Dehydrogenation of propane to propene in the presence or absence Of CO2 over four polymorphs of gallium oxide was investigated. β-Ga2O3 exhibits the highest activity among the polyrnorphs, and it is even more active than chromium oxide catalyst in the presence of CO2• H-2-TPR and XPS studies show that gallium oxide is hardly reduced below 600° 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 β-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 β-Ga2O3. The promoting effect Of CO2 on β-Ga2O3 catalyst is more evident above 550 ° C. © 2005 Elsevier Inc. All rights reserved.