Cu/Zeolite SCR Catalysts for Automotive Diesel NOx Emission Control

摘要

Cu/zeolite catalysts have long been recognized to be highly active in the Selective Catalytic Reduction (SCR) of NOx with NH3 [1-16]. Compared to titania supported vanadia SCR catalysts, which have been successfully commercialized for stationary NOx emission control since the 1970s and installed on certain Heavy Duty Diesel (HDD) vehicles to meet the NOx emission regulations since the early 2000s, Cu/zeolite SCR catalysts exhibit higher NOx conversion efficiency, particularly at low temperatures [11, 17]. In addition, Cu/zeolite SCR catalysts are more tolerant to high temperature excursions. For automotive applications, this is a critical requirement for the SCR component when it is combined with a Diesel Particulate Filter (DPF) in the emission control system. In order to effectively regenerate the DPF component, the entire system is exposed to temperatures above 600 °C periodically. Cu/zeolite SCR catalysts are significantly more stable than vanadium-based SCR catalysts at temperatures above 650 °C.