ethylene glycol cannot be easily separated from 1 , 2 - butanediol or 1 , 3 - butanediol by atmospheric or reduced pressure distillation because of the closeness of their boiling points . ethylene glycol can be readily separated from the butanediols by azeotropic distillation . typical effective agents are ethyl benzene , 3 - heptanone or diisobutyl ketone .