Application Of Mn-based Metal Oxide Catalysts In The Field Of Catalytic Oxidation Of Volatile Organic Compounds

With the development of our country's chemical industry,the problem of volatile organic compounds(VOCs)pollution is becoming more and more serious.Catalytic oxidation is a viable and environmentally friendly technology for VOCs purification.The development of high-performance catalysts is the key of this catalytic oxidation technology.This thesis used manganese based metal oxide catalysts as the research objects and focuses on the influence of the doping of other metal elements and the construction of the three-dimensional ordered macroporous(3DOM)structure on their catalytic performances for propane oxidation.(1)The 3DOM MnZrO_x composite oxide catalysts were prepared via a hard template method,revealing the influence of the microstructure and the doping of zirconium on the physicochemical properties and catalytic performance of the catalyst.The characterization results show that the addition of zirconium is beneficial to the formation of 3DOM structure and amorphous Mn-Zr solid solution,thereby improving the redox performancece,oxygen mobility and oxygen vacancies of the catalyst,making that the catalyst exhibit a higher specific surface area and excellent catalytic performance.Among them,3DOM Mn_0.6Zr_0.4O_x shows the best catalytic activity,good cycling stability and water resistance.Through temperature-programmed surface reaction(TPSR),in situ DRIFTs and kinetic studies over 3DOM and Bulk Mn_0.6Zr_0.4O_x catalysts,it is found that the 3DOM structure plays a significant role in propane adsorption,activation and lattice oxygen migration.At a space velocity of 20000 ml g^-1 h^-1,the propane can be completely oxidized at 340? over 3DOM Mn_0.6Zr_0.4O_x.(2)The 3DOM MnSmO_xcomposite oxide catalysts were prepared via a hard template method and the modification effects of samarium doping on the physicochemical properties and catalytic performances of the catalysts were systematically studied.The characterization results show that the addition of samarium is beneficial to the formation of 3DOM structure and transformation of manganese oxide crystalline phase from Mn₂O₃ to Mn₃O₄,which promotes the redox behavior and surface oxygen mobility.Among all catalysts,the 3DOM Mn_0.85Sm_0.15O_x catalyst exhibits the best catalytic activity and good catalytic stability.At a space velocity of 100000 ml g^-1 h^-1,the E_a for this catalyst is 85 k J mol^-1.Meanwhile,after a long-term reaction of 70 h under water vapor-containing conditions,no deactivation phenomenon was found over the catalyst.(3)The MnNbO_x composite oxide catalysts were prepared via a co-precipitation method,and the effect of niobium doping on the physicochemical properties and catalytic performance of the catalysts were systematically studied.The characterization results illustrate that the Nb-doping is conducive to the formation of Mn₃O₄ crystalline phase,improves the redox behavior and enriches the surface oxygen species and acid sites of the catalyst.These properties are the key factors responsible for the enhancement of catalytic activity.Among all catalysts,Mn_0.85Nb_0.15O_x exhibits the best catalytic activity and good catalytic stability.At a space velocity of 20,000 ml g^-1 h^-1,the propane can be completely oxidized at 310 ? over Mn_0.85Nb_0.15O_x.