| 主权项 |
1. A process for purifying 1,2-propanediol to remove impurities by distillation, comprising:
1. conducting contaminated propanediol into a low boiler column A which comprises a rectifying section and a stripping section, said low boiler column A having less than 20 theoretical plates in the rectifying section and less than 40 theoretical plates in the stripping section, and has a reflux ratio of less than 5 and wherein the bottom temperature of column A is less than 200° C., 1.1 removing low boilers via the top of the column and 1.2 drawing off a 1,2-propanediol stream which still comprises impurities via the bottom of the column, wherein the 1,2-propanediol stream comprises at least 97% by weight 1,2-propanediol, and 2. introducing the 1,2-propanediol stream into a column B for purifying distillation, 2.1 removing purified, low-odor 1,2-propanediol from column B as a liquid side draw, 2.2 drawing off a stream of still-contaminated, odor-containing 1,2-propanediol via the top of column B and 2.3 removing high boilers via the bottom of column B. |
