STEADY-STATE ISOTOPIC TRANSIENT KINETIC-ANALYSIS (SSITKA) INVESTIGATION OF NO REDUCTION WITH CO OVER PEROVSKITE CATALYSTS

The reduction of NO with CO on a perovskite catalyst, LaCoOs3 was inve stigated by means of steady state isotopic transient kinetic analysis (SSITKA). Steady stake reactions were carried out at temperatures of 3 00-700 degrees C, while the isotopic transient experiments were carrie d out at temperatures of 500-700 degrees C. Isotopic switches of (CO)- C-12 to (CO)-C-13 or (NO)-N-14 to (NO)-N-15 were performed after the r eaction reached steady state. In order to determine the effect of read sorption, experiments at various temperatures were carried out as a fu nction 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 vario us temperatures, Both the steady state and the SSITKA results were con sistent with N2O being a precursor in the formation of Nz at temperatu res below 600 degrees C. SSITKA results indicated that the entire cata lyst surface was involved in the reaction, and that, at high temperatu re, CO2 desorption became limiting for the overall reaction. This was most likely due to the rapid formation and slow decomposition of carbo nates on the surface.