A superior cerium-tungsten bimetal oxide catalyst with flower-like structure for selective catalytic reduction of NOx by NH3

A novel flower-like 0.1%WO3/CeO2(f) catalyst with high-efficiency was fabricated for the selective reduction of NOx by NH3. In contrast to traditional WO3/CeO2, this catalyst exhibited a significant SCR performance of 90% NOx conversion and 95% N2 selectivity within a wide temperature range of 175-450.C and great H2O and/or SO2 resistance under a high GHSV of 177,000 h 1. A variety of analytical techniques including SEM, XRD, XPS, NH3-TPD, H2-TPR and in situ DRIFTS-MS were employed for the catalysts characterization to fully understand the reaction mechanism over WO3/CeO2 catalysts. It was found that the flower-like structure promoted a more uniform dispersion of tungsten species on the support and a stronger interaction between WO3 and CeO2, thereby increasing the acid sites and surface vacancies. Moreover, more chemical active oxygen and trivalent cerium species were presented on 0.1% WO3/CeO2(f). In situ DRIFTS-MS and H2-TPR revealed that the reducibility was optimized for 0.1% WO3/CeO2(f). Then NH3 oxidation species could react with gaseous or adsorbed NOx during Eley-Rideal (E-R) pathway for 0.1%WO3/CeO2(f) at a high temperature (300. C). Meanwhile, NOx was reduced into more active bridged nitrates participating in the reaction via Langmuir-Hinshelwood (L-H) route, contributing to its superior deNOx performance. In comparison, the formation of inert adsorbed NH3 oxidization/ deformation species and bridged nitrates suppressed the SCR reaction over 0.1%WO3/CeO2, resulting in its inferior deNOx activity. This study not only provides a new strategy for developing high-efficiency ceria supported NH3-SCR catalyst, but also lays a foundation for investigating the reaction mechanism of cerium-based catalyst for further practical applications.