Role of Micropores in the Oxidative Dehydrogenation of Ethane on MoV(TeNb) Mixed Metal Oxides.
Ezenwa, Sopuruchukwu A.
2018
- Oxidative dehydrogenation (ODH) routes for the catalytic transformation of abundant light alkanes to higher value chemicals have the potential to overcome the current traditional processes and, in doing so, provide significant economic advantages and mitigate environmental concerns. Despite improved energy efficiency prospects, ODH based processes are yet to be fully implemented until catalysts ... read morewith desired performance goals can be developed. MoV based mixed metal oxides with M1 phase are well known to produce high ethylene (C2H4) yields during ethane (C2H6) ODH at moderate reaction temperatures. Improvements of these materials have been limited by insufficient molecular level understandings of the nature of active sites and mechanistic origins of high selectivity. This experimental work examines the role of the micropores of these M1 phase oxides in controlling activity and selectivity. These micropores have similar sizes (0.4 nm) to C2H6, which hints at a well-matched fit that permits C2H6 access to active sites within the pores while cyclohexane (C6H12) remains restricted by size (0.6 nm) to external surface sites. Measured ODH rate ratios, calculated activation enthalpies, and observed product selectivities are used to elucidate the roles of these micropores in the selective ODH of C2H6. These show that micropores stabilize desired C-H activation transition states and destabilize O-insertion reactions by steric hindrance to proximate C-O contact within the tightly confining concave pore walls. These detailed molecular level understandings provide important guidance to the development of improved selective oxidation catalysts for desired transformations that are limited by more favored but undesired reaction pathways.read less
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- tufts:sd.0000833
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