Selective catalytic reduction of NO with propene in the presence of excessoxygen over supported cerium oxides

Selective catalytic reduction of NO with propene in the presence of excess oxygen was investigated by using several CeO2 supported on oxides. Unsuppor ted CeO2 was found not effective for the NO reduction; however it was highl y active for oxidation of NO to NO2 and C3H6 to CO and CO2. The activity of CeO2 for the reduction of NO to N-2 was greatly enhanced by supporting it on Al2O3, ZrO2, Ga2O3, etc. Among them Al2O3 was the best support, but Al2O 3 itself was almost inactive under the conditions presently used (300-400 d egrees C). CeO2/Al2O3 was superior in activity to Pt/Al2O3 and to Pt-CeO2/A l2O3. It was presumed that CeO2 had the oxidizing capability, which allowed oxidative activation of NO without excessive oxidation of propene, and the oxidized NO was successively reduced on Al2O3.