Oxidative dehydrogenation of 4-vinylcyclohexene into styrene over ZrO2 catalyst promoted with Fe2O3 and CaO

The oxidative dehydrogenation of 4-vinylcyclohexene (VCH) into styrene was carried out in the presence of oxygen over a ZrO₂ catalyst promoted with Fe₂O₃ and CaO. Intrinsically, ZrO₂ showed high dehydrogenation activity, which resulted in 80% styrene selectivity with 45% conversion at 425 °C and LHSV 3 h⁻¹. When the ZrO₂ was further promoted with calcium and iron, CaO/Fe₂O₃/ZrO₂, the highest styrene selectivity of 88.9% was obtained as well as the lowest deactivation. The deactivation of catalyst was prohibited properly through the introduction of oxygen in the reactant together with the modification of Fe₂O₃/ZrO₂ with CaO. The CaO/Fe₂O₃/ZrO₂ showed constant catalytic activity and selectivity for more than 50 h without deactivation. The selectivity of styrene was strongly influenced by the mole ratio of O₂/VCH and 95% selectivity with 80% conversion was obtained at O₂/VCH mole ratio of 6 over Fe₂O₃/ZrO₂. It is thought that the oxidative dehydrogenation proceeds through the dehydrogenation (DH) of ring-hydrocarbon of VCH followed by selective combustion of hydrogen (SHC) and the high selectivity of styrene was achieved by the bi-functional role of ZrO₂ for DH and SHC reactions. This revised version was published online in July 2006 with corrections to the Cover Date.