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CN-121972157-A - SO for wet flue gas2Oxidized vanadium-molybdenum composite catalyst and preparation method and application thereof

CN121972157ACN 121972157 ACN121972157 ACN 121972157ACN-121972157-A

Abstract

The invention relates to the technical field of industrial catalysis and flue gas treatment, in particular to a vanadium-molybdenum composite catalyst for catalyzing and oxidizing SO 2 into SO 3 under wet conditions, and a preparation method and application thereof. The catalyst takes V 2 O 5 and MoO 3 as composite active components, is preferably loaded on a carrier after hydrophobic modification, and remarkably improves the activity, stability and poisoning resistance of the catalyst under the conditions of high humidity and low temperature by constructing a V-O-Mo bonded active phase structure and utilizing the electronic modulation effect of MoO 3 on V 2 O 5 and the hydrophobic property thereof. The catalyst is particularly suitable for high-efficiency conversion and recycling recovery of SO 2 in industrial flue gas containing a large amount of water vapor.

Inventors

  • LI SHIWEI
  • BAI ZHISHAN
  • ZHANG WEIJIE
  • LU CHAOJIN

Assignees

  • 华东理工大学

Dates

Publication Date
20260505
Application Date
20260402

Claims (10)

  1. 1. A vanadium-molybdenum composite catalyst for wet flue gas SO 2 oxidation is characterized by comprising a composite oxide active phase containing V-O-Mo structural units, wherein the composite oxide active phase is formed by loading V 2 O 5 and MoO 3 on the surface of a carrier, and the atomic number ratio of Mo to V in the composite oxide active phase is 0.1-1.0.
  2. 2. The vanadium-molybdenum composite catalyst for wet flue gas SO 2 oxidation according to claim 1, wherein the carrier is prepared by modifying porous oxide with surface hydrophobicity of a modifier.
  3. 3. The vanadium molybdenum composite catalyst for wet flue gas SO 2 oxidation according to claim 1, wherein the porous oxide is at least one of titania, silica, alumina.
  4. 4. The vanadium molybdenum composite catalyst for wet flue gas SO 2 oxidation according to claim 3, wherein the modifier is at least one of silane coupling agent, zirconate coupling agent and silazane.
  5. 5. The vanadium molybdenum composite catalyst for wet flue gas SO 2 oxidation according to claim 4, wherein the modifier is methyltriethoxysilane.
  6. 6. A method for preparing a vanadium molybdenum composite catalyst for wet flue gas SO 2 oxidation according to any one of claims 1 to 5, comprising the steps of: a. dissolving a vanadium source and a molybdenum source in a solvent containing a complexing agent, and preparing to obtain a composite precursor solution containing the vanadium source and the molybdenum source; b. Impregnating a carrier in a composite precursor solution to obtain an impregnated material; c. aging and drying the immersed material; d. And C, roasting the dried solid in the step C for 4-6 hours at 400-500 ℃ in an air atmosphere to obtain the catalyst.
  7. 7. The method for preparing a vanadium-molybdenum composite catalyst for wet flue gas SO 2 oxidation according to claim 6, wherein the vanadium source in the step a is at least one of ammonium metavanadate, ammonium vanadate and vanadyl oxalate, and the molybdenum source is at least one of ammonium molybdate, ammonium heptamolybdate and molybdenum nitrate.
  8. 8. The method for preparing a vanadium-molybdenum composite catalyst for wet flue gas SO 2 oxidation according to claim 6, wherein the complexing agent in the step a is at least one of oxalic acid, citric acid and ammonium oxalate.
  9. 9. The method according to claim 1 to 5, wherein the wet condition is that the water vapor volume content in the reaction gas is not less than 5%.
  10. 10. The use according to claim 9, wherein the catalytic oxidation has a reaction temperature of 250-400 ℃.

Description

Vanadium-molybdenum composite catalyst for wet flue gas SO 2 oxidation and preparation method and application thereof Technical Field The invention belongs to the technical field of chemical catalyst preparation and air pollution control, and particularly relates to a vanadium-molybdenum composite catalyst for wet flue gas SO 2 oxidation and a preparation method and application thereof. Background Sulfur dioxide (SO 2) is one of the major atmospheric pollutants, which is mainly derived from fossil fuel combustion, nonferrous metal smelting, and various chemical production processes. Catalytic oxidation of SO 2 to sulfur trioxide (SO 3) is not only a core process link of the sulfuric acid industry, but also a key technical route for realizing flue gas desulfurization and recycling of sulfur elements. At present, the catalyst widely used in industry is a vanadium catalyst which takes vanadium pentoxide (V 2O5) as a main active component, takes alkali metal sulfate such as potassium sulfate (K 2SO4) as a cocatalyst and takes diatomite or special silicon dioxide as a carrier. However, such conventional vanadium-based catalysts are designed and optimized mainly for dry, high temperature (typically operating temperature window between 400 ℃ and 600 ℃) contact sulfuric acid production processes. In modern industry, especially in the flue gas treatment of non-electric industries such as glass, ceramics, steel sintering, small coal-fired boilers and the like, the generated flue gas has the remarkable characteristics of large fluctuation range of SO 2 concentration, low flue gas temperature (generally between 200 ℃ and 400 ℃) and large water vapor content (the volume content can reach 10% -20% or even higher). This "wet" or "high humidity" operating condition poses serious challenges to conventional vanadium catalysts, particularly in terms of: 1. the low-temperature activity is obviously insufficient, namely, the traditional catalyst has higher light-off temperature and lower intrinsic catalytic activity in a low-temperature region below 400 ℃, SO that the conversion rate of SO 2 is not ideal and the requirement of high-efficiency desulfurization cannot be met; 2. The water vapor poisoning effect is prominent in that high concentrations of water vapor compete with reactant SO 2、O2 and product SO 3 for adsorption on the active sites of the catalyst. More importantly, the water vapor can be quickly combined with the generated SO 3 to form a sulfuric acid (H 2SO4) liquid film or acid mist on the surface and in the pore canal of the catalyst, and the liquid film can physically cover and block active sites to prevent the diffusion and contact of reactant molecules, SO that the activity of the catalyst is obviously reduced; 3. The sulfation deactivation is aggravated by the fact that substances such as sulfuric acid or ammonium bisulfate and the like formed are difficult to desorb from the surface of the catalyst in a wet environment, and can generate irreversible sulfation reaction with active components or carriers, so that active sites are permanently deactivated, pulverization of catalyst particles and rise of pressure drop of a reaction bed can be caused, and the service life of the catalyst is greatly shortened. 4. The corrosion risk of equipment is increased, and sulfuric acid generated at low temperature has stronger corrosiveness and forms serious threat to subsequent equipment such as heat exchangers, pipelines and the like. Therefore, how to develop an SO 2 oxidation catalyst which can still keep high activity, high stability and long service life under low temperature and high humidity environment has important significance for widening the application range of flue gas desulfurization technology, improving the pollution control level of non-electric industry and realizing the low temperature and high efficiency recovery of sulfur resources. Disclosure of Invention The invention aims to provide a vanadium-molybdenum composite catalyst for wet flue gas SO 2 oxidation and a preparation method thereof, SO as to solve the problems in the background technology. In order to achieve the aim, the invention provides a vanadium-molybdenum composite catalyst for wet flue gas SO 2 oxidation, which comprises a composite oxide active phase containing V-O-Mo structural units, wherein the composite oxide active phase is formed by loading V 2O5 and MoO 3 on the surface of a carrier, and the atomic number ratio of Mo to V in the composite oxide active phase is 0.1-1.0. As a further improvement, the ratio of the number of atoms of Mo to V in the active component is preferably 0.2 to 0.8, most preferably 0.4 to 0.6. The V 2O5 and MoO 3 are not simply physically mixed, but are formed into a composite metal oxide active phase by forming V-O-Mo chemical bonds in the preparation process, and the composite structure is key to generating a synergistic catalytic effect. As a further improvement, the carrier is prepared by modifying the