Elucidating the role of CO2 in the soft oxidative dehydrogenation of propane over ceria-based catalysts
journal contributionposted on 30.05.2018 by Ewa Nowicka, Christian Reece, Sultan M. Althahban, Khaled M. Mohammed, Simon Kondrat, David J. Morgan, Qian He, David J. Willock, Stanislaw Golunski, Christopher J. Kiely, Graham J. Hutchings
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A mixed oxide support containing Ce, Zr, and Al was synthesized using a physical grinding method and applied in the oxidative dehydrogenation of propane using CO 2 as the oxidant. The activity of the support was compared with that of fully formulated catalysts containing palladium. The Pd/CeZrAlO x material exhibited long-term stability and selectivity to propene (during continuous operation for 140 h), which is not normally associated with dehydrogenation catalysts. From temperature-programmed desorption of NH 3 and CO 2 it was found that the catalyst possessed both acidic and basic sites. In addition, temperature-programmed reduction showed that palladium promoted both the reduction and reoxidation of the support. When the role of CO 2 was investigated in the absence of gas-phase oxidant, using a temporal analysis of products (TAP) reactor, it was found that CO 2 dissociates over the reduced catalyst, leading to formation of CO and selective oxygen species. It is proposed that CO 2 has the dual role of regenerating selective oxygen species and shifting the equilibrium for alkane dehydrogenation by consuming H 2 through the reverse water-gas-shift reaction. These two mechanistic functions have previously been considered to be mutually exclusive.
This work was funded by the European Research Council, through the following grant: After the Goldrush, ERC-AG-291319. C.J.K. gratefully acknowledges funding from the National Science Foundation Major Research Instrumentation program (GR# MRI/DMR-1040229). We thank Diamond Light Source for use of B18 (SP8071-12), with gratitude to Dr. Diego Gianolio. E.N. thanks the Technical University of Berlin and Marie Curie-Sklodowska Action for awarding her IPODI fellowship.