Regulating SnO2 surface by metal oxides possessing redox or acidic properties: The importance of active O2−/O22− and acid sites for toluene deep oxidation

Abstract

To explore the surface doping effects of metal oxides possessing redox (Cr, Co, Mn) or acidic (In, Bi) properties on SnO2, SnO2 doped by different metal oxides has been designed. All the doping metal oxides disperse finely on the SnO2 support surface, which can improves the reaction activity, obeying the order of 1%Mn/SnO2 > 1%Co/SnO2 > 1%Cr/SnO2 > 1%Bi/SnO2 > 1%In/SnO2 > SnO2. By modifying SnO2 surface with Cr, Co and Mn oxides, both the active surface oxygen (O2− and O22−) and acid sites quantities have been significantly improved, thus resulting in remarkable activity increment. Whereas, by modifying SnO2 surface with In and Bi oxides, only the surface acid sites amount has been improved, hence having limited activity improvement effect. 1%Mn/SnO2 catalyst possesses considerable amount of both types of active sites, thus showing the optimal toluene deep oxidation activity in all the catalysts.