Supported transition metal-oxide catalysts for HC-SCR DeNO x with propene

Abstract

The selective catalytic reduction of nitrogen oxides by hydrocarbons (HC-SCR DeNO x ) on supported mixed-oxide catalysts is a promising technology for the treatment of exhaust gases from spark-ignition engines. In this work, the SCR of NO with propene on catalysts with Fe-, Cu-, V- and Ce-oxides supported on Al 2O 3, phosphated Al 2O 3 or SAPO-11, was investigated. As shown by their temperature-programmed reduction-profiles, the catalysts’ behaviour for NO conversion depends mainly on the redox properties of the supported metal oxide. The acidic properties of these catalysts assessed by temperature-programmed reduction of ammonia can be neglected for NO x conversion. Catalysts prepared by sol–gel synthesis are more active for NO x conversion than catalysts prepared by wet impregnation. Probably, this is due to smaller metal oxide particles on the support surface in catalysts from sol–gel synthesis compared to those prepared by excess solution impregnation. Catalysts containing CuO x show highest NO conversion (at 350 °C), CeO x - and FeO x -containing catalysts show moderate NO conversion (at 350–450 °C), whereas VO x - and FeO x -containing catalysts favor total oxidation of propene already at low temperature.