Catalysis Letters, Vol.69, No.1-2, 93-101, 2000
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-degrees 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 O-2/VCH and 95% selectivity with 80% conversion was obtained at O-2/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.