Catalytic activity in methane oxidation of La1-xCaxCoO3-δ (х = 0-1) perovskites prepared by mechanochemical route

Abstract

A number of perovskite-like oxides La1-xCaxCoO3-δ (x = 0-1) prepared by the mechanochemical method were studied in respect of their catalytic activities to methane oxidation. Mechanochemical route as compared with ceramic route results in increase a substitution degree in La1-xCaxСoO3-δ oxides from x=0.3 up to x=0.5 even at lower temperature and duration of calcination. The introduction of calcium resulted in a non-monotonic decrease in the catalytic activity upon an increase in x with the intermediate maximum at x=0.3-0.5. The catalytic activities decreased in the series: LaCoO3> La0.6Ca0.4CoO3 > La0.8Ca0.2CoO3 > Ca2Co2O5. The observed changes in the catalytic activity of the calcium-containing samples correlate with variations in the proportion of weakly bonded oxygen species (or Cо+4 cations) only in the composition range x=0.1-0.4. The higher activity of lanthanum cobaltite may be accounted for by the presence of cobalt oxide particles on the perovskite surface, while the decrease in the activity at x>0.4 by the emergence of calcium oxide on the perovskite surface and by the appearance of the less active brownmillerite phase. *Correspondence to: Isupova LA, Boreskov Institute of Catalysis Siberian Division of Russian Academy of Sciences, Laboratory of the catalysts and supports for high temperature catalytic processes, Novosibirsk, Russia, Tel: +7383-3269-603; E-mail: isupova@catalysis.ru