US 12,459,881 B2
Method for the preparation of 1,2-propanediol
Holger Wiederhold, Darmstadt (DE); and David Bolz, Frankfurt (DE)
Assigned to Evonik Operations GmbH, Essen (DE)
Appl. No. 18/249,660
Filed by Evonik Operations GmbH, Essen (DE)
PCT Filed Oct. 7, 2021, PCT No. PCT/EP2021/077737
§ 371(c)(1), (2) Date Apr. 19, 2023,
PCT Pub. No. WO2022/084057, PCT Pub. Date Apr. 28, 2022.
Claims priority of application No. 20202993 (EP), filed on Oct. 21, 2020.
Prior Publication US 2023/0382832 A1, Nov. 30, 2023
Int. Cl. C07C 29/48 (2006.01); C07C 29/17 (2006.01); C07C 29/84 (2006.01)
CPC C07C 29/48 (2013.01) [C07C 29/172 (2013.01); C07C 29/84 (2013.01)] 13 Claims
 
1. 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 phosphoric acid esters of 1,2-propanediol, and an organic phase (Po);
c) recycling at least a part of the organic phase (Po) to a);
d) heating at least a part of the aqueous phase (Pa) separated in b) to a temperature of more than 140° C. at a pressure sufficient to maintain at least 20% by weight of water of said aqueous phase (Pa) in a liquid phase, wherein d) is performed without adding hydrogen; and
e) recovering the 1,2-propanediol from the at least a part of the aqueous phase (Pa) heated in d).