Abstract

The kinetics of CO oxidation in a strongly oxidizing environment (i.e., P O 2 ⪢ P CO) over a low-loaded Rh/Al 2O 3 catalyst are not significantly affected by the presence of cerium. Under moderately oxidizing or net-reducing conditions, on the other hand, the addition of sufficient amounts of cerum oxides (≥2 wt% Ce) to the Rh/Al 2O 3 catalyst was found to cause the following changes in CO oxidation kinetics: suppression of the CO inhibition effect, decreased sensitivity of the reaction rate to gas-phase O 2 concentration, and decreased apparent activation energy. These cerium-induced changes in the kinetics lead to enhancement of CO oxidation activity and can be rationalized on the basis of a mechanism involving CO 2 formation via a reaction between CO adsorbed on Rh and surface oxygen derived from the neighboring ceria particles. The effects of Ce addition on the CO oxidation kinetics were also independent of whether the Ce was deposited before or after the Rh.

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