US 12,486,210 B2
Method for the preparation of 1,2-propanediol
Holger Wiederhold, Darmstadt (DE); David Bolz, Frankfurt (DE); and Patrik Glatz, Freigericht (DE)
Assigned to Evonik Operations GmbH, Essen (DE)
Appl. No. 18/249,984
Filed by Evonik Operations GmbH, Essen (DE)
PCT Filed Oct. 7, 2021, PCT No. PCT/EP2021/077669
§ 371(c)(1), (2) Date Apr. 21, 2023,
PCT Pub. No. WO2022/084050, PCT Pub. Date Apr. 28, 2022.
Claims priority of application No. 20203021 (EP), filed on Oct. 21, 2020.
Prior Publication US 2023/0382834 A1, Nov. 30, 2023
Int. Cl. C07C 29/48 (2006.01); C07C 29/86 (2006.01)
CPC C07C 29/48 (2013.01) [C07C 29/86 (2013.01)] 16 Claims
 
1. A method for the preparation of 1,2-propanediol, comprising:
a) continuously reacting propene with hydrogen peroxide in the presence of a catalyst mixture, comprising a quaternary ammonium salt and a polytungstophosphate, in a liquid reaction mixture comprising an aqueous phase with a maximum apparent pH of 6 and an organic phase comprising an alkylaromatic hydrocarbon solvent;
b) withdrawing the liquid reaction mixture from a) and adding a water-soluble sulfate salt or sulfuric acid to the liquid reaction mixture, to obtain a mixture comprising from 500 to 10,000 mg/kg of sulfate ions in an aqueous phase;
c) separating the mixture obtained in b) into an aqueous phase (Pa) comprising 1,2 propanediol and an organic phase (Po);
d) recycling at least a part of the organic phase (Po) to the reaction a); and
e) recovering the 1,2-propanediol from the aqueous phase (Pa),
wherein apparent pH is 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.