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CN-121988363-A - Iron-based catalyst, preparation method and application thereof, and method for preparing olefin from synthesis gas

CN121988363ACN 121988363 ACN121988363 ACN 121988363ACN-121988363-A

Abstract

The invention relates to the technical field of catalyst preparation, and provides an iron-based catalyst, a preparation method and application thereof, and a method for preparing olefin from synthesis gas. The iron-based catalyst comprises 30-60 parts by mass of a carrier and 40-70 parts by mass of an active component, wherein the active component comprises a composition with a chemical formula of Fe 100 A a K b O x (Fe 4 N) c in terms of atomic ratio, A comprises at least one of Mo, W and Cr, the value range of a is 5-30, the value range of b is 1-10, the value range of c is 10-25, and x is the total number of oxygen atoms required for meeting the valence of each element in the catalyst. The iron-based catalyst provided by the invention contains the iron oxide and the iron nitride, can be used for Fischer-Tropsch synthesis, is beneficial to improving the olefin selectivity, can further improve the CO conversion rate and the olefin selectivity by limiting the proportion of the iron oxide and the iron nitride on the surface of the catalyst, is suitable for a fluidized bed reactor, and can effectively solve the problem of difficult heat removal in high-temperature Fischer-Tropsch synthesis.

Inventors

  • PANG YINGCONG
  • LI JIANFENG
  • DAI YIMIN

Assignees

  • 中石化（上海）石油化工研究院有限公司
  • 中国石油化工股份有限公司

Dates

Publication Date
20260508
Application Date
20241108

Claims (10)

  1. 1. An iron-based catalyst is characterized by comprising 30-60 parts by mass of a carrier and 40-70 parts by mass of an active component; The active component comprises a composition with a chemical formula of Fe 100 A a K b O x (Fe 4 N) c in terms of atomic ratio; wherein A comprises at least one of Mo, W and Cr, The value range of a is 5-30, B has a value of 1 to 10, C has a value of 10 to 25, X is the total number of oxygen atoms required to satisfy the valence of each element in the catalyst.
  2. 2. The iron-based catalyst according to claim 1, wherein the molar ratio of iron oxide calculated as Fe to iron nitride calculated as Fe on the surface of the iron-based catalyst is 3-5:1.
  3. 3. The iron-based catalyst according to claim 1 or 2, wherein the support comprises at least one of an oxide of Al and an oxide of Zr.
  4. 4. A method for preparing the iron-based catalyst according to any one of claims 1 to 3, which is characterized by comprising the steps of mixing a first Fe precursor with a precipitator to obtain ferric hydroxide precipitate, preparing slurry comprising the ferric hydroxide precipitate, an A precursor, a K precursor, a carrier precursor and water, adding iron nitride powder into the slurry, mixing and stirring, spray-drying and roasting to obtain the iron-based catalyst.
  5. 5. The preparation method of claim 4, wherein the roasting atmosphere is a mixed gas of nitrogen and air, and preferably, the volume ratio of the nitrogen to the air is 2-5:1; and/or the roasting temperature is 500-800 ℃; and/or the roasting time is 0.5-10 h, preferably 1-5 h.
  6. 6. The method according to claim 4 or 5, wherein the molar ratio of the first Fe precursor in terms of Fe element, the a precursor in terms of a element, and the K precursor in terms of K element is 100:5 to 30:1 to 10.
  7. 7. The preparation method of the iron nitride powder according to any one of claims 4 to 6, wherein the preparation method comprises the steps of mixing a second Fe precursor with a precipitator to obtain ferric hydroxide precipitate, vacuum drying the ferric hydroxide precipitate to obtain iron oxide powder, and nitriding the iron oxide powder in a mixed atmosphere comprising ammonia gas and hydrogen gas at a temperature of 500-800 ℃ to obtain iron nitride powder; Preferably, the method comprises the steps of, The temperature of the vacuum drying is 40-80 ℃; and/or the nitriding treatment temperature is 550-750 ℃; And/or the nitriding treatment time is 2-8 hours; And/or in the mixed atmosphere comprising ammonia and hydrogen, the volume ratio of the ammonia to the hydrogen is 0.5-5:1, preferably 1.5-2.5:1.
  8. 8. The method according to claim 7, wherein the molar ratio of the first Fe precursor to the second Fe precursor in terms of Fe element is 100:40 to 100; And/or the ratio of the sum of the mass of the first Fe precursor calculated as Fe 2 O 3 , the A precursor calculated as an oxide of A, the K precursor calculated as K 2 O and the second Fe precursor calculated as Fe 4 N to the mass of the carrier precursor calculated as the carrier is 40-70:30-60.
  9. 9. Use of the iron-based catalyst of any one of claims 1-3 or the iron-based catalyst prepared by the method of any one of claims 4-8 in a synthesis gas to olefins reaction.
  10. 10. A method for preparing olefin by using synthesis gas, which is characterized by comprising the steps of contacting and reacting a raw material comprising the synthesis gas with the iron-based catalyst according to any one of claims 1-3 or the iron-based catalyst prepared by the preparation method according to any one of claims 4-8 to generate light olefin; Preferably, the method comprises the steps of, The reaction temperature is 300-370 ℃; and/or the reaction pressure is 0.5-5.0 MPa; and/or the standard volume space velocity of the catalyst load is 4000-10000 h -1 ; And/or the molar ratio of H 2 to CO in the synthesis gas is 1-4.

Description

Iron-based catalyst, preparation method and application thereof, and method for preparing olefin from synthesis gas Technical Field The invention relates to the technical field of catalyst preparation, in particular to an iron-based catalyst, a preparation method and application thereof, and a method for preparing olefin from synthesis gas. Background The olefin is an important chemical, natural gas or light naphtha fraction is generally used as a raw material in the industry at present, ethylene and propylene are produced by adopting a steam cracking process in an ethylene combined device, and the ethylene can be oligomerized, trimerized and tetramerized to obtain the olefins such as 1-butene, 1-hexene, 1-octene and the like. In addition, vegetable oil processes are also used to synthesize 1-olefins, typically C 12-C18. The Fischer-Tropsch synthesis method is a method for synthesizing various organic hydrocarbons by using synthesis gas as a raw material, and the hydrocarbons contain C 2 + olefin, which is an important route for indirect liquefaction of coal. Typical Fischer-Tropsch catalysts are iron-based catalysts and cobalt-based catalysts. The iron-based catalyst is generally prepared using a precipitation method (precipitated catalyst), a sintering method (sintered catalyst), and an oxide mixing method (fused iron catalyst). Depending on the preparation method and the process conditions used, iron-based catalysts can be used to produce both low carbon light hydrocarbons and high carbon chain saturated hydrocarbons. The cobalt-based catalyst is mostly supported, the preparation method uses a plurality of impregnation methods, and the main active element cobalt is dispersed on the surface of a carrier and is mostly used for producing saturated heavy hydrocarbons. The catalyst is used for Fischer-Tropsch synthesis, and has the problems of low olefin yield, difficult heat removal, easy temperature flying and easy catalyst deactivation because Fischer-Tropsch synthesis, especially high-temperature Fischer-Tropsch synthesis, belongs to a strong heat release process. Disclosure of Invention The invention aims to provide an iron-based catalyst, a preparation method and application thereof, and a method for preparing olefin from synthesis gas, so as to solve the technical problem of low olefin yield of the existing catalyst for Fischer-Tropsch synthesis. In order to achieve the above purpose, the invention adopts the following technical scheme: in a first aspect, the invention provides an iron-based catalyst, which comprises 30-60 parts by mass of a carrier and 40-70 parts by mass of an active component; The active component comprises a composition with a chemical formula of Fe 100AaKbOx(Fe4N)c in terms of atomic ratio; wherein A comprises at least one of Mo, W and Cr, A has a value of 5 to 30, for example, 5, 7, 8, 10, 12, 15, 17, 20, 22, 25, 27, 30, etc., B is 1 to 10, for example, 1,2,3,4, 5, 6, 7, 8, 9, 10, etc., The value of c is 10 to 25, for example, 10, 11, 12.5, 14, 15, 16, 18, 20, 21, 22, 24, 25, etc., X is the total number of oxygen atoms required to satisfy the valence of each element in the catalyst. According to some embodiments of the present invention, the molar ratio of the oxide of iron in terms of Fe to the nitride of iron in terms of Fe on the surface of the iron-based catalyst is 3 to 5:1, for example, may be 3:1, 4:1, 5:1, etc. According to some embodiments of the invention, the support comprises at least one of an oxide of Al and an oxide of Zr. In a second aspect, the invention provides a preparation method of the iron-based catalyst according to the first aspect, which comprises the steps of mixing a first Fe precursor with a precipitator to obtain ferric hydroxide precipitate, preparing slurry comprising the ferric hydroxide precipitate, an A precursor, a K precursor, a carrier precursor and water, adding iron nitride powder into the slurry, mixing, stirring, spray drying and roasting to obtain the iron-based catalyst. According to some embodiments of the invention, the Fe precursor comprises at least one of Fe salts, such as ferric nitrate, ferric chloride, ferric citrate, and the like. According to some embodiments of the invention, the precipitant comprises aqueous ammonia. According to some embodiments of the invention, the a precursor includes at least one of Mo salt, W salt, cr salt, for example Mo salt may be ammonium heptamolybdate or the like, W salt may be ammonium metatungstate or the like, cr salt may be chromium nitrate or the like. According to some embodiments of the invention, the K precursor comprises at least one of K salts, such as KOH, KNO 3, etc. According to some embodiments of the invention, the carrier precursor comprises at least one of an aluminum sol, ammonium meta-tungstate. According to some embodiments of the present invention, the temperature of the mixing and stirring is 70-100 ℃, for example, may be 70 ℃, 75 ℃, 80 ℃, 85 ℃, 90 ℃, 95 ℃, 100 ℃, etc., and