The epoxidation product stream is purified by a process as shown in FIG. 1. A crude propylene oxide product stream, produced by the reaction of propylene and tert-butyl hydroperoxide, containing by weight 96.9% PO, 1.9% acetone, 0.5% water, 0.3% methanol, 600 ppm methyl formate, 400 ppm propionaldehyde, 300 ppm acetaldehyde, and the remainder a mixture of hydrocarbons, is passed via line 1 fed into a liquid contacting device 4 that effects 11 theoretical stages of liquid extraction. The crude PO feed stream is fed into the liquid-liquid extractor at stage 4 from the top. Propylene glycol is fed via line 2 at the top of the contacting device 4. A mixture of branched C8 and C9 saturated hydrocarbons is fed via line 3 to the bottom of the device 4. The ratio by weight of PO:glycol:hydrocarbon streams is 1:1:2. PO is recovered in the light hydrocarbon phase via line 5 with 99.7% efficiency, while 99.99% of water and 99.4% of methanol is rejected in the heavy glycol phase via line 6. In addition, 64% of the acetaldehyde, 32% of the propionaldehyde, 12% of the acetone, and 1% of the methyl formate is rejected in the heavy glycol phase stream via line 6. Essentially all of the hydrocarbon impurities in the crude PO remain in the light phase stream. The liquid-liquid extraction using a glycol and a C7 or greater alkane effectively removes a significant amount of the impurities from the propylene oxide.
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