On Of Mn Catalysts And Its Application In The Catalytic Oxidation Of Toluene

Volatile organic compounds is hazardsrous to the environment and human. To deal with this kind of pollutant over Mn catalysts effectively, the structure of catalysts has been modified properly. According to the mechanism of VOCs over transition metal oxides, the method makes use of K and Ag to modify the catalyst structure and enhance the mobility of lattice oxygen of manganese oxides. It means a lot to catalytic oxidation of VOCs over Mn catalysts in practical application. The main contents of this paper are as follows:1. K is selected to modify the structure of Mn/SBA-15catalysts and its application in the catalytic oxidation of toluene. It proved that different K/Mn molar ratios played different roles in the modification of structure of manganese oxides and its reactivity in the reaction. The K/Mn=0-1/8delcined the surface area and reducibility of catalysts, resulting in the reactivity decreasing in the toluene catalytic oxidation. Increasing the content of K (1/6.5-1/5.5) led to part of MnO2being transformed into Mn2O3. Also high dispersed metal oxides and enhanced reducibility were obtained. Meanwhile the K influnenced electronic properties of the Si-O-Mn bond, which strengthened the interaction between toluene and catalysts. But higher amount of K blocked active centers of catalysts and led to deactivation of catalysts.2. Ag was selected to modify the sturcture of Mn/SBA-15catalysts and its catalytic performance in the toluene catalytic oxidation. The addition of Ag promoted the reactivity of catalysts greatly and its reactivity related closely to the Ag:Mn molar ratio. The catalyst with Ag:Mn=1:3led to part of Ag entering into the sturcture of manganese oxides and Ag1.8Mn8O16mixed phase. Meanwhile, part of MnO2was transformed into Mn2O3. The coexistence of MnO2, Mn2O3and Ag1.8Mn8O16can promote the reactivity of catalysts. Ag also enhanced the dispersion of manganese oxides, reducibility of catalysts and abundant of active oxygen produced. During the progress of toluene catalytic oxidation, a small amount of intermediate benzaldehyde was detected and its formation related to lattice oxygen of catalysts.