CN112569995A - Composition containing epsilon/epsilon' iron carbide and theta iron carbide, preparation method, catalyst and application thereof, and Fischer-Tropsch synthesis method - Google Patents
Composition containing epsilon/epsilon' iron carbide and theta iron carbide, preparation method, catalyst and application thereof, and Fischer-Tropsch synthesis method Download PDFInfo
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- 159000000014 iron salts Chemical class 0.000 claims 1
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- OAVRWNUUOUXDFH-UHFFFAOYSA-H 2-hydroxypropane-1,2,3-tricarboxylate;manganese(2+) Chemical compound [Mn+2].[Mn+2].[Mn+2].[O-]C(=O)CC(O)(CC([O-])=O)C([O-])=O.[O-]C(=O)CC(O)(CC([O-])=O)C([O-])=O OAVRWNUUOUXDFH-UHFFFAOYSA-H 0.000 description 4
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Images
Classifications
-
- 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
- B01J27/00—Catalysts comprising the elements or compounds of halogens, sulfur, selenium, tellurium, phosphorus or nitrogen; Catalysts comprising carbon compounds
- B01J27/20—Carbon compounds
- B01J27/22—Carbides
-
- B01J35/612—
-
- B01J35/613—
-
- 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
Abstract
The invention relates to the field of Fischer-Tropsch synthesis reaction, and discloses a composition containing epsilon/epsilon' iron carbide and theta iron carbide, a preparation method, a catalyst and application thereof, and a Fischer-Tropsch synthesis method. A composition comprising epsilon/epsilon ' iron carbide and theta iron carbide, the composition comprising 95 to 100 mol% of epsilon/epsilon ' iron carbide and theta iron carbide, and 0 to 5 mol% of Fe-containing impurities, based on the total amount of the composition, the Fe-containing impurities being substances containing iron elements other than epsilon/epsilon ' iron carbide and theta iron carbide. Can simply prepare epsilon/epsilon' iron carbide and theta iron carbide, can be used as active components to obtain continuous and stable Fischer-Tropsch synthesis reaction, and has high selectivity of effective products.
Description
Technical Field
The invention relates to the field of Fischer-Tropsch synthesis reaction, in particular to a composition containing epsilon/epsilon' iron carbide and theta iron carbide, a preparation method, a catalyst and application thereof, and a Fischer-Tropsch synthesis method.
Background
The primary energy structure of China is characterized by rich coal, lack of oil and little gas. With the development of economy in China, the dependence of petroleum on the outside is continuously rising.
Fischer-Tropsch synthesis is an increasingly important energy conversion way in recent years, and can convert carbon monoxide and H2The syngas is converted into liquid fuels and chemicals.
The reaction equation for fischer-tropsch synthesis is as follows:
(2n+1)H2+nCO→CnH2n+2+nH2O (1)，
2nH2+nCO→CnH2n+nH2O (2)。
in addition to alkanes and alkenes, industrial fischer-tropsch synthesis can also produce carbon dioxide as a by-product(CO2) And methane (CH)4). The Fischer-Tropsch synthesis reaction has complex mechanism and multiple steps, such as CO dissociation, carbon (C) hydrogenation and CHxChain growth, and hydrogenation and dehydrogenation reactions that result in hydrocarbon product desorption and oxygen (O) removal.
Iron is the cheapest transition metal used in making fischer-tropsch synthesis catalysts. The traditional iron-based catalyst has high water gas shift (CO + H)2O→CO2+H2) Active, therefore, conventional iron-based catalysts typically have a higher CO by-product2Selectivity, typically 25% to 45% of the carbon monoxide of the conversion feedstock. This is one of the major disadvantages of iron-based fischer-tropsch catalysts.
The active phase of the iron-based catalyst is very complicated to change, which causes considerable debate between the nature of the active phase and the Fischer-Tropsch synthesis reaction mechanism of the iron-based catalyst.
CN104399501A discloses epsilon-Fe suitable for low-temperature Fischer-Tropsch synthesis reaction2C, a preparation method of the nano-particles. The initial precursor is skeleton iron, and the reaction system is intermittent discontinuous reaction of polyethylene glycol solvent. CO of this catalyst2Selectivity 18.9%, CH4The selectivity of (2) is 17.3%. The disadvantage is that the method can only be applied to low temperature below 200 ℃, and the reaction can not be continuously completed. This means that such catalysts are not suitable for continuous production under modern Fischer-Tropsch synthesis industrial conditions. However, since the skeleton iron cannot be completely carbonized, epsilon-Fe described in the above document2The nanoparticles of C contain a considerable amount of iron impurity components of the non-iron carbide type, and in fact, the prior art cannot obtain epsilon-Fe free of iron impurities2C pure phase substance, where Fe impurity is non-epsilon-Fe2Various Fe (element) -containing phase components of C.
Accordingly, there is a need for an improved iron-based catalyst for use in fischer-tropsch synthesis reactions.
Disclosure of Invention
The invention aims to solve the problem of how to obtain a pure-phase iron carbide substance without Fe impurities by using an iron-based catalyst, improve the stability of Fischer-Tropsch synthesis reaction, and simultaneously reduce CO2Or CH4Selective reaction of by-productsHigh problems, compositions comprising epsilon/epsilon' iron carbide and theta iron carbide, methods of making, catalysts and uses thereof, and methods of fischer-tropsch synthesis are provided.
In order to achieve the above object, a first aspect of the present invention provides a composition containing epsilon/epsilon ' iron carbide and theta iron carbide, which comprises 95 to 100 mol% of epsilon/epsilon ' iron carbide and theta iron carbide, and 0 to 5 mol% of Fe-containing impurities, which are iron-containing substances other than epsilon/epsilon ' iron carbide and theta iron carbide, based on the total amount of the composition.
In a second aspect, the present invention provides a method of preparing a composition comprising epsilon/epsilon' iron carbide and theta iron carbide, comprising:
(1) preparing epsilon/epsilon' iron carbide, comprising:
(1-1) mixing nanometer iron powder or nanometer powder iron compound capable of obtaining nanometer iron powder by reduction with H2Performing a first surface purification treatment at a temperature of 250-510 ℃;
(1-2) mixing the material obtained in the step (1-1) with H2Pre-treating CO at 80-180 deg.C, and H2The molar ratio to CO is 1.2-2.8: 1;
(1-3) mixing the material obtained in the step (1-2) with H2CO at a temperature of 180-2The molar ratio to CO is 1-3: 1, obtaining pure epsilon/epsilon' iron carbide;
(2) preparing theta iron carbide, comprising:
(2-1) mixing nanometer iron powder or nanometer powder iron compound capable of obtaining nanometer iron powder by reduction with H2At a temperature T1Performing second surface purification treatment at 380-520 ℃;
(2-2) mixing the material obtained in the step (2-1) with H2CO at temperature T2The second carbide preparation is carried out at the temperature of 280-430 ℃ for 20-120H, wherein H2The molar ratio to CO is 5-120: 1, obtaining pure theta iron carbide;
(3) mixing 95-100 molar parts of pure epsilon/epsilon' iron carbide and theta iron carbide and 0-5 molar 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 and theta iron carbide.
In a third aspect, the invention provides a composition comprising epsilon/epsilon' iron carbide and theta iron carbide made by the method of the invention.
In a fourth aspect, the invention provides a catalyst comprising a composition comprising epsilon/epsilon' iron carbide and theta iron carbide as provided by the invention.
In a fifth aspect, the invention provides an application of the composition or the catalyst containing the epsilon/epsilon' iron carbide and the theta iron carbide provided by the invention in Fischer-Tropsch synthesis reaction.
In a sixth aspect, the invention provides the use of a composition or catalyst comprising epsilon/epsilon' iron carbide and theta iron carbide as provided by the invention in the synthesis of C, H fuels and/or chemicals based on the fischer-tropsch synthesis principle.
In a seventh aspect, the present invention provides a fischer-tropsch synthesis reaction process, comprising: under the condition of Fischer-Tropsch synthesis reaction, the synthetic gas is contacted with the composition or the catalyst containing epsilon/epsilon' iron carbide and theta iron carbide provided by the invention.
An eighth aspect of the present invention provides a fischer-tropsch synthesis method, comprising: contacting the synthesis gas with a fischer-tropsch catalyst under fischer-tropsch synthesis reaction conditions, wherein the fischer-tropsch catalyst comprises a Mn component and the epsilon/epsilon' iron carbide and theta iron carbide-containing composition 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 nano iron powder, or common commercial nano iron oxide (Fe) which can be reduced in a Fischer-Tropsch synthesis reactor to generate nano iron2O3) Powder, nano magnetite (Fe)3O4) 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 utilized2) Then the method is finished; no inorganic or organic reaction raw materials are involved, and compared with the prior art, the method is greatly simplified;
(2) the operation steps are simple, and in a preferred embodiment, the whole process of preparing each crystal phase iron carbide can be realized in the same reactor, and then the crystal phase iron carbide and the active phase iron carbide are mixed to form the composition.
(3) The method comprises the steps of respectively preparing 100% purity active phases of epsilon/epsilon' iron carbide and theta iron carbide, and then forming a composition with Fe-containing impurities to further prepare the catalyst. The above iron carbide or composition or catalyst can be used at high temperatures and pressures (e.g., 235 ℃ C., 250 ℃ C., pressures of 2.3-2.5MPa, H)2High carbon chemical potential mu of 1.5-2.0/COC) The continuous reactor has extremely high reaction stability, and breaks through the traditional literature theory that the chemical potential mu of carbon is higherCThe theoretical technical barrier that the epsilon/epsilon' iron carbide can exist stably under the mild condition of less than 200 ℃ is needed, the stable temperature can reach 250 ℃, and CO can be realized2The selectivity is extremely low, so that a high-pressure continuous reactor can be used for keeping continuous and stable reaction for more than 400 hours under the reaction condition of industrial Fischer-Tropsch synthesis, and CO is2The selectivity is below 8% (preferably, 5% or below); at the same time, by-product CH of the reaction4The selectivity is also kept below 13 percent (preferably below 11 percent), and the selectivity of the effective product can reach more than 78 percent (preferably above 84 percent). Is very suitable for the high-efficiency production of oil wax products in the Fischer-Tropsch synthesis industry of the modern coal chemical industry.
Drawings
FIG. 1 is an XRD spectrum of epsilon/epsilon' iron carbide obtained in preparation example 1 provided in the present invention;
fig. 2 is an XRD spectrum of the theta iron carbide prepared in preparation example 2 provided in the present invention.
Detailed Description
The following detailed description of embodiments of the invention refers to the accompanying drawings. It should be understood that the detailed description and specific examples, while indicating the present invention, are given by way of illustration and explanation only, not limitation.
The invention provides a composition containing epsilon/epsilon ' iron carbide and theta iron carbide, which comprises 95-100 mol% of epsilon/epsilon ' iron carbide and theta iron carbide and 0-5 mol% of Fe-containing impurities, wherein the Fe-containing impurities are substances containing iron elements except epsilon/epsilon ' iron carbide and theta iron carbide, based on the total amount of the composition.
The invention provides a composition, wherein the epsilon/epsilon 'iron carbide comprises 100% epsilon-iron carbide and/or 100% epsilon' -iron carbide and 100% theta iron carbide. Further, epsilon/epsilon' iron carbide and theta iron carbide are combined in the composition with other Fe-containing impurities. Under the limitation of the composition content of the composition, the composition containing the epsilon/epsilon' iron carbide and the theta iron carbide provided by the invention can be used alone or combined with other components when being applied to a Fischer-Tropsch synthesis catalyst, so that the stability of the Fischer-Tropsch synthesis reaction of the Fischer-Tropsch synthesis catalyst is improved, and CO is reduced2Or CH4Selectivity of by-products.
In the present invention, the composition contains highly pure epsilon/epsilon 'iron carbide and theta iron carbide, and mossbauer spectrum analysis is performed, and it can be observed on the obtained mossbauer spectrum that the crystal phase contains pure epsilon/epsilon' iron carbide and theta iron carbide. Preferably, the composition has a specific surface area of 4 to 60m2A/g, preferably of 5 to 40m2(ii) in terms of/g. The specific surface area may be represented by N2The BET adsorption and desorption method (2). The composition comprises epsilon/epsilon' iron carbide of hexagonal, pseudo-hexagonal or trigonal system, and theta iron carbide of orthorhombic system.
In the present invention, it is further preferred that the composition comprises 97 to 100 mol% of epsilon/epsilon' iron carbide and theta iron carbide and 0 to 3 mol% of Fe-containing impurities, based on the total amount of the composition. Can be determined by XRD and Mossbauer spectrometry analysis, and can also be determined according to the preparation charge of the composition.
In the present invention, the Fe-containing impurities are at least one of iron carbide, iron oxide, iron hydroxide, iron sulfide, and iron salt other than epsilon/epsilon' iron carbide and theta iron carbide. The Fe-containing impurities may be introduced by solution impregnation, sputtering, atomic deposition or mixing.
In a specific embodiment provided by the present invention, the mole ratio of epsilon/epsilon' iron carbide to theta iron carbide is a: b, itWherein 0 < a < 100, 0 < b < 100, preferably 0 < a < 75, 0 < b < 75. The molar ratio of the iron carbides of the two phases in the above range can produce a synergistic effect, optimizing the dissociation path of CO and the hydrogenation path of the C species and CHxIncrease the catalytic activity and decrease CH4With CO2And adjusting the product distribution.
In a second aspect, the present invention provides a method of preparing a composition comprising epsilon/epsilon' iron carbide and theta iron carbide, comprising:
(1) preparing epsilon/epsilon' iron carbide, comprising:
(1-1) mixing nanometer iron powder or nanometer powder iron compound capable of obtaining nanometer iron powder by reduction with H2Performing a first surface purification treatment at a temperature of 250-510 ℃;
(1-2) mixing the material obtained in the step (1-1) with H2Pre-treating CO at 80-180 deg.C, and H2The molar ratio to CO is 1.2-2.8: 1;
(1-3) mixing the material obtained in the step (1-2) with H2CO at a temperature of 180-2The molar ratio to CO is 1-3: 1, obtaining pure epsilon/epsilon' iron carbide;
(2) preparing theta iron carbide, comprising:
(2-1) mixing nanometer iron powder or nanometer powder iron compound capable of obtaining nanometer iron powder by reduction with H2At a temperature T1Performing second surface purification treatment at 380-520 ℃;
(2-2) mixing the material obtained in the step (2-1) with H2CO at temperature T2The second carbide preparation is carried out at the temperature of 280-430 ℃ for 20-120H, wherein H2The molar ratio to CO is 5-120: 1, obtaining pure theta iron carbide;
(3) mixing 95-100 molar parts of pure epsilon/epsilon' iron carbide and theta iron carbide and 0-5 molar 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 and theta iron carbide.
In the preparation method provided by the invention, the steps (1) and (2) are used for preparing iron carbide with different crystal forms. The preparation raw material is nano iron powder, and the average particle diameter of the nano iron powder can be measured by using an X-ray diffraction method. Preferably, the average grain diameter of the nano iron powder is 4-35nm, and more preferably 10-27 nm. The nano-powder iron compound may be a compound containing an iron element, and preferably, the nano-powder iron compound is at least one selected from nano iron oxide powder, nano magnetite powder, nano goethite powder and nano iron hydrated oxide powder. The nanometer iron powder and the nanometer powder iron compound are used as raw materials for preparing epsilon/epsilon' iron carbide and theta iron carbide.
In the invention, if the raw materials in the steps (1-1) and (2-1) are nano iron powder, the steps (1-1) and (2-1) can play a role in carrying out surface purification treatment on the nano iron powder; if the raw materials in the steps (1-1) and (2-1) are nano powder iron compounds capable of obtaining nano iron powder through in-situ reduction, the steps (1-1) and (2-1) can simultaneously play a role in reducing the nano powder iron compounds to generate nano iron powder and performing surface purification treatment on the generated nano iron powder.
One embodiment provided by the present invention produces pure epsilon/epsilon' iron carbide.
Preferably, H in step (1-1)2Can be represented by H2Introducing the mixture into the reaction system in the form of a flow, and simultaneously controlling H2The pressure of the stream is used to control the pressure of the first surface purification treatment, preferably, in step (1-1), the pressure of the first surface purification treatment is 0.1 to 15atm, preferably 0.2 to 2.5atm, and the time is 0.5 to 8h, preferably 1 to 7 h.
In some embodiments of the invention, H2The amount of (C) may be selected depending on the amount of the raw material to be treated, and preferably, in step (1-1), H2The gas flow rate of (b) is 500-.
In step (1-2) of the process provided by the present invention, H2And CO may be (H)2+ CO) mixed gas flow to participate in the pretreatment process; at the same time, by controlling (H)2+ CO) mixed gas stream pressure to control the pressure of the pretreatment process. Preferably, in step (1-2)The pressure of the pretreatment is 0.05-7atm, preferably 0.05-2.5atm, and the time is 15-90min, preferably 25-75 min.
In some embodiments of the present invention, preferably, in step (1-2), H2The total gas flow rate with CO is 200-.
In step (1-3) of the method provided by the present invention, conditions are provided to effect the production of the first carbide to obtain pure epsilon/epsilon' iron carbide. H2And CO may be (H)2+ CO) in the form of a mixed gas stream into the first carbide production process; at the same time, by controlling (H)2+ CO) mixed gas stream pressure to control the pressure of the first carbide making process. Preferably, in the step (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), H2The total gas flow rate with CO is 200-.
In some embodiments of the present invention, it is preferred that H in step (1-2)2The molar ratio to CO is larger than that of H in the step (1-3)2Molar ratio to CO.
According to a preferred embodiment of the present invention, the first carbide preparation further comprises: : in the step (1-3), the temperature is simultaneously raised from the pretreatment temperature to 180-280 ℃ at a temperature raising rate of 0.2-5 ℃/min. In this preferred embodiment, the resulting phase-pure epsilon/epsilon' iron carbide is capable of having better effective product selectivity in the fischer-tropsch synthesis reaction. Further preferably, the temperature is raised from the temperature of the pretreatment to 200 ℃ and 270 ℃ at a temperature raising rate of 0.2-2.5 ℃/min. In the temperature rise 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 80-180 ℃ to 180-280 ℃ in the step (1-3) at a temperature raising rate of 0.2-5 ℃/min, preferably from 80-180 ℃ to 200-270 ℃ at a temperature raising rate of 0.2-2.5 ℃/min.
In the present invention, the steps (1-2) and (1-3) are set to the time of performing the pretreatment and the carbide production, respectivelyTemperature of H2Molar ratio to CO. The temperature and H set in the implementation of the step (1-2) and the step (1-3) respectively2The molar ratio to CO is not the same. And (3) in the process of the temperature rising operation, the temperature settings in the steps (1-2) and (1-3) are different.
Another embodiment provided by the present invention produces pure theta iron carbide.
Preferably, H in step (2-1)2Can be represented by H2Introducing the mixture into the reaction system in the form of a flow, and simultaneously controlling H2The pressure of the stream to control the pressure of the second surface cleaning treatment, preferably, in the step (2-1), the pressure of the second surface cleaning treatment is 0 to 25atm, preferably 0.01 to 3 atm; the time is 1-40h, preferably 2-18 h.
In the step (2-1) provided by the present invention, H2The amount of (C) may be selected depending on the amount of the raw material to be treated, and preferably, in the step (2-1), H2The gas flow rate of (b) is 400-22000mL/h/g, more preferably 1000-18000 mL/h/g.
In the step (2-2) provided by the present invention, conditions for achieving the production of the second carbide are provided so as to obtain pure θ iron carbide. H2And CO may be (H)2+ CO) in the form of a mixed gas stream into the second carbide production process; at the same time, by controlling (H)2+ CO) mixed gas stream to control the pressure of the second carbide making process. Preferably, in the step (2-3), the second carbide is prepared at a pressure of 0 to 28atm, preferably 0.01 to 20atm, for a time of 20 to 120 hours, preferably 24 to 80 hours.
In some embodiments of the present invention, preferably, in step (2-2), H2The total gas flow rate with CO is 200-.
In the step (2-2) provided by the present invention, the second carbide preparation further includes: in the step (2-2), the temperature change operation is carried out at the same time from the temperature T1Cooling or heating to temperature T at variable temperature rate of 0.2-5 deg.C/min2. In the preferred embodiment, the resulting phase-pure theta iron carbide can have better effective product selectivity in the fischer-tropsch synthesis reaction. Further preferably, from the temperature T1Cooling or heating to 300-400 ℃ at a temperature change rate of 0.2-2.5 ℃/min.
In the present invention, "mL/h/g" in the iron carbide production process means the volume of gas introduced per gram of the material per hour, unless otherwise specified.
In one embodiment of the method of the present 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 the epsilon/epsilon' iron carbide. In the process of preparing the theta iron carbide, the second surface purification treatment and the second carbide preparation can be carried out in the same Fischer-Tropsch synthesis reactor. In-situ characterization equipment can be used to track the crystal phase transition of the material during the preparation process.
In the invention, the pure-phase epsilon/epsilon' iron carbide and the pure-phase theta iron carbide can be obtained through the steps (1) and (2) in the method provided by the invention.
The invention provides a method step (3) for realizing the composition containing epsilon/epsilon' iron carbide and theta iron carbide. Wherein the pure phase epsilon/epsilon' iron carbide and the pure phase theta iron carbide are mixed into the pure phase iron carbide. Preferably, the mole ratio of epsilon/epsilon' iron carbide to theta iron carbide is a: b, wherein a is more than 0 and less than 100, b is more than 0 and less than 100, preferably, a is more than 0 and less than or equal to 75, and b is more than 0 and less than or equal to 75.
In some embodiments of the invention, the epsilon/epsilon' iron carbide and theta iron carbide-containing compositions comprise Fe-containing impurities that may be incorporated by external means. Preferably, in step (3), 97 to 100 molar parts of pure epsilon/epsilon' iron carbide and theta iron carbide are mixed with 0 to 3 molar parts of Fe-containing impurities.
In the step (3) of the method provided by the invention, the mixing is carried out by mixing pure epsilon/epsilon' iron carbide and theta iron carbide powder with Fe-containing impurity powder in a glove box according to the dosage requirement under the inert gas protection condition.
In a third aspect, the invention provides compositions comprising epsilon/epsilon' iron carbide and theta iron carbide produced by the process of the invention. The composition comprises 95 to 100 mol% of epsilon/epsilon 'iron carbide and theta iron carbide and 0 to 5 mol% of Fe-containing impurities, wherein the Fe-containing impurities are substances containing iron elements except the epsilon/epsilon' iron carbide and the theta iron carbide, based on the total amount of the composition.
Preferably, the composition comprises 97 to 100 mol% of epsilon/epsilon' iron carbide and theta iron carbide, and 0 to 3 mol% of impurities containing Fe.
Preferably, the specific surface area of the composition is between 4 and 60m2A/g, preferably of 5 to 40m2/g。
Preferably, the mole ratio of epsilon/epsilon' iron carbide to theta iron carbide is a: b, wherein a is more than 0 and less than 100, b is more than 0 and less than 100, preferably, a is more than 0 and less than or equal to 75, and b is more than 0 and less than or equal to 75.
In a fourth aspect, the invention provides a catalyst comprising a composition comprising epsilon/epsilon' iron carbide and theta iron carbide as provided by the invention. Preferably, the catalyst may also comprise other components, such as promoters.
In the embodiment provided by the present invention, preferably, the content of the epsilon/epsilon' iron carbide and theta iron carbide-containing composition is 75 wt% or more and less than 100 wt%, and the content of the auxiliary agent is more than 0 wt% and 25 wt% or less, based on the total amount of the catalyst.
In the embodiment provided by the invention, preferably, the catalyst can be prepared by introducing the auxiliary agent by a method of impregnation, atomic deposition, sputtering or chemical deposition.
In a fifth aspect, the invention provides an application of the composition or the catalyst containing the epsilon/epsilon' iron carbide and the theta iron carbide provided by the invention in Fischer-Tropsch synthesis reaction.
In a sixth aspect, the invention provides the use of a composition or catalyst comprising epsilon/epsilon' iron carbide and theta iron carbide as provided by the invention in the synthesis of C, H fuels and/or chemicals based on the fischer-tropsch synthesis principle.
In a seventh aspect, the present invention provides a fischer-tropsch synthesis reaction process, comprising: under the condition of Fischer-Tropsch synthesis reaction, the synthetic gas is contacted with the composition or the catalyst containing epsilon/epsilon' iron carbide and theta iron carbide provided by the invention.
The composition or the catalyst containing the epsilon/epsilon' iron carbide and the theta iron carbide is adopted to carry out the Fischer-Tropsch synthesis reaction, and the Fischer-Tropsch synthesis reaction can be carried out at a high temperatureThe conditions for carrying out the Fischer-Tropsch synthesis reaction, for example, include: the temperature is 235 ℃ and 250 ℃, and the pressure is 2.3-2.5 MPa. But also can be used for realizing better effective product selectivity; the effective product is prepared from CO and H2Produced by the reaction, except for CH4With CO2Products containing carbon other than C, including but not limited to2And C2The above hydrocarbons, alcohols, aldehydes, ketones, esters, and the like.
In the present invention, the pressure refers to gauge pressure unless otherwise specified.
In some embodiments of the invention, preferably, the fischer-tropsch synthesis reaction is carried out in a high temperature, high pressure continuous reactor. The composition or the catalyst containing the epsilon/epsilon' iron carbide and the theta iron carbide can realize that the Fischer-Tropsch synthesis reaction can be continuously and stably kept for over 400 hours in a high-temperature high-pressure continuous reactor.
An eighth aspect of the present invention provides a fischer-tropsch synthesis method, comprising: contacting the synthesis gas with a fischer-tropsch catalyst under fischer-tropsch synthesis reaction conditions, wherein the fischer-tropsch catalyst comprises a Mn component and the epsilon/epsilon' iron carbide and theta iron carbide-containing composition provided by the invention.
In a specific embodiment provided by the present invention, the composition of the fischer-tropsch catalyst may further comprise, based on the total amount of the fischer-tropsch catalyst, the content of the composition containing epsilon/epsilon' iron carbide and theta iron carbide is 75 wt% or more and less than 100 wt%, and the content of Mn is more than 0 wt% and 25 wt% or less. In the fischer-tropsch catalyst, Mn may be present as an oxide and may be incorporated into the fischer-tropsch catalyst by methods including, but not limited to, impregnation, chemical deposition, sputtering, atomic deposition.
The present invention will be described in detail below by way of examples. In the following examples and comparative examples,
in-situ XRD detection in the process of preparing the iron carbide, an X-ray diffractometer (Rigaku company, model D/max-2600/PC) is used for monitoring the crystal phase change of the material;
the obtained iron carbide and iron carbide composition were subjected to Mossbauer spectrometer (Transmission)57Fe，57Co (Rh) source sine velocity spectrometer)Detecting Mossbauer spectra;
the BET specific surface area of the iron carbide composition was measured by a nitrogen adsorption method;
carrying out Fischer-Tropsch synthesis reaction:
carrying out gas chromatography (Agilent 6890 gas chromatography) on the product obtained by the reaction;
the effect of the reaction is calculated by the following formula:
CO2selectivity%2Mole number/(moles of CO in feed-moles of CO in discharge)]×100％；
CH4Selectivity%4Mole/(mole of CO in the feed x CO conversion% (1-CO)2Selectivity%))]×100％；
Effective product selectivity ═ 1-CO2Selective% CH4Selectivity%]×100％。
Space-time conversion rate (mmol/h/g) of raw material COFe) (moles of CO in feed-moles of CO in discharge)/reaction time/weight of Fe element;
space-time yield (mmol/h/g) for efficient product formationFe) Reaction of C2And C2The above number of moles of hydrocarbon/reaction time/weight of Fe element.
Preparation example 1
(1) Taking 10.0g of nano iron powder, the average grain diameter is 20nm, and H with the pressure of 1atm and the gas flow rate of 8500mL/H/g at 390 DEG C2Carrying out first surface purification treatment for 2.5 h;
(2) cooling the product obtained in the step (1) to 160 ℃, and reacting the product with H at 160 DEG C2Mixed gas with CO (pressure 1.5atm, total gas flow 7000mL/H/g, H)2Contacting with CO at a molar ratio of 2.0:1) for pretreatment for 45 min;
(3) change H2The conditions of the gas mixture with CO were: pressure 2.1atm, total gas flow 13000mL/H/g, H2The molar ratio of the carbon to CO is 1.5:1, the temperature is raised from 160 ℃ to 250 ℃ at the temperature rise 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 Mossbauer spectroscopy), and the pure epsilon/epsilon' iron carbide is recordedIs iron carbide 1.
The preparation method of 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 embodiment of Chinese patent application ' epsilon/epsilon ' iron carbide composition, preparation method, catalyst and application thereof and Fischer-Tropsch synthesis method ', and the whole content of the method is introduced into the invention.
Preparation example 2
(a) Taking 10.0g of nano iron powder, the average grain diameter is 17nm, and under the conditions of 520 ℃, the pressure is 3atm and the gas flow is 18000mL/H/g of H2Then, carrying out second surface purification treatment for 2 h;
(b) cooling the product obtained in step (a) to 400 ℃ at a rate of 2.5 ℃/min and reacting the product with H at the temperature2And (3) contacting with mixed gas of CO to prepare a second carbide, wherein the conditions are as follows: pressure 20atm, total gas flow 20000mL/H/g, H2The molar ratio of the catalyst to CO is 100:1, and the treatment time is 24 hours. Pure theta iron carbide (determined by mossbauer spectroscopy) was obtained and reported as iron carbide 2.
The preparation method of the pure theta iron carbide provided by the invention is not limited to the preparation example 2, and the specific implementation method for preparing the pure theta iron carbide is described in the embodiment of the Chinese patent application 'theta iron carbide-containing composition, the preparation method, the catalyst and the application thereof and the Fischer-Tropsch synthesis method', and the whole content of the method is introduced into the invention.
Example 1
Under the protection of Ar gas, 74 molar parts of iron carbide 1, 25 molar parts of iron carbide 2 and 1 molar part of ferrous oxide (namely Fe-containing impurities) are mixed. After mixing, it is designated as iron carbide composition 1.
Example 2
29 parts by mole of iron carbide 1, 69 parts by mole of iron carbide 2 and 2 parts by mole of ferrous oxide (i.e. containing Fe impurities) are mixed under Ar gas. After mixing, it is designated as iron carbide composition 2.
Example 3
Under the protection of Ar gas, 85 molar parts of iron carbide 1, 14 molar parts of iron carbide 2 and 1 molar part of ferrous oxide (namely Fe-containing impurities) are mixed. After mixing, it was designated as iron carbide composition 3.
Example 4
Under Ar gas protection, 10 molar parts of iron carbide 1, 87 molar parts of iron carbide 2 and 3 molar parts of ferrous oxide (i.e. Fe-containing impurities) are mixed. After mixing, it was designated as iron carbide composition 4.
Comparative example 1
Under the protection of Ar gas, 79 mol parts of iron carbide 1, 14 mol parts of iron carbide 2 and 7 mol parts of ferrous oxide (namely Fe-containing impurities) are mixed. After mixing, it was designated as iron carbide composition D1.
Comparative example 2
Under the protection of Ar gas, 14 molar parts of iron carbide 1, 80 molar parts of iron carbide 2 and 6 molar parts of ferrous oxide (namely Fe-containing impurities) are mixed. After mixing, it was designated as iron carbide composition D2.
Examples 5 to 8
Respectively taking 1-4 parts of iron carbide composition in N2Adding manganese citrate solution by immersion method under protection, and adding N at 25 deg.C2And drying the gas flow for 24 hours to obtain the Fischer-Tropsch catalyst 1-4 correspondingly. Wherein the amount of the added manganese citrate solution is impregnated, so that the obtained Fischer-Tropsch catalysts 1-4 respectively and correspondingly contain 85 wt% of iron carbide composition 1-4 and 15 wt% of MnO2。
Comparative examples 3 to 4
Respectively taking iron carbide compositions D1-D2 as the balance of N2Adding manganese citrate solution by immersion method under protection, and adding N at 25 deg.C2And drying the gas flow for 24h to obtain the Fischer-Tropsch catalysts D1-D2. Wherein the added manganese citrate solution is impregnated in an amount which enables the obtained Fischer-Tropsch catalysts D1-D2 to respectively contain 85 wt% of iron carbide composition D1-D2 and 15 wt% of MnO2。
Test example
Mossbauer spectroscopy was performed on iron carbide 1-2, and the results of the determination of the Fe compound content are shown in Table 1. Wherein the content of the Fe compound is expressed in mol percent.
TABLE 1
In the preparation examples 1 and 2, in-situ XRD detection technology is adopted, and an X-ray diffractometer (Rigaku company, model D/max-2600/PC) is used for monitoring the crystal phase change of the material. The XRD test result of preparation example 1 is shown in FIG. 1, in which the curve is such that iron carbide 1 having a crystal phase of ε -Fe with a purity of 100% is obtained after all the carbonization steps are completed2C and epsilon-Fe2.2C, i.e. epsilon/epsilon' iron carbide, and together an XRD standard card PDF-89-2005 showing 2 theta equal to 37.7 °, 41.4 °, 43.2 °, 57.2 °, 68.0 °, 76.8 °, 82.9 ° in full agreement with the standard card. The crystallinity of the generated target product epsilon/epsilon 'iron carbide is good, all characteristic peaks of the epsilon/epsilon' iron carbide are well corresponded, the purity is extremely high, and no other impurities exist.
The XRD test result of preparation example 2 is shown in FIG. 2, in which the curve is that of iron carbide 2 obtained after completion of all the carbonization steps and the crystal phase thereof is an orthorhombic system theta-Fe with a purity of 100%3C, that is, θ iron carbide, has all characteristic peaks at 36.6 °, 37.8 °, 42.9 °, 43.8 °, 44.6 °, 45.0 °, 45.9 °, 48.6 °, and 49.1 ° of 2 θ main peak, and θ -Fe3The C standard card PDF-65-2142 is completely consistent. The generated target product theta iron carbide has good crystallinity, well corresponds to all characteristic peaks of the theta iron carbide, has extremely high purity and does not contain any other impurities.
Mossbauer spectra and BET specific surface area measurements were performed for iron carbide compositions 1-4 and D1-D2, respectively, and the results are shown in Table 2.
TABLE 2
Evaluation example
In a fixed bed continuous reactor, the performance evaluation of the catalytic reaction is respectively carried out on Fischer-Tropsch catalysts 1-4, D1-D2 and iron carbide compositions 1-2. The catalyst loading was 10.0 g.
Evaluation conditions were as follows: t is 250 deg.C, P is 2.50MPa, H2：CO＝1.8：1，(H2+ CO) in total amount of 38000mL/h/g-Fe(standard state flux, relative to Fe element). The reaction is carried out, the reaction product passes through gasThe evaluation data of the reaction performance of the reaction time 24h and the reaction time 400h by the analysis of the phase chromatography are shown in tables 3 and 4.
TABLE 3
TABLE 4
As can be seen from the above examples, comparative examples and data in tables 1 to 4, the Fischer-Tropsch synthesis reaction of the composition or catalyst containing epsilon/epsilon' iron carbide and theta iron carbide prepared by the invention is carried out under industrial conditions, and shows that the space-time conversion rate of raw material CO is high in a limited condition range, the reaction performance is better, and the ultralow CO content is2And (4) selectivity. At the same time, CH4Low selectivity and high selectivity of effective products.
Further long-period experiments are carried out, and as can be seen from the data of the reaction time of 400h in the table 4, after the composition or the catalyst containing epsilon/epsilon' iron carbide and theta iron carbide prepared under the limited conditions provided by the invention runs for a long time, the CO conversion rate and the product selectivity are stable and have no obvious change, and the stability is greatly superior to that of the iron carbide in the prior art.
The composition or the catalyst containing the epsilon/epsilon' iron carbide and the theta iron carbide prepared under the limited conditions can be suitable for a high-temperature high-pressure continuous reactor, has high reaction stability, and CO2Very low selectivity: under the condition of industrial Fischer-Tropsch synthesis reaction, a high-pressure continuous reactor can be used for keeping continuous and stable reaction for more than 400h, and CO is generated2The selectivity is below 8% (preferably, 5% or below); at the same time, its by-product CH4The selectivity is also kept below 13% (preferably below 11%),the selectivity of the effective product can reach more than 78 percent (preferably more than 84 percent). Wherein the catalyst effective product formation space-time yield of the preferred conditions (catalyst 1-2) can reach 130mmol/h/g-FeThe method is very suitable for producing oil and wax products efficiently in the Fischer-Tropsch synthesis industry of the modern coal chemical industry.
The preferred embodiments of the present invention have been described in detail above with reference to the accompanying drawings, but the present invention is not limited thereto. Within the scope of the technical idea of the invention, numerous simple modifications can be made to the technical solution of the invention, including combinations of the individual specific technical features in any suitable way. The invention is not described in detail in order to avoid unnecessary repetition. Such simple modifications and combinations should be considered within the scope of the present disclosure as well.
Claims (23)
1. A composition comprising epsilon/epsilon ' iron carbide and theta iron carbide, which comprises 95 to 100 mol% of epsilon/epsilon ' iron carbide and theta iron carbide, and 0 to 5 mol% of Fe-containing impurities, which are substances containing iron elements other than epsilon/epsilon ' iron carbide and theta iron carbide, based on the total amount of the composition.
2. The composition according to claim 1, wherein the composition has a specific surface area of 4-60m2A/g, preferably of 5 to 40m2/g。
3. The composition of claim 1 or 2, wherein the composition comprises 97-100 mol% of epsilon/epsilon' iron carbide and theta iron carbide, and 0-3 mol% of Fe-containing impurities, based on the total amount of the composition.
4. The composition of any one of claims 1-3, wherein the Fe-containing impurities are at least one of iron carbides other than epsilon/epsilon' and theta iron carbides, iron oxides, iron hydroxides, iron sulfides, iron salts.
5. The composition according to any one of claims 1 to 4, wherein the molar ratio of epsilon/epsilon' iron carbide and theta iron carbide is a: b, wherein a is more than 0 and less than 100, b is more than 0 and less than 100, preferably, a is more than 0 and less than or equal to 75, and b is more than 0 and less than or equal to 75.
6. A method of making a composition comprising epsilon/epsilon' iron carbide and theta iron carbide, comprising:
(1) preparing epsilon/epsilon' iron carbide, comprising:
(1-1) mixing nanometer iron powder or nanometer powder iron compound capable of obtaining nanometer iron powder by reduction with H2Performing a first surface purification treatment at a temperature of 250-510 ℃;
(1-2) mixing the material obtained in the step (1-1) with H2Pre-treating CO at 80-180 deg.C, and H2The molar ratio to CO is 1.2-2.8: 1;
(1-3) mixing the material obtained in the step (1-2) with H2CO at a temperature of 180-2The molar ratio to CO is 1-3: 1, obtaining pure epsilon/epsilon' iron carbide;
(2) preparing theta iron carbide, comprising:
(2-1) mixing nanometer iron powder or nanometer powder iron compound capable of obtaining nanometer iron powder by reduction with H2At a temperature T1Performing second surface purification treatment at 380-520 ℃;
(2-2) mixing the material obtained in the step (2-1) with H2CO at temperature T2The second carbide preparation is carried out at the temperature of 280-430 ℃ for 20-120H, wherein H2The molar ratio to CO is 5-120: 1, obtaining pure theta iron carbide;
(3) mixing 95-100 molar parts of pure epsilon/epsilon' iron carbide and theta iron carbide and 0-5 molar 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 and theta iron carbide.
7. The method according to claim 6, wherein in the step (3), the mole ratio of epsilon/epsilon' iron carbide to theta iron carbide is a: b, wherein a is more than 0 and less than 100, b is more than 0 and less than 100, preferably, a is more than 0 and less than or equal to 75, and b is more than 0 and less than or equal to 75.
8. The method of claim 6 or 7, wherein the nanopowder iron compound is at least one of a nanopowder of iron oxide, magnetite, goethite and iron oxide.
9. The method according to any one of claims 6-8, wherein the average grain diameter of the nano-iron powder is 4-35nm, preferably 10-27 nm.
10. The method according to any one of claims 6 to 9, wherein in step (1-1), the pressure of the first surface purification treatment is 0.1 to 15atm, preferably 0.2 to 2.5 atm; the time is 0.5 to 8 hours, preferably 1 to 7 hours;
further preferably, in step (1-1), H2The gas flow rate of (b) is 500-.
11. The method according to any one of claims 6 to 9, wherein in step (1-2), the pressure of the pretreatment is 0.05 to 7atm, preferably 0.05 to 2.5atm, and the time is 15 to 90min, preferably 25 to 75 min;
further preferably, in step (1-2), H2The total gas flow rate with CO is 200-.
12. The method according to any one of claims 6 to 9, wherein in step (1-3), 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 10h, preferably 1.5 to 8 h;
further preferably, in step (1-3), H2The total gas flow rate with CO is 200-.
13. The method of any of claims 6-9, wherein the first carbide making further comprises: simultaneously performing temperature rise operation in the step (1-3), wherein the temperature is raised from the pretreatment temperature to 180-280 ℃ at the temperature rise rate of 0.2-5 ℃/min;
preferably, the temperature is raised from the temperature of the pretreatment to 200 ℃ and 270 ℃ at a temperature raising rate of 0.2-2.5 ℃/min.
14. The method according to any one of claims 6 to 9, wherein in the step (2-1), the pressure of the second surface purification treatment is 0 to 25atm, preferably 0.01 to 3 atm; the time is 1 to 40 hours, preferably 2 to 18 hours;
further preferably, in step (2-1), H2The gas flow rate of (b) is 400-22000mL/h/g, more preferably 1000-18000 mL/h/g.
15. The method according to any one of claims 6 to 9, wherein in step (2-2), the second carbide is prepared at a pressure of 0 to 28atm, preferably 0.01 to 20atm, for a time of 20 to 120h, preferably 24 to 80 h;
further preferably, in step (2-2), H2The total gas flow rate with CO is 200-.
16. The method of any of claims 6-9, wherein the second carbide making further comprises: in the step (2-2), the temperature change operation is carried out at the same time from the temperature T1Cooling or heating to temperature T at variable temperature rate of 0.2-5 deg.C/min2；
Preferably, from the temperature T1Cooling or heating to 300-400 ℃ at a temperature change rate of 0.2-2.5 ℃/min.
17. The method as claimed in any one of claims 6 to 16, wherein 97 to 100 molar parts of pure epsilon/epsilon' iron carbide and theta iron carbide, and 0 to 3 molar parts of Fe-containing impurities are mixed in step (3).
18. A composition comprising epsilon/epsilon' iron carbide and theta iron carbide made by the method of any one of claims 6-17.
19. A catalyst comprising the epsilon/epsilon' iron carbide and theta iron carbide-containing composition of any of claims 1-5 and 18.
20. Use of a composition comprising epsilon/epsilon' iron carbide and theta iron carbide according to any one of claims 1 to 5 and 18 or a catalyst according to claim 19 in a fischer-tropsch synthesis reaction.
21. Use of a composition comprising epsilon/epsilon' iron carbide and theta iron carbide according to any of claims 1-5 and 18 or a catalyst according to claim 19 for the synthesis of C, H fuels and/or chemicals based on the fischer-tropsch principle.
22. A process for fischer-tropsch synthesis comprising: contacting synthesis gas with a composition comprising epsilon/epsilon' iron carbide and theta iron carbide according to any one of claims 1 to 5 and 18 or a catalyst according to claim 19 under fischer-tropsch synthesis reaction conditions;
preferably, the fischer-tropsch synthesis is carried out in a high temperature high pressure continuous reactor.
23. A process for fischer-tropsch synthesis comprising: contacting synthesis gas with a fischer-tropsch catalyst under fischer-tropsch synthesis reaction conditions, wherein the fischer-tropsch catalyst comprises a Mn component and the epsilon/epsilon' iron carbide and theta iron carbide-containing composition of any one of claims 1 to 5 and 18.
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Citations (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| EP0361349A2 (en) * | 1988-09-26 | 1990-04-04 | Seisan Kaihatsu Kagaku Kenkyusho | Magnetic fine particles of epsilon' iron carbide |
| CN104399501A (en) * | 2014-11-09 | 2015-03-11 | 复旦大学 | High-activity iron-based low-temperature Fischer-Tropsch synthesis catalyst and preparation method thereof |
| US20160045901A1 (en) * | 2013-03-19 | 2016-02-18 | Korea Institute Of Energy Research | Iron-based catalyst and method for preparing the same and use thereof |
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2020
- 2020-09-30 CN CN202011068975.XA patent/CN112569995B/en active Active
Patent Citations (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| EP0361349A2 (en) * | 1988-09-26 | 1990-04-04 | Seisan Kaihatsu Kagaku Kenkyusho | Magnetic fine particles of epsilon' iron carbide |
| US20160045901A1 (en) * | 2013-03-19 | 2016-02-18 | Korea Institute Of Energy Research | Iron-based catalyst and method for preparing the same and use thereof |
| CN104399501A (en) * | 2014-11-09 | 2015-03-11 | 复旦大学 | High-activity iron-based low-temperature Fischer-Tropsch synthesis catalyst and preparation method thereof |
Non-Patent Citations (1)
| Title |
|---|
| 刘润雪;刘任杰;徐艳;吕静;李振花;: "铁基费托合成催化剂研究进展", 化工进展 * |
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| CN112569995B (en) | 2023-07-11 |
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