Structure, acidity and activity of CuO x/WO x–ZrO 2 catalyst for selective catalytic reduction of NO by NH 3

Abstract

A series of CuO x /WO x –ZrO 2 catalysts were synthesized by impregnating different amounts of copper on the coprecipitated WO x –ZrO 2 support and were characterized by XRD, BET, XPS, NH 3/NO chemisorption, NH 3-TPO and NH 3-SCR activity measurements. A wide temperature range (200–320 °C) in which NO conversion exceeds 80% is achieved on the 10 wt.% CuO x /WO x –ZrO 2 catalyst. The activity and selectivity of the catalysts for ammonia oxidation and NH 3-SCR reaction are determined by the strength and amount of Lewis acid sites and Brønsted acid sites, which are adjusted by the formation of WO x –ZrO 2 solid solutions and the addition of copper oxides. Two different reaction routes, “ammonia–NO 2 route” at low temperatures (<200 °C) and “amine–NO/NO 2” at high temperatures (>250 °C), are presented for SCR reaction over CuO x /WO x –ZrO 2 catalysts.