Steering the structure and reactivity of Ag/Al2O3 by the addition of multi-functional WOx for NOx reduction by ethanol

Abstract

Ag/Al2O3 has shown promising deNOx activity for (O)HC-SCR but has not yet been commercialized due to its narrow operating temperature range. Here, we developed AgW/Al2O3 exhibiting superior reactivity for ethanol-SCR compared to Ag/Al2O3 in the entire reaction temperature range. STEM-EDS visibly confirmed the hierarchical structure of AgW/Al2O3 where W was highly dispersed over Al2O3, and Ag species in contact with W had a narrow size distribution. UV–vis, H2-TPR, and DRIFT results demonstrated that the abundant metallic Ag in AgW/Al2O3 accelerated the activation of ethanol into acetaldehyde, leading to improved NOx conversion at low to medium temperatures, while ethylene formed over W-induced Brønsted acid sites appeared to contribute to maintaining the high-temperature deNOx capacity. DFT calculations further supported that AgW/Al2O3 is more reactive toward acetaldehyde formation than Ag/Al2O3, and the corresponding active phases of AgW/Al2O3 were predicted to be predominantly metallic Ag along with Ag ionically bonded with WO3.