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

Abstract

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.