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CN-122006763-A - Method for preparing carbon-based molybdenum carbide heterojunction catalyst by self-activation of carboxyl modified lignin and application of carbon-based molybdenum carbide heterojunction catalyst

CN122006763ACN 122006763 ACN122006763 ACN 122006763ACN-122006763-A

Abstract

The invention discloses a method for preparing a carbon-based molybdenum carbide heterojunction catalyst by self-activation of carboxyl modified lignin and application of the carbon-based molybdenum carbide heterojunction catalyst, and belongs to the technical field of catalyst preparation. The catalyst is prepared from carboxyl modified lignin and a molybdenum source serving as raw materials through dissolution coordination and inert gas controlled flow temperature roasting, and comprises a carbon carrier and molybdenum carbide nano-particles loaded on the carbon carrier, wherein the crystal phase of the molybdenum carbide nano-particles is MoC-Mo 2 C heterogeneous crystal phase. The carbon defect generated by pyrolysis of the lignin after carboxyl modification can be used for in-situ carburizing and reducing molybdenum oxide to generate MoC, and the reducing atmosphere generated by activation pore-forming of the lignin can be used for promoting reduction and carburization of the molybdenum oxide to generate Mo 2 C, so that a molybdenum carbide heterogeneous crystal phase structure is formed. The high-activity MoC-Mo 2 C heterojunction with high distribution is prepared by utilizing lignin residues, and the space-time conversion rate and stability of CO prepared by CO 2 hydrogenation are improved.

Inventors

  • SUN HAO
  • YUAN HAOBIN
  • LIAO HAIQUAN
  • JIN CAN
  • MA MINGZHE
  • Wang Caikang
  • PAN XUEYUAN
  • SUN KANG
  • JIANG JIANCHUN

Assignees

  • 中国林业科学研究院林产化学工业研究所

Dates

Publication Date
20260512
Application Date
20260320

Claims (10)

  1. 1. A method for preparing a carbon-based molybdenum carbide heterojunction catalyst by using carboxyl modified lignin as a raw material is characterized in that the catalyst is obtained by taking carboxyl modified lignin and a molybdenum source as raw materials and performing dissolution coordination and inert gas controlled flow temperature roasting, wherein the catalyst comprises a carbon carrier and molybdenum carbide nano particles loaded on the carbon carrier, and the crystalline phase of the molybdenum carbide nano particles is MoC-Mo 2 C heterogeneous crystalline phase.
  2. 2. The method for preparing the carboxyl modified lignin is characterized by comprising the steps of adding lignin into salicylic acid, adding concentrated sulfuric acid, heating and refluxing for reaction, washing out excessive salicylic acid with hot water after the reaction is finished, and drying to obtain the carboxyl modified lignin, wherein the mass ratio of the lignin to the salicylic acid to the concentrated sulfuric acid is 1:1.5-2.5:0.3-0.4, and the heating and refluxing reaction is carried out for 1.5-2.5 hours at 180-220 ℃.
  3. 3. The method according to claim 1, wherein the molybdenum source is at least one of ammonium molybdate, sodium molybdate, potassium molybdate or phosphomolybdic acid, the mass ratio of the molybdenum source to the carboxyl modified lignin is 4:11-7:11, and the molybdenum source is added in an amount such that the Mo content is 30wt% to 60wt% of the total mass of the obtained catalyst.
  4. 4. The method of claim 1, wherein the solubilization coordination is sufficient to solubilize the carboxy-modified lignin and the molybdenum source into an aqueous ammonia solution having a mass fraction of 0.10% -0.15%.
  5. 5. The method of claim 1, wherein the firing temperature is 750-850 ℃, the inert atmosphere is nitrogen or argon, the firing time is 2-5 h, and the inert atmosphere flow rate is 2-10 mL/min.
  6. 6. The carbon-based molybdenum carbide heterojunction catalyst prepared by the method of any one of claims 1-5.
  7. 7. The use of the carbon-based molybdenum carbide heterojunction catalyst of claim 6 in the preparation of CO by hydrogenation of CO 2 .
  8. 8. The use according to claim 7, wherein the carbon-based molybdenum carbide heterojunction catalyst is added to a reactor and CO is produced at a volume ratio of 450-550 ° C, H 2 to CO 2 of 2:1-4:1, a space velocity of 200000-400000 mL/g/h, and a pressure of 0.05-0.15 MPa.
  9. 9. The use according to claim 7, characterized by the steps of: (1) Adding 10g lignin into 20g salicylic acid, adding 3.4 g concentrated sulfuric acid, and heating and refluxing at 200 ℃ for 2 hours, washing off excessive salicylic acid with hot water after the reaction is finished, and drying at 60 ℃ to obtain carboxyl modified lignin; (2) Adding ammonium molybdate and carboxyl modified lignin into an ammonia water solution, stirring at a speed of 600 r/min and at a temperature of 80 ℃ for 4 h, drying the mixture in an 80 ℃ oven for 8 h, wherein the mass ratio of the ammonium molybdate to the carboxyl modified lignin is 5:11-7:11, and the addition amount of the molybdenum source is such that the content of Mo is 34-46 wt% of the total mass of the obtained catalyst; (3) Loading the dried sample into a tube furnace, removing air in the tube furnace, and roasting for 3 h under the conditions of 800 ℃ and 2 mL/min nitrogen flow rate to obtain a carbon-based molybdenum carbide heterojunction catalyst; (4) The catalyst was added to a reactor and H 2 /CO 2 was introduced to produce CO at a volume ratio of 500℃ C, H 2 to CO 2 of 2:1, a space velocity of 300000 mL/g/H and a pressure of 0.1 MPa.
  10. 10. The use according to claim 9, characterized in that the mass ratio of ammonium molybdate to carboxy-modified lignin is 5:11-6:11 and the molybdenum source is added in such an amount that the Mo content is 34-41 wt% of the total mass of the resulting catalyst.

Description

Method for preparing carbon-based molybdenum carbide heterojunction catalyst by self-activation of carboxyl modified lignin and application of carbon-based molybdenum carbide heterojunction catalyst Technical Field The invention belongs to the technical field of catalyst preparation, and particularly relates to a method for preparing a carbon-based molybdenum carbide heterojunction catalyst by self-activation of carboxyl modified lignin and application thereof. Background The larger atomic gaps in the Mo atomic lattice accommodate the insertion of smaller radius carbon atoms, thereby forming a mesenchymal alloy compound. The intercalation of carbon atoms increases the distance between Mo atoms, causing the d-band shrinkage of Mo and the increase in fermi level density, which in turn gives molybdenum carbide noble-like properties. The preparation of CO by catalytic hydrogenation of CO 2 is one of important ways for achieving the aim of double carbon, and compared with other catalysts, molybdenum carbide has the advantages of high selectivity, good stability, low cost and the like, and has good application potential in CO 2 hydrogenation reaction. However, molybdenum carbide has a plurality of crystal phases of alpha, eta, gamma, beta and the like, and how to directionally synthesize a molybdenum carbide catalyst with high activity is still one of the current hot spots and difficulties. Meanwhile, in the traditional carburizing and reducing process for preparing molybdenum carbide, a large amount of reducing gases such as carbon-containing gases (methane, ethane, ethylene and the like) and hydrogen are required to be introduced, so that the problems of high cost, serious gas waste, difficult tail gas treatment, great potential safety hazard and the like exist, and only molybdenum carbide with a single crystal phase can be prepared, thereby influencing the conversion rate of CO 2 in the preparation of CO by hydrogenation. Lignin is the remainder of the paper industry and the biological refining industry, and the economic and environmental benefits of the biomass industry can be remarkably improved by high-value utilization of lignin. However, direct use of lignin does not promote complete conversion of molybdenum precursor to molybdenum carbide. Therefore, development of a preparation method for modifying lignin, which does not need to add carbon-containing and reducing atmosphere and can directionally regulate and control molybdenum carbide heterogeneous crystal phase is needed. Disclosure of Invention The invention solves the technical problem of providing a carbon-based molybdenum carbide heterojunction catalyst. The invention aims to provide a method for preparing a carbon-based molybdenum carbide heterojunction catalyst by self-activating carboxyl modified lignin. The invention also aims to provide an application of the carbon-based molybdenum carbide heterojunction catalyst in CO 2 hydrogenation preparation of CO. The modified lignin is utilized to form a high-reducibility carbon skeleton and promote molybdenum oxide to be subjected to in-situ carburizing reduction to generate molybdenum carbide, reducing gases (CO and H 2) generated by pyrolysis and self-activation of lignin in a tube furnace are reserved by reducing the flow rate of nitrogen, the carburizing rate of modified lignin derived carbon is regulated and controlled by adopting a regulating temperature, so that the formation of a high-dispersion molybdenum carbide heterojunction on the surface of a carbon material is promoted, and finally, the space-time conversion rate, selectivity and stability of CO prepared by CO 2 hydrogenation are improved. The technical scheme adopted by the invention is as follows in order to solve the technical problems: A method for preparing a carbon-based molybdenum carbide heterojunction catalyst by using carboxyl modified lignin as a raw material and performing dissolution coordination and inert gas controlled flow temperature roasting on the raw material comprises a carbon carrier and molybdenum carbide nano-particles supported on the carbon carrier, wherein the crystal phase of the molybdenum carbide nano-particles is MoC-Mo 2 C heterogeneous crystal phase. The preparation method of the carboxyl modified lignin comprises the steps of adding lignin into salicylic acid, adding concentrated sulfuric acid, heating and refluxing for reaction, washing out excessive salicylic acid with hot water after the reaction is finished, and drying to obtain the carboxyl modified lignin, wherein the mass ratio of the lignin to the salicylic acid to the concentrated sulfuric acid is 1:1.5-2.5:0.3-0.4, the mass ratio of the salicylic acid to the concentrated sulfuric acid is 180-220 ℃ for heating and refluxing for reaction for 1.5-2.5 hours, the mass ratio of the salicylic acid to the concentrated sulfuric acid is analytically pure, the mass ratio of the salicylic acid to the concentrated sulfuric acid is 98%, and preferably, the m