Selective catalytic reduction of NO with CO on Pt/W-Ce-Zr catalysts

Various Pt catalysts (Pt/ZrO2, Pt/CeO2, Pt/CeZrO, Pt/WO3/ZrO2 and Pt/WO3/CeZrO) were prepared and characterized, and their catalytic reduction reactions of NO by CO, with or without the presence of excess oxygen, were investigated. The results of temperature-programmed experiments showed that CO could be easily oxidized over Pt/CeO2 and Pt/CeZrO while the introduction of WO3 into the catalyst (Pt/WO3/CeZrO) inhibited the reduction of catalyst surface; NO could not dissociate over those catalysts in oxidized state but after CO reduction at a low temperature, NO dissociation took place only over Pt/CeO2 and Pt/CeZrO catalysts. For NO + CO reaction, those easily reduced catalysts Pt/CeO2 and Pt/CeZrO exhibited better catalytic performances, and NO could be rapidly converted below 350 A degrees C. For the reaction with the presence of excess O-2, the NO conversions were significantly inhibited, but better NO conversions were obtained over the tungstate-contained catalysts when compared with Pt/CeO2 and Pt/CeZrO. The higher activities of Pt/W-Ce-Zr catalysts were attributed to their high acidities.