Ethylbenzene dehydrogenation to styrene in the presence of carbon dioxide over chromia-based catalysts

The dehydrogenation of ethylbenzene to styrene in the presence of carbon dioxide over chromia-based catalysts prepared in different ways was investigated. The 25% Cr2O3/Al2O3 supported catalyst and the 20% Cr2O3-SiO2 mixed oxide catalyst display the highest activities for the reaction. XRD characterization of the catalysts reveals that the activity depends on the amount of dispersed chromia species in the catalysts. A combination of XPS and TPR studies shows that both Cr6+ and Cr3+ species are present in the precalcined catalysts and the Cr6+ species are probably the precursors of the active sites of the catalysts with higher activity. Under the same reaction conditions, the supported chromia and chromia mixed oxide catalysts give better catalytic performance than Fe2O3/Al2O3 and V/MgO catalysts.