Purification of a raw 1,4-butandiol aqueous solution comprises using a distillation apparatus with three columns

摘要

Purification of a raw 1,4-butandiol aqueous solution comprises using a distillation apparatus with three columns to give very high purity. Purification of raw 1,4-butandiol (BDO) in a 20-50 wt.% aqueous solution containing 0.1-5 wt.% /=g-butyrolactone and 0.3-2 wt.% THF comprises: (i) charging the solution to a first distillation column at 1-2 bar and sump temperature 100-140 deg C to give a condensed head that is at least partially returned to the column and a sump containing 5-15 wt.% water; (ii) transferring the sump to a second distillation column at 0.02-0.2 bar and sump temperature 160-220 deg C and cooling and condensing the head and returning it to the column; (iii) charging the sump liquid along with the BDO solution of 96% purity from the first column to a third distillation column of pressure 0.02-2 bar and 140-180 deg C, condensing the vapor, returning it to the column and returning the sump liquid to the second column to give a sump BDO of purity at least 99 wt.%.