Oxidation of ethane on high specific surface SmCoO3 and PrCoO3 perovskites

An adapted sol-gel method allowed synthesizing SmCoO3 and PrCoO3 oxides with high specific surface (ca. 28 m(2) g(-1)) and a relatively clean perovskite phase at 600 degrees C, a temperature much lower than the one required in ceramic methods. The perovskites were investigated as catalysts for the oxidation of ethane in the temperature range 300-400 degrees C. Both catalysts were very active: ethane was activated already at 300 degrees C, i.e., 100 degrees C below the temperatures previously reported for perovskites. The main product was CO2 on both catalysts, but on PrCoO3 oxidehydrogenation (ODH) to ethylene was observed already at 300 degrees C, with the low selectivity. Even so, this was quite unusual for simple perovskites, and for such a low temperature. TPR data showed that praseodymium decreases the reducibility of Co3+ in the perovskite, what could explain the observed ODH, and suggest it proceeds via a Mars-van Krevelen mechanism. Kinetic study showed a similar apparent activation energy for both catalysts (ca. 80 kJ/mol), but a difference in the nature of the participating oxygen species: while on PrCoO3 both adsorbed and lattice species contribute to the reaction, on SmCoO3 contribution of adsorbed species is practically negligible, due to its very high oxygen lability. The results show that these simple perovskites may be promising catalysts for ethane oxidation at relatively low temperatures. (C) 2009 Elsevier B.V. All rights reserved.