GB734812A - A process for separating 3- and 4-picoline from mixtures thereof - Google Patents

Abstract

3- and 4-Picoline are separated from a mixture thereof which may contain 2 : 6-lutidine by adding water and sulphur dioxide to the mixture, fractionating it, collecting a fraction highly enriched in 3-picoline and a fraction highly enriched in 4-picoline, and removing water and sulphur dioxide from these fractions. This removal may be effected (1) by distilling the fractions with a liquid which forms an azeotrope with water, e.g. benzene or toluene or (2) by adding NH3 or NaOH and an auxiliary liquid immiscible with water to the fractions (e.g. benzene or toluene), separating the picoline auxiliary liquid layer, and distilling it. 2 : 6-Lutidine, if present, may be separated from the mixture before adding the water and sulphur dioxide, or it may be separated from the isomer fractions. In an example water and sulphur dioxide were added to a mixture of 3- and 4-picoline and the mixture distilled in a column of 18 theoretical plates, at a reflux ratio of 20 : 1 and at a head of column temperature of 97-98 DEG C. whilst adding further sulphur dioxide to the mixture. The first 35 per cent and the last 30 per cent of the distillate were separately collected and distilled with toluene to obtain 3-and 4-picoline respectively. The rest of the distillate was recycled. Specifications 580,048 and 585,108 are referred to.