Catalysts for NOx selective catalytic reduction by hydrocarbons (HC-SCR)

This short review concerns the efficient catalysts for HC-SCR discovered more than 20 years ago. In 1990, Iwamoto proposed Cu ion-exchanged ZSM-5, and it was the first powerful catalyst for HC-SCR. This paper presents first metal ion-exchanged zeolites and the influence of various parameters on the catalysts activities (acidity, O-2 content, etc.). In the second part, this paper reviews supported metal catalysts, base metal oxides, hybrid catalysts and the possible reducing agents to remove NOx. It can be inferred that the most active catalysts for HC-SCR should have acidic sites, an active phase like copper or cobalt, or for a wider activity, elements such as silver or a mixture of metals. For low deactivation, they should contain noble metals such as platinum, rhodium or tin. (C) 2014 Elsevier B.V. All rights reserved.