Isotopic study of the La0.7Ag0.3MnOδ≤3 perovskite-catalyzed soot oxidation in presence of NO

Soot oxidation process over La0.7Ag0.3MnOδ≤3 (LAM) and LaMnO3 (LM) catalysts was studied through 18O2 isotopic labelling experiments in the presence and absence of NO, using catalyst-soot mixtures under loose contact conditions. Isotopic exchange experiments evidenced that silver-particles enhanced oxygen exchange capacity, explained by the increase of oxygen active sites formed due to the charge compensation mechanism in the perovskite-like structure due to silver incorporation, and metallic-silver-segregated on catalytic surface. This enhanced oxygen exchange ability leads to the improvement of the catalytic soot oxidation capacity. The elucidated reaction-pathway indicated that catalyst oxygen is transferred to soot, and then gas-phase-oxygen occupies the vacancies created. Furthermore, 16-oxygen species coming from catalyst play an important role in the formation of NOx-adsorbed species that lead to NO2 formation, which assists soot oxidation. The desorption of NO2 was favored with Ag-particles presence because it promoted the formation of less thermally stable adsorbed NOx species.The authors want to thank the University of Antioquia for the financial support received through the CODI project No 2015-7828. L.U. thanks the Colombian Administrative Department of Science, Technology and Innovation (COLCIENCIAS), for the Ph.D. Scholarship granted; to the ENLAZA-MUNDOS program from Mayor’s office in Medellín, for the partial-support to an international internship; and to Professor Agustín Bueno from MCMA research group at materials institute of University of Alicante (IUMA), for the international internship