Extractive distillation of propylene oxide

An extractive distn. process for the distn. of impure propylene oxide feedstock in an extractive distn. column to remove oxygenated contaminants, including water, methanol and acetone, from the impure propylene oxide, comprises: (a) introducing impure propylene oxide feedstock into the lower half of an extractive distn. column; (b) introducing an extractive distn. agent consisting of a mixt. of polyoxypropylene glycol cpds. into the distn. column above the point of introduction of the feedstock, in the ratio of feedstock to extractive distn. agent of 1:1-20:1, pref. 2:1-10:1; (c) withdrawing a lighter distn. fraction from the distn. column consisting of anhydrous propylene oxide contaminated with reduced quantities of the methanol; and (d) withdrawing a heavier distn. fraction from the distn. column contg. all of the polyoxypropylene glycols, acetone and water and a portion of the methanol introduced into the distn. column. The extractive distn. agent consists of a mixt. of polyoxypropylene glycols having an ave. molecular wt. of 180-220 and formula HO-[CH2-CH(Me)-O]n-CH2-CH(Me)-OH (I), in which n = 1-4.