Purification of propylene oxide using an aqueous acetone extractive distillation agent

Contaminants, including methanol can be removed from an impure propylene oxide feedstock (120) comprising propylene oxide contaminated with from 50 to 1000 ppm of methanol and from 0 to 1 wt.% of acetone, in an extractive distillation process by introducing the impure propylene oxide feedstock (120) into the lower half of a second distillation column (200) having at least 25 theoretical plates, introducing an extractive distillation agent (202) comprising an acetone/water blend containing 20 to 30 wt.% of acetone and, correspondingly, 80 to 70 wt.% of water, at a point 4 to 7 theoretical plates above the crude propylene oxide feed point, at a ratio of feedstock (120) to extractive distillation agent (202) of from 5:1 to 20:1, and withdrawing from the distillation column an overhead distillate fraction (212) comprising propylene oxide contaminated with not more than 60 ppm of methanol, not more than 0.02 wt.% of acetone and not more than 0.3 wt.% of water, and an aqueous bottoms distillate fraction (210) containing substantially all of the methanol, acetone and water introduced into said distillation column (200).