Method of separating phosgene and hydrogen chloride

Patent metadata

Field	Value
Publication number	US-2024300817-A1
Application number	US-202218277415-A
Country	US
Kind code	A1
Filing date	Feb 10, 2022
Priority date	Feb 17, 2021
Publication date	Sep 12, 2024
Grant date	—

Abstract

A process of separating phosgene and hydrogen chloride, comprises: conveying a mixed stream containing hydrogen chloride and phosgene into a distillation column; withdrawing from the distillation column a bottom stream containing phosgene; withdrawing a top stream containing hydrogen chloride; compressing at least a portion of the top stream and at least partially condensing the compressed top stream to form a liquid stream, decompressing at least a portion of the liquid stream to form a cooled liquid stream and a cooled gas stream; and recycling the cooled liquid stream to the top of the distillation column as a reflux; the process additionally comprising temporarily introducing an absorbing solvent into the distillation column, in particular during starting-up and/or shutting-down of the process. The process allows for safe operation even when hydrogen chloride production only gradually begins or decreases, without the necessity of storing hydrogen chloride.

First claim

1 .- 11 . (canceled)

12 . A process of separating phosgene and hydrogen chloride, comprising:
conveying a mixed stream containing hydrogen chloride and phosgene into a distillation column; withdrawing from the distillation column a bottom stream containing phosgene; withdrawing a top stream containing hydrogen chloride; compressing at least a portion of the top stream and at least partially condensing the compressed top stream to form a liquid stream, decompressing at least a portion of the liquid stream to form a cooled liquid stream and a cooled gas stream; and recycling the cooled liquid stream to the top of the distillation column as a reflux; the process additionally comprising temporarily introducing an absorbing solvent into the distillation column, wherein the absorbing solvent is introduced at the top of the distillation column and/or into the reflux liquid.

13 . The process according to claim 12 , wherein the absorbing solvent is introduced during starting-up and/or shutting-down of the process.

14 . The process according to claim 12 , wherein the absorbing solvent is selected from monochlorobenzene and dichlorobenzene.

15 . The process according to claim 12 , wherein the absorbing solvent is mixed with the liquid stream before decompressing and is introduced into the distillation column with the recycled cooled liquid stream.

16 . The process according to claim 12 , wherein the pressure drop during decompressing is at least 5 bar.

17 . The process according to claim 12 , wherein the mixed stream is conveyed into the distillation column as a side feed, the distillation column having a rectifying section above the side feed and a stripping section below the side feed.

18 . The process according to claim 12 , wherein the compressed top stream is directed to a rectifying column and a stream obtained at the bottom of the rectifying column is recycled to the top of the distillation column.

19 . The method according to claim 12 , wherein the liquid stream is heat-exchanged in a heat exchanger with the top stream before the top stream is compressed.

20 . The method according to claim 12 , wherein an uncondensed portion of the top stream is heat-exchanged in a heat exchanger with the compressed top stream that is to be condensed.

21 . The method according to claim 12 , comprising withdrawing a gaseous side stream from the distillation column via a side takeoff, at least partially condensing the side stream in a first cooler, recycling a liquid fraction into the distillation column and supplying a gaseous portion to a second cooler, wherein in the second cooler the gaseous portion is heat-exchanged with the top stream.

22 . The method according to claim 21 , wherein the top stream, before being fed to the second cooler, is heat-exchanged with the condensed top stream.

Assignees

• Basf Se

Inventors

• Mattke Torsten
• Thiele Kai
• Ferbitz Jens
• Van Den Abeel Peter
• Pallasch Hans-Juergen

Classifications

• C07C263/20

  Separation; Purification · CPC title

• C01B7/0731

  by extraction · CPC title

• B01D2257/2064

  Chlorine · CPC title

• B01D2256/26

  Halogens or halogen compounds · CPC title

• B01D53/002

  by condensation · CPC title