Reaction mechanism of direct decomposition of nitric oxide over Co- and Mn-based perovskite-type oxides

Abstract

Kinetics of NO decomposition have been investigated over La_0.8Sr_0.2CoO₃ and La_0.4Sr_0.6Mn_0.8Ni_0.2O₃ perovskite-type oxides. The NO decomposition reaction was practically first-order for NO in the range 0.1–0.5 vol.% NO. The activity was decreased by the presence of gaseous oxygen up to 9 vol.% with the reaction order between −0.16 and −0.82 depending on temperature, contact time and catalyst. A reaction mechanism has been proposed in which a pair of adjacent oxide ion vacancies serves as the active site, the reaction starts with the successive adsorption of two NO molecules at the active site, and the release of oxygen is equilibrated with the gas phase. The derived rate equation satisfactorily explains the experimental results.