(651b) Alkali Promoted Mg6MnO8 Redox-Catalysts for Chemical Looping-Oxidative Dehydrogenation of Ethane: Mechanistic Investigations
- Conference: AIChE Annual Meeting
- Year: 2017
- Proceeding: 2017 Annual Meeting
- Group: Catalysis and Reaction Engineering Division
- Time: Thursday, November 2, 2017 - 8:20am-8:40am
We have reported a model Mg6MnO8 catalyst system with excellent CL-ODH properties. This system is interesting due to its facile lattice oxygen (O2-) transport ability, and the very strong effects of alkali promoters on product selectivity. Without promotion Mg6MnO8 is highly active for deep oxidation, but the use of alkali salts as promoters significantly shifts the product selectivity towards ethylene even at high ethane conversions (>70% single pass). In this work, we describe the mechanistic aspects of promoted and unpromoted Mg6MnO8 redox catalysts. Extensive characterizations, including surface characterization, temperature programed reactions, and in-situ DRIFTS were performed. We also explored the lattice oxygen behavior with TGA, O18 labeling experiments, and in-situ XRD. These experimental data indicate that alkali salt promoters suppress ethane and ethylene surface activation while the bulk structure maintains fast lattice oxygen transport during the redox reactions.