Preparation of aromatic hydrocarbons by the catalytic treatment of the products of the coking of coal and of the pyrolysis and thermal cracking of petroleum

Abstract

1. An investigation was made of the catalytic aromatization of thermal-cracking distillates and the dealkylation of the hydrocarbons of coal-tar distillate in presence of toluene and of the crude toluene fraction of light pyrolysis oil. 2. Under optimum conditions the use of somewhat elevated pressure (3–15 atm) accelerates the reactions of aromatization, dealkylation, and alkylation of the original hydrocarbons and directs the process toward the maximum formation of xylenes. Depending on the composition of the raw material, the yield of xylene fraction on the amount of material consumed in one passage varies in the range 37.5–38%, that of benzene in the range 14–27.2%, that of light gasoline in the range 2.2–8.5%, and that of the alkylbenzene fraction of b.p. 149–180° in the range 14.4–20.6%. 3. The presence of toluene in the mixture favors the aromatization of the hydrocarbons of cracking distillate with appreciable suppression of coke- and gas-formation processes. In the formation of xylenes, in addition to the aromatization of the original hydrocarbons, the dealkylation of polyalkylbenzenes and the conjugated alkylation of toluene are of great importance. The xylene fractions of the catalyzates consist mainly of a mixture of the three isomeric xylenes and are notable for their low contents of ethylbenzene.