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CN-121988353-A - Iron-based catalyst and preparation method and application thereof

CN121988353ACN 121988353 ACN121988353 ACN 121988353ACN-121988353-A

Abstract

The invention belongs to the technical field of catalysts, and discloses an iron-based catalyst, a preparation method and application thereof. The preparation method of the iron-based catalyst comprises the steps of mixing ferric salt, organic acid salt and an organic solvent, crystallizing to obtain a solid, then impregnating the solid with a modified solution, drying, and then roasting in a reducing atmosphere to obtain the iron-based catalyst, wherein the modified solution comprises an alkyl trimethyl ammonium bromide solution. The iron-based catalyst prepared by the preparation method can realize high CO 2 conversion rate and high olefin selectivity and has excellent oxidation resistance stability.

Inventors

  • YANG LE
  • LIANG WEIBIN
  • DONG HAIFENG

Assignees

  • 中山大学
  • 惠州市绿色能源与新材料研究院

Dates

Publication Date
20260508
Application Date
20260128

Claims (10)

  1. 1. A method for preparing an iron-based catalyst, comprising the steps of: Mixing ferric salt, organic acid salt and organic solvent, crystallizing to obtain solid, then impregnating the solid with modified solution, drying, and roasting in reducing atmosphere to obtain the iron-based catalyst; The modifying solution comprises an alkyl trimethyl ammonium bromide solution.
  2. 2. The method of claim 1, wherein the alkyl trimethylammonium bromide solution comprises a cetyl trimethylammonium bromide solution and/or a dodecyl trimethylammonium bromide solution.
  3. 3. The method according to claim 1, wherein the iron salt comprises one of ferric nitrate, ferric sulfate or ferric chloride or a hydrate thereof, and/or the organic acid salt is an organic acid sodium salt.
  4. 4. The method according to claim 1, wherein the organic acid salt comprises at least one of sodium citrate and sodium acetate, and/or the molar ratio of the iron salt to the organic acid salt is 10 (20-30).
  5. 5. The method according to claim 4, wherein the molar ratio of sodium citrate to sodium acetate in the organic acid salt is 1.7 (20-30), and/or the crystallization temperature is 150-220 ℃, and/or the crystallization time is 4-8 hours.
  6. 6. The method according to claim 1, wherein the hexadecyl trimethyl ammonium bromide solution has a mass concentration of 0.1 to 0.8 g/mL and/or the dodecyl trimethyl ammonium bromide solution has a mass concentration of 0.2 to 0.6 g/mL.
  7. 7. The method according to claim 1, wherein the reducing atmosphere comprises hydrogen gas, the volume fraction of hydrogen gas in the reducing atmosphere is 1-8%, and/or the flow rate of the reducing atmosphere is 150-250 mL/min, and/or the baking temperature is 400-550 ℃ and the baking time is 1-3 hours.
  8. 8. An iron-based catalyst prepared by the preparation method of any one of claims 1 to 7.
  9. 9. Use of the iron-based catalyst prepared by the preparation method of any one of claims 1-7 in the fields of catalytic hydrogenation and oxidation.
  10. 10. A method for preparing olefin by CO 2 hydrogenation, which is characterized by comprising the following steps: The iron-based catalyst prepared by the preparation method of any one of claims 1-7 is taken, and H 2 , protective gas and CO 2 are introduced, heated and reacted to obtain olefin.

Description

Iron-based catalyst and preparation method and application thereof Technical Field The invention belongs to the technical field of catalysts, and particularly relates to an iron-based catalyst and a preparation method and application thereof. Background With the development of global economy, the rapid increase in fossil energy consumption has resulted in a dramatic increase in carbon dioxide emissions, resulting in serious environmental problems. In order to mitigate excessive emissions of carbon dioxide and reduce reliance on fossil fuels, a route to produce high value chemical products and carbon neutral fuels from captured carbon dioxide using renewable hydrogen energy has received widespread attention. The olefin industry is a key link of extending the basic petrochemical industry to downstream industrial chains such as organic raw materials, synthetic materials, new chemical materials, special chemicals and the like, provides raw materials for various downstream industries, and is a material basis for economic development. As downstream demand remains high, olefins and downstream derivatives are in long-term supply and demand. The olefin downstream products have high-end and large differentiation space, and the new chemical material products downstream of the olefin play an important role in the industrial upgrading process. Under the condition that the problems of excess capacity and homogenization competition in the traditional industries such as oil refining, chemical fertilizers, chlor-alkali and the like are increasingly outstanding, the olefin industry becomes an important direction of high-quality development of petrochemical industry. In addition, the long-chain olefins are available in a relatively poor market. Aiming at the problems in the aspects of low-carbon olefin production, long-chain olefin market supply and the like, the development of a brand new production process is needed. The technology for preparing olefin by thermally catalyzing CO 2 hydrogenation has the dual functions of carbon emission reduction and high-value chemical supply, and is outstanding in a plurality of production routes. The hydrogenation of CO 2 to olefins is mainly divided into two routes (1) a methanol intermediate route (CO 2-MeOH）：CO2 is firstly converted into methanol on a metal oxide, the methanol synthesizes olefins on a molecular sieve acid site, and the reaction product is mainly low-carbon olefins. (2) CO 2 -FTS route, namely, a first step RWGS reaction (reverse water gas shift reaction), CO 2 is firstly adsorbed on a Fe 3O4 structure containing oxygen vacancies to form a Fe (CO 3) intermediate, and because the interaction of Fe-O in Fe (CO 3) is stronger than that of C-O, the bond of Fe (CO 3) can be broken to remove CO, the rest O-Fe-O structure can react with H 2 to dehydrate to generate a Fe-O structure containing oxygen vacancies again so as to realize RWGS cyclic reaction, a second step FTS reaction (Fischer-Tropsch synthesis reaction), fe xCy firstly reacts with H 2 to generate alkane, and alkane products are dehydrated to form a Fe xCy structure containing carbon vacancies. Then, CO generated in the RWGS reaction process occupies carbon hole sites in the Fe xCy structure to form an Fe-C-O structure, and O in the structure reacts with H 2 to be dehydrated to generate Fe xCy again, so that the cyclic reaction process of preparing hydrocarbon by hydrogenating CO is realized. Fe 3O4 and Fe 5C2 are generally considered to be the active phases of the RWGS reaction and FTS reaction, respectively, and in particular Fe 5C2 plays a key role in chain growth and LAOs (linear alpha-olefin) selectivity. Therefore, LAOs is generally produced by CO2 hydrogenation over Fe-based catalysts via the CO-FTS route, and a high LAOs selectivity can be obtained by regulating the ratio of the amounts of Fe 3O4 to Fe 5C2. iron-based materials have proven to be suitable candidates for hydrogenation of carbon dioxide to lower olefins. However, conventional iron-based catalysts present significant challenges in the hydrogenation of CO 2 to olefins. First, the chemical inertness of the CO 2 molecule makes its initial activation difficult and the CO 2 conversion of conventional catalysts is generally not high. Second, the reaction follows a complex Fischer-Tropsch synthesis path, the product distribution is broad, and olefin selectivity is often difficult to break through the 50-60% limit. More importantly, a large amount of water (H 2 O) generated in the reaction process oxidizes and even damages the critical Fe 5C2 active phase, so that the catalyst is quickly deactivated, and the stability is extremely poor. The relevant literature clearly indicates that the phase transition of Fe 5C2 to Fe 3O4 caused by H 2 O is the main cause of catalyst deactivation. In the prior art, researchers usually regulate and control the catalytic performance by introducing metal assistants (such as Zn, K and Mn) or constructing a composi