Crystal Phase-Dependent Ga-H Chemistry and H 2 Roles in Ga 2 O 3 -Catalyzed Propane Dehydrogenation Reaction

Roles of H 2 in the oxide-catalyzed propane dehydrogenation reaction (PDH) are interesting. Here we report phase-dependent H 2 roles in the Ga 2 O 3 -catalyzed PDH reaction, in which H 2 co-feeding suppresses the PDH reaction catalyzed by α-Ga 2 O 3 with an unchanged apparent activation energy and a negative reaction order against H 2 but promotes the PDH reaction catalyzed by β-Ga 2 O 3 with a decreased apparent activation energy and a positive reaction order against H 2 . The Ga-H hydride species formed by H 2 activation on α-Ga 2 O 3 is much more stable than that on β-Ga 2 O 3 . During the PDH reaction with co-fed H 2 at 500 °C, the irreversibly adsorbed Ga α-Ga2O3 -H species is inert toward C 3 H 8 activation and blocks the active site to decrease the C 3 H 8 conversion but meanwhile promotes the C 3 H 6 desorption to increase the TOF, whereas the reversibly adsorbed Ga β-Ga2O3 -H species reactively activates C 3 H 8 at a decreased barrier to promote the PDH reaction via the formation of the more active dynamically cycled Ga β-Ga2O3 -H active site.