Structure, acidity and activity of CuOx/WOx-ZrO2 catalyst for selective catalytic reduction of NO by NH3

A series of CuOx/WOx-ZrO2 catalysts were synthesized by impregnating different amounts of copper on the coprecipitated WOx-ZrO2 support and were characterized by XRD, BET, XPS, NH3/NO chemisorption, NH3-TPO and NH3-SCR activity measurements. A wide temperature range (200-320 degrees C) in which NO conversion exceeds 80% is achieved on the 10 wt.% CuOx/WOx-ZrO2 catalyst. The activity and selectivity of the catalysts for ammonia oxidation and NH3-SCR reaction are determined by the strength and amount of Lewis acid sites and Bronsted acid sites, which are adjusted by the formation of WOx-ZrO2 solid solutions and the addition of copper oxides. Two different reaction routes, "ammonia-NO2 route" at low temperatures (<200 degrees C) and "amine-NO/NO2" at high temperatures (>250 degrees C), are presented for SCR reaction over CuOx/WOx-ZrO2 catalysts. (C) 2010 Elsevier Inc. All rights reserved.