Effect of CO on NO oxidation over platinum based catalysts for hybrid fast SCR process

The oxidation characteristics of NO over Pt/TiO 2 (anatase, rutile) catalysts have been determined in a fixed bed reactor as a function of O 2, CO and SO 2 concentrations in the presence of 8% water. The conversion of NO to NO 2 increases with increasing O 2 concentration up to 12% and it levels off. This saturation effect is more pronounced over rutile-Pt/TiO 2 (r-Pt/TiO 2) than that of anatase-Pt/TiO 2 (a-Pt/TiO 2). The presence of CO increases NO oxidation significantly and this enhanced effect is more pronounced on a-Pt/TiO 2 than that on r-Pt/TiO 2 with increasing CO concentration at lower temperatures. The same effect is also observed on the catalysts with different Pt and tungsten oxide (WO 3) loadings. With increasing Pt and WO 3 loadings on TiO 2 support (Pt–WO 3/TiO 2), formation of NO 2 is high even at lower temperatures. The presence of SO 2 significantly suppresses the oxidation of NO over both r-Pt/TiO 2 and a-Pt/TiO 2 catalysts but it is less pronounced due to low stability of sulfate on a-Pt/TiO 2.