Patent ID: 7084310

Claim:
A process for the continuous preparation of propylene glycols, which comprises the steps (i) to (iii): (i) reacting propylene with hydrogen peroxide to give a mixture comprising propylene oxide, and monopropylene glycol, dipropylene glycol and tripropylene glycol as by-products, wherein from this mixture, a mixture comprising monopropylene glycol, dipropylene glycol and tripropylene glycol is separated via the bottoms and crude propylene oxide is separated via the top in a distillation column; (ii) reacting the crude propylene oxide obtained in step (i) with water to give a mixture comprising monopropylene glycol, dipropylene glycol and tripropylene glycol; (iii) combining the propylene glycol mixtures obtained in steps (i) and (ii) and separating off the respective propylene glycols by distillation, wherein in (i), an aqueous hydrogen peroxide solution is used and wherein water is removed from the mixture obtained in (ii) prior to combination and separation in step (iii).