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

Abstract

Various Pt catalysts (Pt/ZrO(2), Pt/CeO(2), Pt/CeZrO, Pt/WO(3)/ZrO(2) and Pt/WO(3)/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/CeO(2) and Pt/CeZrO while the introduction of WO(3) into the catalyst (Pt/WO(3)/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/CeO(2) and Pt/CeZrO catalysts. For NO + CO reaction, those easily reduced catalysts Pt/CeO(2) 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/CeO(2) and Pt/CeZrO. The higher activities of Pt/W-Ce-Zr catalysts were attributed to their high acidities.