Dehydrogenation of propane to propene over different polymorphs of gallium oxide

Dehydrogenation of propane to propene in the presence or absence Of CO2 over four polymorphs of gallium oxide was investigated. beta-Ga2O3 exhibits the highest activity among the polyrnorphs, and it is even more active than chromium oxide catalyst in the presence of CO2 center dot H-2-TPR and XPS studies show that gallium oxide is hardly reduced below 600 degrees C. The dehydrogenation reaction is suggested to proceed through a heterolytic dissociation reaction pathway, and it is enhanced by CO2 because of the existence of the reverse water gas shift reaction and the Boudouard reaction. The high catalytic activity of beta-Ga2O3 is probably associated with an abundance of surface medium-strong acid sites related to the coordinatively unsaturated Ga3+ cations and the conjugated effect of proton and oxide. Furthermore, increasing the reaction temperature facilitates the activation Of CO2 over beta-Ga2O3. The promoting effect Of CO2 on beta-Ga2O3 catalyst is more evident above 550 degrees C. (c) 2005 Elsevier Inc. All rights reserved.