Spinel Structured M-Ti Mixed Oxide Catalysts For Low-temperature Selective Catalytic Reduction Of NO_x With NH₃

Nitrogen oxides(NOx)is harmful to environment and human’s health.Selective catalytic reduction(SCR)of NOx with NH3 is a widely adopted methods for denitration technology in commercial use.However,the working temperature of commercial catalyst must be in the range of 573K-673K,and it is not easy for the factory to meet the ever-increasing demand of denitration efficiency by using the method of SCR of NOx with NH3 under this high temperature.Therefore,the development of low-temperature NH3-SCR denitration catalyst has become a very important issue.Spinel structured catalyst(AB2O4)is one kind of the hottest research field.In this paper,position A is selected as Ti in AB2O4,and Mn,Co,Mn and Co,Mn and Cr are selected as position B in AB2O4,respectively.Meanwhile,the ratio of A and B is 1:2.TiMn2O4 and TiCo2O4 catalysts were prepared by sol-gel and co-precipitation methods,respectively.The results of calcination temperature and preparation method on the physical-chemical properties and the catalytic performance in the low-temperature SCR reaction of the catalysts were investigated.TiMn2O4 catalyst synthesized by sol-gel method and calcined at 400℃ showed the excellent performance.NOx conversion can reach 100%(at 175-250℃).For the corresponding TiCo2O4 catalyst prepared at same condition,it is the highest NO,conversion was only 85%.Metal component Co was added into the catalyst to further improve catalytic activity.The effect of the Co/Mn and calcination temperature on the physical-chemical properties and the performance in the low-temperature SCR reaction of TiCo,MnyO4 catalysts were evaluated.The addition of Co further improved the NOx conversion of the catalysts in the low temperature zone and widened the temperature window with the highest activity.The characterization results indicated that the addition of Co increased the amounts of surface Mn4+and enhanced the formation of catalysts for the SCR reaction was improved.Metal component Cr was added into the catalyst to further improve the SO2-poisoning resistances.The effect of the Cr/Mn on the physical-chemical properties and the performance in the low-temperature SCR reaction of TiCrxMnyO4 catalysts were evaluated.The characterization and catalytic results indicated that the addition of Cr increased the amounts of chemical adsorbed oxygen and greatly improved the SO2-poisoning resistance performance.