provided by the invention, the powder of pure epsilon/epsilon' iron carbide, chi iron carbide and theta iron carbide and the powder of Fe-containing impurity are mixed according to the dosage requirement in a glove box under the protection of inert gas.
In a third aspect, the invention provides a composition comprising epsilon/epsilon' iron carbide, chi iron carbide and theta iron carbide produced by the method of the invention. The composition comprises 95-100mol% of epsilon/epsilon 'iron carbide, chi iron carbide and theta iron carbide, and 0-5mol% of Fe-containing impurities, wherein the Fe-containing impurities are iron-containing substances except epsilon/epsilon' iron carbide, chi iron carbide and theta iron carbide.
Preferably, the composition comprises 97-100 mole% epsilon' iron carbide, chi iron carbide and theta iron carbide, and 0-3 mole% Fe-containing impurities.
Preferably, the specific surface area of the composition is in the range of 4-60m 2 Preferably 5-40m 2 /g。
Preferably, the mole ratio of ε/ε' iron carbide, χ iron carbide, and θ iron carbide is a: b: c, wherein a is more than 0 and less than 100, b is more than 0 and less than 100, c is more than 0 and less than 100, and preferably a is more than 0 and less than or equal to 90,0, b is more than or equal to 75,0, and c is more than or equal to 90.
In a fourth aspect, the invention provides a catalyst comprising a composition comprising epsilon/epsilon' iron carbide, chi iron carbide, and theta iron carbide as provided herein. Preferably, the catalyst may also comprise other components, such as adjuvants.
In the specific embodiment provided by the invention, preferably, the content of the composition containing epsilon/epsilon' iron carbide, chi iron carbide and theta iron carbide is more than 75wt% and less than 100wt%, and the content of the auxiliary agent is more than 0wt% and less than 25wt%, based on the total amount of the catalyst.
In the specific embodiment provided by the invention, the catalyst can be prepared by introducing the auxiliary agent by a dipping, atomic deposition, sputtering or chemical deposition method.
In a fifth aspect, the invention provides the use of a composition or catalyst comprising epsilon/epsilon' iron carbide, chi iron carbide and theta iron carbide as provided herein in a Fischer-Tropsch synthesis reaction.
In a sixth aspect, the invention provides the use of a composition or catalyst comprising epsilon/epsilon' iron carbide, chi iron carbide and theta iron carbide as provided herein for the synthesis of C, H fuels and/or chemicals based on the fischer-tropsch synthesis principle.
In a seventh aspect the invention provides a method of fischer-tropsch synthesis comprising: under Fischer-Tropsch reaction conditions, the synthesis gas is contacted with a composition or catalyst comprising epsilon/epsilon' iron carbide, chi iron carbide and theta iron carbide as provided by the invention.
The Fischer-Tropsch reaction can be performed at high temperature and high pressure using the composition or catalyst of the invention comprising epsilon/epsilon' iron carbide, chi iron carbide and theta iron carbide, for example, the Fischer-Tropsch reaction conditions include: the temperature is 235-250 ℃ and the pressure is 2.3-2.5MPa. But also can be particularly better in the selectivity of effective products; the effective products are CO and H 2 Generated by reaction, except CH 4 With CO 2 Other carbon-containing products, including, but not limited to, C 2 C 2 The above hydrocarbons, alcohols, aldehydes, ketones, esters, and the like.
In the present invention, unless otherwise specified, the pressure refers to gauge pressure.
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 epsilon/epsilon' iron carbide, chi iron carbide and theta iron carbide can realize that the Fischer-Tropsch synthesis reaction can keep continuous stable reaction for more than 400 hours in a high-temperature high-pressure continuous reactor.
In an eighth aspect the invention provides a method of fischer-tropsch synthesis comprising: the synthesis gas is contacted with a Fischer-Tropsch catalyst under Fischer-Tropsch reaction conditions, wherein the Fischer-Tropsch catalyst comprises a Mn component and a composition comprising epsilon/epsilon' iron carbide, chi iron carbide and theta iron carbide provided by the invention.
In the specific embodiment provided by the invention, the composition of the Fischer-Tropsch catalyst can be further taken as the total amount of the Fischer-Tropsch catalyst, the composition containing epsilon/epsilon' iron carbide, chi iron carbide and theta iron carbide is more than 75wt% and less than 100wt%, and the Mn content is more than 0wt% and less than 25 wt%. In the fischer-tropsch catalyst, mn may be present in the form of oxides and may be introduced 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 by examples. In the following examples and comparative examples,
in-situ XRD detection during the preparation of the iron carbide is carried out by using an X-ray diffractometer (Rigaku company, model D/max-2600/PC) to monitor the crystal phase change of the material;
the obtained iron carbide and iron carbide composition is subjected to Mossburger spectrometer (Transmission 57 Fe， 57 Carrying out Mossburger spectrum detection by a Co (Rh) source sine velocity spectrometer;
the BET specific surface area of the iron carbide composition is determined by nitrogen adsorption;
in the Fischer-Tropsch synthesis:
carrying out gas chromatographic analysis (Agilent 6890 gas chromatography) on the product obtained by the reaction;
the reaction effect is calculated by the following formula:
CO 2 selectivity% 2 Mole/(mole of CO in feed-mole of CO in discharge)]×100％；
CH 4 Selectivity = [ CH in discharge ] 4 Mole number/(mole number of CO in feed X CO conversion (1-CO) 2 Selectivity%))]×100％；
Effective product selectivity% = [1-CO 2 Selectivity% -CH 4 Selectivity%]×100％。
Space-time conversion rate (mmol/h/g) of raw material CO Fe ) = (moles of CO in feed-moles of CO in discharge)/reaction time/weight of Fe element;
space-time yield (mmol/h/g) of the effective product Fe ) C of =reaction 2 C (C) 2 The above hydrocarbon mole number/reaction time/Fe element weight.
Preparation example 1
(1) 10.0g of nano iron powder is taken, the average grain diameter is 18nm, and the pressure is 1atm at 390 ℃ and the gas flow rate is 8500mL/H/g of H 2 Performing first surface purification treatment for 2.5 hours;
(2) Cooling the product obtained in the step (1) to 160 ℃, and reacting with H at 160 DEG C 2 Mixed gas with CO (pressure 1.5atm, total gas flow 7000mL/H/g, H 2 Contact with CO in a molar ratio of 2.0:1) for pretreatment for 45min;
(3) Change H 2 The conditions of the mixture gas with CO are as follows: pressure of 2.1atm, total gasFlow 13000mL/H/g, H 2 The molar ratio of the iron carbide to CO is 1.5:1, the temperature is increased from 160 ℃ to 250 ℃ at the heating rate of 1.5 ℃/min under the condition, and then the material obtained in the step (2) is subjected to first carbide preparation to obtain pure epsilon/epsilon' iron carbide (determined by Mossburg spectrum) which is denoted as iron carbide 1.
The preparation method of the pure epsilon/epsilon ' iron carbide provided by the invention is not limited to preparation example 1, and the specific implementation method for preparing the pure epsilon/epsilon ' iron carbide is described in the examples of the Chinese patent application ' epsilon/epsilon ' iron carbide-containing composition, the preparation method, the catalyst and the application and the Fischer-Tropsch synthesis method ', and the whole content of the method is incorporated into the invention.
Preparation example 2
(a) 10.0g of nano iron powder is taken, the average grain diameter is 17nm, and the pressure is 0.9atm at 350 ℃ and the gas flow is 10000mL/H/g of H 2 Performing third surface purification treatment for 10 hours;
(b) Cooling the product from step (a) to 35 ℃ and reacting with an O-containing catalyst at this temperature 2 Surface passivation treatment is carried out by gas contact, O in gas 2 The volume concentration of (2) is 1%, the pressure is 0.01atm, the gas flow rate is 1800mL/h/g, and the treatment time is 38h;
(c) Will contain O 2 Is changed into H 2 And CO under the following conditions: pressure 0.15atm, total gas flow 2000mL/H/g, H 2 And (2) heating the mixture from 35 ℃ to 300 ℃ at a heating rate of 0.2 ℃/min under the condition, and then preparing a third carbide from the product obtained in the step (b) to obtain pure χ iron carbide (determined by Mossburg spectrum), which is denoted as iron carbide 2.
The preparation method of the pure χ -iron carbide provided by the invention is not limited to preparation example 2, and the specific implementation method for preparing the pure χ -iron carbide is described in the examples of the Chinese patent application 'composition containing χ -iron carbide, the preparation method, the catalyst and the application and the Fischer-Tropsch synthesis method', and the whole content of the method is incorporated into the invention.
Preparation example 3
(i) 10.0g of nano iron powder is taken, the average grain diameter is 20nm, and the pressure is 3atm at 520 ℃ and the gas flow is 18000mL/H/g of H 2 Downward feedingPerforming second surface purification treatment for 2h;
(ii) Cooling the product obtained in step (i) to 400 ℃ at a rate of 2.5 ℃/min, and reacting with H at this temperature 2 And (3) carrying out second carbide preparation by contacting with the mixed gas of CO, wherein the conditions are as follows: pressure 20atm, total gas flow 20000mL/H/g, H 2 The molar ratio to CO is 100:1, and the treatment time is 24 hours. Pure theta iron carbide (measured by musburger spectrum) was obtained and designated as iron carbide 3;
the preparation method of the pure theta iron carbide provided by the invention is not limited to preparation example 3, and the specific implementation method for preparing the pure theta iron carbide is described in the examples of the Chinese patent application of the composition containing the theta iron carbide, the preparation method, the catalyst and the application and the Fischer-Tropsch synthesis method, and the whole content of the composition is incorporated into the invention.
Example 1
Under the protection of Ar gas, 88 mole parts of iron carbide 1,5 mole parts of iron carbide 2,6 mole parts of iron carbide 3 are mixed with 1 mole part of ferrous oxide (i.e. Fe-containing impurities). After mixing, this was designated as iron carbide composition 1.
Example 2
Under the protection of Ar gas, 10 mole parts of iron carbide 1, 74 mole parts of iron carbide 2 and 15 mole parts of iron carbide 3 are mixed with 1 mole part of ferrous oxide (namely Fe-containing impurities). After mixing, this was designated iron carbide composition 2.
Example 3
Under the protection of Ar gas, 8 mole parts of iron carbide 1,6 mole parts of iron carbide 2, 83 mole parts of iron carbide 3 and 3 mole parts of ferrous oxide (namely Fe-containing impurities) are mixed. After mixing, this was designated as iron carbide composition 3.
Example 4
Under the protection of Ar gas, 91 mole parts of iron carbide 1,4 mole parts of iron carbide 2,4 mole parts of iron carbide 3 are mixed with 1 mole part of ferrous oxide (i.e. Fe-containing impurities). After mixing, this was designated iron carbide composition 4.
Example 5
7 parts by mole of iron carbide 1, 80 parts by mole of iron carbide 2, 11 parts by mole of iron carbide 3 are mixed with 2 parts by mole of ferrous oxide (i.e., fe-containing impurities) under Ar gas protection. After mixing, this was designated as iron carbide composition 5.
Example 6
Under the protection of Ar gas, 3 parts of iron carbide 1,4 parts of iron carbide 2, 92 parts of iron carbide 3 and 1 part of ferrous oxide (namely Fe-containing impurities) are mixed. After mixing, this was designated iron carbide composition 6.
Comparative example 1
Under the protection of Ar gas, 75 mole parts of iron carbide 1, 10 mole parts of iron carbide 2,5 mole parts of iron carbide 3 and 10 mole parts of ferrous oxide (namely Fe-containing impurities) are mixed. After mixing, the mixture was designated as iron carbide composition D1.
Comparative example 2
Under the protection of Ar gas, 10 mole parts of iron carbide 1, 70 mole parts of iron carbide 2, 13 mole parts of iron carbide 3 and 7 mole parts of ferrous oxide (namely Fe-containing impurities) are mixed. After mixing, this was designated as iron carbide composition D2.
Comparative example 3
Under the protection of Ar gas, 8 mole parts of iron carbide 1,6 mole parts of iron carbide 2, 77 mole parts of iron carbide 3 and 9 mole parts of ferrous oxide (i.e. Fe-containing impurities) are mixed. After mixing, this was designated as iron carbide composition D3.
Examples 7 to 12
Iron carbide compositions 1-6 were taken separately, at N 2 Under protection, respectively adding manganese citrate solution by impregnation method, and adding N at 25deg.C 2 And drying the gas flow for 24 hours to obtain the Fischer-Tropsch catalyst 1-6. Wherein the amount of manganese citrate solution added by impregnation is such that the resulting Fischer-Tropsch catalysts 1-6 respectively contain 85wt% of the iron carbide composition 1-6, 15wt% of MnO 2 。
Comparative examples 4 to 6
Taking iron carbide compositions D1-D3, respectively, in N 2 Under protection, respectively adding manganese citrate solution by impregnation method, and adding N at 25deg.C 2 And drying the air flow for 24 hours to obtain the Fischer-Tropsch catalysts D1-D3. Wherein the amount of manganese citrate solution added is impregnated such that the resulting Fischer-Tropsch catalysts D1-D3 respectively contain 85wt% of the iron carbide composition D1-D3, 15wt% of MnO 2 。
Test case
Mossburg spectrum measurement is carried out on the iron carbide 1-3, and the measured Fe compound content results are shown in Table 1. Wherein the content unit of Fe compound is mole percent.
TABLE 1
Figure BDA0002711720850000181
Preparation examples 1, 2 and 3 were subjected to in-situ XRD detection, and the change in crystal phase of the material was monitored by using an X-ray diffractometer (model D/max-2600/PC, manufactured by Rigaku Co.). The XRD test results of preparation 1 are shown in FIG. 1, which shows iron carbide 1 obtained after completion of all carbonization steps, and having a crystal phase of 100% pure ε -Fe 2 C and ε -Fe 2.2 C, namely epsilon/epsilon' iron carbide, and together with an XRD standard card PDF-89-2005, the 2 theta = 37.7 DEG, 41.4 DEG, 43.2 DEG, 57.2 DEG, 68.0 DEG, 76.8 DEG, 82.9 DEG are completely consistent with the standard card. The produced target product epsilon/epsilon 'iron carbide has good crystallinity, well corresponds to all characteristic peaks of epsilon/epsilon' iron carbide, has extremely high purity and does not contain any other impurities.
The XRD test results of preparation 2 are shown in FIG. 2, which shows that iron carbide 2 obtained after completion of all carbonization steps has a crystal phase of χ -Fe with 100% purity 5 C 2 Namely, χ iron carbide, the curve shows the main 2θ peaks=35.7 °, 39.3 °, 40.8 °, 41.1 °, 42.7 °, 43.4 °, 44.0 °, 44.6 °, 45.0 °, 45.6 °, 47.2 °, 50.2 ° and χ -Fe as all characteristic peaks 5 C 2 Standard card PDF-89-8968 is completely identical. The produced target product of the X-iron carbide has good crystallinity, well corresponds to all characteristic peaks of the X-iron carbide, has extremely high purity and does not contain any other impurities.
The XRD test results of preparation 3 are shown in FIG. 3, which shows that iron carbide 3 obtained after completion of all carbonization steps has a crystal phase of 100% pure orthorhombic theta-Fe 3 C, i.e. theta iron carbide, with 2 theta main peak = 36.6 °, 37.8 °, 42.9 °, 43.8 °, 44.6 °, 45.0 °, 45.9 °, 48.6 °, 49.1 ° all characteristic peaks and theta-Fe 3 The C standard card PDF-65-2142 is completely consistent. Raw materialsThe crystallization degree of the formed target product theta iron carbide is good, all characteristic peaks of the theta iron carbide are well corresponding, the purity is extremely high, and no other impurities exist.
Mossburg spectra and BET specific surface areas were measured for iron carbide compositions 1-6 and D1-D3, respectively, and the results are shown in Table 2.
TABLE 2
Figure BDA0002711720850000191
Figure BDA0002711720850000201
Evaluation example
Catalytic performance evaluations were performed on Fischer-Tropsch catalysts 1-6, D1-D3, and iron carbide compositions 1-3, respectively, in a fixed bed continuous reactor. The catalyst loading was 10.0g.
Evaluation conditions: t=250 ℃, p=2.40 mpa, h 2 ：CO＝1.8：1，(H 2 +CO) total = 48000mL/h/g- Fe (standard state flow, relative to the Fe element). The reaction was carried out, and the reaction products were analyzed by gas chromatography, and the evaluation data of the reaction performance for 24 hours and 400 hours of the reaction were shown in tables 3 and 4.
TABLE 3 Table 3
Figure BDA0002711720850000202
TABLE 4 Table 4
Figure BDA0002711720850000203
Figure BDA0002711720850000211
As can be seen from the above examples, comparative examples and the data in tables 1-4, the invention was modified to contain epsilon/epsilon' carbonizationThe composition or catalyst of iron, χ -iron carbide and θ -iron carbide is used in Fischer-Tropsch synthesis under industrial conditions, and exhibits high space-time conversion rate of raw material CO, better reactivity, and ultra-low CO in a limited range of conditions 2 Selectivity. At the same time CH 4 The selectivity is low, and the selectivity of effective products is high.
Further conducting long-period experiments, it can be seen from the data of reaction 400h in Table 4 that the composition or catalyst containing epsilon/epsilon' iron carbide, chi iron carbide and theta iron carbide prepared under the limiting conditions provided by the invention can keep stable both CO conversion rate and product selectivity after long-term operation, has no obvious change, and has stability greatly superior to that of the iron carbide in the prior art.
The composition or the catalyst containing epsilon/epsilon' iron carbide, chi iron carbide and theta iron carbide prepared by the invention can be suitable for a high-temperature high-pressure continuous reactor, has high reaction stability and CO 2 The selectivity is extremely low: under the condition of industrial Fischer-Tropsch synthesis reaction, a high-pressure continuous reactor can be used for maintaining continuous stable reaction for more than 400 hours, and CO thereof 2 The selectivity is below 8% (preferably 4% or below); at the same time, its by-product CH 4 The selectivity is kept below 12% (preferably below 8%) and the selectivity of the effective product is above 80% (preferably above 88%). Wherein the space-time yield of the catalyst-effective product of the preferred conditions (catalysts 1 to 3) is up to 135mmol/h/g- Fe The method is very suitable for the modern industrial Fischer-Tropsch synthesis of products such as gasoline, diesel oil and the like which are produced in high efficiency in large industries.
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, a number of simple variants of the technical solution of the invention are possible, including combinations of individual specific technical features in any suitable way. The various possible combinations of the invention are not described in detail in order to avoid unnecessary repetition. Such simple variations and combinations are likewise to be regarded as being within the scope of the present disclosure.

Claims (106)

1. A composition comprising epsilon/epsilon ' iron carbide, chi iron carbide and theta iron carbide, said composition comprising 95 to 100 mole percent epsilon/epsilon ' iron carbide, chi iron carbide and theta iron carbide, and 0 to 5 mole percent Fe-containing impurities, based on the total amount of said composition, of an elemental iron-containing material other than epsilon/epsilon ' iron carbide, chi iron carbide and theta iron carbide; the Fe-containing impurity is not 0;
the preparation method of the composition comprises the following steps:
(1) Preparing epsilon/epsilon' iron carbide, comprising:
(1-1) mixing a nano-iron powder or a nano-powder iron compound capable of obtaining a nano-iron powder by reduction with H 2 Performing a first surface cleaning treatment at a temperature of 250-510 ℃;
(1-2) mixing the material obtained in the step (1-1) with H 2 Pretreating CO at 80-180deg.C, H 2 The molar ratio of the catalyst to CO is 1.2-2.8:1, a step of;
(1-3) mixing the material obtained in the step (1-2) with H 2 Preparing first carbide by CO at 180-280 deg.C, H 2 The molar ratio of CO to CO is 1-3:1, obtaining pure epsilon/epsilon' iron carbide;
(2) Preparing theta iron carbide, comprising:
(2-1) mixing a nano-iron powder or a nano-powder iron compound capable of obtaining a nano-iron powder by reduction with H 2 At temperature T 1 Performing a second surface cleaning treatment at 380-520 ℃;
(2-2) mixing the material obtained in the step (2-1) with H 2 CO at temperature T 2 Preparing a second carbide at 280-430 ℃ for 20-120H, wherein H 2 The mol ratio of CO to CO is 5-120:1, obtaining pure theta iron carbide;
(3) Preparing χ iron carbide, comprising:
(3-1) mixing a nano-iron powder or a nano-powder iron compound capable of obtaining a nano-iron powder by reduction with H 2 Performing a third surface cleaning treatment at a temperature of 350-510 ℃;
(3-2) mixing the material obtained in the step (3-1) with an O-containing material 2 Surface passivation treatment is carried out on the gas at the temperature of 0-50 ℃, and the gas contains O 2 O in gas 2 The volume concentration of (2) is 1-5%;
(3-3) mixing the material obtained in the step (3-2) with H 2 Preparing a third carbide by CO at 250-430 ℃ and H 2 The mol ratio of CO to CO is 8-100:1, obtaining pure χ iron carbide;
(4) 95-100 mole parts of pure epsilon/epsilon' iron carbide, chi iron carbide and theta iron carbide and 0-5 mole parts of Fe-containing impurities are mixed under the protection of inert gas.
2. The composition according to claim 1, wherein the specific surface area of the composition is 4-60m 2 /g。
3. The composition according to claim 2, wherein the specific surface area of the composition is 5-40m 2 /g。
4. A composition according to any one of claims 1 to 3, wherein the composition comprises 97-100mol% epsilon/epsilon' iron carbide, chi iron carbide and theta iron carbide, and 0-3mol% Fe-containing impurities, based on the total amount of the composition.
5. A composition according to any one of claims 1-3, wherein the Fe-containing impurities are at least one of epsilon/epsilon' iron carbide, chi iron carbide and theta iron carbide other than iron carbide, iron oxides, iron hydroxides, iron sulfides, iron salts.
6. The composition of claim 4, wherein the Fe-containing impurities are at least one of epsilon/epsilon' iron carbide, chi iron carbide, and iron carbide other than theta iron carbide, iron oxides, iron hydroxides, iron sulfides, iron salts.
7. The composition according to any one of claims 1-3, 6, wherein the molar ratio of epsilon/epsilon' iron carbide, chi iron carbide and theta iron carbide is a: b: c, wherein 0 < a < 100,0 < b < 100, and 0 < c < 100.
8. The composition of claim 7, wherein 0 < a.ltoreq. 90,0 < b.ltoreq. 75,0 < c.ltoreq.90.
9. The composition of claim 4, wherein the mole ratio of epsilon/epsilon' iron carbide, chi iron carbide, and theta iron carbide is a: b: c, wherein 0 < a < 100,0 < b < 100, and 0 < c < 100.
10. The composition of claim 9, wherein 0 < a.ltoreq. 90,0 < b.ltoreq. 75,0 < c.ltoreq.90.
11. The composition of claim 5, wherein the mole ratio of epsilon/epsilon' iron carbide, chi iron carbide, and theta iron carbide is a: b: c, wherein 0 < a < 100,0 < b < 100, and 0 < c < 100.
12. The composition of claim 11, wherein 0 < a.ltoreq. 90,0 < b.ltoreq. 75,0 < c.ltoreq.90.
13. A method of preparing a composition comprising epsilon/epsilon' iron carbide, chi iron carbide and theta iron carbide, comprising:
(1) Preparing epsilon/epsilon' iron carbide, comprising:
(1-1) mixing a nano-iron powder or a nano-powder iron compound capable of obtaining a nano-iron powder by reduction with H 2 Performing a first surface cleaning treatment at a temperature of 250-510 ℃;
(1-2) mixing the material obtained in the step (1-1) with H 2 Pretreating CO at 80-180deg.C, H 2 The molar ratio of the catalyst to CO is 1.2-2.8:1, a step of;
(1-3) mixing the material obtained in the step (1-2) with H 2 Preparing first carbide by CO at 180-280 deg.C, H 2 The molar ratio of CO to CO is 1-3:1, obtaining pure epsilon/epsilon' iron carbide;
(2) Preparing theta iron carbide, comprising:
(2-1) nanometer iron powder or nanometer iron which can be obtained by reductionPowder nano powder iron compound and H 2 At temperature T 1 Performing a second surface cleaning treatment at 380-520 ℃;
(2-2) mixing the material obtained in the step (2-1) with H 2 CO at temperature T 2 Preparing a second carbide at 280-430 ℃ for 20-120H, wherein H 2 The mol ratio of CO to CO is 5-120:1, obtaining pure theta iron carbide;
(3) Preparing χ iron carbide, comprising:
(3-1) mixing a nano-iron powder or a nano-powder iron compound capable of obtaining a nano-iron powder by reduction with H 2 Performing a third surface cleaning treatment at a temperature of 350-510 ℃;
(3-2) mixing the material obtained in the step (3-1) with an O-containing material 2 Surface passivation treatment is carried out on the gas at the temperature of 0-50 ℃, and the gas contains O 2 O in gas 2 The volume concentration of (2) is 1-5%;
(3-3) mixing the material obtained in the step (3-2) with H 2 Preparing a third carbide by CO at 250-430 ℃ and H 2 The mol ratio of CO to CO is 8-100:1, obtaining pure χ iron carbide;
(4) Mixing 95-100 mol parts of pure epsilon/epsilon' iron carbide, chi iron carbide and theta iron carbide and 0-5 mol parts of Fe-containing impurities under the protection of inert gas;
wherein the Fe-containing impurities are iron-containing substances except epsilon/epsilon' iron carbide, chi iron carbide and theta iron carbide.
14. The method of claim 13, wherein in step (4), the mole ratio of epsilon/epsilon' iron carbide, chi iron carbide, and theta iron carbide is a: b: c, wherein 0 < a < 100,0 < b < 100, and 0 < c < 100.
15. The method of claim 14, wherein 0 < a.ltoreq. 90,0 < b.ltoreq. 75,0 < c.ltoreq.90.
16. The method of any one of claims 13-15, wherein the nano-powder iron compound is at least one of nano-iron oxide powder, nano-magnetite powder, nano-goethite powder, and nano-iron oxyhydroxide powder.
17. The method of any one of claims 13-15, wherein the nano-iron powder has an average grain diameter of 4-35nm.
18. The method of claim 17, wherein the nano-iron powder has an average grain diameter of 10-27nm.
19. The method of claim 16, wherein the nano-iron powder has an average grain diameter of 4-35nm.
20. The method of claim 19, wherein the nano-iron powder has an average grain diameter of 10-27nm.
21. The method according to any one of claims 13-15, 18-20, wherein in step (1-1), the pressure of the first surface cleaning treatment is 0.1-15atm; the time is 0.5-8h;
and/or, in the step (1-1), H 2 The gas flow rate of (2) is 500-20000mL/h/g.
22. The method according to claim 21, wherein in the step (1-1), the pressure of the first surface cleaning treatment is 0.2-2.5atm; the time is 1-7h;
and/or, in the step (1-1), H 2 The gas flow rate of (2) is 2500-15000mL/h/g.
23. The method according to claim 16, wherein in the step (1-1), the pressure of the first surface cleaning treatment is 0.1-15atm; the time is 0.5-8h;
and/or, in the step (1-1), H 2 The gas flow rate of (2) is 500-20000mL/h/g.
24. The method according to claim 23, wherein in the step (1-1), the pressure of the first surface cleaning treatment is 0.2-2.5atm; the time is 1-7h;
and/or, in the step (1-1), H 2 The gas flow rate of (2) is 2500-15000mL/h/g.
25. The method according to claim 17, wherein in the step (1-1), the pressure of the first surface cleaning treatment is 0.1-15atm; the time is 0.5-8h;
and/or, in the step (1-1), H 2 The gas flow rate of (2) is 500-20000mL/h/g.
26. The method according to claim 25, wherein in the step (1-1), the pressure of the first surface cleaning treatment is 0.2-2.5atm; the time is 1-7h;
and/or, in the step (1-1), H 2 The gas flow rate of (2) is 2500-15000mL/h/g.
27. The method according to any one of claims 13-15, 18-20, wherein in step (1-2), the pre-treatment is performed at a pressure of 0.05-7atm for 15-90min;
and/or, in the step (1-2), H 2 The total gas flow rate with CO is 200-8000mL/h/g.
28. The method of claim 27, wherein in step (1-2), the pre-treatment is performed at a pressure of 0.05-2.5atm for a time of 25-75min;
and/or, in the step (1-2), H 2 The total gas flow rate with CO is 1000-6500mL/h/g.
29. The method according to claim 16, wherein in the step (1-2), the pressure of the pretreatment is 0.05-7atm for 15-90min;
and/or, in the step (1-2), H 2 The total gas flow rate with CO is 200-8000mL/h/g.
30. The method of claim 29, wherein in step (1-2), the pre-treatment is performed at a pressure of 0.05-2.5atm for a time of 25-75min;
and/or, in the step (1-2), H 2 The total gas flow rate with CO is 1000-6500mL/h/g.
31. The method according to claim 17, wherein in the step (1-2), the pressure of the pretreatment is 0.05-7atm for 15-90min;
and/or, in the step (1-2), H 2 The total gas flow rate with CO is 200-8000mL/h/g.
32. The method of claim 31, wherein in step (1-2), the pre-treatment is performed at a pressure of 0.05-2.5atm for a time of 25-75min;
and/or, in the step (1-2), H 2 The total gas flow rate with CO is 1000-6500mL/h/g.
33. The method according to any one of claims 13 to 15, 18 to 20, wherein in step (1 to 3), the first carbide is prepared at a pressure of 0.09 to 10atm for a time of 0.5 to 10 hours;
and/or, in the step (1-3), H 2 The total gas flow rate with CO is 200-20000mL/h/g.
34. The method of claim 33, wherein in step (1-3), the first carbide is prepared at a pressure of 0.15-3atm for a time of 1.5-8 hours;
and/or, in the step (1-3), H 2 The total gas flow rate with CO is 4000-15000mL/h/g.
35. The method according to claim 16, wherein in the step (1-3), the first carbide is prepared at a pressure of 0.09-10atm for a time of 0.5-10 hours;
and/or, in the step (1-3), H 2 The total gas flow rate with CO is 200-20000mL/h/g.
36. The method of claim 35, wherein in step (1-3), the first carbide is prepared at a pressure of 0.15-3atm for a time of 1.5-8 hours;
and/or, in the step (1-3), H 2 The total gas flow rate with CO is 4000-15000mL/h/g.
37. The method according to claim 17, wherein in the step (1-3), the first carbide is prepared at a pressure of 0.09-10atm for a time of 0.5-10 hours;
and/or, in the step (1-3), H 2 The total gas flow rate with CO is 200-20000mL/h/g.
38. The method according to claim 37, wherein in the step (1-3), the first carbide is prepared at a pressure of 0.15-3atm for a time of 1.5-8 hours;
and/or, in the step (1-3), H 2 The total gas flow rate with CO is 4000-15000mL/h/g.
39. The method of any one of claims 13-15, 18-20, wherein the first carbide preparation further comprises: and (3) simultaneously carrying out temperature rising operation in the step (1-3), and rising the temperature from the temperature of the pretreatment to 180-280 ℃ at a temperature rising rate of 0.2-5 ℃/min.
40. The method of claim 39, wherein the temperature from the pretreatment is raised to 200-270 ℃ at a ramp rate of 0.2-2.5 ℃/min.
41. The method of claim 16, wherein the first carbide preparation further comprises: and (3) simultaneously carrying out temperature rising operation in the step (1-3), and rising the temperature from the temperature of the pretreatment to 180-280 ℃ at a temperature rising rate of 0.2-5 ℃/min.
42. The method of claim 41, wherein the temperature from the pretreatment is raised to 200-270 ℃ at a rate of rise of 0.2-2.5 ℃/min.
43. The method of claim 17, wherein the first carbide preparation further comprises: and (3) simultaneously carrying out temperature rising operation in the step (1-3), and rising the temperature from the temperature of the pretreatment to 180-280 ℃ at a temperature rising rate of 0.2-5 ℃/min.
44. The method of claim 43, wherein the temperature from the pretreatment is raised to 200-270 ℃ at a rate of rise of 0.2-2.5 ℃/min.
45. The method according to any one of claims 13-15, 18-20, wherein in step (2-1), the pressure of the second surface cleaning treatment is 0-25atm; the time is 1-40h;
and/or, in the step (2-1), H 2 The gas flow rate of (2) is 400-22000mL/h/g.
46. The method according to claim 45, wherein in the step (2-1), the pressure of the second surface cleaning treatment is 0.01-3atm; the time is 2-18h;
and/or, in the step (2-1), H 2 The gas flow rate of (C) is 1000-18000mL/h/g.
47. The method according to claim 16, wherein in the step (2-1), the pressure of the second surface cleaning treatment is 0 to 25atm; the time is 1-40h;
and/or, in the step (2-1), H 2 The gas flow rate of (2) is 400-22000mL/h/g.
48. The method according to claim 47, wherein in the step (2-1), the pressure of the second surface cleaning treatment is 0.01-3atm; the time is 2-18h;
and/or, in the step (2-1), H 2 The gas flow rate of (C) is 1000-18000mL/h/g.
49. The method according to claim 17, wherein in the step (2-1), the pressure of the second surface cleaning treatment is 0 to 25atm; the time is 1-40h;
and/or, in the step (2-1), H 2 The gas flow rate of (2) is 400-22000mL/h/g.
50. The method according to claim 49, wherein in the step (2-1), the pressure of the second surface cleaning treatment is 0.01-3atm; the time is 2-18h;
and/or, in the step (2-1), H 2 The gas flow rate of (C) is 1000-18000mL/h/g.
51. The method according to any one of claims 13-15, 18-20, wherein in step (2-2), the second carbide is prepared at a pressure of 0-28atm for a time of 20-120 hours;
And/or, in the step (2-2), H 2 The total gas flow rate with CO is 200-35000mL/h/g.
52. The method according to claim 51, wherein in the step (2-2), the second carbide is prepared at a pressure of 0.01-20atm for a time of 24-80 hours;
and/or, in the step (2-2), H 2 The total gas flow rate with CO is 1200-20000mL/h/g.
53. The method according to claim 16, wherein in the step (2-2), the second carbide is prepared at a pressure of 0-28atm for a time of 20-120 hours;
and/or, in the step (2-2), H 2 The total gas flow rate with CO is 200-35000mL/h/g.
54. The method of claim 53, wherein in step (2-2), the second carbide is prepared at a pressure of 0.01-20atm for a time of 24-80 hours;
and/or, in the step (2-2), H 2 The total gas flow rate with CO is 1200-20000mL/h/g.
55. The method according to claim 17, wherein in the step (2-2), the second carbide is prepared at a pressure of 0-28atm for a time of 20-120 hours;
and/or, in the step (2-2), H 2 The total gas flow rate with CO is 200-35000mL/h/g.
56. The method according to claim 55, wherein in the step (2-2), the second carbide is prepared at a pressure of 0.01-20atm for a time of 24-80 hours;
And/or, in the step (2-2), H 2 The total gas flow rate with CO is 1200-20000mL/h/g.
57. The method of any one of claims 13-15, 18-20, wherein the second carbide preparation further comprises: in the step (2-2), the temperature change operation is carried out simultaneously, and the temperature is changed from the temperature T 1 Cooling or heating to temperature T at a variable temperature rate of 0.2-5deg.C/min 2 。
58. The method of claim 57, wherein the temperature T is selected from the group consisting of 1 The temperature is reduced or increased to 300-400 ℃ at a variable temperature rate of 0.2-2.5 ℃/min.
59. The method of claim 16, wherein the second carbide preparation further comprises: in the step (2-2), the temperature change operation is carried out simultaneously, and the temperature is changed from the temperature T 1 Cooling or heating to temperature T at a variable temperature rate of 0.2-5deg.C/min 2 。
60. The method of claim 59, wherein the temperature T is selected from 1 The temperature is reduced or increased to 300-400 ℃ at a variable temperature rate of 0.2-2.5 ℃/min.
61. The method of claim 17, wherein the second carbide preparation further comprises: in the step (2-2), the temperature change operation is carried out simultaneously, and the temperature is changed from the temperature T 1 Cooling or heating to temperature T at a variable temperature rate of 0.2-5deg.C/min 2 。
62. The method of claim 61, wherein the temperature T is selected from 1 The temperature is reduced or increased to 300-400 ℃ at a variable temperature rate of 0.2-2.5 ℃/min.
63. The method according to any one of claims 13-15, 18-20, wherein in step (3-1), the pressure of the third surface cleaning treatment is 0.12-18atm; the time is 1.2-30h;
and/or, in the step (3-1), H 2 The gas flow rate of (2) is 600-25000mL/h/g.
64. The method according to claim 63, wherein in the step (3-1), the pressure of the third surface cleaning treatment is 0.22-2.5atm; the time is 2-12h;
and/or, in the step (3-1), H 2 The gas flow rate of (C) is 1200-16000mL/h/g.
65. The method according to claim 16, wherein in the step (3-1), the pressure of the third surface cleaning treatment is 0.12-18atm; the time is 1.2-30h;
and/or, in the step (3-1), H 2 The gas flow rate of (2) is 600-25000mL/h/g.
66. The method according to claim 65, wherein in the step (3-1), the pressure of the third surface cleaning treatment is 0.22-2.5atm; the time is 2-12h;
and/or, in the step (3-1), H 2 The gas flow rate of (C) is 1200-16000mL/h/g.
67. The method according to claim 17, wherein in the step (3-1), the pressure of the third surface cleaning treatment is 0.12-18atm; the time is 1.2-30h;
and/or, in the step (3-1), H 2 The gas flow rate of (2) is 600-25000mL/h/g.
68. The method according to claim 67, wherein in step (3-1), the pressure of the third surface purification treatment is 0.22-2.5atm; the time is 2-12h;
and/or, in the step (3-1), H 2 The gas flow rate of (C) is 1200-16000mL/h/g.
69. The method according to any one of claims 13-15, 18-20, wherein in step (3-2), the surface passivation treatment is performed at a pressure of 0-1.6atm for a time of 5-72 hours;
and/or, in step (3-2), the O-containing 2 The gas flow rate of the gas is 400-12000mL/h/g.
70. The method of claim 69, wherein in the step (3-2), the surface passivation treatment is performed at a pressure of 0 to 0.09atm for a time of 10 to 56 hours;
and/or, in step (3-2), the O-containing 2 The gas flow rate of the gas is 1400-8500mL/h/g.
71. The method of claim 16, wherein in the step (3-2), the surface passivation treatment is performed at a pressure of 0-1.6atm for a time of 5-72 hours;
and/or, in step (3-2), the O-containing 2 The gas flow rate of the gas is 400-12000mL/h/g.
72. The method of claim 71, wherein in the step (3-2), the surface passivation treatment is performed at a pressure of 0-0.09atm for a time of 10-56 hours;
And/or, in step (3-2), the O-containing 2 The gas flow rate of the gas is 1400-8500mL/h/g.
73. The method of claim 17, wherein in the step (3-2), the surface passivation treatment is performed at a pressure of 0-1.6atm for a time of 5-72 hours;
and/or, in step (3-2), the O-containing 2 The gas flow rate of the gas is 400-12000mL/h/g.
74. The method of claim 73, wherein in the step (3-2), the surface passivation treatment is performed at a pressure of 0-0.09atm for a time of 10-56 hours;
and/or, in step (3-2), the O-containing 2 The gas flow rate of the gas is 1400-8500mL/h/g.
75. The method according to any one of claims 13 to 15, 18 to 20, wherein in step (3-3), the third carbide is prepared at a pressure of 0.08 to 12atm for a time of 0.3 to 30 hours;
and/or, in the step (3-3), H 2 The total gas flow rate with CO is 250-21000mL/h/g.
76. The method according to claim 75, wherein in step (3-3), the third carbide is prepared at a pressure of 0.15-2.5atm for a time of 0.5-2.4 hours;
and/or, in the step (3-3), H 2 The total gas flow rate with CO is 2000-18000mL/h/g.
77. The method according to claim 16, wherein in the step (3-3), the third carbide is prepared at a pressure of 0.08-12atm for a time of 0.3-30 hours;
And/or, in the step (3-3), H 2 The total gas flow rate with CO is 250-21000mL/h/g.
78. The method according to claim 77, wherein in step (3-3), the pressure of the third carbide preparation is 0.15-2.5atm for 0.5-2.4 hours;
and/or, in the step (3-3), H 2 The total gas flow rate with CO is 2000-18000mL/h/g.
79. The method according to claim 17, wherein in the step (3-3), the third carbide is prepared at a pressure of 0.08-12atm for a time of 0.3-30 hours;
and/or, in the step (3-3), H 2 The total gas flow rate with CO is 250-21000mL/h/g.
80. The method of claim 79, wherein in step (3-3), the third carbide is prepared at a pressure of 0.15-2.5atm for a time of 0.5-2.4 hours;
and/or, in the step (3-3), H 2 The total gas flow rate with CO is 2000-18000mL/h/g.
81. The method of any one of claims 13-15, 18-20, wherein the third carbide preparation further comprises: and (3-3) simultaneously carrying out temperature rising operation, wherein the temperature of the surface passivation treatment is raised to 250-430 ℃ at a temperature rising rate of 0.2-5 ℃/min.
82. The method of claim 81, wherein the temperature from the surface passivation treatment is raised to 260-400 ℃ at a ramp rate of 0.2-2.5 ℃/min.
83. The method of claim 16, wherein the third carbide preparation further comprises: and (3-3) simultaneously carrying out temperature rising operation, wherein the temperature of the surface passivation treatment is raised to 250-430 ℃ at a temperature rising rate of 0.2-5 ℃/min.
84. The method of claim 83, wherein the temperature from the surface passivation treatment is raised to 260-400 ℃ at a ramp rate of 0.2-2.5 ℃/min.
85. The method of claim 17, wherein the third carbide preparation further comprises: and (3-3) simultaneously carrying out temperature rising operation, wherein the temperature of the surface passivation treatment is raised to 250-430 ℃ at a temperature rising rate of 0.2-5 ℃/min.
86. The method of claim 85 wherein the temperature from the surface passivation process is raised to 260-400 ℃ at a ramp rate of 0.2-2.5 ℃/min.
87. The method of any one of claims 13-15, 18-20, 22-26, 28-32, 34-38, 40-44, 46-50, 52-56, 58-62, 64-68, 70-74, 76-80, 82-86, wherein in step (4), 97-100 parts by mole of pure epsilon/epsilon' iron carbide, chi iron carbide, and theta iron carbide, 0-3 parts by mole of Fe-containing impurities are mixed.
88. The method of claim 16, wherein in step (4), 97-100 parts by mole of pure epsilon/epsilon' iron carbide, chi iron carbide, and theta iron carbide, 0-3 parts by mole of Fe-containing impurities are mixed.
89. The method of claim 17, wherein in step (4), 97-100 mole parts of pure epsilon/epsilon' iron carbide, chi iron carbide, and theta iron carbide, 0-3 mole parts of Fe-containing impurities are mixed.
90. The method of claim 21, wherein in step (4), 97-100 parts by mole of pure epsilon/epsilon' iron carbide, chi iron carbide, and theta iron carbide, 0-3 parts by mole of Fe-containing impurities are mixed.
91. The method of claim 27, wherein in step (4), 97-100 parts by mole of pure epsilon/epsilon' iron carbide, chi iron carbide, and theta iron carbide, 0-3 parts by mole of Fe-containing impurities are mixed.
92. The method of claim 33, wherein in step (4), 97-100 parts by mole of pure epsilon/epsilon' iron carbide, chi iron carbide, and theta iron carbide, 0-3 parts by mole of Fe-containing impurities are mixed.
93. The method of claim 39, wherein in step (4), 97-100 parts by mole of pure epsilon/epsilon' iron carbide, chi iron carbide, and theta iron carbide, 0-3 parts by mole of Fe-containing impurities are mixed.
94. The method of claim 45, wherein in step (4), 97-100 parts by mole of pure epsilon/epsilon' iron carbide, chi iron carbide, and theta iron carbide, 0-3 parts by mole of Fe-containing impurities are mixed.
95. The method of claim 51, wherein in step (4), 97-100 parts by mole of pure ε/ε' iron carbide, χ iron carbide, and θ iron carbide, 0-3 parts by mole of Fe-containing impurities are mixed.
96. The method of claim 57, wherein in step (4), 97-100 parts by mole of pure ε/ε' iron carbide, χ iron carbide, and θ iron carbide, 0-3 parts by mole of Fe-containing impurities are mixed.
97. The method of claim 63, wherein in step (4), 97-100 parts by mole of pure epsilon/epsilon' iron carbide, chi iron carbide, and theta iron carbide, 0-3 parts by mole of Fe-containing impurities are mixed.
98. The method of claim 69, wherein in step (4), 97-100 parts by mole of pure epsilon/epsilon' iron carbide, chi iron carbide, and theta iron carbide, 0-3 parts by mole of Fe-containing impurities are mixed.
99. The method of claim 75, wherein in step (4), 97-100 parts by mole of pure epsilon/epsilon' iron carbide, chi iron carbide, and theta iron carbide, 0-3 parts by mole of Fe-containing impurities are mixed.
100. The method of claim 81, wherein in step (4), 97-100 parts by mole of pure epsilon/epsilon' iron carbide, chi iron carbide, and theta iron carbide, 0-3 parts by mole of Fe-containing impurities are mixed.
101. A catalyst comprising a composition of any one of claims 1-12 comprising epsilon/epsilon' iron carbide, chi iron carbide, and theta iron carbide.
102. Use of a composition comprising epsilon/epsilon' iron carbide, chi iron carbide and theta iron carbide as claimed in any one of claims 1 to 12 or a catalyst as claimed in claim 101 in a fischer-tropsch synthesis reaction.
103. Use of a composition comprising epsilon/epsilon' iron carbide, chi iron carbide and theta iron carbide as defined in any one of claims 1-12 or a catalyst as defined in claim 101 for the synthesis of C, H fuels and/or chemicals based on the fischer-tropsch synthesis principle.
104. A method of fischer-tropsch synthesis comprising: contacting the synthesis gas with a composition comprising epsilon/epsilon' iron carbide, chi iron carbide and theta iron carbide as claimed in any one of claims 1 to 12 or a catalyst as claimed in claim 101 under fischer-tropsch reaction conditions.
105. The process of claim 104, wherein the fischer-tropsch synthesis is carried out in a high temperature, high pressure continuous reactor.
106. A method of fischer-tropsch synthesis comprising: contacting the synthesis gas with a fischer-tropsch catalyst under fischer-tropsch reaction conditions, wherein the fischer-tropsch catalyst comprises a Mn component and a composition comprising epsilon/epsilon' iron carbide, χ iron carbide and θ iron carbide according to any one of claims 1 to 12.
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