Process for the separation of naphthalene and its derivatives from benzene and its derivatives

Naphthalenes of differing carbon number are separated from alkyl benzenes of comparable carbon number by liquid-liquid extraction with a sulpholane type solvent to obtain an extract enriched in naphthalenes and a raffinate enriched in benzenes. The difference in carbon number between the highest and lowest hydrocarbons in the feed is preferably from 5-8; suitable feeds are obtained from coker gas oil and cycle gas oil from a catalytic cracking. The sulpholane solvent may contain alkyl substituents or polar groups containing oxygen, nitrogen, sulphur or halogen, e.g. those described in Specification 625,505. The specific gravity of the sulpholane is preferably at least 0.2 above or below that of the feed and is used in a weight ratio to feed of 0.2-2.0. In a preferred embodiment a feed e.g. boiling from 160-315 DEG C. also containing saturated hydrocarbons is distilled to obtain a fraction boiling below the naphthalene-containing feed, e.g. 160-205 DEG C., having a higher saturate content than the total feed, and a side stream, e.g. boiling from 195-235 DEG C. which is subjected to extraction, and the lower boiling fraction is used as a countersolvent in the extraction, being introduced at the end where the extract is removed. The naphthalenes are preferably recovered from the extract by a further extraction with a non-polar solvent immiscible with the sulpholane and boiling below the naphthalenes, e.g. a C1-10 paraffin, which is used in a weight ratio to extract of 0.2-2.0 and separated from the naphthalene by distillation.