CN112569980B - Composition containing precipitated epsilon/epsilon' iron carbide and chi iron carbide, preparation method, catalyst, application and Fischer-Tropsch synthesis method - Google Patents

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

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CN112569980B
CN112569980B CN202011059127.2A CN202011059127A CN112569980B CN 112569980 B CN112569980 B CN 112569980B CN 202011059127 A CN202011059127 A CN 202011059127A CN 112569980 B CN112569980 B CN 112569980B
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epsilon
iron carbide
carbide
iron
precipitated
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CN112569980A (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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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, a catalyst and application thereof, and a Fischer-Tropsch synthesis method. A composition comprising precipitated epsilon/epsilon ' iron carbide and chi iron carbide, said composition comprising 95 to 100 mole% of precipitated epsilon/epsilon ' iron carbide and chi iron carbide, and 0 to 5 mole% of Fe-containing impurities, said Fe-containing impurities being iron-containing species other than epsilon/epsilon ' iron carbide and chi iron carbide, based on the total amount of said composition; wherein the specific surface area of the composition is 40-320m 2 And/g. The epsilon/epsilon' iron carbide and the chi 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 precipitated epsilon/epsilon' iron carbide and chi 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 precipitated epsilon/epsilon' iron carbide and chi 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 discontinuous reaction of polyglycol solvent. 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 contains a considerable amount of non-iron carbide type iron impurity components in the nano-particles, and in fact, the prior art cannot obtain pure-phase iron carbide materials free of iron impurities, where Fe impurities refer to various Fe (elemental) containing phase components other than iron carbide.
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 a selectivity of byproducts provides 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.
To achieve the above object, a first aspect of the present invention provides a composition containing precipitated epsilon/epsilon ' iron carbide and chi iron carbide, the composition comprising 95 to 100mol% of precipitated epsilon/epsilon ' iron carbide and chi iron carbide, and 0 to 5mol% of Fe-containing impurities, which are iron-containing elemental substances 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 40-320m 2 /g。
In a second aspect, the invention provides 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 with an alkaline precipitant, 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 H 2 Performing a first reduction at a temperature of 450-580 ℃;
(1-2) mixing the material obtained in the step (1-1) with H 2 Pretreating CO at 90-185 deg.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 200-300 deg.C, H 2 The molar ratio of the catalyst to CO is 1 to 3.2:1, a step of; obtaining precipitated epsilon/epsilon' iron carbide;
(2) Preparing precipitated χ iron carbide, comprising:
(2-1) reacting the precursor with H 2 Performing a second reduction at a temperature of 450-610 ℃;
(2-2) mixing the material obtained in the step (2-1) 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%;
(2-3) mixing the material obtained in the step (2-2) with H 2 Preparing second carbide by CO at 260-430 deg.C, H 2 The mol ratio of CO to CO is 7-110:1, a step of; obtaining precipitated type X iron carbide;
(3) Mixing 95-100 mole parts of precipitated epsilon/epsilon' iron carbide and chi iron carbide and 0-5 mole 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 comprising precipitated epsilon/epsilon' iron carbide and chi iron carbide produced by the method of 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 herein.
In a fifth aspect, the invention provides the use of a composition or catalyst comprising precipitated epsilon/epsilon' iron carbide and chi iron carbide as provided herein in a Fischer-Tropsch synthesis reaction.
In a sixth aspect, the invention provides a composition or catalyst comprising precipitated epsilon/epsilon' iron carbide and chi iron carbide as provided herein for use in a fischer-tropsch based synthesis reaction of C, H fuels and/or chemicals.
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 precipitated epsilon/epsilon' iron carbide and chi 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 precipitated epsilon/epsilon' iron carbide and chi iron carbide as 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 of the synthesis precursor can be commercial ferric salt, and when active phase carbide is synthesized, only the original reaction gas (carbon monoxide and hydrogen) of a Fischer-Tropsch synthesis reaction system is utilized, and no inorganic or organic reaction raw material is involved, so that compared with the prior art, the method is greatly simplified;
(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 provided by the invention can prepare epsilon/epsilon 'iron carbide and chi iron carbide with 100% purity by a separate precipitation method, and then the epsilon/epsilon' iron carbide and the chi iron carbide and Fe-containing impurities form a composition to further prepare the catalyst. The above iron carbide or composition or catalyst can be used for high temperature and high pressure (for example, temperature of 235-260 ℃, pressure of 2.0-2.5MPa, H) 2 The reaction stability of the continuous reactor is extremely high, which breaks the traditional paperTheory of the literature "pure iron carbide cannot exist stably under reaction conditions" theoretical technical barriers that can achieve stable temperatures up to 260 ℃, 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 7%), the effective product selectivity is above 81% (preferably above 89%), and the method is very suitable for the high-efficiency production of the oil wax products in the modern coal industry Fischer-Tropsch synthesis industry.
Drawings
FIG. 1 is an XRD spectrum of precipitated epsilon/epsilon' iron carbide as prepared in preparation example 1 provided in the present invention;
FIG. 2 is an XRD spectrum of precipitated χ -iron carbide produced in preparation example 2 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.
The first aspect of the present invention provides a composition comprising precipitated epsilon/epsilon ' iron carbide and chi iron carbide, said composition comprising 95 to 100 mole% of precipitated epsilon/epsilon ' iron carbide and chi iron carbide, and 0 to 5 mole% of Fe-containing impurities, based on the total amount of the composition, said Fe-containing impurities being an elemental iron-containing material other than epsilon/epsilon ' iron carbide and chi iron carbide; wherein the specific surface area of the composition is 40-320m 2 /g。
The present invention provides compositions wherein the precipitated epsilon/epsilon 'iron carbide is comprised of epsilon-iron carbide having a purity of 100% and/or epsilon' -iron carbide having a purity of 100% and chi iron carbide having a purity of 100%. Further, precipitated epsilon' and chi iron carbides may constitute the composition with other Fe-containing impurities. Under the limitation of the composition content, the invention provides a combination containing precipitated epsilon/epsilon' iron carbide and chi iron carbide When the material can be applied to the Fischer-Tropsch synthesis catalyst, the material can be singly used or combined with other components to realize the improvement of the stability of the Fischer-Tropsch synthesis catalyst in the Fischer-Tropsch synthesis reaction and the reduction of CO 2 Or CH (CH) 4 By-product selectivity.
In some embodiments of the invention, the compositions contain high purity precipitated epsilon/epsilon 'and chi iron carbides, and musburg analysis can be performed to observe that the crystalline phases comprise pure epsilon/epsilon' and chi iron carbides on the musburg results obtained. Preferably, the specific surface area of the composition is 50-270m 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 and monoclinic chi iron carbide.
In some embodiments of the invention, it is further preferred that the composition comprises 97-100 mole% precipitated epsilon/epsilon' iron carbide and chi 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, preferably, the Fe-containing impurity is at least one of iron carbide, iron oxide, iron hydroxide, iron sulfide, iron salt other than epsilon/epsilon' iron carbide and chi iron carbide. The Fe-containing impurities may be introduced by solution impregnation, sputtering, atomic deposition or mixing.
In the specific embodiment provided by the invention, the mol 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, and preferably a is more than 0 and less than or equal to 75,0 and b is more than or equal to 75. The molar ratio of the two phases of iron carbide can produce a coordinated effect within 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 precipitated epsilon/epsilon' iron carbide and chi iron carbide, comprising:
mixing and coprecipitating an aqueous solution containing ferric salt with an alkaline precipitant, 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 H 2 Performing a first reduction at a temperature of 450-580 ℃;
(1-2) mixing the material obtained in the step (1-1) with H 2 Pretreating CO at 90-185 deg.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 200-300 deg.C, H 2 The molar ratio of the catalyst to CO is 1 to 3.2:1, a step of; obtaining precipitated epsilon/epsilon' iron carbide;
(2) Preparing precipitated χ iron carbide, comprising:
(2-1) reacting the precursor with H 2 Performing a second reduction at a temperature of 450-610 ℃;
(2-2) mixing the material obtained in the step (2-1) 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%;
(2-3) mixing the material obtained in the step (2-2) with H 2 Preparing second carbide by CO at 260-430 deg.C, H 2 The mol ratio of CO to CO is 7-110:1, a step of; obtaining precipitated type X iron carbide;
(3) Mixing 95-100 mole parts of precipitated epsilon/epsilon' iron carbide and chi iron carbide and 0-5 mole 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.
The precursor is prepared first according to one embodiment of the invention. In this preparation process, preferably, the iron salt may be a water-soluble iron salt commonly used in the art, the iron salt is selected from water-soluble iron salts, and may be commercially available, for example, the iron salt is at least one of ferric nitrate, ferric chloride, ferrous ammonium sulfate, and ferric ammonium citrate. The alkaline precipitant 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 conditions of the precipitation include: the pH value is 6-9, and the temperature is 45-90 ℃.
In the preparation process of the precursor, the precipitate is washed, which may be a solid obtained by washing with deionized water for a plurality of times until the conductivity of the washing filtrate is lower than 290 mu S/cm and solid-liquid separation is carried out for a plurality of times in the washing process. Preferably, the solid is firstly dried for 6 to 10 hours at the temperature of 35 to 80 ℃ and the vacuum degree of 250 to 1200 Pa; drying the dried material at 75-180 ℃ for 3-24 hours, and roasting the obtained material at 250-580 ℃ for 1-10 hours. And obtaining the precursor.
The present invention provides one embodiment for preparing precipitated epsilon/epsilon' iron carbide.
In some embodiments of the present invention, the step (1-1) may serve to simultaneously generate nano iron powder in situ from the iron element in the precursor and reduce the generated nano iron powder.
In some embodiments of the present invention, 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 reduction, preferably in step (1-1), which is 0.1 to 15atm, preferably 0.3 to 2.6atm, for 0.7 to 15 hours, preferably 1 to 12 hours.
In some embodiments of the invention, H 2 The amount of (C) may be selected according to the amount of the precursor to be treated, preferably H in the step (1-1) 2 The gas flow rate of (C) is 600-25000mL/h/g, more preferably 2800-22000mL/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 the step (1-2)The pretreatment pressure is 0.05-7atm, preferably 0.08-4.5atm, and the time is 15-120min, preferably 20-90min.
In some embodiments of the present invention, preferably, in step (1-2), H 2 The total gas flow with CO is 300-12000mL/h/g, more preferably 1500-9000mL/h/g.
In step (1-3) of the method provided by the present invention, conditions are provided to effect the preparation of the first carbide to obtain precipitated epsilon/epsilon' 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 (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 2.5-12h;
In some embodiments of the present invention, preferably, in step (1-3), H 2 The total gas flow with CO is 500-30000mL/h/g, more preferably 3000-25000mL/h/g.
In a preferred embodiment of the present invention, the first carbide manufacturing method further includes: and (3) simultaneously performing temperature rising operation, and rising the temperature from the pretreatment temperature to 200-300 ℃ at a temperature rising 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 reaction. Further preferably, the temperature from the pretreatment is raised 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: the temperature is raised from 90 to 185℃to 200 to 300℃in step (1-3) at a temperature-raising rate of 0.2 to 5℃per minute, preferably from 90 to 185℃to 210 to 290℃at a temperature-raising rate of 0.2 to 2.5℃per minute.
One embodiment of the present invention prepares precipitated χ iron carbide.
In some embodiments of the present invention, the step (2-1) may serve to simultaneously generate nano iron powder in situ from the iron element in the precursor and reduce the generated nano iron powder.
In some embodiments of the present invention, 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 reduction, preferably in step (2-1), which is 0.1 to 15atm, preferably 0.3 to 2.6atm; the time is 0.7-15h, preferably 1-12h.
In some embodiments of the invention, H 2 The amount of (c) may be selected according to the amount of the precursor to be treated, preferably H 2 The gas flow rate of (C) is 600-25000mL/h/g, more preferably 2800-22000mL/h/g.
In the step (2-2) 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 (2-2), 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 (2-2), the O-containing 2 The gas flow rate of the gas is 400-12000mL/h/g, more preferably 1400-8500mL/h/g.
In step (2-3) of the method provided by the present invention, conditions are provided to achieve the preparation of the second 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 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 0.08-12atm, 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 (2-3), H 2 The total gas flow rate with CO is 250-21000mL/h/g, more preferably 2000-18000mL/h/g。
In a preferred embodiment of the present invention, the second carbide preparation further comprises: and (3) simultaneously carrying out temperature rising operation in the step (2-3), and rising the temperature of the surface passivation treatment to 250-430 ℃ at a temperature rising rate of 0.2-5 ℃/min. In this preferred embodiment, the precipitated χ iron carbide obtained may have 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 (2-2). Namely, the temperature raising operation is: the temperature is raised from 0 to 50℃to 250 to 430℃in step (2 to 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 another preferred embodiment of the present invention, the first reduction, pretreatment and first carbide preparation may be performed in the same Fischer-Tropsch reactor during the preparation of precipitated epsilon/epsilon' iron carbide. During the preparation of precipitated χ -iron carbide, the second reduction, surface passivation treatment, and second carbide preparation may be performed in the same Fischer-Tropsch reactor. In-situ characterization equipment can be used for tracking the crystal phase transition of materials in the preparation process.
In the invention, the precipitated epsilon/epsilon' iron carbide and precipitated chi iron carbide can be obtained through the steps (1) and (2) in the method provided by the invention.
In the method step (3), precipitated epsilon/epsilon' iron carbide and chi iron carbide are mixed to form precipitated iron carbide. The result of said mixing is such that preferably 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, and preferably a is more than 0 and less than or equal to 75,0 and b is more than or equal to 75.
In some embodiments of the invention, the composition comprising precipitated epsilon/epsilon' iron carbide and chi iron carbide may comprise Fe-containing impurities that are incorporated by way of external addition. Preferably, in step (3), 97-100 mole parts of precipitated epsilon/epsilon' iron carbide and chi iron carbide are mixed with 0-3 mole parts of Fe-containing impurities.
In the step (3) of the method provided by the invention, the powder of the precipitated epsilon/epsilon' iron carbide and the powder of the chi iron carbide and the powder of the 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 precipitated epsilon/epsilon' iron carbide and chi iron carbide produced by the method of the invention. The composition comprises 95-100mol% of precipitated epsilon/epsilon 'iron carbide and chi iron carbide, and 0-5mol% of Fe-containing impurities, based on the total amount of the composition, wherein the Fe-containing impurities are iron-containing substances except epsilon/epsilon' iron carbide and chi iron carbide.
Preferably, the composition comprises 97-100 mole% precipitated epsilon/epsilon' iron carbide and chi iron carbide, and 0-3 mole% Fe-containing impurities, based on the total amount of the composition.
Preferably, the specific surface area of the composition is 40-320m 2 Preferably 50-270m 2 /g。
Preferably, the mole ratio of ε/ε' iron carbide to χ iron carbide is a: b, wherein a is more than 0 and less than 100, b is more than 0 and less than 100, and preferably a is more than 0 and less than or equal to 75,0 and b is more 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 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 precipitated epsilon/epsilon' iron carbide and chi 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 precipitated epsilon/epsilon' iron carbide and chi 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 precipitated epsilon/epsilon' iron carbide and chi 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 precipitated epsilon/epsilon' iron carbide and chi iron carbide as provided by the invention.
The Fischer-Tropsch reaction using the precipitated epsilon/epsilon' iron carbide and chi iron carbide containing composition or catalyst of the present invention can be carried out at high temperatures and pressures, 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 the precipitated epsilon/epsilon' iron carbide and the precipitated chi 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 precipitated epsilon/epsilon' iron carbide and chi iron carbide as provided by the invention.
In the specific embodiment provided by the invention, the composition of the Fischer-Tropsch catalyst can be further 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 75wt% and less than 100wt%, and the content of Mn 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%
The feed CO space-time conversion rate (mmol/h/g-Fe) = (moles of CO in feed-moles of CO in discharge)/reaction time/Fe element weight;
space-time yield (mmol/h/g-Fe) =c of reaction of the effective product formation 2 C (C) 2 The above hydrocarbon mole number/reaction time/Fe element weight.
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 at the temperature of 60 ℃ and the pH value of 7.2 to obtain precipitate slurry, washing the precipitate slurry by deionized water, filtering the precipitate slurry to obtain a filter cake, drying the filter cake at 120 ℃ for 24h, and roasting the filter cake at 350 ℃ for 5h to obtain a precursor.
(2) Precursor and H 2 At a pressure of 2.0atm, H 2 The flow rate of the catalyst is 20000mL/h/g, and the first reduction is carried out for 1h at the temperature of 460 ℃;
(3) Cooling the product obtained in the step (2) to 160 ℃, and reacting with H at 160 DEG C 2 The mixture with CO (pressure 4.5atm, total gas flow 9000mL/H/g, H 2 Contact with CO in a molar ratio of 2:1) for pretreatment for 20min;
(4) Will H 2 The condition of the mixed gas with CO is as follows: pressure 3.5atm, total gas flow 12000mL/H/g, H 2 And (3) heating the mixture from 160 ℃ to 270 ℃ at a heating rate of 2.5 ℃/min under the condition, and then carrying out first carbide preparation with the material obtained in the step (3) for 2.5 hours to obtain precipitated iron carbide, wherein the precipitated iron carbide is determined to be pure epsilon/epsilon' iron carbide by Mossburg spectrum, and is denoted 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 concrete implementation method for preparing the precipitated epsilon/epsilon ' iron carbide is described in the examples of the Chinese patent application containing the precipitated epsilon/epsilon ' iron carbide composition, the preparation method, the catalyst and the application of the precipitated epsilon/epsilon ' iron carbide composition and the Fischer-Tropsch synthesis method, and the whole content of the precipitated epsilon/epsilon ' iron carbide composition is incorporated 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 at the temperature of 55 ℃ and the pH value of 6.5 to obtain precipitate slurry, washing with deionized water, filtering to obtain a filter cake, drying at 110 ℃ for 24h, and roasting at 400 ℃ for 10h to obtain a precursor.
(b) Precursor and H 2 At a pressure of 1.8atm, H 2 The flow rate of 18000mL/h/g, and the second reduction is carried out for 1h at the temperature of 460 ℃;
(c) Cooling the product from step (b) to 35 ℃ and reacting with an O-containing catalyst at this temperature 2 Inert gas contact surfacePassivation treatment, O in gas 2 The volume concentration of (2) is 1%, the pressure is 0.08atm, the gas flow rate is 7500mL/h/g, and the treatment time is 20h;
(d) Will contain O 2 Is changed into H 2 And CO under the following conditions: pressure 2.0atm, total gas flow 18000mL/H/g, H 2 And (2) heating the mixture from 35 ℃ to 360 ℃ at a heating rate of 2.0 ℃/min under the condition, and then preparing a second carbide from the product obtained in the step (c) for 2.5 hours to obtain precipitated iron carbide, wherein the precipitated iron carbide is determined to be pure χ iron carbide by Mosburg spectrum, and is denoted as iron carbide 2.
The preparation method of the precipitated type χ -iron carbide provided by the invention is not limited to preparation example 2, and the specific implementation method for preparing the precipitated type χ -iron carbide is described in the examples of the Chinese patent application containing the precipitated type χ -iron carbide composition, the preparation method, the catalyst and the application and the Fischer-Tropsch synthesis method.
Example 1
Under the protection of Ar gas, 72 parts by mole (based on 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 impurity) are mixed. After mixing, this was designated as iron carbide composition 1.
Example 2
26 parts by mole of iron carbide 1, 72 parts by mole of iron carbide 2 and 2 parts by mole of ferrous oxide (i.e., fe-containing impurities) are mixed under Ar gas protection. After mixing, this was designated iron carbide composition 2.
Example 3
Under the protection of Ar gas, 79 mole parts of iron carbide 1 and 20 mole parts of iron carbide 2 are mixed with 1 mole part of ferrous oxide (namely Fe-containing impurities). After mixing, this was designated as iron carbide composition 3.
Example 4
Under the protection of Ar gas, 20 mole parts of iron carbide 1, 77 mole parts of iron carbide 2 and 3 mole parts of ferrous oxide (i.e. Fe-containing impurities) are mixed. After mixing, this was designated iron carbide composition 4.
Comparative example 1
Under the protection of Ar gas, 79 mole parts of iron carbide 1, 14 mole parts of iron carbide 2 and 7 mole parts of ferrous oxide (i.e. 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, 14 mole parts of iron carbide 1, 80 mole parts of iron carbide 2 and 6 mole parts of ferrous oxide (namely Fe-containing impurities) are mixed. After mixing, this was designated as iron carbide composition D2.
Examples 5 to 8
Iron carbide compositions 1-4 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 air flow for 24 hours to obtain the Fischer-Tropsch catalyst 1-4. Wherein the amount of manganese citrate solution added by impregnation is such that the resulting Fischer-Tropsch catalysts 1-4 respectively contain 85wt% of iron carbide composition 1-6, 15wt% of MnO 2
Comparative examples 3 to 4
Taking iron carbide compositions D1-D2, 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-D2. Wherein the amount of manganese citrate solution added is impregnated such that the resulting Fischer-Tropsch catalysts D1-D2 respectively contain 85wt% of the iron carbide composition D1-D2, 15wt% of MnO 2
Test case
Mossburg spectrum measurement is carried out on the iron carbide 1-2, 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 BDA0002711719170000161
In which preparation examples 1 and 2 were subjected to in situ XRD detection technique, 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 that carbide 1 obtained after completion of all carbonization steps has a crystal phase of epsilon-Fe with 100% purity 2 C and ε -Fe 2.2 C, i.e. epsilon/epsilonThe curve of 'iron carbide' and one XRD standard card PDF-89-2005 shows that 2 theta = 37.7 degrees, 41.4 degrees, 43.2 degrees, 57.2 degrees, 68.0 degrees, 76.8 degrees and 82.9 degrees 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 carbide 2 obtained after completion of all carbonization steps has a crystal phase of X-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.
Mossburg spectra and BET specific surface areas were measured 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
Catalytic performance evaluations were performed on Fischer-Tropsch catalysts 1-4, D1-D2, and iron carbide compositions 1-2, respectively, in a fixed bed continuous reactor. The catalyst loading was 10.0g.
Evaluation conditions: t=240 ℃, p=2.3 mpa, h 2 :CO=1.8:1,(H 2 +CO) total = 40000mL/h/g- Fe (standard state flow, relative to the Fe element). 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 are shown in tables 3 and 4.
TABLE 3 Table 3
Figure BDA0002711719170000172
TABLE 4 Table 4
Figure BDA0002711719170000173
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Figure BDA0002711719170000181
As can be seen from the above examples, comparative examples and the data in tables 1-4, the compositions or catalysts prepared according to the present invention comprising precipitated epsilon/epsilon' iron carbide and chi iron carbide are subjected to Fischer-Tropsch reactions under commercial conditions, exhibiting high space-time conversion rates of raw CO over a defined range of conditions, better reactivity, and ultra-low CO 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 precipitated epsilon/epsilon' iron carbide and chi 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 the precipitated epsilon/epsilon' iron carbide and the precipitated chi iron carbide 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 7%) and the selectivity of the effective product is above 81% (preferably above 89%). Wherein the preferred conditions (catalyst1-2) the space-time yield of the catalyst-effective product of 160mmol/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 (64)

1. A composition comprising precipitated epsilon/epsilon ' iron carbide and chi iron carbide, said composition comprising 95 to 100 mole% of precipitated epsilon/epsilon ' iron carbide and chi iron carbide, and 0 to 5 mole% of Fe-containing impurities, said Fe-containing impurities being elemental iron-containing materials other than epsilon/epsilon ' iron carbide and chi iron carbide, based on the total amount of said composition;
wherein the specific surface area of the composition is 40-320m 2 /g; the Fe-containing impurity is not 0;
the preparation method of the composition comprises the following steps:
mixing and coprecipitating an aqueous solution containing ferric salt with an alkaline precipitant, 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 H 2 Performing a first reduction at a temperature of 450-580 ℃;
(1-2) mixing the material obtained in the step (1-1) with H 2 Pretreating CO at 90-185 deg.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 200-300 deg.C, H 2 The molar ratio of the catalyst to CO is 1 to 3.2:1, a step of; obtaining precipitated epsilon/epsilon' iron carbide;
(2) Preparing precipitated χ iron carbide, comprising:
(2-1) reacting the precursor with H 2 Performing a second reduction at a temperature of 450-610 ℃;
(2-2) mixing the material obtained in the step (2-1) 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%;
(2-3) mixing the material obtained in the step (2-2) with H 2 Preparing second carbide by CO at 260-430 deg.C, H 2 The mol ratio of CO to CO is 7-110:1, a step of; obtaining precipitated type X iron carbide;
(3) 95-100 mole parts of precipitated epsilon/epsilon' iron carbide and chi iron carbide and 0-5 mole parts of Fe-containing impurities are mixed under inert gas.
2. The composition according to claim 1, wherein the specific surface area of the composition is 50-270m 2 /g。
3. Composition according to claim 1 or 2, wherein the composition comprises 97-100mol% precipitated epsilon/epsilon' iron carbide and chi iron carbide, and 0-3mol% Fe-containing impurities, based on the total amount of the composition.
4. The composition according to claim 1 or 2, wherein the Fe-containing impurities are at least one of iron carbide other than epsilon/epsilon' iron carbide and χ iron carbide, iron oxides, iron hydroxides, iron sulfides, iron salts.
5. A composition according to claim 3, wherein the Fe-containing impurities are at least one of iron carbide other than epsilon/epsilon' iron carbide and χ iron carbide, iron oxides, iron hydroxides, iron sulfides, iron salts.
6. Composition according to any one of claims 1-2 and 5, wherein the molar ratio of precipitated epsilon/epsilon' iron carbide to χ iron carbide is a: b, wherein 0 < a < 100, and 0 < b < 100.
7. The composition of claim 6, wherein 0 < a.ltoreq. 75,0 < b.ltoreq.75.
8. A composition according to claim 3, wherein the molar ratio of precipitated epsilon/epsilon' iron carbide to chi iron carbide is a: b, wherein 0 < a < 100, and 0 < b < 100.
9. The composition of claim 8, wherein 0 < a.ltoreq. 75,0 < b.ltoreq.75.
10. The composition of claim 4, wherein the molar ratio of precipitated epsilon/epsilon' iron carbide to chi iron carbide is a: b, wherein 0 < a < 100, and 0 < b < 100.
11. The composition of claim 10, wherein 0 < a.ltoreq. 75,0 < b.ltoreq.75.
12. 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 with an alkaline precipitant, 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 H 2 Performing a first reduction at a temperature of 450-580 ℃;
(1-2) mixing the material obtained in the step (1-1) with H 2 Pretreating CO at 90-185 deg.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 200-300 deg.C, H 2 Molar ratio to CO of1-3.2:1, a step of; obtaining precipitated epsilon/epsilon' iron carbide;
(2) Preparing precipitated χ iron carbide, comprising:
(2-1) reacting the precursor with H 2 Performing a second reduction at a temperature of 450-610 ℃;
(2-2) mixing the material obtained in the step (2-1) 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%;
(2-3) mixing the material obtained in the step (2-2) with H 2 Preparing second carbide by CO at 260-430 deg.C, H 2 The mol ratio of CO to CO is 7-110:1, a step of; obtaining precipitated type X iron carbide;
(3) Mixing 95-100 mole parts of precipitated epsilon/epsilon' iron carbide and chi iron carbide and 0-5 mole 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.
13. The method of claim 12, wherein in step (3), the molar ratio of precipitated epsilon/epsilon' iron carbide to χ iron carbide is a: b, wherein 0 < a < 100, and 0 < b < 100.
14. The method of claim 13, wherein 0 < a.ltoreq. 75,0 < b.ltoreq.75.
15. The method of any one of claims 12-14, wherein the iron salt is selected from water-soluble iron salts;
the alkaline precipitant is at least one of sodium carbonate, sodium bicarbonate, potassium carbonate, potassium bicarbonate, sodium hydroxide, potassium hydroxide and ammonia water;
and/or, firstly, drying the solid for 6-10h at the temperature of 35-80 ℃ and the vacuum degree of 250-1200 Pa; drying the dried material at 75-180 ℃ for 3-24 hours, and roasting the obtained material at 250-580 ℃ for 1-10 hours.
16. The method of claim 15, wherein the iron salt is selected from at least one of ferric nitrate, ferric chloride, ferrous ammonium sulfate, and ferric ammonium citrate.
17. The method according to any one of claims 12 to 14, 16, wherein in step (1-1), the pressure of the first reduction is 0.1 to 15atm for 0.7 to 15 hours;
And/or, in the step (1-1), H 2 The gas flow rate of (2) is 600-25000mL/h/g.
18. The method of claim 17, wherein in step (1-1), the pressure of the first reduction is 0.3-2.6atm for 1-12 hours;
and/or, in the step (1-1), H 2 The gas flow rate of (2) is 2800-22000mL/h/g.
19. The method of claim 15, wherein in step (1-1), the pressure of the first reduction is 0.1-15atm for 0.7-15 hours;
and/or, in the step (1-1), H 2 The gas flow rate of (2) is 600-25000mL/h/g.
20. The method of claim 19, wherein in step (1-1), the pressure of the first reduction is 0.3-2.6atm for 1-12 hours;
and/or, in the step (1-1), H 2 The gas flow rate of (2) is 2800-22000mL/h/g.
21. The method according to any one of claims 12 to 14, 16, wherein in step (1-2), the pre-treatment is performed at a pressure of 0.05 to 7atm for 15 to 120 min;
and/or, in the step (1-2), H 2 The total gas flow rate with CO is 300-12000mL/h/g.
22. The method of claim 21, wherein in step (1-2), the pre-treatment is performed at a pressure of 0.08-4.5atm for a time of 20-90min;
And/or, in the step (1-2), H 2 The total gas flow rate with CO is 1500-9000mL/h/g.
23. The method according to claim 15, wherein in the step (1-2), the pressure of the pretreatment is 0.05-7atm for 15-120 min;
and/or, in the step (1-2), H 2 The total gas flow rate with CO is 300-12000mL/h/g.
24. The method of claim 23, wherein in step (1-2), the pre-treatment is performed at a pressure of 0.08-4.5atm for a time of 20-90min;
and/or, in the step (1-2), H 2 The total gas flow rate with CO is 1500-9000mL/h/g.
25. A method according to any one of claims 12 to 14, 16, wherein in step (1-3), the first carbide is prepared at a pressure of 0.1-10atm for a time of 1.5-15 hours;
and/or, in the step (1-3), H 2 The total gas flow rate with CO is 500-30000mL/h/g.
26. The method of claim 25, wherein in the step (1-3), the first carbide is prepared at a pressure of 0.2-4.5atm for a time of 2.5-12 hours;
and/or, in the step (1-3), H 2 The total gas flow rate with CO is 3000-25000 mL/h/g.
27. The method according to claim 15, wherein in the step (1-3), the first carbide is prepared at a pressure of 0.1-10atm for a time of 1.5-15 hours;
And/or, in the step (1-3), H 2 The total gas flow rate with CO is 500-30000mL/h/g.
28. The method of claim 27, wherein in the step (1-3), the first carbide is prepared at a pressure of 0.2-4.5atm for a time of 2.5-12 hours;
and/or, in the step (1-3), H 2 The total gas flow rate with CO is 3000-25000 mL/h/g.
29. The method of any one of claims 12-14, 16, wherein the first carbide manufacturing method further comprises: and (3) simultaneously performing temperature rising operation, and rising the temperature from the pretreatment temperature to 200-300 ℃ at a temperature rising rate of 0.2-5 ℃/min.
30. The method of claim 29, wherein the temperature from the pretreatment is raised to 210-290 ℃ at a ramp rate of 0.2-2.5 ℃/min.
31. The method of claim 15, wherein the first carbide manufacturing method further comprises: and (3) simultaneously performing temperature rising operation, and rising the temperature from the pretreatment temperature to 200-300 ℃ at a temperature rising rate of 0.2-5 ℃/min.
32. The method of claim 31, wherein the temperature from the pretreatment is raised to 210-290 ℃ at a ramp rate of 0.2-2.5 ℃/min.
33. The method according to any one of claims 12-14, 16, wherein in step (2-1), the pressure of the second reduction is 0.1-15atm; the time is 0.7-15h;
and/or, in the step (2-1), H 2 The gas flow rate of (2) is 600-25000mL/h/g.
34. The method of claim 33, wherein in step (2-1), the pressure of the second reduction is 0.3-2.6atm; the time is 1-12h;
and/or, in the step (2-1), H 2 The gas flow rate of (2) is 2800-22000mL/h/g.
35. The method of claim 15, wherein in step (2-1), the pressure of the second reduction is 0.1-15atm; the time is 0.7-15h;
and/or, in the step (2-1), H 2 The gas flow rate of (2) is 600-25000mL/h/g.
36. The method of claim 35, wherein in step (2-1), the pressure of the second reduction is 0.3-2.6atm; the time is 1-12h;
and/or, in the step (2-1), H 2 The gas flow rate of (2) is 2800-22000mL/h/g.
37. The method according to any one of claims 12 to 14, 16, wherein in step (2-2), the surface passivation treatment is performed at a pressure of 0 to 1.6atm for a time of 5 to 72 hours;
and/or, in the step (2-2), the O-containing 2 The gas flow rate of the gas is 400-12000mL/h/g.
38. The method of claim 37, wherein in the step (2-2), the surface passivation treatment is performed at a pressure of 0-0.09atm for a time of 10-56 hours;
and/or, in the step (2-2), the O-containing 2 The gas flow rate of the gas is 1400-8500mL/h/g.
39. The method of claim 15, wherein in the step (2-2), the surface passivation treatment is performed at a pressure of 0-1.6atm for a time of 5-72 hours;
and/or, in the step (2-2), the O-containing 2 The gas flow rate of the gas is 400-12000mL/h/g.
40. The method of claim 39, wherein in the step (2-2), 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 the step (2-2), the O-containing 2 The gas flow rate of the gas is 1400-8500mL/h/g.
41. The method according to any one of claims 12 to 14, 16, wherein in step (2-3), the second carbide is prepared at a pressure of 0.08-12atm for a time of 0.3-30 hours;
and/or, in the step (2-3), H 2 The total gas flow rate with CO is 250-21000mL/h/g.
42. The method according to claim 41, wherein in the step (2-3), the second 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 (2-3), H 2 The total gas flow rate with CO is 2000-18000 mL/h/g.
43. The method according to claim 15, wherein in the step (2-3), the second carbide is prepared at a pressure of 0.08-12atm for a time of 0.3-30 hours;
and/or, in the step (2-3), H 2 The total gas flow rate with CO is 250-21000mL/h/g.
44. The method according to claim 43, wherein in the step (2-3), the second 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 (2-3), H 2 The total gas flow rate with CO is 2000-18000 mL/h/g.
45. The method of any one of claims 12-14, 16, wherein the second carbide preparation further comprises: and (3) simultaneously carrying out temperature rising operation in the step (2-3), and rising the temperature of the surface passivation treatment to 250-430 ℃ at a temperature rising rate of 0.2-5 ℃/min.
46. A method as claimed in claim 45, wherein the temperature from the surface passivation treatment is raised to 260-400 ℃ at a rate of rise of 0.2-2.5 ℃/min.
47. The method of claim 15, wherein the second carbide preparation further comprises: and (3) simultaneously carrying out temperature rising operation in the step (2-3), and rising the temperature of the surface passivation treatment to 250-430 ℃ at a temperature rising rate of 0.2-5 ℃/min.
48. A method according to claim 47, wherein the temperature from the surface passivation treatment is raised to 260-400 ℃ at a rate of rise of 0.2-2.5 ℃/min.
49. The method of any one of claims 12-14, 16, 18-20, 22-24, 26-28, 30-32, 34-36, 38-40, 42-44, 46-48, wherein in step (3), 97-100 mole parts of precipitated epsilon/epsilon' iron carbide and χ -iron carbide, 0-3 mole parts of Fe-containing impurities are mixed.
50. The method of claim 15, wherein in step (3), 97-100 mole parts of precipitated epsilon/epsilon' iron carbide and chi iron carbide, 0-3 mole parts of Fe-containing impurities are mixed.
51. The method of claim 17, wherein in step (3), 97-100 mole parts of precipitated epsilon/epsilon' iron carbide and chi iron carbide, 0-3 mole parts of Fe-containing impurities are mixed.
52. The method of claim 21, wherein in step (3), 97-100 mole parts of precipitated epsilon/epsilon' iron carbide and chi iron carbide, 0-3 mole parts of Fe-containing impurities are mixed.
53. The method of claim 25, wherein in step (3), 97-100 mole parts of precipitated epsilon/epsilon' iron carbide and chi iron carbide, 0-3 mole parts of Fe-containing impurities are mixed.
54. The method of claim 29, wherein in step (3), 97-100 mole parts of precipitated epsilon/epsilon' iron carbide and chi iron carbide, 0-3 mole parts of Fe-containing impurities are mixed.
55. The method of claim 33, wherein in step (3), 97-100 mole parts of precipitated epsilon/epsilon' iron carbide and chi iron carbide, 0-3 mole parts of Fe-containing impurities are mixed.
56. The method of claim 37, wherein in step (3), 97-100 mole parts of precipitated epsilon/epsilon' iron carbide and chi iron carbide, 0-3 mole parts of Fe-containing impurities are mixed.
57. The method of claim 41, wherein in step (3), 97-100 parts by mole of precipitated epsilon/epsilon' iron carbide and chi iron carbide, 0-3 parts by mole of Fe-containing impurities are mixed.
58. The method of claim 45, wherein in step (3), 97-100 parts by mole of precipitated epsilon/epsilon' iron carbide and chi iron carbide, 0-3 parts by mole of Fe-containing impurities are mixed.
59. A catalyst comprising the composition comprising precipitated epsilon/epsilon' iron carbide and chi iron carbide of any one of claims 1-11.
60. Use of a composition comprising precipitated epsilon/epsilon' iron carbide and chi iron carbide as defined in any one of claims 1 to 11 or a catalyst as defined in claim 59 in a fischer-tropsch synthesis reaction.
61. Use of a composition comprising precipitated epsilon/epsilon' iron carbide and chi iron carbide as defined in any one of claims 1 to 11 or of a catalyst as defined in claim 59 in a fischer-tropsch based synthesis reaction of C, H fuels and/or chemicals.
62. A method of fischer-tropsch synthesis comprising: contacting the synthesis gas with a composition comprising precipitated epsilon/epsilon' iron carbide and chi iron carbide as claimed in any one of claims 1 to 11 or a catalyst as claimed in claim 59 under fischer-tropsch reaction conditions.
63. The process of claim 62 wherein the Fischer-Tropsch synthesis is carried out in a high temperature, high pressure continuous reactor.
64. A method of fischer-tropsch synthesis comprising: contacting 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 precipitated epsilon/epsilon' iron carbide and chi iron carbide as claimed in any one of claims 1 to 11.
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