Steady State Isotopic Transient Kinetic Analysis (SSITKA) Investigation of NO Reduction with CO over Perovskite Catalysts

Abstract

The reduction of NO with CO on a perovskite catalyst, LaCoO[sub 3], was investigated by means of steady state isotopic transient kinetic analysis (SSITKA). Steady state reactions were carried out at temperature of 300--700 C, while the isotopic transient experiments were carried out at temperatures of 500--700 C. Isotopic switches of [sup 12]CO to [sup 13]CO or [sup 14]NO to [sup 15]NO were performed after the reaction reached steady state. In order to determine the effect of readsorption, experiments at various temperatures were carried out as a function of space velocity. The SSITKA results for NO reduction with CO indicated that all the species (reactants and products) had measurable surface lifetimes and concentrations on the catalyst surface at various temperatures. Both the steady state and the SSITKA results were consistent with N[sub 2]O being a precursor in the formation of N[sub 2] at temperature below 600 C. SSITKA results indicated that the entire catalyst surface was involved in the reaction, and that, at high temperature, CO[sub 2] desorption became limiting for the overall reaction. This was most likely due to the rapid formation and slow decomposition of carbonates on the surface.