Purification of propylene oxide

Sepn. of hexenes, hexanes, pentenes, pentanes, butenes, MeOH, water and O-contg. impurities and opt. also isobutylene and hydrocarbons from propylene oxide (PO) comprises (i) fractional distn. to give a bottoms fraction comprising PO, hexanes, hexenes, water and only residual amts. of pentenes and pentanes; (ii) extractive distn. of the bottoms with a 2-6C alkylene glycol extractant to give an overhead fraction comprising PO, hexenes, hexanes, water and residual amts. of pentenes, pentanes and high boiling O-contg. impurities; (iii) extractive distn. of the overhead fraction with a 7-10C alkane hydrocarbon extractant to give an overhead prod. comprising extractant and PO enriched with high-boiling O-contg. impurities and a bottoms fraction comprising extractant, PO, hexenes, hexanes and residual amts. of pentenes and pentanes; and (iv) extractive distn. of the bottoms fraction with a 7-10C alkane hydrocarbon extractant to give an overhead fraction comprising PO.