Successive Operation of Dehydrogenation-Hydrogenolysis for Methylcyclohexane

The combination reaction comprising successive operations of dehydrogenation and hydrogenolysis for methylcyclohexane have been studied using a conventional flow apparatus. Dehydrogenation was carried out over a commercial chromia-alumina catalyst at temperatures ranging from 300 to 640°C under an atmospheric pressure, while hydrogenolysis ranging from 575 to 752°C.Complete conversion of methylcyclohexane was attained under an optimum condition studied. Main products of the combination reaction were composed of benzene, toluene, methane, ethane, ethylene, propylene, butenes, butadiene and hydrogen, accompanied by limited amounts of propane and cyclopentane. Reactions in the hydrogenolysis zone were the demethylation of toluene, and the concurrent thermal cracking of methylcyclohexane unreacted and of methylcyclopentane isomerized in preceeding zone. Methylcyclohexane and methylcyclopentane were consumed faster than toluene in the hydrogenolysis zone, as can be estimated from half lives of the corresponding compounds. It was shown that sufficiently pure benzene and toluene are obtained by a conventional distillation, while gases are rich in olefin content.