Supported transition metal-oxide catalysts for HC-SCR DeNOx with propene

The selective catalytic reduction of nitrogen oxides by hydrocarbons (HC-SCR DeNOx) 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 Al2O3, phosphated Al2O3 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 NOx conversion. Catalysts prepared by sol–gel synthesis are more active for NOx 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 CuOx show highest NO conversion (at 350 °C), CeOx- and FeOx-containing catalysts show moderate NO conversion (at 350–450 °C), whereas VOx- and FeOx-containing catalysts favor total oxidation of propene already at low temperature.