Selective hydrogen oxidation in the presence of C3 hydrocarbons using perovskite oxygen reservoirs

Perovskite-type oxides, ABO, can be successfully applied as solid oxygen reservoirs in redox reactions such as selective hydrogen combustion. This reaction is part of a novel process for propane oxidative dehydrogenation, wherein the lattice oxygen of the perovskite is used to combust hydrogen selectively, from the dehydrogenation mixture at 550 degrees C This gives three key advantages: it shifts the dehydrogenation equilibrium to the side of the desired products, heat is generated, thus aiding the endothermic dehydrogenation, and it simplifies product separation (H2O vs H-2). Furthermore, the process is safer since it uses the catalysts' lattice oxygen instead of gaseous O-2. We screened fourteen perovskites for activity selectivity and stability in selective hydrogen combustion. The catalytic properties depend strongly on the composition. Changing the B atom in a series of LaBO3 perovskites shows that Mn and Co give a higher selectivity than Fe and Cr. Replacing some of the La atoms with Sr or Ca also affects the catalytic properties. Doping with Sr increases the selectivity of the LaFeO3 perovskite, but yields a catalyst with low selectivity in the case of LaCrO3. Conversely, doping LaCrO3 with Ca increases the selectivity, The best results are achieved with Sr-doped LaMnO3, with selectivities of up to 93% and activities of around 150 mu molOm(-2). This catalyst, La0.9Sr0.1MnO3, shows excellent stability, even after 125 redox cycles at 550 degrees C (70h on stream). Notably, the activity per unit surface area of the perovskite catalysts is higher than that of doped cerios, the current benchmark of solid oxygen reservoirs.