Effect of CO-pretreatment on the CuO-V2O5/gamma-Al2O3 catalyst for NO reduction by CO

The influence of CO-pretreatment on the properties of CuO-V2O5/gamma-Al2O3 catalysts was investigated in the reduction of NO by CO. Catalytic performance results showed that the pretreated CuO-V2O5/gamma-Al2O3 exhibited extremely high activity and selectivity. For example, NO conversion can be remarkably enhanced from 13.8% to 100.0% for the 03Cu01V catalyst. For the catalyst characterization, the XRD results suggested that copper oxide and vanadium oxide were highly dispersed on the surface of gamma-Al2O3 and the TPR results gave evidence for the existence of Cu2+-O-V5+ species. The XPS and EPR results demonstrated that Cu2+ and V5+ were reduced to lower valence states (Cu2+ -> Cu+, V5+ -> V4+) by the CO-pretreatment, which was proved by in situ FT-IR to be beneficial to the adsorption of CO and dissociation of NO. In addition, the interaction between the dispersed copper oxide and vanadium oxide species upon the gamma-Al2O3 support before and after CO-pretreatment was tentatively discussed, using the concept of SSOV ( surface synergetic oxygen vacancy) which was proposed elsewhere. According to this concept, the dispersed Cu2+-O-V5+ species could be reduced to Cu+-Upsilon-V4+ (Upsilon represents an oxygen vacancy) by CO-pretreatment and it was considered to be the primary active species for the reaction. Based on the discussion of the experiment results, a possible mechanism was proposed.