Methoxypropanols separation combining membrane separation and distillation

A process for separating 1-methoxypropan-2-ol from an aqueous stream comprising 1-methoxypropan-2-ol and 2-methoxypropan-1-ol, wherein the process comprises:

• (a) Providing a stream S0 comprising 1-methoxypropan-2-ol, 2-methoxypropan-1-ol and water, and having a molar ratio of 1-methoxypropan-2-ol:
• 2-methoxypropan-1-ol in the range of from 1:5 to 5:1;
• (b) separating 1-methoxypropan-2-ol and 2-methoxypropan-1-ol from the stream S0 provided in (a) by distillation comprising subjecting the stream S0 provided in (a) to distillation conditions in a distillation unit comprising a distillation column B, obtaining a (top) stream S1 comprising 1-methoxypropan-2-ol, 2-methoxypropan-1-ol and water, which is enriched in 1-methoxypropan-2-ol and 2-methoxypropan-1-ol compared to the stream S0 and a bottoms stream S1a comprising water and being depleted of 1-methoxypropan-2-ol and 2-methoxypropan-1-ol compared to S0;
• wherein the distillation column B is operated at a pressure of >2 bar;
• (c.1) separation of the stream S1 obtained in (b) with at least one membrane unit M comprising at least one membrane module, obtaining a stream S2 which is depleted of water and further enriched in 1-methoxypropan-2-ol and 2-methoxypropan-1-ol compared to the stream S1, and a stream S2a comprising water;
• (c.2) subjecting the stream S2 obtained in (c.1) to distillation conditions in a distillation unit comprising a distillation column C, obtaining a stream S3, which is depleted of water and further enriched in 1-methoxypropan-2-ol and 2-methoxypropan-1-ol compared to the stream S2, and a stream S3a comprising water;
• (d) separating 1-methoxypropan-2-ol from the stream S3 obtained in (c.2) by distillation, comprising subjecting the stream S2 obtained in (c.2) to distillation conditions in a distillation unit comprising a distillation column D, obtaining a stream S5 comprising ≥95 weight-% 1-methoxypropan-2-ol and ≤0.5 weight-% of 2-methoxypropan-1-ol, based on the total weight of stream S5, and a stream S4 comprising ≥95 weight-% 2-methoxypropan-1-ol based on the total weight of stream S4;
• (e) optionally recirculating at least a part of the stream S3a to (c.1).