Stoichiometric and non-stoichiometric perovskite-based catalysts: Consequences on surface properties and on catalytic performances in the decomposition of N2O from nitric acid plants

摘要

Catalytic activity for the N2O decomposition into N2 was investigated on perovskite-based materials in the presence of 5vol% NO, 6vol% O2 and 15vol% H2O. This feed is typical of industrial conditions for nitric acid plants operating at high temperature (850-900 °C). The catalytic properties were found to be sensitive to the surface composition as revealed by XRD and XPS. Surface reconstructions on La and Co deficient perovskites induced surface La or Co enrichment. The latter governed the catalytic properties at medium and high temperature and was related to change in oxygen mobility. The presence of water was found as an outstanding parameter to speed up structural changes at the surface. However the presence of water had globally a negative impact in the catalytic activity in N2O decomposition. Surface changes which determined the extent of deactivation were more accentuated on Co-deficient perovskites due to La2O3 segregation. Higher resistance to deactivation was obtained on La-deficient perovskites such as La_(0.8)CoO3 and Lao.9Coo.8Feo.2O3. Surface reconstruction was evidenced at high temperature in severe reaction conditions.