Conversion of hydrocarbons over cobalt oxide catalysts II: The effect of catalyst pretreatment on the conversion of cyclohexene

Abstract

A cobalt oxide catalyst pretreated by air and/or hydrogen was used in a study of the catalytic conversion of cyclohexene using a flow technique. The catalytic activity was measured in the temperature range 410–490 °C at space velocities of (7.00–12.14) × 10 -2 min -1 at normal pressure. The gaseous and liquid products of the disproportionation reaction were analysed chromatographically. The gaseous products were methane and hydrogen and the liquid products were cyclohexane and benzene, together with unreacted cyclohexene. The kinetics of gaseous products revealed a zero-order reaction. The apparent activation energy was calculated to be 31.5 ± 0.5 kcal mol -1 independent of the space velocity. Artificial cyclohexene-benzene and cyclohexane-cyclohexene mixtures were prepared. It was shown that the presence of benzene and/or cyclohexane increases the rate of dehydrogenation of cyclohexene. The formation of different products and the gain in the mass of the catalyst after participation in cyclohexene conversion are explained in terms of the formation of condensation products on the catalyst surface which may decompose in various ways to give reaction products.