Hexane total oxidation on LaMO3 (M = Mn, Co, Fe) perovskite-type oxides

LaMO3 (M = Mn, Fe, Co) perovskites were prepared by calcining the citrate precursors at 800 degreesC for 5 h. PdO 3%/Al2O3, a largely used combustion catalyst, was also studied for comparison. The catalytic behavior was examined in the hexane total oxidation. The following activity scale was found: LaFeO3 > LaCoO3 > LaMnO3. >3% PdO/Al2O3, the three perovskites activating the C-H bond cleavage of hexane better than PdO/Al2O3. At temperature around 250-300 degreesC mobile surface oxygen species are involved in the oxidation process, whereas at T > 300 degreesC oxygen mobile species are no more present and so, particularly for LaCoO3 and PdO/Al2O3, the activation mechanism becomes more energetic. The activity values were compared with those obtained from the total oxidation of methane. (C) 2001 Elsevier Science B.V. All rights reserved.