INFRARED STUDY OF THE OXIDATION OF CARBON-MONOXIDE OVER PT/AL2O3

The oxidation of CO over Pt/Al2O3 has been studied in a flow reactor under in situ conditions using FTIR. The IR spectrum of adsorbed CO and the rate of CO2 formation were measured simultaneously during temperature-programmed heating of the catalyst between 293 and 573 K. Under conditions of an excess of oxygen in the gas flow, the IR band of linearly adsorbed CO initially shifted to lower frequency and then became invariant. The temperature for the onset of this invariance was concordant with the attainment of ca. 80% CO conversion regardless of the O2: CO ratio within the range 1-35:1. Results are discussed in terms of the formation of isolated regions on the catalyst surface containing CO only.