GB1139710A - Process for obtaining very pure aromatics from a crude benzole product, or fractions of this product, by extractive distillation - Google Patents

Abstract

1,139,710. Extractive distillation. HEINRICH KOPPERS G.m.b.H. 18 Dec., 1967 [23 Dec., 1966], No. 57390/67. Heading C5E. Pure aromatic compounds are obtained from crude benzole feedstocks by a process comprising extractive distillation using propylene carbonate as the selective solvent and distillation of the aromatic extract which is then washed with H 2 SO 4 , the following operating conditions being observed: (a) passing the propylene carbonate at 20-90‹ C. to a tray near the top of the extractive distillation column, and passing the feedstock at its boiling point to a tray in the lower half of the column, which is operated with little or no reflux; (b) keeping the aromatic extract from the bottom of the extractive distillation column for at least an hour at 100‹ C. before passing to the distillation still. The propylene carbonate obtained as bottom product of the still may be recycled to the extractive distillation column, up to 5 weight per cent thereof first being diverted and regenerated to remove high-boiling impurities. The sulphuric acid wash may be performed in a plurality of stages. Examples describe the recovery of pure benzene and toluene from benzole feedstocks.