Xylene from Coal-Tar Light Oil: the 137.5–142 °C Cut

Commercial xylene is the part of coal-tar light oil that boils at about 140 °C: a mixture of the three xylenes, mostly meta, with a fifth or so para. The light oil is washed with strong sulphuric acid and caustic soda as for benzol (Lunge, 1887). In the steam distillation the fraction above 136 °C is solvent naphtha; redistilled, its 137.5–142 °C cut is xylene (Thorpe, 1913). It is the raw material for para-xylene and so for PET. The picture: our diagram of the route.