Part-stream distillation

Patent metadata

Field	Value
Publication number	US-10316007-B2
Application number	US-201515521924-A
Country	US
Kind code	B2
Filing date	Oct 27, 2015
Priority date	Oct 27, 2014
Publication date	Jun 11, 2019
Grant date	Jun 11, 2019

Abstract

A continuous process for preparing propylene oxide proceeds by (a) reacting propene with hydrogen peroxide in a reaction apparatus in the presence acetonitrile as solvent, obtaining a stream S0 containing propylene oxide, acetonitrile, water, at least one further component B; (b) separating propylene oxide from S0, obtaining stream S1 containing acetonitrile, water and B; (c) dividing S1 into streams S2 and S3; (d) subjects S3 to vapor-liquid fractionation in a first fractionation unit, obtaining vapor fraction stream S4a being depleted, relative to S3, of at least one of B and obtaining liquid bottoms stream S4b, and subjecting at least part of vapor fraction stream S4a to vapor-liquid fractionation in a second fractionation unit, obtaining vapor fraction stream S4c and liquid bottoms stream S4 being depleted, relative to S4a, of at least one of B; (e) recycling at least a portion of S4 to (a).

First claim

The invention claimed is:

1. A continuous process for the preparation of propylene oxide, comprising
(a) reacting propene, optionally admixed with propane, with hydrogen peroxide in a reaction apparatus in the presence of acetonitrile as solvent, obtaining a stream S0 leaving the reaction apparatus, S0 containing propylene oxide, acetonitrile, water, at least one further component B, optionally propene and optionally propane, wherein the normal boiling point of the at least one component B is higher than the normal boiling point of acetonitrile and wherein the decadic logarithm of the octanol-water partition coefficient (log K OW ) of the at least one component B is greater than zero;
(b) separating propylene oxide from S0, optionally after having separated propene and optionally propane, obtaining a stream S1 containing acetonitrile, water and the at least one further component B;
(c) dividing S1 into two streams S2 and S3, wherein the total weight of S3 relative to the total weight of S1 is in the range of from 0.01 to 25%;
(d) subjecting S3 to a vapor-liquid fractionation in a first fractionation unit, obtaining a vapor fraction stream S4a being depleted, relative to S3, of at least one of the at least one component B and obtaining a liquid bottoms stream S4b, and subjecting at least part of the vapor fraction stream S4a to a vapor-liquid fractionation in a second fractionation unit, obtaining a vapor fraction stream S4c and a liquid bottoms stream S4 being depleted, relative to S4a, of at least one of the at least one component B;
(e) recycling at least a portion of S4, optionally after work-up, to (a), and recycling at least a portion of S2, optionally after work-up, to (a).

2. The process of claim 1 , wherein in (c), the total weight of S3 relative to the total weight of S1 is in the range of from 0.05 to 20%.

3. The process of claim 1 , wherein from 90 to 99.9 weight-% of S1 consist of acetonitrile and water and wherein from 0.01 to 5 weight-% of S1 consist of the at least one component B.

4. The process of claim 1 , wherein S3 is fed to the top of the first fractionation unit and the at least part of the vapor fraction stream S4a is fed to the bottom of the second fractionation unit, wherein in (d), the first fractionation unit is operated at an absolute pressure at the top of the first fractionation unit in the range of from 0.5 to 5 bar and wherein the second fractionation unit is operated at an absolute pressure in the bottom of the second fractionation unit in the range of from 65 to 95% of the pressure at the top of the first fractionation unit.

5. The process of claim 1 , wherein in (d), the number of theoretical trays of the first fractionation unit is in the range of from 1 to 100 and the number of theoretical trays of the second fractionation unit is in the range of from 1 to 100.

6. The process of claim 1 , wherein in (d), the first fractionation unit is operated without reflux, the at least part of the vapor fraction stream S4a subjected to the vapor-liquid fractionation in the second fractionation unit not being condensed prior to subjecting to the vapor-liquid fractionation in the second fractionation unit, and the second fractionation unit is operated with reflux, wherein a fraction of the vapor fraction stream S4c is used, after condensation, as reflux and wherein the reflux ratio is in the range of from 0.5:1 to 1:1.

7. The process of claim 1 , wherein from 10 to 30 weight-% of the liquid bottoms stream S4b consist of acetonitrile and from 0.1 to 10 weight-% of the liquid bottoms stream S4b consist of the at least one further component B.

8. The process of claim 1 , wherein from 90 to 99.99 weight-% of S4 consist of acetonitrile and water, and wherein from 0.0001 to 0.2 weight-% of S4 consist of the at least one component B.

9. The process of claim 1 , wherein (e) comprises working-up S4, said working-up comprising combining at least a portion of S4 with S2 obtaining a liquid stream.

10. The process of claim 9 , wherein (e) comprises subjecting the liquid stream to acetonitrile-water separation obtaining a stream enriched in acetonitrile, and recycling said stream enriched in acetonitrile, optionally after further work-up, to (a).

11. The process of claim 10 , wherein (e) comprises
(i) preparing a liquid stream S5 by adding a liquid stream P to S2, or to at least the portion of S4, or to the liquid stream obtained from combining S2 and at least the portion of S4,
wherein P comprises at least 95 weight-% of C3, based on the total weight of P,
wherein C3 is propene optionally admixed with propane with a minimum weight ratio of propene relative to propane of 7:3, and
wherein P is added in an amount so that in S5, the weight ratio of C3 relative to acetonitrile is in the range of from 0.2:1 to 5:1;
(ii) subjecting S5 to a temperature of 92° C. at most and a pressure of at least 10 bar, obtaining a first liquid phase L1 and a second liquid phase L2,
wherein at least 95 weight-% of L1 consist of C3, acetonitrile, water and the at least one component B, the water content of L1 being less than 10 weight % based on the total weight of L1, and
wherein at least 95 weight-% of L2 consist of C3, acetonitrile, water and the at least one component B, the C3 content of L2 being 5 weight-% at most, based on the total weight of L2, and the acetonitrile content of L2 being less than 45 weight-% based on the total weight of L2;
(iii) separating L1 from L2;
(iv) recycling L1 as the stream enriched in acetonitrile, optionally after further work-up, to (a).

12. The process of claim 11 , further comprising working up L1, said working-up comprising subjecting L1 to a distillation stage wherefrom a bottoms stream BL1 is obtained, wherein at least 95 weight-% of BL1 consist of C3, acetonitrile, water and the at least one component B, wherein the C3 content of BL1 is in the range of from 7 to 18 weight-%, and recycling BL1 as the stream enriched in acetonitrile, optionally without any further work-up, to (a).

13. The process of claim 12 , wherein from 0.01 to 5 weight-%, of BL1 consist of the at least one component B.

14. The process of claim 1 , wherein (b) comprises
(I) separating propene, optionally together with propane, and oxygen which is optionally additionally contained in S0, from S0, obtaining a stream S01 enriched in propylene oxide, acetonitrile, water, and the at least one component B, wherein at least 99 weight-% of S01 consist of acetonitrile, water, the at least one component B and propylene oxide; wherein for separation, a fractionation unit is used, wherein at the top of the fractionation unit, liquid acetonitrile, optionally admixed with liquid water, is added as entraining agent;
(II) separating propylene oxide from S01, obtaining a stream S02 enriched in acetonitrile, water and the at least one component B, wherein at least 95 weight-% of S02 consist of acetonitrile, water and the at least one component B, and wherein the weight ratio of acetonitrile relative to water is greater than 1:1, wherein S02 is subjected to (c) as S1.

15. The process of claim 14 , wherein (b) further comprises
(IIIa) subjecting S02 obtained from (II) to hydrogenation; and/or
(IIIb) subjecting the stream obtained from (II) or (IIIa) to distillation to obtain a bottoms stream,
wherein the hydrogenated stream obtained from (IIIa) or the bottoms stream obtained from (IIIb) is subjected to (c) as S1.

16. The process of claim 1 , wherein in (a), propene is reacted with hydrogen peroxide in the presence of a heterogeneous catalyst, said heterogeneous catalyst comprising a zeolite.

Assignees

• Basf Se
• Dow Global Technologies Llc

Inventors

• Teles Joaquim Henrique
• Riedel Dominic
• Seelig Bianca
• Kampe Philip
• Weber Markus
• Schroeder Alexander
• Parvulescu Andrei-Nicolae
• Mueller Ulrich
• Urbanczyk Daniel
• Weidenbach Meinolf
• Witzl Werner J
• Baer Holger

Classifications

• C07D303/04

  containing only hydrogen and carbon atoms in addition to the ring oxygen atoms · CPC title

• C07D301/32

  Separation; Purification · CPC title

• C07D301/12 Primary

  with hydrogen peroxide or inorganic peroxides or peracids · CPC title

• B01D3/146

  Multiple effect distillation · CPC title