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

Abstract

The influence of CO-pretreatment on the properties of CuO–V₂O₅/γ-Al₂O₃ catalysts was investigated in the reduction of NO by CO. Catalytic performance results showed that the pretreated CuO–V₂O₅/γ-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 γ-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 γ-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⁺–ϒ–V⁴⁺ (ϒ 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.