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 m² g⁻¹) and a relatively clean perovskite phase at 600 °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 °C. Both catalysts were very active: ethane was activated already at 300 °C, i.e., 100 °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 °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.