Activity enhancement of copper-containing oxide catalysts by addition of cesium in the reduction of nitric oxide

Catalytic reduction of nitric oxide in the presence of propylene and oxygen over alumina and copper-containing oxide catalysts has been studied. The optimum temperature for this reaction is dependent upon the composition of the catalysts: 640 K on Cu-Cs/Al₂O₃, 680 K on Cu/Al₂O₃, and 780 K on Al₂O₃. IR spectroscopic measurements show that an isocyanate (–NCO) intermediate formed on Cu-Cs/Al₂O₃ is more reactive with NO to give N₂ than the intermediate produced on Al₂O₃ and Cu/Al₂O₃. Electron donation from Cs to Cu may activate the intermediate.