Controlling selectivity in the chemical looping oxidative dehydrogenation of propane through interface engineering
Alexander Oing, Felix Donat, Christoph R. Müller
Abstract
The oxidative dehydrogenation of propane has the potential to reduce significantly the energy demand of propylene production. However, low propylene selectivity and the need for expensive air separation hamper its commercial implementation. In the herein presented chemical looping-based scheme for propylene production, gaseous oxygen is supplied in situ by a perovskite oxygen carrier (Sr1−xCaxFeO3−δ) while propane is dehydrogenated over a physically separated catalyst (VOx/SiO2), thus allowing for high systematic flexibility, as each component can be optimized individually. To prevent over-oxidation of propane to COx at the gas-oxygen carrier interface, a NaNO3-based surface modification is developed, which melts under operating conditions and wets the surface of the oxygen carrier, forming a non-porous diffusion barrier for gaseous hydrocarbons, thereby completely inhibiting over-oxidation. We demonstrate stable operation over 250 redox cycles at 500 °C (14.5% propane conversion at 68% propylene selectivity), matching the performance of the benchmark VOx/SiO2 with co-fed oxygen. Oxidative dehydrogenation of propane could lower the energy demand for propylene production, but low selectivity and costly air separation limit its viability. Here, the authors demonstrate that a molten NaNO3 shell enables selective oxygen permeation, suppressing hydrocarbon over-oxidation in chemical looping oxygen uncoupling.