Structure sensitivity of gallium oxide catalyzed propane dehydrogenation reaction co-fed with hydrogen

Developing efficient propane dehydrogenation (PDH) processes without uses of expensive Pt- and toxic CrOx-based catalysts are of broad interest and great importance. Co-feeding of hydrogen is a widely-adopted strategy to improve catalytic performance of various catalysts in the PDH reaction. Herein, we systematically study the promotion effect of co-fed H2 on different oxide catalysts in the PDH reaction. It comes mainly from the alleviated poisoning effect on ZnO and additionally from H2 reduction-enhanced coordination-unsaturated Zr3+ active sites on ZrO2, while mainly from the formation of dynamically-cycles metastable gallium hydride species on Ga2O3 capable of activating the C–H bond activation of propane at significantly reduced barriers (C3H8+2Ga(III)Ga2O3-H*=C3H6+2H2+2Ga(III)Ga2O3). During the Ga2O3-catalyzed PDH reaction with co-fed H2, the Ga(III)Ga2O3-H* species initially forms by H2 dissociation, then reacts with C3H8 to produce C3H6 and H2, and finally gets recovered by H2 dissociation, leading to the dynamically-cycled hydride active site on Ga2O3 with greatly enhanced catalytic performance. Such a hydride catalysis is highly sensitive to the structure of Ga2O3, being more efficiently on Ga2O3{111} facets than on Ga2O3{100} facets. A fine Ga2O3 nanocatalyst with a high ratio of exposed {111} facets and a large specific surface area is fabricated to give a C3H6 space-time yield (STY) as high as 4.9 kgC3H6/(kgcatalyst h) with a C3H6 selectivity of 96.5% and a good recyclability in the PDH reaction with co-fed H2 at 550 ºC. These results provide an alternative strategy for developing none-Pt- and none-toxic CrOx-based PDH catalysts.