Pure Aromatic Hydrocarbons from Petroleum Fractions by Dehydrogenation-Hydrogenolysis Combination Process

Abstract

Catalytic dehydrogenation of ethylcyclohexane, thermal hydrogenolysis of ethylbenzene and ethylcyclohexane, and the combination process comprising successive operations of dehydrogenation and hydrogenolysis for ethylcyclohexane, kerosene and gas oil have been studied using a conventional flow apparatus. Dehydrogenation has been carried out over a commercial chromia-alumina catalyst at temperatures ranging from 485 to 565°C under an atmospheric pressure, while hydrogenolysis at temperatures from 710 to 760°C also under an atmospheric pressure.Main products in the dehydrogenation of ethylcyclohexane are hydrogen, ethylbenzene, xylenes, benzene, and toluene. Those in the hydrogenolysis of ethylbenzene are benzene, toluene, and styrene. The hydrogenolysis of ethylcyclohexane results in a production of gases containing an appreciable amount of ethylene. Product distributions in the combination process for ethylcyclohexane are compatible with those found in the separate studies of the individual component reactions. Thus liquids produced are very high in aromatic content, while gases are rich in olefin content.The combination process has been further examined for kerosene and gas oil. It has been found that the liquids obtained from these higher hydrocarbons consisted of benzene, naphthalene and their alkyl derivatives but neither paraffins nor olefins whose boiling points are higher than that of benzene were present. Sufficiently pure components of aromatic hydrocarbons are obtainable from the liquid products by a conventional distillation. An additional advantage in the combination process is the production of gases of high ethylene content. A model plant of the combination process is presented for the separation of benzene, toluene and xylenes.