Insight into the remarkable enhancement of NH3-SCR performance of Ce-Sn oxide catalyst by tungsten modification

Abstract

A series of W-modified Ce-Sn catalysts were fabricated and investigated for the selective catalytic reduction (SCR) of NOx (NO and NO2) by NH3. All the prepared Ce-W-Sn ternary oxide catalysts showed higher deNOx efficiency than the Ce-Sn catalysts, among which the Ce1W0.24Sn2Ox catalyst prepared by the coprecipitation method showed the highest NOx conversion. The mechanism by which W modification improved the structure and function of the Ce1Sn2Oy catalyst was systematically investigated by various methods. The corresponding results suggested that Ce-doped tetragonal SnO2 (t-Sn(Ce)O2) was the main active phase in the Ce1Sn2Oy catalyst for the NH3-SCR reaction. The W species regulated the structure by promoting the formation of the t-Sn(Ce)O2 active phase while preventing the generation of the Sn-doped cubic CeO2 (c-Ce(Sn)O2) phase. In addition, the highly dispersed W species on the surface of the Ce1W0.24Sn2Ox catalyst also coupled with Ce species to form new Ce-O-W active sites. The W modification also promoted the ability of the catalysts to oxidize NO to NO2 at 150–300 °C and suppressed the occurrence of excess NH3 oxidation especially at high temperature. The optimal structure and physico-chemical properties induced by W species contributed to superior NH3-SCR performance.