Abstract: In the production of aromatic hydrocarbon from coking crude by-product benzene after a vaporization stage in which the crude benzene is evaporated to leave a residue, the crude benzene is subjected to pressure refining in the presence of hydrogen. The residue is distilled to form high and low boiling fractions and at least the gas pressure and temperature of the distillation stage is controlled so that the sump product apart from styrene is substantially free from aromatic hydrocarbons with less than 9 carbon atoms. The rate of withdrawal of the vaporization residue from the vaporizing column is controlled, depending upon the concentration of polymer formers in the crude benzene to be in the range of 6 to 40% of the rate of feed of the coking by-product benzene to the vaporizing column.