Method for the preparation of 1,2-propanediol and dipropylene glycol

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

• a) continuously reacting propene with hydrogen peroxide in the presence of a catalyst mixture, comprising a phase transfer catalyst and a heteropolytungstate, in a liquid reaction mixture comprising an aqueous phase with a maximum apparent pH of 6 and an organic phase, to obtain 1,2-propanediol and dipropylene glycol;
• b) separating the liquid reaction mixture into an aqueous phase (Pa) comprising 1,2-propanediol and dipropylene glycol, and an organic phase (Po);
• c) recycling at least a part of the separated organic phase (Po) to a);
• and
• d) recovering the 1,2-propanediol and the dipropylene glycol from the separated aqueous phase (Pa);
• wherein reaction heat generated in a) is at least partially removed,
• adjusting a ratio of the 1,2-propanediol to the dipropylene glycol by adjusting a weight ratio of the hydrogen peroxide to water fed to a),
• wherein the weight ratio of the hydrogen peroxide to water is varied within a range of from 0.05 to 1.5;
• and
• wherein the ratio of 1,2-propanediol to dipropylene glycol is reduced by increasing the weight ratio of hydrogen peroxide to water fed to a) or the ratio of 1,2-propanediol to dipropylene glycol is increased by reducing the weight ratio of hydrogen peroxide to water fed to step a).