An integrated study of Pt/WO3/SiO2 catalysts for the NO$z.sbnd;CO reaction III. FTIR kinetic study and correlation of promotional effects

Abstract The kinetics of the NOCO reaction and promotion mechanism of WO 3 on Pt WO 3 SiO 2 catalysts was studied by FTIR spectroscopy in an in situ recycle IR microreacto. It was found that addition of WO 3 to Pt SiO 2 increased activity toward the NOCO reaction. The kinetics displayed an inhibition behavior with increasing CO concentration, but WO 3 served to decrease CO surface coverage during the inhibited regime. However, the rate of NO dissociation over Pt was slowest for the most active (tungsta-containing) catalysts. Characterization studies showed previously that addition of WO 3 resulted in the decoration of Pt crystallites by suboxides of WO 3 . The promotional effects and kinetic results are explained in terms of the participation of PtWO x adlineation sites, which resulted from the decoration effect. Using this concept, a correlation between the increased activity and the concentration of adlineation sites successfully explained the kinetics and IR results obtained with all the catalysts used. The addition of WO 3 to Pt SiO 2 is believed to produce a small number of adlineation sites having very high NO dissociation activity.