SE362064

1302325 Pure benzene by extractive distillation METALLGESELLSCHAFT AG 20 May 1971 [1 June 1970] 16154/71 Heading C5E Pure benzene is recovered from a feedstock which, other than benzene, contains only non- aromatic compounds by extractive distillation with a selective solvent wherein the evaporative ratio V (the heat quantity to be supplied to the sump of the column to evaporate the recovered pure benzene V times) and the solvent ratio L (the amount of solvent to be supplied to the extractive distillation column related to the amount of recovered pure benzene) meet the relation V=0À6L + CwhereC = -0À5 to + 1À5 and L = 1-10; the benzene content of the overhead product being maintained at 10-30 wt. per cent. Suitable solvents are dimethyl formamide, butyrolactone, tetrahydrothiophene dioxide, propylene carbonate or, preferably, N- methylpyrrolidone. The amount of non-aromatic compounds boiling above 100‹ C., e.g. methylcyclohexane and iso-octane, in the feedstock should not be more than 1 wt. per cent.