EXTRACTING METHOD OF GLYCOL

摘要

PROBLEM TO BE SOLVED: To efficiently extract glycols such as ethylene glycol in high purity by adding a specified proportion of alcohol to carbon dioxide to prepare supercritical carbon dioxide, using the obtd. supercritical carbon dioxide as an extracting medium, and bringing the extracting medium into contact with the material to be treated containing glycols. SOLUTION: Carbon dioxide in a supercritical state is prepared as an extracting medium by adding 0.3-5 pts.wt., preferably 0.3-2.5 pts.wt. alcohol to 100 pts.wt. carbon dioxide. The extracting medium is brought into contact with the material to be treated containing glycols. The alcohol to be added may be any alcohol such as methanol, ethanol, propanol, and butanol. The material to be treated is preferably heated to a temp. range higher than the boiling point of the alcohol added and lower than the boiling point of glycols to be extracted. Thereby, for example, glycols in a used engine coolant can be recovered in high efficiency and high purity and can be used again.