Selective Hydrogen Oxidation in the Presence of C3 Hydrocarbons Using Perovskite Oxygen Reservoirs

✍ Scribed by Jurriaan Beckers; Ruben Drost; Ilona van Zandvoort; Paul F. Collignon; Gadi Rothenberg

• Publisher: John Wiley and Sons
• Year: 2008
• Tongue: English
• Weight: 338 KB
• Volume: 9
• Category: Article
• ISSN: 1439-4235
• DOI: 10.1002/cphc.200800039

✦ Synopsis

Abstract

Perovskite‐type oxides, ABO~3~, 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 °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 (H~2~O 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 LaBO~3~ 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 LaFeO~3~ perovskite, but yields a catalyst with low selectivity in the case of LaCrO~3~. Conversely, doping LaCrO~3~ with Ca increases the selectivity. The best results are achieved with Sr‐doped LaMnO~3~, with selectivities of up to 93 % and activities of around 150 μmol O m^−2^. This catalyst, La~0.9~Sr~0.1~MnO~3~, shows excellent stability, even after 125 redox cycles at 550 °C (70 h on stream). Notably, the activity per unit surface area of the perovskite catalysts is higher than that of doped cerias, the current benchmark of solid oxygen reservoirs.