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CN-122006761-A - Molybdenum carbide photo-thermal CO with controllable crystal phase and morphology2Preparation method of hydrogenation catalyst

CN122006761ACN 122006761 ACN122006761 ACN 122006761ACN-122006761-A

Abstract

The invention discloses a preparation method of a molybdenum carbide photo-thermal CO 2 hydrogenation catalyst with a crystal phase and a controllable morphology, wherein molybdate is used as a molybdenum source, aromatic organic amine is used as a morphology and crystal phase guiding agent, a molybdenum carbide catalyst with a specific microstructure is prepared through in-situ carbonization and reduction by regulating and controlling a molecular space configuration in a precursor, the precise regulation and control of molybdenum carbide crystal phases (cubic phase alpha-MoC and hexagonal phase beta-Mo 2 C) and microcosmic morphologies (one-dimensional nanowires, multi-stage porous structures and the like) are realized through selecting organic amine with different molecular structures such as aniline and phenylenediamine, the prepared catalyst has a high specific surface area and excellent light capturing capacity, and has excellent photo-thermal conversion efficiency, catalytic activity and stability in a photo-thermal CO 2 hydrogenation reduction reaction, and the process is simple and safe, so that the problems that morphology is difficult to control and dangerous gas is required to be used in the traditional molybdenum carbide preparation are solved.

Inventors

  • LIU XIANGLEI
  • Zhou Luhao
  • XUAN YIMIN

Assignees

  • 南京航空航天大学

Dates

Publication Date
20260512
Application Date
20260206

Claims (10)

  1. 1. The preparation method of the molybdenum carbide photo-thermal CO 2 hydrogenation catalyst with a crystal phase and controllable morphology is characterized by comprising the following steps: dissolving a molybdenum source and organic amine in deionized water, forming a uniform mixed solution under the stirring condition, and dripping hydrochloric acid into the mixed solution until gel-like precipitation occurs; step (2) magnetically stirring the mixed solution prepared in the step (1) under a heating condition to obtain precursor gel containing organic-inorganic hybridization; And (3) placing the precursor gel in a carbonization atmosphere, calcining at a high temperature, and naturally cooling to obtain the molybdenum carbide photo-thermal catalyst.
  2. 2. The method for preparing a molybdenum carbide photo-thermal CO 2 hydrogenation catalyst with controllable crystal phase and morphology according to claim 1, wherein the molybdenum source in the step (1) is ammonium molybdate tetrahydrate; The organic amine is one or more of aniline, o-phenylenediamine, m-phenylenediamine, p-phenylenediamine, 4-chloro-o-phenylenediamine and dopamine hydrochloride; The molar ratio of molybdenum atoms to organic amine in the molybdenum source is 1-3.5; The concentration of hydrochloric acid dropwise added into the mixed solution is 0.5-2 mol/L.
  3. 3. The preparation method of the molybdenum carbide photo-thermal CO 2 hydrogenation catalyst with controllable crystalline phase and morphology according to claim 1, wherein in the heating condition in the step (2), the heating temperature is 50-90 ℃, water bath heating or oil bath heating is adopted, and the heating time is 3-h-10 h.
  4. 4. The method for preparing the molybdenum carbide photo-thermal CO 2 hydrogenation catalyst with controllable crystal phase and morphology according to claim 1, wherein the carbonization condition in the high-temperature calcination treatment in the step (3) is that the carbonization atmosphere is nitrogen, argon and hydrogen-nitrogen mixed gas; the carbonization temperature is 600-900 ℃; the temperature rising rate is 1-5 ℃ per minute; The heat preservation time is 2-10 h.
  5. 5. Use of a molybdenum carbide photo-thermal CO 2 hydrogenation catalyst with controllable crystal phase and morphology prepared by the preparation method according to any one of claims 1-4 in a reaction for preparing carbon monoxide by photo-thermal CO 2 hydrogenation.
  6. 6. The application according to claim 5, characterized in that it comprises the following steps: step (61) catalyst loading and pretreatment; Calibrating optical power in the step (62); Step (63) catalyst filling and reaction operation; and (4) photo-thermal catalytic reaction and on-line detection.
  7. 7. The method of claim 6, wherein the catalyst loading and pretreatment in step (61) is performed by using a flow photo-thermal reactor, using a 300W xenon lamp as a simulated solar light source, without using any additional electric heating device, focusing the light source by using a Fresnel lens, adjusting the distance from the xenon lamp to a quartz window of the reactor to match the diameter of the focused light spot with the diameter of the catalyst bed, ensuring that the light spot completely covers the surface of the catalyst, and precisely controlling the output power of the light source by adjusting the current of the xenon lamp.
  8. 8. The method according to claim 6, wherein the calibrating of the optical power in step (62) is performed by calibrating the actual optical power reaching the surface of the catalyst by using an optical power meter before each test, and placing a quartz plate which is the same as the material and thickness of the window of the reactor on the probe of the optical power meter during the calibrating process, and ensuring that the position of the quartz plate is at the same level as the catalyst bed in the reactor.
  9. 9. The method according to claim 6, wherein the catalyst filling and reaction operation in the step (63) is specifically that the molybdenum carbide catalyst prepared by weighing 10-15 mg is uniformly spread in a quartz crucible with the diameter of 8 mm, the reaction gas passes through a catalyst bed layer in a top-down flow mode, the composition of the raw material gas is as CO 2 :H 2 :N 2 =1:1:0.5, and the total flow rate is 25 mL/min, wherein N 2 is used as an internal standard gas for quantitative analysis of subsequent products.
  10. 10. The method of claim 6, wherein the photo-thermal catalytic reaction and the on-line detection in step (64) are performed by turning on a light source, converting light energy into heat energy by means of photo-thermal effect of a catalyst to drive the reaction, monitoring real-time temperature during the reaction by a thermocouple inserted in a catalyst bed, condensing and drying reaction tail gas, and then entering an on-line gas chromatograph, and detecting the product by using a thermal conductivity detector and a hydrogen flame ionization detector.

Description

Preparation method of crystal phase and morphology controllable molybdenum carbide photo-thermal CO 2 hydrogenation catalyst Technical Field The invention relates to a preparation method of a crystal phase and morphology controllable molybdenum carbide photo-thermal CO 2 hydrogenation catalyst. Background The transition metal carbide, especially molybdenum carbide, has electronic structure and catalytic characteristic similar to noble metal, and is known as quasi-platinum catalyst, and has wide application foreground in hydrogenation, dehydrogenation, isomerization, electrocatalysis and other fields. In particular, in the photocatalytic CO 2 reduction reaction, molybdenum carbide is paid attention to because of its excellent light absorption capacity and unique C-Mo active site, however, research shows that the photocatalytic performance of molybdenum carbide is highly dependent on its crystal structure and microstructure, different crystal phases have different electron state densities and substrate adsorption energies, and the microstructure (such as a one-dimensional nanowire and a multi-stage pore structure) directly determines the light capturing efficiency, specific surface area and reaction mass transfer kinetics. Therefore, the realization of precise regulation and control of the crystal phase and morphology of the molybdenum carbide is a key for improving the photo-thermal CO 2 hydrogenation performance of the molybdenum carbide. The main flow technology for preparing the molybdenum carbide catalyst still faces a plurality of challenges, and the existing industrial or laboratory preparation mostly adopts a temperature programming carburization method, namely, the molybdenum oxide precursor is reduced and carbonized at high temperature by utilizing the mixed gas of hydrogen and hydrocarbon gas (such as methane, ethane, propane and the like). The method needs flammable and explosive hydrocarbon gas, the reaction temperature is usually higher (700 ℃), the equipment requirement is high, the large-scale production is difficult, the carbon source gas is easy to crack at high temperature, and an amorphous carbon deposition layer is formed on the surface of the catalyst. In addition, after prolonged treatment at high temperatures, the product tends to sinter severely, with a generally very low specific surface area, limiting the exposure of the active sites. In order to overcome the defects of a programmed temperature carburization method, an organic-inorganic hybridization method is developed, a hybridization precursor is formed by utilizing the coordination effect between organic amine and molybdate ions, and molybdenum carbide is generated by utilizing the carbonization reduction capability of an organic matter under inert atmosphere, so that the method has the advantages of simple process, environment friendliness and safety. However, the prior art is mostly limited to the preparation of molybdenum carbide with a specific morphology by using a single specific organic amine (such as aniline or hexamethylenetetramine), and lacks a systematic strategy for regulating the molecular structure of the organic amine with respect to the evolution law of the final crystal phase and the microscopic morphology of the molybdenum carbide. Disclosure of Invention The invention aims to provide a preparation method of a crystal phase and morphology controllable molybdenum carbide photo-thermal CO 2 hydrogenation catalyst, which can overcome the defects of serious sintering of a product, difficult precise regulation and control of the crystal phase and morphology, insufficient exposure of active sites and the like in the existing molybdenum carbide preparation technology. The preparation method of the molybdenum carbide photo-thermal CO 2 hydrogenation catalyst with a crystal phase and controllable morphology comprises the following steps: dissolving a molybdenum source and organic amine in deionized water, forming a uniform mixed solution under the stirring condition, and dripping hydrochloric acid into the mixed solution until gel-like precipitation occurs; step (2) magnetically stirring the mixed solution prepared in the step (1) under a heating condition to obtain precursor gel containing organic-inorganic hybridization; And (3) placing the precursor gel in a carbonization atmosphere, calcining at a high temperature, and naturally cooling to obtain the molybdenum carbide photo-thermal catalyst. Further, in step (1), the molybdenum source is ammonium molybdate tetrahydrate; The organic amine is one or more of aniline, o-phenylenediamine, m-phenylenediamine, p-phenylenediamine, 4-chloro-o-phenylenediamine and dopamine hydrochloride; The molar ratio of molybdenum atoms to organic amine in the molybdenum source is 1-3.5; The concentration of hydrochloric acid dropwise added into the mixed solution is 0.5-2 mol/L. Further, in the heating condition in the step (2), the heating temperature is 50-90 ℃, water bath heating or