In situ FT-IR Study on the Transient States of Adsorbed Species during CO Oxidation by O2 and NO over Pt/γ-Al2O3 Catalyst

The transient state of adsorbed species during the CO-NO reaction on Pt/gamma-Al2O3 catalyst was monitored using in situ FT-IR. Experiments were performed at the low temperature region for elevating adsorption rate. The amount of adsorbed species on the surface was calculated from band-area of absorbance. The change in the CO consumption rate in the CO-O-2 reaction was viewed by relating to that in the relative area of linear-CO on the catalyst. The experiments where catalyst was exposed to gaseous NO showed that the increase in the concentration of NO in the feed stream resulted in the increase in the relative area of nitrate species as bridge-NO and in a concomitant decrease in that of linear-NO. An argument is made in that bridge-NO was formed by binding gas phase NO onto the chemisorbed atomic oxygen that was formed in the dissociation of linear-NO. The participation of chemisorbed atomic oxygen in CO oxidation by NO over Pt/gamma-Al2O3 at low temperature was viewed in the results of experiment where the catalyst was exposed to gases containing a fixed amount of CO and varied amount of NO.