CN112569984A - Supported theta-containing iron carbide composition, preparation method thereof, catalyst and application thereof, and Fischer-Tropsch synthesis method - Google Patents
Supported theta-containing iron carbide composition, preparation method thereof, catalyst and application thereof, and Fischer-Tropsch synthesis method Download PDFInfo
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- 229910001567 cementite Inorganic materials 0.000 title claims abstract description 237
- 239000000203 mixture Substances 0.000 title claims abstract description 109
- 239000003054 catalyst Substances 0.000 title claims abstract description 59
- 238000002360 preparation method Methods 0.000 title claims abstract description 19
- 238000001308 synthesis method Methods 0.000 title abstract description 7
- XEEYBQQBJWHFJM-UHFFFAOYSA-N Iron Chemical compound [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 claims abstract description 303
- 229910052742 iron Inorganic materials 0.000 claims abstract description 114
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- 235000000011 iron ammonium citrate Nutrition 0.000 claims description 44
- 239000004313 iron ammonium citrate Substances 0.000 claims description 44
- 238000000034 method Methods 0.000 claims description 42
- 229910052799 carbon Inorganic materials 0.000 claims description 31
- 230000015572 biosynthetic process Effects 0.000 claims description 24
- 238000006243 chemical reaction Methods 0.000 claims description 24
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- MCMNRKCIXSYSNV-UHFFFAOYSA-N Zirconium dioxide Chemical compound O=[Zr]=O MCMNRKCIXSYSNV-UHFFFAOYSA-N 0.000 claims description 14
- 230000008569 process Effects 0.000 claims description 13
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- GWEVSGVZZGPLCZ-UHFFFAOYSA-N Titan oxide Chemical compound O=[Ti]=O GWEVSGVZZGPLCZ-UHFFFAOYSA-N 0.000 claims description 7
- 150000002505 iron Chemical class 0.000 claims description 6
- ZKATWMILCYLAPD-UHFFFAOYSA-N niobium pentoxide Inorganic materials O=[Nb](=O)O[Nb](=O)=O ZKATWMILCYLAPD-UHFFFAOYSA-N 0.000 claims description 5
- URLJKFSTXLNXLG-UHFFFAOYSA-N niobium(5+);oxygen(2-) Chemical compound [O-2].[O-2].[O-2].[O-2].[O-2].[Nb+5].[Nb+5] URLJKFSTXLNXLG-UHFFFAOYSA-N 0.000 claims description 5
- PNEYBMLMFCGWSK-UHFFFAOYSA-N aluminium oxide Inorganic materials [O-2].[O-2].[O-2].[Al+3].[Al+3] PNEYBMLMFCGWSK-UHFFFAOYSA-N 0.000 claims description 4
- 239000000446 fuel Substances 0.000 claims description 4
- 238000010438 heat treatment Methods 0.000 claims description 4
- 229910052739 hydrogen Inorganic materials 0.000 claims description 4
- 239000011261 inert gas Substances 0.000 claims description 4
- 159000000014 iron salts Chemical class 0.000 claims description 4
- VCJMYUPGQJHHFU-UHFFFAOYSA-N iron(3+);trinitrate Chemical compound [Fe+3].[O-][N+]([O-])=O.[O-][N+]([O-])=O.[O-][N+]([O-])=O VCJMYUPGQJHHFU-UHFFFAOYSA-N 0.000 claims description 4
- 239000007864 aqueous solution Substances 0.000 claims description 3
- 235000013980 iron oxide Nutrition 0.000 claims description 3
- 239000000377 silicon dioxide Substances 0.000 claims description 3
- MBMLMWLHJBBADN-UHFFFAOYSA-N Ferrous sulfide Chemical class [Fe]=S MBMLMWLHJBBADN-UHFFFAOYSA-N 0.000 claims description 2
- 229910021578 Iron(III) chloride Inorganic materials 0.000 claims description 2
- IMBKASBLAKCLEM-UHFFFAOYSA-L ferrous ammonium sulfate (anhydrous) Chemical compound [NH4+].[NH4+].[Fe+2].[O-]S([O-])(=O)=O.[O-]S([O-])(=O)=O IMBKASBLAKCLEM-UHFFFAOYSA-L 0.000 claims description 2
- -1 iron carbides Chemical class 0.000 claims description 2
- 235000014413 iron hydroxide Nutrition 0.000 claims description 2
- RBTARNINKXHZNM-UHFFFAOYSA-K iron trichloride Chemical compound Cl[Fe](Cl)Cl RBTARNINKXHZNM-UHFFFAOYSA-K 0.000 claims description 2
- VBMVTYDPPZVILR-UHFFFAOYSA-N iron(2+);oxygen(2-) Chemical class [O-2].[Fe+2] VBMVTYDPPZVILR-UHFFFAOYSA-N 0.000 claims description 2
- NCNCGGDMXMBVIA-UHFFFAOYSA-L iron(ii) hydroxide Chemical class [OH-].[OH-].[Fe+2] NCNCGGDMXMBVIA-UHFFFAOYSA-L 0.000 claims description 2
- 239000002245 particle Substances 0.000 claims description 2
- FRHBOQMZUOWXQL-UHFFFAOYSA-L ammonium ferric citrate Chemical compound [NH4+].[Fe+3].[O-]C(=O)CC(O)(CC([O-])=O)C([O-])=O FRHBOQMZUOWXQL-UHFFFAOYSA-L 0.000 claims 1
- 238000001354 calcination Methods 0.000 claims 1
- CURLTUGMZLYLDI-UHFFFAOYSA-N Carbon dioxide Chemical compound O=C=O CURLTUGMZLYLDI-UHFFFAOYSA-N 0.000 description 139
- 229910002092 carbon dioxide Inorganic materials 0.000 description 77
- 239000001569 carbon dioxide Substances 0.000 description 69
- 239000000243 solution Substances 0.000 description 48
- AUALKMYBYGCYNY-UHFFFAOYSA-E triazanium;2-hydroxypropane-1,2,3-tricarboxylate;iron(3+) Chemical compound [NH4+].[NH4+].[NH4+].[Fe+3].[Fe+3].[Fe+3].[O-]C(=O)CC(O)(CC([O-])=O)C([O-])=O.[O-]C(=O)CC(O)(CC([O-])=O)C([O-])=O.[O-]C(=O)CC(O)(CC([O-])=O)C([O-])=O.[O-]C(=O)CC(O)(CC([O-])=O)C([O-])=O AUALKMYBYGCYNY-UHFFFAOYSA-E 0.000 description 43
- 239000000047 product Substances 0.000 description 39
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 description 27
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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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- 229940097206 manganese citrate Drugs 0.000 description 4
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- 238000004519 manufacturing process Methods 0.000 description 4
- UGFAIRIUMAVXCW-UHFFFAOYSA-N Carbon monoxide Chemical compound [O+]#[C-] UGFAIRIUMAVXCW-UHFFFAOYSA-N 0.000 description 3
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- 239000003921 oil Substances 0.000 description 3
- 238000002791 soaking Methods 0.000 description 3
- 238000004544 sputter deposition Methods 0.000 description 3
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 3
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 description 2
- 239000004215 Carbon black (E152) Substances 0.000 description 2
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- UFHFLCQGNIYNRP-UHFFFAOYSA-N Hydrogen Chemical compound [H][H] UFHFLCQGNIYNRP-UHFFFAOYSA-N 0.000 description 1
- 239000002202 Polyethylene glycol Substances 0.000 description 1
- 150000001298 alcohols Chemical class 0.000 description 1
- 150000001299 aldehydes Chemical class 0.000 description 1
- 150000001335 aliphatic alkanes Chemical class 0.000 description 1
- 150000001336 alkenes Chemical class 0.000 description 1
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 description 1
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- 239000007788 liquid Substances 0.000 description 1
- 238000005259 measurement Methods 0.000 description 1
- 229910052757 nitrogen Inorganic materials 0.000 description 1
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- 239000001301 oxygen Substances 0.000 description 1
- 229910052760 oxygen Inorganic materials 0.000 description 1
- 239000003208 petroleum Substances 0.000 description 1
- 229920001223 polyethylene glycol Polymers 0.000 description 1
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- OGIDPMRJRNCKJF-UHFFFAOYSA-N titanium oxide Inorganic materials [Ti]=O OGIDPMRJRNCKJF-UHFFFAOYSA-N 0.000 description 1
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- 229910052723 transition metal Inorganic materials 0.000 description 1
- 150000003624 transition metals Chemical class 0.000 description 1
- 229910003145 α-Fe2O3 Inorganic materials 0.000 description 1
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
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
- B01J35/00—Catalysts, in general, characterised by their form or physical properties
- B01J35/60—Catalysts, in general, characterised by their form or physical properties characterised by their surface properties or porosity
- B01J35/61—Surface area
- B01J35/613—10-100 m2/g
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
- B01J35/00—Catalysts, in general, characterised by their form or physical properties
- B01J35/60—Catalysts, in general, characterised by their form or physical properties characterised by their surface properties or porosity
- B01J35/61—Surface area
- B01J35/615—100-500 m2/g
-
- C—CHEMISTRY; METALLURGY
- C10—PETROLEUM, GAS OR COKE INDUSTRIES; TECHNICAL GASES CONTAINING CARBON MONOXIDE; FUELS; LUBRICANTS; PEAT
- C10G—CRACKING HYDROCARBON OILS; PRODUCTION OF LIQUID HYDROCARBON MIXTURES, e.g. BY DESTRUCTIVE HYDROGENATION, OLIGOMERISATION, POLYMERISATION; RECOVERY OF HYDROCARBON OILS FROM OIL-SHALE, OIL-SAND, OR GASES; REFINING MIXTURES MAINLY CONSISTING OF HYDROCARBONS; REFORMING OF NAPHTHA; MINERAL WAXES
- C10G2/00—Production of liquid hydrocarbon mixtures of undefined composition from oxides of carbon
- C10G2/30—Production of liquid hydrocarbon mixtures of undefined composition from oxides of carbon from carbon monoxide with hydrogen
- C10G2/32—Production of liquid hydrocarbon mixtures of undefined composition from oxides of carbon from carbon monoxide with hydrogen with the use of catalysts
- C10G2/33—Production of liquid hydrocarbon mixtures of undefined composition from oxides of carbon from carbon monoxide with hydrogen with the use of catalysts characterised by the catalyst used
- C10G2/331—Production of liquid hydrocarbon mixtures of undefined composition from oxides of carbon from carbon monoxide with hydrogen with the use of catalysts characterised by the catalyst used containing group VIII-metals
- C10G2/332—Production of liquid hydrocarbon mixtures of undefined composition from oxides of carbon from carbon monoxide with hydrogen with the use of catalysts characterised by the catalyst used containing group VIII-metals of the iron-group
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- Chemical & Material Sciences (AREA)
- Engineering & Computer Science (AREA)
- Organic Chemistry (AREA)
- Chemical Kinetics & Catalysis (AREA)
- Materials Engineering (AREA)
- Oil, Petroleum & Natural Gas (AREA)
- General Chemical & Material Sciences (AREA)
- Catalysts (AREA)
Abstract
The invention relates to the field of Fischer-Tropsch synthesis reaction, and discloses a composition containing supported theta iron carbide, a preparation method, a catalyst and application thereof, and a Fischer-Tropsch synthesis method. A supported theta iron carbide-containing composition comprising 55 to 90 wt.% of a carrier and 10 to 45 wt.% of an iron component, based on the total amount of the composition, wherein the iron component comprises 95 to 100 mol% of the theta iron carbide and 0 to 5 mol% of an Fe-containing impurity, which is an iron-containing substance other than iron carbide, based on the total amount of the iron component. Can simply and conveniently prepare the theta iron carbide which is used as an active component 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 supported 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 (CO) as a by-product2) And methane (CH)4). The Fischer-Tropsch synthesis reaction has complex mechanism and multiple steps, such as CO dissociation, carbon (C) hydrogenation and CHxChain growth, and hydrogenation and dehydrogenation reactions that result in hydrocarbon product desorption and oxygen (O) removal.
Iron is the cheapest transition metal used in making fischer-tropsch synthesis catalysts. The traditional iron-based catalyst has high water gas shift (CO + H)2O→CO2+H2) Active, therefore, conventional iron-based catalysts typically have a higher CO by-product2Selectivity, typically 25% to 45% of the carbon monoxide of the conversion feedstock. This is one of the major disadvantages of iron-based fischer-tropsch catalysts.
The active phase of the iron-based catalyst is very complicated to change, which causes considerable debate between the nature of the active phase and the Fischer-Tropsch synthesis reaction mechanism of the iron-based catalyst.
CN104399501A discloses epsilon-Fe suitable for low-temperature Fischer-Tropsch synthesis reaction2C, a preparation method of the nano-particles. The initial precursor is skeleton iron, and the reaction system is intermittent discontinuous reaction of polyethylene glycol solvent. CO of this catalyst2Selectivity 18.9%, CH4The selectivity of (2) is 17.3%. The disadvantage is that the method can only be applied to low temperature below 200 ℃, and the reaction can not be continuously completed. This means that such catalysts are not suitable for continuous production under modern Fischer-Tropsch synthesis industrial conditions. (however, since the skeleton iron cannot be completely carbonized, epsilon-Fe described in this document2The nanoparticles of C contain a considerable amount of iron impurity components of the non-iron carbide type, and in fact, the prior art cannot obtain pure phase materials of iron carbide free of iron impurities, which are various Fe (element) -containing phase components of non-iron carbide.
Accordingly, there is a need for an improved iron-based catalyst for use in fischer-tropsch synthesis reactions.
Disclosure of Invention
The 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 reduce the content of Fe impuritiesLow CO2Or CH4The problem of overhigh selectivity of byproducts provides a supported theta iron carbide composition, a preparation method, a catalyst and application thereof and a Fischer-Tropsch synthesis method.
In order to achieve the above object, a first aspect of the present invention provides a supported theta iron carbide-containing composition comprising 55 to 90 wt% of a carrier and 10 to 45 wt% of an iron component, based on the total amount of the composition, wherein the iron component comprises 95 to 100 mol% of the theta iron carbide and 0 to 5 mol% of an Fe-containing impurity which is an iron-containing substance other than the theta iron carbide, based on the total amount of the iron component.
In a second aspect, the present invention provides a method of preparing a composition comprising supported theta iron carbide, comprising:
(1) soaking the carrier in a ferric salt water solution, and drying and roasting the soaked carrier to obtain a precursor;
(2) reacting the precursor with H2At a temperature T1Performing precursor reduction at the temperature of 340-;
(3) mixing the material obtained in the step (2) with H2CO at temperature T2The preparation of carbide is carried out at the temperature of 280 ℃ and 420 ℃ for 20-120H, wherein H2The molar ratio to CO is 5-120: 1, obtaining load type theta iron carbide;
(4) mixing the load type theta iron carbide and Fe-containing impurities under the protection of inert gas;
wherein the amount of the supported theta iron carbide and the amount of the Fe-containing impurity are such that the resulting composition comprises 55 to 90 wt.% of the carrier and 10 to 45 wt.% of the iron component, based on the total amount of the composition; the iron component comprises 95-100 mol% of theta iron carbide and 0-5 mol% of Fe-containing impurities, based on the total amount of the iron component;
wherein the Fe-containing impurities are iron-containing substances except the theta iron carbide.
In a third aspect, the invention provides a composition containing supported theta iron carbide prepared by the method provided by the invention.
In a fourth aspect, the invention provides a catalyst comprising the supported theta iron carbide-containing composition provided by the invention.
In a fifth aspect, the invention provides an application of the supported theta iron carbide-containing composition or the catalyst provided by the invention in Fischer-Tropsch synthesis reaction.
In a sixth aspect, the invention provides a use of the supported theta iron carbide-containing composition or catalyst provided by the invention in synthesis of C, H fuel and/or chemicals based on the fischer-tropsch synthesis principle.
In a seventh aspect, the invention provides a fischer-tropsch synthesis process comprising: under the condition of Fischer-Tropsch synthesis reaction, the synthesis gas is contacted with the composition or the catalyst containing the supported theta iron carbide provided by the invention.
An eighth aspect of the present invention provides a fischer-tropsch synthesis method, comprising: the synthesis gas is contacted with a Fischer-Tropsch catalyst under Fischer-Tropsch synthesis reaction conditions, wherein the Fischer-Tropsch catalyst comprises a Mn component and the supported 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 iron source of the main raw material for synthesizing the precursor can be commercial iron salt, and when active phase carbide is synthesized, only original reaction gas (carbon monoxide and hydrogen) of a Fischer-Tropsch synthesis reaction system is used, so that no inorganic or organic matter reaction raw material is involved, and the method is greatly simplified compared with the prior art;
(2) the operation steps are simple and convenient, and in the preferred embodiment, the whole process of preparing the load type theta iron carbide only needs two steps of precursor reduction and carbide preparation, and the preparation of the active phase can be realized in situ in the same reactor;
(3) the method comprises the steps of preparing 100% purity active phase theta iron carbide loaded on a carrier, and then forming a composition with Fe-containing impurities to further prepare the catalyst. The iron carbide or the composition or the catalyst can be used for a high-temperature high-pressure (for example, 265-Stable existence of theoretical technical barrier, stable temperature up to 350 ℃ 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 less than 12% (preferably, less than 6%); at the same time, its by-product CH4The selectivity is also kept at 14 percent (preferably, the selectivity can reach below 7 percent), the selectivity of the effective product can reach above 74 percent (preferably, the selectivity can reach above 85 percent), and the method is very suitable for the high-efficiency production of oil wax products in the Fischer-Tropsch synthesis industry of the modern coal chemical industry.
Drawings
FIG. 1 is an in situ XRD spectrum of a process for preparing a supported iron theta carbide according to example 1 provided in the present invention; wherein the preparation of the C-iron carbide is completed before the reduction of the A-precursor and after the reduction of the B-precursor.
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 supported theta iron carbide-containing composition, which comprises 55-90 wt% of a carrier and 10-45 wt% of an iron component based on the total amount of the composition, wherein the iron component comprises 95-100 mol% of the theta iron carbide and 0-5 mol% of Fe-containing impurities based on the total amount of the iron component, and the Fe-containing impurities are iron-containing substances except the theta iron carbide.
The invention provides a composition containing supported theta iron carbide, which comprises the theta iron carbide with the purity of 100%. Further, the supported theta iron carbide may be combined with other Fe-containing impurities. Under the limit of the content, the supported theta-iron carbide-containing composition provided by the invention can be used alone or in combination with other components when being applied to a Fischer-Tropsch synthesis catalyst, so that the stability of the Fischer-Tropsch synthesis catalyst in Fischer-Tropsch synthesis reaction can be improved, and CO can be greatly reduced2Or CH4Selectivity of by-products.
In some embodiments of the invention, the composition comprises a high purity supported theta iron carbide, and XRD and mossbauer spectroscopy analyses are performed to observe that the crystalline phase comprises pure theta iron carbide from the obtained XRD and mossbauer spectroscopy results. Preferably, the specific surface area of the composition is from 40 to 500m2Per g, preferably from 45 to 350m2(ii) in terms of/g. The specific surface area may be represented by N2The BET adsorption and desorption method (2). Orthorhombic theta iron carbide of the composition.
In some embodiments of the invention, it is further preferred that the composition comprises 60 to 85 wt.% of the carrier and 15 to 40 wt.% of the iron component, based on the total amount of the composition. Can be determined by elemental analysis. The support may be selected from at least one of silica, alumina, titania, niobium pentoxide, and zirconia.
In some embodiments of the invention, it is further preferred that the iron component comprises 97 to 100 mol% of the theta iron carbide and 0 to 3 mol% of the Fe-containing impurities, based on the total amount of the iron component. Can be determined by XRD and Mossbauer spectrometry analysis, and can also be determined according to the preparation charge of the composition.
In some embodiments of the invention, the Fe-containing impurities are at least one of iron carbide, iron oxides, iron hydroxides, iron sulfides, iron salts other than theta iron carbide. The Fe-containing impurities may be introduced by solution impregnation, sputtering, atomic deposition or mixing.
In a second aspect, the invention provides a method of preparing a composition comprising supported theta iron carbide, comprising:
(1) soaking the carrier in a ferric salt water solution, and drying and roasting the soaked carrier to obtain a precursor;
(2) reacting the precursor with H2At a temperature T1Performing precursor reduction at the temperature of 340-;
(3) mixing the material obtained in the step (2) with H2CO at temperature T2The preparation of carbide is carried out at the temperature of 280 ℃ and 420 ℃ for 20-120H, wherein H2The molar ratio to CO is 5-120: 1, obtaining load type theta iron carbide;
(4) mixing the load type theta iron carbide and Fe-containing impurities under the protection of inert gas;
wherein the amount of the supported theta iron carbide and the amount of the Fe-containing impurity are such that the resulting composition comprises 55 to 90 wt.% of the carrier and 10 to 45 wt.% of the iron component, based on the total amount of the composition; the iron component comprises 95-100 mol% of theta iron carbide and 0-5 mol% of Fe-containing impurities, based on the total amount of the iron component;
wherein the Fe-containing impurities are iron-containing substances except the theta iron carbide.
In some embodiments of the present invention, the iron salt may be a water-soluble iron salt commonly used in the art, and the iron salt may be selected from water-soluble iron salts, which may be commercially available, for example, at least one of ferric nitrate, ferric chloride, ferrous ammonium sulfate, and ferric ammonium citrate.
In some embodiments of the invention, the support may be a conventional choice in the art, for example, the catalyst support is at least one of silica, alumina, titania, niobium pentoxide, and zirconia. In the present invention, it is preferable that the particle size of the carrier is 30 to 200. mu.m.
In some embodiments of the invention, preferably, the impregnation is such that the iron content in the impregnated support after drying is from 10 to 30% by weight. The impregnation may be a routine choice in the art as long as the loading of iron in the impregnated support is achieved, preferably the impregnation is a saturated impregnation.
In a preferred embodiment of the present invention, the drying and baking process comprises: firstly, drying the impregnated carrier at 20-30 ℃ for 0.5-4h, then drying at 35-80 ℃ and a vacuum degree of 250-. The above drying process can be performed in an oven, and the roasting process can be performed in a muffle furnace.
In some embodiments of the present invention, step (2) may simultaneously perform in-situ generation of nano iron powder from iron element in the precursor and reduction of the generated nano iron powder.
In some embodiments of the invention, H in step (2)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 reduction of the precursor, preferably, in step (1), said precursor is also at a pressure of 0.1 to 15atm, preferably 0.3 to 2.6atm, for a time of 0.7 to 15h, preferably 1 to 12 h.
In some embodiments of the invention, H2The amount of (C) is selected depending on the amount of the raw material to be treated, and preferably, in the step (2), H2The gas flow rate of (b) is 600-25000mL/h/g, more preferably 2800-22000 mL/h/g.
In step (3) of the method provided by the invention, conditions for realizing the preparation of the carbide are provided so as to obtain the supported theta iron carbide. H2And CO may be (H)2+ CO) in the form of a mixed gas stream into the carbide production process; at the same time, by controlling (H)2+ CO) mixed gas stream pressure to control the pressure of the carbide making process. Preferably, in the step (3), the 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 (3), H2The total gas flow rate with CO is 200-.
In a preferred embodiment of the present invention, the carbide preparation further comprises: in the step (3), temperature changing operation is carried out at the same time, and the temperature is changed 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 obtained supported 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 another preferred embodiment of the present invention, the precursor reduction and carbide preparation process is more convenient in the operation steps performed in the 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 some embodiments of the present invention, obtaining the supported theta iron carbide can be achieved by the processes of steps (1) to (3). As determined by XRD and/or mossbauer spectroscopy.
In some embodiments of the present invention, the Fe-containing impurities contained in the supported theta iron carbide-containing composition may be incorporated by external means. Preferably, 60 to 85 wt% of a carrier and 15 to 40 wt% of an iron component, based on the total amount of the composition; the iron component comprises 97 to 100 mol% of pure theta iron carbide and 0 to 3 mol% of Fe-containing impurities, based on the total amount of the iron component.
In the step (4) of the method provided by the invention, the mixing is carried out by mixing the powder of the supported theta iron carbide and the powder containing the Fe impurities in a glove box according to the dosage requirement under the protection of inert gas.
In a third aspect, the invention provides a theta-containing iron carbide composition produced by the method of the invention. The composition comprises 55-90 wt% of a carrier and 10-45 wt% of an iron component based on the total amount of the composition, wherein the iron component comprises 95-100 mol% of theta iron carbide and 0-5 mol% of Fe-containing impurities, and the Fe-containing impurities are iron-containing substances except the theta iron carbide, based on the total amount of the iron component.
Preferably, the composition comprises 60-85 wt.% of the carrier and 15-40 wt.% of the iron component, based on the total amount of the composition; the iron component comprises 97 to 100 mol% of theta iron carbide and 0 to 3 mol% of Fe-containing impurities, based on the total amount of the iron component.
Preferably, the specific surface area of the composition is from 40 to 500m2Per g, preferably from 45 to 350m2/g。
In a fourth aspect, the invention provides a catalyst comprising the supported theta iron carbide-containing composition provided by the invention. Preferably, the catalyst may also comprise other components, such as promoters.
In the specific embodiment provided by the present invention, preferably, the supported θ iron carbide-containing composition is contained in an amount of 75 wt% or more and less than 100 wt%, and the auxiliary is contained in an amount of more than 0 wt% and 25 wt% or less, based on the total amount of the catalyst.
In the embodiment provided by the invention, preferably, the catalyst can be prepared by introducing the auxiliary agent by a method of impregnation, atomic deposition, sputtering or chemical deposition.
In a fifth aspect, the invention provides a use of the theta-containing iron carbide composition or catalyst provided by the invention in a fischer-tropsch synthesis reaction.
In a sixth aspect, the invention provides the use of a composition or catalyst comprising theta iron carbide according to the invention in a Fischer-Tropsch based synthesis reaction of C, H fuel and/or chemicals.
In a seventh aspect, the invention provides a fischer-tropsch synthesis process comprising: under the condition of Fischer-Tropsch synthesis reaction, the synthesis gas is contacted with the composition or the catalyst containing the theta iron carbide provided by the invention.
The Fischer-Tropsch synthesis reaction carried out by the supported theta iron carbide-containing composition or the catalyst can be carried out at high temperature and high pressure, and for example, the Fischer-Tropsch synthesis reaction conditions comprise that: the temperature is 265 ℃ and 350 ℃, and the pressure is 1.5-3.5 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 theta iron carbide can realize that the Fischer-Tropsch synthesis reaction can be continuously and stably carried out for more than 400 hours in a high-temperature high-pressure continuous reactor.
An eighth aspect of the present invention provides a fischer-tropsch synthesis method, comprising: 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 theta iron carbide-containing composition provided herein.
In a specific embodiment provided by the invention, the composition of the fischer-tropsch catalyst can further include, based on the total amount of the fischer-tropsch catalyst, the content of the supported theta iron carbide-containing composition is 75 wt% or more and less than 100 wt%, and the content of Mn is greater than 0 wt% and less than 25 wt%. In the fischer-tropsch catalyst, Mn may be present as an oxide and may be incorporated into the fischer-tropsch catalyst by methods including, but not limited to, impregnation, chemical deposition, sputtering, atomic deposition.
The present invention will be described in detail below by way of examples. In the following examples and comparative examples,
in-situ XRD detection in the process of preparing the iron carbide, an X-ray diffractometer (Rigaku company, model D/max-2600/PC) is used for monitoring the crystal phase change of the material;
the obtained iron carbide and iron carbide composition were subjected to Mossbauer spectrometer (Transmission)57Fe，57A Co (Rh) source sinusoidal velocity spectrometer) to perform Mossbauer spectrum detection;
the BET specific surface area of the iron carbide composition was measured by a nitrogen adsorption method;
carrying out Fischer-Tropsch synthesis reaction:
carrying out gas chromatography (Agilent 6890 gas chromatography) on the product obtained by the reaction;
the effect of the reaction is calculated by the following formula:
CO2selectivity%2Mole number/(moles of CO in feed-moles of CO in discharge)]×100％；
CH4Selectivity%4Mole/(mole of CO in the feed x CO conversion% (1-CO)2Selectivity%))]×100％；
Effective product selectivity ═ 1-CO2Selective% CH4Selectivity%]×100％
Raw material CO space-time conversion rate (mmol/h/g)-Fe) (moles of CO in feed-moles of CO in discharge)/reaction time/weight of Fe element;
efficient product formation space-time yield (mmol/h/g)-Fe) Reaction of C2And C2The above number of moles of hydrocarbon/reaction time/weight of Fe element.
Example 1
(1) Weighing 20g of silicon oxide as a carrier, and then impregnating with an aqueous ferric ammonium citrate solution, wherein the aqueous ferric ammonium citrate solution is weighed and prepared according to the content of 30 wt% of the simple substance iron in the final carrier. Drying the impregnated carrier at 30 ℃ for 2h, then drying the impregnated carrier in a vacuum drying oven at 40 ℃ and the vacuum degree of 300Pa for 8h, drying the dried material in an oven at 120 ℃ for 24h, and roasting the obtained material in a muffle furnace at 500 ℃ for 5 h. Obtaining a load type iron-based precursor;
(2) mixing the precursor with H2At a pressure of 2.6atm, H2The flow rate of the precursor is 22000mL/h/g, and the precursor is reduced for 12h at the temperature of 450 ℃;
(3) cooling the product obtained in the step (2) from 450 ℃ to 400 ℃ at the speed of 1.5 ℃/min, and reacting with H at the temperature2And the carbon is contacted with CO mixed gas to prepare the supported carbide, wherein the conditions are as follows: pressure 20atm, total gas flow 20000mL/H/g, H2The molar ratio of the iron carbide to CO is 60:1, the treatment time is 24 hours, the loaded iron carbide is obtained, and the loaded iron is pure theta iron carbide determined by Mossbauer spectroscopy and is marked as the loaded iron carbide 1;
(4) supported iron carbide 1 in 97 molar parts was mixed with ferrous oxide (i.e. Fe-containing impurities) in 3 molar parts under Ar gas. After mixing, the mixture was designated as supported iron carbide composition 1.
Example 2
(1) Weighing 20g of titanium oxide as a carrier, and then soaking the carrier by using a ferric ammonium citrate aqueous solution, wherein the ferric ammonium citrate aqueous solution is weighed and prepared according to the content of 10 wt% of simple substance iron in the final carrier. Drying the impregnated carrier at 30 ℃ for 2h, then drying the impregnated carrier in a vacuum drying oven at 40 ℃ and the vacuum degree of 300Pa for 8h, drying the dried material in an oven at 120 ℃ for 24h, and roasting the obtained material in a muffle furnace at 500 ℃ for 5 h. Obtaining a load type iron-based precursor;
(2) mixing the precursor with H2At a pressure of 0.3atm, H2The flow rate of the precursor is 2800mL/h/g, and the precursor is reduced for 1h at the temperature of 450 ℃;
(3) cooling the product obtained in the step (2) from 450 ℃ to 300 ℃ at the speed of 1.5 ℃/min, and reacting with H at the temperature2And the carbon is contacted with CO mixed gas to prepare the supported carbide, wherein the conditions are as follows: pressure 0.01atm, total gas flow 1200mL/H/g, H2The molar ratio of the iron carbide to CO is 60:1, the treatment time is 80 hours, and the loaded iron carbide is obtained, is determined to be pure theta iron carbide by Mossbauer spectroscopy and is marked as loaded iron carbide 2;
(4) supported iron carbide 2at 97 molar parts was mixed with ferrous oxide (i.e. Fe-containing impurities) at 3 molar parts under Ar gas. After mixing, it was designated as supported iron carbide composition 2.
Example 3
(1) Weighing 20g of alumina as a carrier, and then impregnating with an aqueous ferric ammonium citrate solution, wherein the aqueous ferric ammonium citrate solution is weighed and prepared according to the content of 25 wt% of the elemental iron in the final carrier. Drying the impregnated carrier at 30 ℃ for 2h, then drying the impregnated carrier in a vacuum drying oven at 40 ℃ and the vacuum degree of 300Pa for 8h, drying the dried material in an oven at 120 ℃ for 24h, and roasting the obtained material in a muffle furnace at 500 ℃ for 5 h. Obtaining a load type iron-based precursor;
(2) mixing the precursor with H2At a pressure of 1.5atm, H2The flow of the precursor is 10000mL/h/g, and the precursor is reduced for 6h at the temperature of 450 ℃;
(3) cooling the product obtained in the step (2) from 450 ℃ to 350 ℃ at the speed of 1.5 ℃/min, and reacting with H at the temperature2And the carbon is contacted with CO mixed gas to prepare the supported carbide, wherein the conditions are as follows: pressure 10atm, total gas flow 10000mL/H/g, H2The molar ratio of the iron carbide to CO is 60:1, the treatment time is 48 hours, and the loaded iron carbide is obtained, is determined to be pure theta iron carbide by Mossbauer spectroscopy and is marked as loaded iron carbide 3;
(4) 99 molar parts of supported iron carbide 3 are mixed with 1 molar part of ferrous oxide (i.e. Fe-containing impurities) under Ar gas protection. After mixing, it was designated as supported iron carbide composition 3.
Example 4
(1) - (3) Process according to example 1, except that "precursor with H" is used in step (2)2Replacement of "precursor with H" at a pressure of 3atm2And under the pressure of 2.6 atm', obtaining the loaded iron carbide, and determining that the loaded iron is pure theta iron carbide through Mossbauer spectrum, and marking as the loaded iron carbide 4.
(4) Under the protection of Ar gas, 98 mol parts of supported iron carbide 4 is mixed with 2 mol parts of ferrous oxide (namely, Fe-containing impurities). After mixing, it was designated as supported iron carbide composition 4.
Example 5
(1) - (3) Process according to example 1, except that "precursor with H" is used in step (2)2Replacement of "precursor with H" at a pressure of 0.08atm2And under the pressure of 2.6 atm', obtaining the loaded iron carbide, and determining that the loaded iron is pure theta iron carbide through Mossbauer spectrum, and marking as the loaded iron carbide 5.
(4) Supported iron carbide 5 in 97 molar parts was mixed with ferrous oxide (i.e. Fe-containing impurities) in 3 molar parts under Ar gas. After mixing, it was designated as supported iron carbide composition 5.
Example 6
(1) Weighing 20g of niobium pentoxide as a carrier, and then impregnating with an aqueous ferric ammonium citrate solution, wherein the aqueous ferric ammonium citrate solution is weighed and prepared according to the content of 25 wt% of the elemental iron in the final carrier. Drying the impregnated carrier at 30 ℃ for 2h, then drying the impregnated carrier in a vacuum drying oven at 40 ℃ and the vacuum degree of 300Pa for 8h, drying the dried material in an oven at 120 ℃ for 24h, and roasting the obtained material in a muffle furnace at 500 ℃ for 5 h. Obtaining a load type iron-based precursor;
(2) mixing the precursor with H2At a pressure of 1.5atm, H2The flow of the precursor is 10000mL/h/g, and the precursor is reduced for 13h at the temperature of 450 ℃;
(3) cooling the product obtained in the step (2) from 450 ℃ to 350 ℃ at the speed of 1.5 ℃/min, and reacting at the temperatureH2And the carbon is contacted with CO mixed gas to prepare the supported carbide, wherein the conditions are as follows: pressure 10atm, total gas flow 10000mL/H/g, H2The molar ratio of the iron carbide to CO is 60:1, the treatment time is 48 hours, and the loaded iron carbide is obtained, is determined to be pure theta iron carbide by Mossbauer spectroscopy and is marked as loaded iron carbide 3;
(4) under the protection of Ar gas, 98 mol parts of supported iron carbide 6 and 2 mol parts of ferrous oxide (namely Fe-containing impurities) are mixed. After mixing, it was designated as supported iron carbide composition 6.
Example 7
(1) Weighing 20g of niobium pentoxide as a carrier, and then impregnating with an aqueous ferric ammonium citrate solution, wherein the aqueous ferric ammonium citrate solution is weighed and prepared according to the content of 25 wt% of the elemental iron in the final carrier. Drying the impregnated carrier at 30 ℃ for 2h, then drying the impregnated carrier in a vacuum drying oven at 40 ℃ and the vacuum degree of 300Pa for 8h, drying the dried material in an oven at 120 ℃ for 24h, and roasting the obtained material in a muffle furnace at 500 ℃ for 5 h. Obtaining a load type iron-based precursor;
(2) mixing the precursor with H2At a pressure of 1.5atm, H2The flow of the precursor is 10000mL/h/g, and the precursor is reduced for 0.5h at the temperature of 450 ℃;
(3) cooling the product obtained in the step (2) from 450 ℃ to 350 ℃ at the speed of 1.5 ℃/min, and reacting with H at the temperature2And the carbon is contacted with CO mixed gas to prepare the supported carbide, wherein the conditions are as follows: pressure 10atm, total gas flow 10000mL/H/g, H2The molar ratio of the iron carbide to CO is 60:1, the treatment time is 48 hours, and the loaded iron carbide is obtained, is determined to be pure theta iron carbide by Mossbauer spectroscopy and is marked as loaded iron carbide 7;
(4) 99 molar parts of supported iron carbide 7 are mixed with 1 molar part of ferrous oxide (i.e. Fe-containing impurities) under Ar gas protection. After mixing, it was designated as supported iron carbide composition 7.
Example 8
(1) Weighing 20g of silicon oxide as a carrier, and then impregnating with an aqueous ferric ammonium citrate solution, wherein the aqueous ferric ammonium citrate solution is weighed and prepared according to the content of 25 wt% of the elemental iron in the final carrier. Drying the impregnated carrier at 30 ℃ for 2h, then drying the impregnated carrier in a vacuum drying oven at 40 ℃ and the vacuum degree of 300Pa for 8h, drying the dried material in an oven at 120 ℃ for 24h, and roasting the obtained material in a muffle furnace at 500 ℃ for 5 h. Obtaining a load type iron-based precursor;
(2) mixing the precursor with H2At a pressure of 1.5atm, H2The flow rate of the precursor is 23000mL/h/g, and the precursor is reduced for 6h at the temperature of 450 ℃;
(3) cooling the product obtained in the step (2) from 450 ℃ to 350 ℃ at the speed of 1.5 ℃/min, and reacting with H at the temperature2And the carbon is contacted with CO mixed gas to prepare the supported carbide, wherein the conditions are as follows: pressure 10atm, total gas flow 10000mL/H/g, H2The molar ratio of the iron carbide to CO is 60:1, the treatment time is 48 hours, and the loaded iron carbide is obtained, is determined to be pure theta iron carbide by Mossbauer spectroscopy and is marked as loaded iron carbide 8;
(4) 99 molar parts of supported iron carbide 8 are mixed with 1 molar part of ferrous oxide (i.e. Fe-containing impurities) under Ar gas protection. After mixing, it was designated as supported iron carbide composition 8.
Example 9
(1) Weighing 20g of silicon oxide as a carrier, and then impregnating with an aqueous ferric ammonium citrate solution, wherein the aqueous ferric ammonium citrate solution is weighed and prepared according to the content of 25 wt% of the elemental iron in the final carrier. Drying the impregnated carrier at 30 ℃ for 2h, then drying the impregnated carrier in a vacuum drying oven at 40 ℃ and the vacuum degree of 300Pa for 8h, drying the dried material in an oven at 120 ℃ for 24h, and roasting the obtained material in a muffle furnace at 500 ℃ for 5 h. Obtaining a load type iron-based precursor;
(2) mixing the precursor with H2At a pressure of 1.5atm, H2The flow rate of the precursor is 500mL/h/g, and the precursor is reduced for 10 hours at the temperature of 450 ℃;
(3) cooling the product obtained in the step (2) from 450 ℃ to 350 ℃ at the speed of 1.5 ℃/min, and reacting with H at the temperature2And the carbon is contacted with CO mixed gas to prepare the supported carbide, wherein the conditions are as follows: pressure 10atm, total gas flow 10000mL/H/g, H2The molar ratio of the catalyst to CO is 60:1, the treatment time is 48 hours, and the load is obtainedThe model iron carbide, the loaded iron is pure theta iron carbide determined by Mossbauer spectroscopy, and is marked as loaded iron carbide 9;
(4) under the protection of Ar gas, 98 mol parts of supported iron carbide 9 and 2 mol parts of ferrous oxide (namely Fe-containing impurities) are mixed. After mixing, it was designated as supported iron carbide composition 9.
Example 10
(1) Weighing 20g of silicon oxide as a carrier, and then impregnating with an aqueous ferric ammonium citrate solution, wherein the aqueous ferric ammonium citrate solution is weighed and prepared according to the content of 25 wt% of the elemental iron in the final carrier. Drying the impregnated carrier at 30 ℃ for 2h, then drying the impregnated carrier in a vacuum drying oven at 40 ℃ and the vacuum degree of 300Pa for 8h, drying the dried material in an oven at 120 ℃ for 24h, and roasting the obtained material in a muffle furnace at 500 ℃ for 5 h. Obtaining a load type iron-based precursor;
(2) mixing the precursor with H2At a pressure of 1.5atm, H2The flow of the precursor is 10000mL/h/g, and the precursor is reduced for 6h at the temperature of 450 ℃;
(3) cooling the product obtained in the step (2) from 450 ℃ to 410 ℃ at the speed of 1.5 ℃/min, and reacting with H at the temperature2And the carbon is contacted with CO mixed gas to prepare the supported carbide, wherein the conditions are as follows: pressure 10atm, total gas flow 10000mL/H/g, H2The molar ratio of the iron carbide to CO is 60:1, the treatment time is 48 hours, and the loaded iron carbide is obtained, is determined to be pure theta iron carbide by Mossbauer spectroscopy and is marked as loaded iron carbide 10;
(4) supported iron carbide 10at 97 molar parts was mixed with ferrous oxide (i.e. Fe-containing impurities) at 3 molar parts under Ar gas. After mixing, this is designated as supported iron carbide composition 10.
Example 11
(1) Weighing 20g of silicon oxide as a carrier, and then impregnating with an aqueous ferric ammonium citrate solution, wherein the aqueous ferric ammonium citrate solution is weighed and prepared according to the content of 25 wt% of the elemental iron in the final carrier. Drying the impregnated carrier at 30 ℃ for 2h, then drying the impregnated carrier in a vacuum drying oven at 40 ℃ and the vacuum degree of 300Pa for 8h, drying the dried material in an oven at 120 ℃ for 24h, and roasting the obtained material in a muffle furnace at 500 ℃ for 5 h. Obtaining a load type iron-based precursor;
(2) mixing the precursor with H2At a pressure of 1.5atm, H2The flow of the precursor is 10000mL/h/g, and the precursor is reduced for 6h at the temperature of 450 ℃;
(3) cooling the product obtained in the step (2) from 450 ℃ to 270 ℃ at the speed of 1.5 ℃/min, and reacting the product with H at the temperature2And the carbon is contacted with CO mixed gas to prepare the supported carbide, wherein the conditions are as follows: pressure 10atm, total gas flow 10000mL/H/g, H2The molar ratio of the iron carbide to CO is 60:1, the treatment time is 48 hours, and the loaded iron carbide is obtained, is determined to be pure theta iron carbide by Mossbauer spectroscopy and is marked as loaded iron carbide 11;
(4) 99 molar parts of supported iron carbide 11 are mixed with 1 molar part of ferrous oxide (i.e. Fe-containing impurities) under Ar gas protection. After mixing, it was designated as supported iron carbide composition 11.
Example 12
(1) Weighing 20g of zirconia as a carrier, and then impregnating with an aqueous ferric ammonium citrate solution, wherein the aqueous ferric ammonium citrate solution is weighed and prepared according to the content of 25 wt% of the elemental iron in the final carrier. Drying the impregnated carrier at 30 ℃ for 2h, then drying the impregnated carrier in a vacuum drying oven at 40 ℃ and the vacuum degree of 300Pa for 8h, drying the dried material in an oven at 120 ℃ for 24h, and roasting the obtained material in a muffle furnace at 500 ℃ for 5 h. Obtaining a load type iron-based precursor;
(2) mixing the precursor with H2At a pressure of 1.5atm, H2The flow of the precursor is 10000mL/h/g, and the precursor is reduced for 6h at the temperature of 450 ℃;
(3) cooling the product obtained in the step (2) from 450 ℃ to 350 ℃ at the speed of 1.5 ℃/min, and reacting with H at the temperature2And the carbon is contacted with CO mixed gas to prepare the supported carbide, wherein the conditions are as follows: pressure 10atm, total gas flow 10000mL/H/g, H2The molar ratio of the iron carbide to CO is 60:1, the treatment time is 85 hours, the loaded iron carbide is obtained, and the loaded iron is pure theta iron carbide determined by Mossbauer spectroscopy and is marked as loaded iron carbide 12;
(4) 99 molar parts of supported iron carbide 12 are mixed with 1 molar part of ferrous oxide (i.e. Fe-containing impurities) under Ar gas protection. After mixing, this is designated as supported iron carbide composition 12.
Example 13
(1) Weighing 20g of zirconia as a carrier, and then impregnating with an aqueous ferric ammonium citrate solution, wherein the aqueous ferric ammonium citrate solution is weighed and prepared according to the content of 25 wt% of the elemental iron in the final carrier. Drying the impregnated carrier at 30 ℃ for 2h, then drying the impregnated carrier in a vacuum drying oven at 40 ℃ and the vacuum degree of 300Pa for 8h, drying the dried material in an oven at 120 ℃ for 24h, and roasting the obtained material in a muffle furnace at 500 ℃ for 5 h. Obtaining a load type iron-based precursor;
(2) mixing the precursor with H2At a pressure of 1.5atm, H2The flow of the precursor is 10000mL/h/g, and the precursor is reduced for 6h at the temperature of 450 ℃;
(3) cooling the product obtained in the step (2) from 450 ℃ to 350 ℃ at the speed of 1.5 ℃/min, and reacting with H at the temperature2And the carbon is contacted with CO mixed gas to prepare the supported carbide, wherein the conditions are as follows: pressure 10atm, total gas flow 10000mL/H/g, H2The molar ratio of the iron carbide to CO is 60:1, the treatment time is 18 hours, and the loaded iron carbide is obtained, is determined to be pure theta iron carbide by Mossbauer spectroscopy and is marked as loaded iron carbide 13;
(4) under the protection of Ar gas, 98 mol parts of supported iron carbide 13 is mixed with 2 mol parts of ferrous oxide (namely, Fe-containing impurities). After mixing, it was designated as supported iron carbide composition 13.
Example 14
(1) Weighing 20g of silicon oxide as a carrier, and then impregnating with an aqueous ferric ammonium citrate solution, wherein the aqueous ferric ammonium citrate solution is weighed and prepared according to the content of 25 wt% of the elemental iron in the final carrier. Drying the impregnated carrier at 30 ℃ for 2h, then drying the impregnated carrier in a vacuum drying oven at 40 ℃ and the vacuum degree of 300Pa for 8h, drying the dried material in an oven at 120 ℃ for 24h, and roasting the obtained material in a muffle furnace at 500 ℃ for 5 h. Obtaining a load type iron-based precursor;
(2) mixing the precursor with H2At a pressure of 1.5atm, H210000 mL/h-g, carrying out precursor reduction for 6h at the temperature of 450 ℃;
(3) cooling the product obtained in the step (2) from 450 ℃ to 350 ℃ at the speed of 1.5 ℃/min, and reacting with H at the temperature2And the carbon is contacted with CO mixed gas to prepare the supported carbide, wherein the conditions are as follows: pressure 22atm, total gas flow 10000mL/H/g, H2The molar ratio of the iron carbide to CO is 60:1, the treatment time is 48 hours, and the loaded iron carbide is obtained, is determined to be pure theta iron carbide by Mossbauer spectroscopy and is marked as loaded iron carbide 14;
(4) 99 molar parts of supported iron carbide 14 are mixed with 1 molar part of ferrous oxide (i.e. Fe-containing impurities) under Ar gas. After mixing, the mixture is designated as supported iron carbide composition 14.
Example 15
(1) Weighing 20g of silicon oxide as a carrier, and then impregnating with an aqueous ferric ammonium citrate solution, wherein the aqueous ferric ammonium citrate solution is weighed and prepared according to the content of 25 wt% of the elemental iron in the final carrier. Drying the impregnated carrier at 30 ℃ for 2h, then drying the impregnated carrier in a vacuum drying oven at 40 ℃ and the vacuum degree of 300Pa for 8h, drying the dried material in an oven at 120 ℃ for 24h, and roasting the obtained material in a muffle furnace at 500 ℃ for 5 h. Obtaining a load type iron-based precursor;
(2) mixing the precursor with H2At a pressure of 1.5atm, H2The flow of the precursor is 10000mL/h/g, and the precursor is reduced for 6h at the temperature of 450 ℃;
(3) cooling the product obtained in the step (2) from 450 ℃ to 350 ℃ at the speed of 1.5 ℃/min, and reacting with H at the temperature2And the carbon is contacted with CO mixed gas to prepare the supported carbide, wherein the conditions are as follows: pressure 0.005atm, total gas flow 10000mL/H/g, H2The molar ratio of the iron carbide to CO is 60:1, the treatment time is 48 hours, and the loaded iron carbide is obtained, is determined to be pure theta iron carbide by Mossbauer spectroscopy and is marked as loaded iron carbide 15;
(4) under the protection of Ar gas, 98 mol parts of supported iron carbide 15 and 2 mol parts of ferrous oxide (namely Fe-containing impurities) are mixed. After mixing, it was designated as supported iron carbide composition 15.
Example 16
(1) Weighing 20g of silicon oxide as a carrier, and then impregnating with an aqueous ferric ammonium citrate solution, wherein the aqueous ferric ammonium citrate solution is weighed and prepared according to the content of 25 wt% of the elemental iron in the final carrier. Drying the impregnated carrier at 30 ℃ for 2h, then drying the impregnated carrier in a vacuum drying oven at 40 ℃ and the vacuum degree of 300Pa for 8h, drying the dried material in an oven at 120 ℃ for 24h, and roasting the obtained material in a muffle furnace at 500 ℃ for 5 h. Obtaining a load type iron-based precursor;
(2) mixing the precursor with H2At a pressure of 1.5atm, H2The flow of the precursor is 10000mL/h/g, and the precursor is reduced for 6h at the temperature of 450 ℃;
(3) cooling the product obtained in the step (2) from 450 ℃ to 350 ℃ at the speed of 1.5 ℃/min, and reacting with H at the temperature2And the carbon is contacted with CO mixed gas to prepare the supported carbide, wherein the conditions are as follows: pressure 10atm, total gas flow 22000mL/H/g, H2The molar ratio of the iron carbide to CO is 60:1, the treatment time is 48 hours, and the loaded iron carbide is obtained, is determined to be pure theta iron carbide by Mossbauer spectroscopy and is marked as loaded iron carbide 16;
(4) supported iron carbide 16 in 97 molar parts was mixed with ferrous oxide (i.e., Fe-containing impurities) in 3 molar parts under Ar gas. After mixing, the mixture is marked as supported iron carbide composition 16.
Example 17
(1) Weighing 20g of silicon oxide as a carrier, and then impregnating with an aqueous ferric ammonium citrate solution, wherein the aqueous ferric ammonium citrate solution is weighed and prepared according to the content of 25 wt% of the elemental iron in the final carrier. Drying the impregnated carrier at 30 ℃ for 2h, then drying the impregnated carrier in a vacuum drying oven at 40 ℃ and the vacuum degree of 300Pa for 8h, drying the dried material in an oven at 120 ℃ for 24h, and roasting the obtained material in a muffle furnace at 500 ℃ for 5 h. Obtaining a load type iron-based precursor;
(2) mixing the precursor with H2At a pressure of 1.5atm, H2The flow of the precursor is 10000mL/h/g, and the precursor is reduced for 6h at the temperature of 450 ℃;
(3) cooling the product obtained in the step (2) from 450 ℃ to 350 ℃ at the speed of 1.5 ℃/min, and reacting at the temperatureH2And the carbon is contacted with CO mixed gas to prepare the supported carbide, wherein the conditions are as follows: pressure 10atm, total gas flow 150mL/H/g, H2The molar ratio of the iron carbide to CO is 60:1, the treatment time is 48 hours, and the loaded iron carbide is obtained, is determined to be pure theta iron carbide through Mossbauer spectroscopy and is marked as loaded iron carbide 17;
(4) 99 molar parts of supported iron carbide 17 are mixed with 1 molar part of ferrous oxide (i.e. Fe-containing impurities) under Ar gas protection. After mixing, this was designated as supported iron carbide composition 17.
Example 18
(1) Weighing 20g of silicon oxide as a carrier, and then impregnating with an aqueous ferric ammonium citrate solution, wherein the aqueous ferric ammonium citrate solution is weighed and prepared according to the content of 25 wt% of the elemental iron in the final carrier. Drying the impregnated carrier at 30 ℃ for 2h, then drying the impregnated carrier in a vacuum drying oven at 40 ℃ and the vacuum degree of 300Pa for 8h, drying the dried material in an oven at 120 ℃ for 24h, and roasting the obtained material in a muffle furnace at 500 ℃ for 5 h. Obtaining a load type iron-based precursor;
(2) mixing the precursor with H2At a pressure of 1.5atm, H2The flow of the precursor is 10000mL/h/g, and the precursor is reduced for 6h at the temperature of 450 ℃;
(3) cooling the product obtained in the step (2) from 450 ℃ to 350 ℃ at the speed of 3 ℃/min, and reacting the product with H at the temperature2And the carbon is contacted with CO mixed gas to prepare the supported carbide, wherein the conditions are as follows: pressure 10atm, total gas flow 10000mL/H/g, H2The molar ratio of the iron carbide to CO is 60:1, the treatment time is 48 hours, and the loaded iron carbide is obtained, is determined to be pure theta iron carbide by Mossbauer spectroscopy and is marked as loaded iron carbide 18;
(4) supported iron carbide 18 in 98 molar parts was mixed with 2 molar parts of ferrous oxide (i.e. Fe-containing impurities) under Ar gas. After mixing, this is designated as supported iron carbide composition 18.
Example 19
(1) Weighing 20g of silicon oxide as a carrier, and then impregnating with an aqueous ferric ammonium citrate solution, wherein the aqueous ferric ammonium citrate solution is weighed and prepared according to the content of 25 wt% of the elemental iron in the final carrier. Drying the impregnated carrier at 30 ℃ for 2h, then drying the impregnated carrier in a vacuum drying oven at 40 ℃ and the vacuum degree of 300Pa for 8h, drying the dried material in an oven at 120 ℃ for 24h, and roasting the obtained material in a muffle furnace at 500 ℃ for 5 h. Obtaining a load type iron-based precursor;
(2) mixing the precursor with H2At a pressure of 1.5atm, H2The flow of the precursor is 10000mL/h/g, and the precursor is reduced for 6h at the temperature of 450 ℃;
(3) cooling the product obtained in the step (2) from 450 ℃ to 350 ℃ at the speed of 0.1 ℃/min, and reacting with H at the temperature2And the carbon is contacted with CO mixed gas to prepare the supported carbide, wherein the conditions are as follows: pressure 10atm, total gas flow 10000mL/H/g, H2The molar ratio of the iron carbide to CO is 60:1, the treatment time is 48 hours, and the loaded iron carbide is obtained, is determined to be pure theta iron carbide by Mossbauer spectroscopy and is marked as loaded iron carbide 19;
(4) supported iron carbide 19 in 97 molar parts was mixed with 3 molar parts of ferrous oxide (i.e. Fe-containing impurities) under Ar gas. After mixing, this was designated as supported iron carbide composition 19.
Comparative example 1
(1) Weighing 20g of silicon oxide as a carrier, and then impregnating with an aqueous ferric ammonium citrate solution, wherein the aqueous ferric ammonium citrate solution is weighed and prepared according to the content of 25 wt% of the elemental iron in the final carrier. Drying the impregnated carrier at 30 ℃ for 2h, then drying the impregnated carrier in a vacuum drying oven at 40 ℃ and the vacuum degree of 300Pa for 8h, drying the dried material in an oven at 120 ℃ for 24h, and roasting the obtained material in a muffle furnace at 500 ℃ for 5 h. Obtaining a load type iron-based precursor;
(2) mixing the precursor with H2At a pressure of 1.5atm, H2The flow of the precursor is 10000mL/h/g, and the precursor is reduced for 6h at the temperature of 620 ℃;
(3) cooling the product obtained in the step (2) from 620 ℃ to 350 ℃ at the speed of 1.5 ℃/min, and reacting with H at the temperature2And the carbon is contacted with CO mixed gas to prepare the supported carbide, wherein the conditions are as follows: pressure 10atm, total gas flow 10000mL/H/g, H2The molar ratio of the catalyst to CO is 60:1, the treatment time is 48 hours, and the load is obtainedType iron carbide, marked as load type iron carbide D1;
(4) 99 molar parts of supported iron carbide D1 was mixed with 1 molar part of ferrous oxide (i.e. Fe-containing impurities) under Ar gas. After mixing, it was designated as supported iron carbide composition D1.
Comparative example 2
(1) Weighing 20g of silicon oxide as a carrier, and then impregnating with an aqueous ferric ammonium citrate solution, wherein the aqueous ferric ammonium citrate solution is weighed and prepared according to the content of 25 wt% of the elemental iron in the final carrier. Drying the impregnated carrier at 30 ℃ for 2h, then drying the impregnated carrier in a vacuum drying oven at 40 ℃ and the vacuum degree of 300Pa for 8h, drying the dried material in an oven at 120 ℃ for 24h, and roasting the obtained material in a muffle furnace at 500 ℃ for 5 h. Obtaining a load type iron-based precursor;
(2) mixing the precursor with H2At a pressure of 1.5atm, H2The flow of the precursor is 10000mL/h/g, and the precursor is reduced for 6h at the temperature of 320 ℃;
(3) heating the product obtained in the step (2) from 320 ℃ to 350 ℃ at the speed of 1.5 ℃/min, and reacting with H at the temperature2And the carbon is contacted with CO mixed gas to prepare the supported carbide, wherein the conditions are as follows: pressure 10atm, total gas flow 10000mL/H/g, H2The molar ratio of the carbon to CO is 60:1, and the treatment time is 48 hours, so that load type iron carbide is obtained and is marked as load type iron carbide D2;
(4) 99 molar parts of supported iron carbide D2 was mixed with 1 molar part of ferrous oxide (i.e. Fe-containing impurities) under Ar gas. After mixing, it was designated as supported iron carbide composition D2.
Comparative example 3
(1) Weighing 20g of zirconia as a carrier, and then impregnating with an aqueous ferric ammonium citrate solution, wherein the aqueous ferric ammonium citrate solution is weighed and prepared according to the content of 25 wt% of the elemental iron in the final carrier. Drying the impregnated carrier at 30 ℃ for 2h, then drying the impregnated carrier in a vacuum drying oven at 40 ℃ and the vacuum degree of 300Pa for 8h, drying the dried material in an oven at 120 ℃ for 24h, and roasting the obtained material in a muffle furnace at 500 ℃ for 5 h. Obtaining a load type iron-based precursor;
(2) will be ahead ofDriver and H2At a pressure of 1.5atm, H2The flow of the precursor is 10000mL/h/g, and the precursor is reduced for 6h at the temperature of 450 ℃;
(3) cooling the product obtained in the step (2) from 450 ℃ to 350 ℃ at the speed of 1.5 ℃/min, and reacting with H at the temperature2And the carbon is contacted with CO mixed gas to prepare the supported carbide, wherein the conditions are as follows: pressure 10atm, total gas flow 10000mL/H/g, H2The molar ratio of the carbon to the CO is 130:1, and the treatment time is 48 hours, so that load type iron carbide is obtained and is marked as load type iron carbide D3;
(4) 99 molar parts of supported iron carbide D3 was mixed with 1 molar part of ferrous oxide (i.e. Fe-containing impurities) under Ar gas. After mixing, it was designated as supported iron carbide composition D3.
Comparative example 4
(1) Weighing 20g of zirconia as a carrier, and then impregnating with an aqueous ferric ammonium citrate solution, wherein the aqueous ferric ammonium citrate solution is weighed and prepared according to the content of 25 wt% of the elemental iron in the final carrier. Drying the impregnated carrier at 30 ℃ for 2h, then drying the impregnated carrier in a vacuum drying oven at 40 ℃ and the vacuum degree of 300Pa for 8h, drying the dried material in an oven at 120 ℃ for 24h, and roasting the obtained material in a muffle furnace at 500 ℃ for 5 h. Obtaining a load type iron-based precursor;
(2) mixing the precursor with H2At a pressure of 1.5atm, H2The flow of the precursor is 10000mL/h/g, and the precursor is reduced for 6h at the temperature of 450 ℃;
(3) cooling the product obtained in the step (2) from 450 ℃ to 350 ℃ at the speed of 1.5 ℃/min, and reacting with H at the temperature2And the carbon is contacted with CO mixed gas to prepare the supported carbide, wherein the conditions are as follows: pressure 10atm, total gas flow 10000mL/H/g, H2The molar ratio of the carbon to the CO is 3:1, and the treatment time is 48 hours, so that load type iron carbide is obtained and is marked as load type iron carbide D4;
(4) 99 molar parts of supported iron carbide D4 was mixed with 1 molar part of ferrous oxide (i.e. Fe-containing impurities) under Ar gas. After mixing, it was designated as supported iron carbide composition D4.
Comparative example 5
The procedure of example 1 was followed except that (4) 91 parts by mole of supported iron carbide 1 was mixed with 9 parts by mole of ferrous oxide (i.e., Fe-containing impurities) under Ar gas. After mixing, it was designated as supported iron carbide composition D5.
Examples 20 to 38
Respectively taking 1-19 of load type 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 1-19 correspondingly. Wherein the amount of the added manganese citrate solution is impregnated, so that the obtained Fischer-Tropsch catalysts 1-19 respectively and correspondingly contain 85 wt% of supported iron carbide composition 1-19 and 15 wt% of MnO2。
Comparative examples 6 to 10
Respectively taking supported iron carbide compositions D1-D5 as carrier 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-D5. Wherein the added manganese citrate solution is impregnated in an amount which enables the obtained Fischer-Tropsch catalysts D1-D5 to respectively contain 85 wt% of supported iron carbide compositions D1-D5 and 15 wt% of MnO2。
Test example
Mossbauer spectroscopy was performed on iron carbides 1 to 19 and D1 to D4, 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
| Iron carbide numbering | Theta iron carbide content (mol%) | Other Fe-containing impurities content (mol%) |
| 1-24 | 100.0 | 0.0 |
| D1 | 54.0 | 46.0 |
| D2 | 41.0 | 59.0 |
| D3 | 38.0 | 62.0 |
| D4 | 40.0 | 60.0 |
In the method, the whole process of preparing the iron carbide 1 in the example 1 adopts an in-situ XRD detection technology, and an X-ray diffractometer (Rigaku company, model D/max-2600/PC) is used for monitoring the crystal phase change of the material. As shown in FIG. 1, curve A is shown before the reduction of the precursor in step (1), curve B is shown after the reduction of the precursor, and curve C is shown after the preparation of the carbide is completed. Wherein curve A is alpha-Fe2O3The characteristic peaks 2 theta of the card are 33.3 degrees, 35.7 degrees, 41.0 degrees, 49.5 degrees, 54.2 degrees, 57.6 degrees, 62.7 degrees and the like which are completely consistent with the standard card PDF-02-0919. B is alpha-Fe crystal phase, and the characteristic peaks 2 theta are 44.7 degrees, 65.0 degrees and 82.3 degrees, which are consistent with alpha-Fe XRD standard card PDF-65-4899. Curve C is an orthorhombic system of theta-Fe with a purity of 100%3C, i.e., θ iron carbide, which shows 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 obtained spectrogram can clearly see the change process from the nanometer iron powder to the target carbide. Generated byThe 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 1-24 and D1-D7, 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 1-24, D1-D7 and iron carbide compositions 1-3. The catalyst loading was 10.0 g.
Evaluation conditions were as follows: t315 deg.C, P2.35 MPa, H2：CO＝1.9：1，(H2+ CO) in a total amount of 55000mL/h/g-Fe(standard state flux, relative to Fe element). The reaction was carried out, the reaction product was analyzed by gas chromatography, and the evaluation data of the reactions for 24h and 400h 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 supported theta carbon prepared by the present inventionThe iron oxide or the composition or the catalyst is used for carrying out the Fischer-Tropsch synthesis reaction under the industrial condition, shows high space-time conversion rate of the raw material CO within a limited condition range, has better reaction performance and ultralow CO2And (4) selectivity. At the same time, CH4Low selectivity and high selectivity of effective products.
Further long-period experiments are carried out, and the data of the reaction for 400h in the table 4 show that after the supported theta iron carbide composition or the catalyst 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 load type theta iron carbide or the composition or the catalyst prepared under the limited condition of the invention can be suitable for a high-temperature high-pressure continuous reactor, has high reaction stability and CO2Very low selectivity: under the condition of industrial Fischer-Tropsch synthesis reaction, a high-pressure continuous reactor can be used for keeping continuous and stable reaction for more than 400h, and CO is generated2The selectivity is below 12% (preferably, 6% or below can be achieved); at the same time, its by-product CH4The selectivity is also kept below 14 percent (preferably below 7 percent), and the selectivity of the effective product can reach above 74 percent (preferably above 87 percent). Wherein the space-time yield of the catalyst effective product under the preferred conditions can reach 255mmol/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.
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| US20120245236A1 (en) * | 2011-03-26 | 2012-09-27 | Suib Steven L | Fischer-tropsch catalysts containing iron or cobalt selective towards higher hydrocarbons |
| 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 |
| CN108479834A (en) * | 2018-03-19 | 2018-09-04 | 南京大学 | A kind of fischer-tropsch synthetic catalyst and preparation method thereof |
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| US20120245236A1 (en) * | 2011-03-26 | 2012-09-27 | Suib Steven L | Fischer-tropsch catalysts containing iron or cobalt selective towards higher hydrocarbons |
| 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 |
| CN108479834A (en) * | 2018-03-19 | 2018-09-04 | 南京大学 | A kind of fischer-tropsch synthetic catalyst and preparation method thereof |
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