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 °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 Brønsted 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 °C) and “amine–NO/NO2” at high temperatures (>250 °C), are presented for SCR reaction over CuOx/WOx–ZrO2 catalysts.