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CN-122006759-A - Vanadium phosphorus oxide catalyst and preparation method and application thereof

CN122006759ACN 122006759 ACN122006759 ACN 122006759ACN-122006759-A

Abstract

The invention relates to the field of catalyst preparation, and discloses a vanadium-phosphorus-oxygen catalyst, a preparation method and application thereof, wherein the vanadium-phosphorus-oxygen catalyst comprises 20-35 wt% of vanadium, 15-25 wt% of phosphorus, 40-65 wt% of oxygen, 0.2-0.5 wt% of iron and 0.02-0.1 wt% of lithium, based on the total amount of the catalyst. The vanadium phosphorus oxide catalyst provided by the invention has high stability of phosphorus element, and has higher catalytic activity and stability in the reaction of preparing maleic anhydride by hydrocarbon selective oxidation.

Inventors

  • CHEN BINGXU
  • GU LONGQIN
  • ZENG WEI
  • XI PENGBO

Assignees

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

Dates

Publication Date
20260512
Application Date
20241111

Claims (12)

  1. 1. The vanadium-phosphorus-oxygen catalyst is characterized by comprising 20-35 wt% of vanadium, 15-25 wt% of phosphorus, 40-65 wt% of oxygen, 0.2-0.5 wt% of iron and 0.02-0.1 wt% of lithium, wherein the total amount of the catalyst is taken as a reference.
  2. 2. The catalyst according to claim 1, wherein the content of vanadium element is 25 to 30 wt%, the content of phosphorus element is 17 to 22 wt%, the content of oxygen element is 48 to 58 wt%, the content of iron element is 0.2 to 0.4 wt%, and the content of lithium element is 0.03 to 0.05 wt%, based on the total amount of the catalyst.
  3. 3. Catalyst according to claim 1 or 2, wherein elemental iron, elemental lithium and part of elemental phosphorus, calculated as lithium iron phosphate, represent 0.5-5 wt%, preferably 0.5-2 wt%, calculated as vanadium pentoxide, of elemental vanadium.
  4. 4. A catalyst according to any one of claims 1 to 3, wherein at least part of the elemental phosphorus and elemental iron in the catalyst are present as iron phosphate; and/or, the catalyst has diffraction peaks at 20.3 ° ± 0.2 °, 25.8 ° ± 0.2 ° and 48.5 ° ± 0.2 ° of 2Θ, as characterized by XRD; Preferably, the catalyst has diffraction peaks at 12.5°±0.2°、18.5°±0.2°、20.3°±0.2°、22.8°±0.2°、25.8°±0.2°、26.5°±0.2°、28.4°±0.2°、29.3°±0.2°、29.9°±0.2°、38.0°±0.2°、43.2°±0.2°、48.5°±0.2° and 49.8++0.2° 2 theta.
  5. 5. The preparation method of the vanadium phosphorus oxide catalyst is characterized by comprising the following steps: (1) Carrying out solvothermal reaction on a vanadium source, a phosphorus source and a lithium iron phosphate compound in the presence of a solvent; (2) Carrying out heat treatment on the solid product obtained in the step (1); (3) Activating the precursor after the heat treatment obtained in the step (2); the method further comprises a shaping treatment performed after step (2) or after step (3).
  6. 6. The method of claim 5, wherein in step (1), the vanadium source is selected from at least one of vanadium oxide, ammonium metavanadate and vanadium organic acid, preferably vanadium oxide; preferably, the vanadium source is vanadium pentoxide; In the step (1), the phosphorus source is phosphoric acid; Preferably, the molar ratio of the vanadium source calculated as vanadium element to the phosphorus source calculated as phosphorus element is in the range of 0.6-1.1:1, preferably 0.7-1.1:1.
  7. 7. The method according to claim 5 or 6, wherein in step (1), the mass of the lithium iron phosphate is 0.5-5%, preferably 0.5-2% of the mass of the vanadium source calculated as vanadium pentoxide.
  8. 8. The method according to any one of claims 5 to 7, wherein in step (1), the solvent is an organic solvent; preferably, the solvent is an organic alcohol; preferably, the mass-to-volume ratio of the vanadium source to the solvent is 0.05-0.1g/mL.
  9. 9. The process according to any one of claims 5-8, wherein in step (1), the solvothermal reaction is carried out under heated reflux conditions, preferably for a time of 2-20h; And/or, in the step (2), the temperature of the heat treatment is 250-400 ℃ and the time is 10-25h; And/or in the step (3), the activation treatment is carried out in the presence of at least one of oxygen-containing gas, inert gas, carbon dioxide and water vapor, wherein the temperature is 250-480 ℃ and the time is 1-20h.
  10. 10. A vanadium phosphorus oxide catalyst prepared by the method of any one of claims 5-9.
  11. 11. Use of the vanadium phosphorus oxide catalyst according to any one of claims 1-4 and 10 in the production of maleic anhydride by hydrocarbon selective oxidation.
  12. 12. The use according to claim 11, wherein the use is the selective oxidation of n-butane to maleic anhydride; Preferably, the process conditions for the application include a concentration of n-butane of 1-1.7% by volume, a space velocity of 1000-3000hr -1 , a temperature of 300-500 ℃, and a pressure of 0.08-0.2MPa.

Description

Vanadium phosphorus oxide catalyst and preparation method and application thereof Technical Field The invention relates to the field of catalyst preparation, in particular to a vanadium phosphorus oxide catalyst, a preparation method and application thereof. Background The gas phase selective oxidation of hydrocarbons is an important catalytic reaction, and can be used for preparing various oxidation products such as organic anhydride compounds and the like. One of the typical products is maleic anhydride (maleic anhydride). Maleic anhydride (maleic anhydride, MA) is an important organic chemical raw material and fine chemical product, is the third largest anhydride next to phthalic anhydride and acetic anhydride worldwide today, and has wide application. With the improvement of global environmental awareness, maleic anhydride is used as an upstream raw material of degradable plastic materials such as polybutylene terephthalate (PBAT) and polybutylene succinate (PBS), and the application space of the maleic anhydride is continuously expanded under the promotion of the current plastic inhibition command, so that the development and utilization prospect is quite wide The production route of maleic anhydride is mainly three, namely benzene oxidation method, n-butane oxidation method and butene (C4 fraction) oxidation method. Among them, the n-butane oxidation process is the mainstream process of the current maleic anhydride production, and this reaction is a typical selective oxidation reaction. Compared with benzene oxidation, the n-butane oxidation has high carbon atom utilization rate, and the process is more green and economical. The core of the reaction is vanadium phosphorus oxygen catalyst (VPO) composed of vanadium, oxygen and phosphorus elements, and the catalyst is required to have high activity, high selectivity, high stability and the like in industrial application. The V, P and O elements in the VPO catalyst all play respective roles and are combined with each other to play a synergistic role. The existence of the P element plays a role in modulating the V valence state, is just coordination of P, and can well balance the V valence state, so that the stability of the catalyst is improved. However, the P element is very easy to run off in the high-temperature reaction process, so that the P element in the VPO catalyst is gradually reduced along with the progress of the reaction. According to patent application CN114682278a, phosphorus loss results in an increase in n-butane conversion, while maleic anhydride selectivity and yield decrease. Therefore, the industrial use generally adds a trace amount of organic compound containing P into the raw material gas to slow down the influence of the loss of the catalyst P, thereby prolonging the service life of the catalyst. Disclosure of Invention The invention aims to solve the problems of low maleic anhydride selectivity and yield and poor catalyst stability in the prior art, and provides a vanadium-phosphorus-oxygen catalyst, a preparation method and application thereof. The inventor of the invention finds that in the research process, the existing method for adding a trace amount of organic compound containing P into raw material gas to slow down the influence of loss of the catalyst P, thereby prolonging the service life of the catalyst has the defects that the P supplementing process generates extra production operation cost and the instability of the production process is increased. The inventor of the present invention found in the course of further research that if the proper stable P component can be introduced into the catalyst, the P loss in the reaction process can be effectively alleviated, and the phosphorus supplementing process can be reduced or even avoided in the production process. The lithium iron phosphate compound is a compound containing Li, fe, P and O elements, and the addition of Li and Fe can play a role in promoting hydrocarbon selective oxidation. Currently, the most widely used electrode materials for lithium ion batteries are those in which the P element remains stable as a phosphate compound after pyrolysis. Therefore, if lithium iron phosphate can be introduced into the vanadium phosphorus oxide catalyst precursor, the preparation of the VPO hydrocarbon selective oxidation catalyst with high performance and high stability is expected. In order to achieve the above object, a first aspect of the present invention provides a vanadium phosphorus oxygen catalyst comprising vanadium element, phosphorus element, oxygen element, iron element and lithium element, wherein the content of vanadium element is 20 to 35 wt%, the content of phosphorus element is 15 to 25 wt%, the content of oxygen element is 40 to 65 wt%, the content of iron element is 0.2 to 0.5 wt%, and the content of lithium element is 0.02 to 0.1 wt%, based on the total amount of the catalyst. Preferably, in the catalyst, at least part of the phosphorus element and the