A METHOD FOR THE PREPARATION OF 1,2-PROPANEDIOL

The method for preparing 1,2-propanediol comprises step a) of 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; step b) of separating the reaction mixture into an aqueous phase (Pa) comprising 1,2-propanediol and an organic phase (Po); step c) of recycling at least part of the separated organic phase (Po) to the reaction step a); and step d) of recovering 1,2-propanediol from the separated aqueous phase (Pa); wherein in step d) 1,2-propanediol is separated from the aqueous phase (Pa) by distillation and the apparent pH of the separated aqueous phase (Pa) is adjusted to at least 9 prior to the distillation to reduce the content of formic acid and acetic acid in the recovered 1,2-propanediol.