Patent ID: 6024840
Filing Date: 2000-02-15
Classification: C07D

Abstract:
A method of purifying a crude epoxidation reaction product comprised of 2 to 10 weight percent propylene oxide, 60 to 85 weight percent methanol, 10 to 25 weight percent water and 0.01 to 0.1 weight percent acetaldehyde comprising the steps of(a) feeding the crude epoxidation reaction product to a first fractionator having from 20 to 60 theoretical vapor-liquid contacting stages;(b) subjecting the crude epoxidation reaction product to fractional distillation within the first fractionator at a top pressure of 15 to 50 psia, a bottoms temperature of 80.degree. C. to 110.degree. C., and a reflux:distillate ratio of 10:1 to 30:1;(c) withdrawing a first overhead stream comprised of propylene oxide and at least 2 weight percent methanol and having a reduced level of acetaldehyde as compared to the crude epoxidatimn reaction product from the first fractionator;(d) withdrawing a first bottoms stream comprised of methanol, water and at least 99% of the acetaldehyde present in the crude epoxidation reaction product from the first fractionator, wherein methanol is present in the first fractionator at a concentration effective to render the acetaldehyde less volatile than the propylene oxide.