Method for the preparation of 1,2-propanediol

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

• a) reacting propene with hydrogen peroxide at a temperature of from 50 to 110° C. in the presence of a catalyst mixture, comprising a phase transfer catalyst and a polytungstophosphate, 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 solution of known pH for measuring dilute aqueous solutions;
• b) separating the liquid reaction mixture into an aqueous phase (Pa) comprising 1,2-propanediol and an organic phase (Po);
• c) recycling at least a part of the organic phase (Po) to a);
• and
• d) recovering the 1,2-propanediol from the aqueous phase (Pa);
• wherein the method further comprises at least one of
• e) reacting a tungstate with hydrogen peroxide and phosphoric acid at a temperature of from 5 to 40° C., in the presence of the phase transfer catalyst, in a liquid mixture comprising an aqueous phase and an organic phase, followed by passing at least a part of a resulting organic phase (Poc) comprising polytungstophosphate and the phase transfer catalyst to a).