Method for the preparation of 1,2-propanediol

A method for the preparation of 1,2-propanediol, comprising:

• a) reacting propene with hydrogen peroxide in the presence of a catalyst mixture comprising a phase transfer catalyst, phosphoric acid, and a heteropolytungstate, in a liquid reaction mixture comprising an aqueous phase with a maximum apparent pH of 6 and an organic phase, wherein apparent pH refers to a value determined by measurement with a glass electrode employing a commercial pH meter calibrated with aqueous buffer solutions of known pH for measuring dilute aqueous solutions;
• b) separating the liquid reaction mixture into an aqueous phase (Pa) comprising 1,2-propanediol and formic acid, and an organic phase (Po);
• c) recycling at least a part of the organic phase (Po) to a);
• d) contacting at least a part of the aqueous phase (Pa) separated in b) with a palladium catalyst to provide a treated aqueous phase, wherein no hydrogen is added in d);
• and
• e) recovering the 1,2-propanediol from the treated aqueous phase provided in d).