Enhanced Catalytic CO Oxidation Activity and SO2 Resistance of Pt/Mo/TiO2 Catalysts by NH3 Pretreatment of Mo/TiO2

In this study, Pt/N-Mo/TiO2and Pt/Mo/TiO2catalysts were prepared by the two-step impregnation method for catalytic CO oxidation, with the obtained Mo/TiO2pretreated or not with NH3before Pt loading. The Pt/N-1Mo/TiO2catalyst exhibited superior catalytic activity compared to Pt/1Mo/TiO2and Pt/N-xMo/TiO2(x= 0, 0.5, 2, 3, 5), indicating the essential role of N-modification of Mo/TiO2with an optimal MoO3loading. TheT90decreased from 133 °C for Pt/1Mo/TiO2to 105 °C for Pt/N-1Mo/TiO2under a feed gas consisting of 8000 ppm CO, 16% O2, 3% H2O and balanced N2. For both Pt/1Mo/TiO2and Pt/N-1Mo/TiO2catalysts, the H2O in the feed gas showed promotive effects on CO oxidation, while SO2caused some deactivation at low temperatures. Under the same feed gas composition (8000 ppm CO, 16% O2, 10% H2O, 50 ppm SO2and balanced N2) and temperature (185 °C), Pt/N-1Mo/TiO2demonstrated superior SO2resistance compared to Pt/1Mo/TiO2. CO conversion on Pt/N-1Mo/TiO2remained above 99% during a 12-h SO2resistance test, while that on Pt/1Mo/TiO2gradually decreased to 26%. Characterization results show that NH3pretreatment of 1Mo/TiO2significantly improved the dispersion of Pt and enhanced the dissociation of adsorbed H2O into highly reactive hydroxyl (*OH) species, partially explaining the better activity of Pt/N-1Mo/TiO2compared with Pt/1Mo/TiO2. H2O might promote CO oxidation by facilitating the formation of easily decomposable bicarbonate and formate intermediates. SO2impeded the Pt reduction process on Pt/1Mo/TiO2while it hardly affected that on Pt/N-1Mo/TiO2, explaining their difference in SO2resistance.