Tricyanohexane purification methods

Patent metadata

Field	Value
Publication number	US-11560353-B2
Application number	US-202017138591-A
Country	US
Kind code	B2
Filing date	Dec 30, 2020
Priority date	Dec 30, 2019
Publication date	Jan 24, 2023
Grant date	Jan 24, 2023

Abstract

The present disclosure relates generally to processes for recovering tricyanohexane (TCH) via purification of by-product or co-product streams of adiponitrile production. In particular, the present disclosure relates to a process for purifying tricyanohexane (TCH), the process having the steps of (a) separating an adiponitrile process stream comprising adiponitrile and TCH to form a first overhead lights stream comprising low-boiling components and high-boiling components and a first bottoms heavies stream comprising high-boiling components and solid impurities; and (b) separating the first overhead lights stream in a distillation column to form a second overhead lights stream comprising low-boiling components, a second bottoms heavies stream comprising high-boiling components, and a TCH stream comprising TCH and less than 10 wt. % impurities; wherein the distillation column is a low pressure distillation column.

First claim

We claim:

1. A process for purifying tricyanohexane (TCH), the process comprising:
a) separating an adiponitrile process stream comprising adiponitrile and TCH by flashing the adiponitrile process stream, treating the adiponitrile process stream in a wiped film evaporator, and/or treating the adiponitrile process stream in a falling film evaporator to form a first overhead lights stream comprising low-boiling components and high-boiling components and a first bottoms heavies stream comprising high-boiling components and solid impurities; and
b) separating the first overhead lights stream in one or more distillation columns to form a second overhead lights stream comprising low-boiling components, a heavies stream comprising high-boiling components, and a TCH stream comprising TCH and less than 10 wt. % impurities;
wherein the one or more distillation columns are operated at low pressure.

2. The process of claim 1 , wherein the one or more distillation columns are operated under vacuum.

3. The process of claim 1 , wherein the one or more distillation columns are operated with a column top pressure less than 100 mm Hg.

4. The process of claim 1 , wherein the one or more distillation columns are operated with a column bottom pressure less than 100 mm Hg.

5. The process of claim 1 , wherein the one or more distillation columns comprise a reboiler and the reboiler is operated at a temperature greater than 250° C.

6. The process of claim 1 , wherein the one or more distillation columns comprise a reboiler and the reboiler utilizes a hot oil system.

7. The process of claim 1 , wherein step a) is carried out at a temperature of at least 250° C.

8. The process of claim 1 , wherein the TCH stream comprises less than 1 wt. % impurities.

9. The process of claim 1 , further comprising recycling at least a portion of the bottoms heavies stream produced in step b), comprising from 5 wt. % to 40 wt. % high-boiling components.

10. The process of claim 1 , wherein step b) further comprises:
separating the first overhead lights stream in a first distillation column to form the second overhead lights stream and a second bottoms heavies stream; and
separating the second bottoms heavies stream in a second distillation column to form a third bottoms heavies stream and a third overhead stream comprising TCH.

11. The process of claim 10 , further comprising recycling at least a portion of the third bottoms heavies stream to the second bottoms heavies stream and/or to the first overhead lights stream.

12. The process of claim 1 , wherein the purified TCH stream comprises less than 0.1 wt. % impurities, less than 20 ppm water, and/or less than 5 ppm metals.

13. The process of claim 1 , wherein the adiponitrile process stream is a co-product stream produced by an adiponitrile production and/or an adiponitrile purification process.

14. The process of claim 13 , wherein the first bottoms heavies stream and/or the second overhead lights stream is recycled to the adiponitrile process stream.

15. A process for purifying TCH, the process comprising:
a) separating an adiponitrile process stream comprising adiponitrile and TCH by flashing the adiponitrile process stream, treating the adiponitrile process stream in a wiped film evaporator, and/or treating the adiponitrile process stream in a falling film evaporator to form a first overhead lights stream comprising low-boiling components and high-boiling components, and a first bottoms heavies stream comprising high-boiling components and solid impurities;
b) separating the first overhead lights stream to form a second overhead lights stream comprising low-boiling components, and a second bottoms heavies stream comprising TCH and heavies;
c) distilling the second bottoms heavies stream to form a third overhead lights stream comprising TCH and less than 5 wt. % impurities, and a third bottoms heavies stream comprising heavies;
wherein step b) or step c) comprises distilling in a low pressure distillation column.

16. A process for purifying TCH, the process comprising:
a) separating an adiponitrile process stream comprising adiponitrile and TCH to form a first overhead lights stream comprising low-boiling components and high-boiling components, and a first bottoms heavies stream comprising high-boiling components and solid impurities;
b) distilling the first overhead lights stream to form a second overhead lights stream comprising low-boiling components, a second bottoms heavies stream comprising heavies, and a side draw comprising TCH and lights;
c) separating the side draw in a flash vessel to form a third bottoms heavies stream comprising TCH and less than 5 wt. % impurities wherein step b) comprises distilling in a low pressure distillation column.

17. A process for purifying TCH, the process comprising:
a) separating an adiponitrile process stream by flashing the adiponitrile process stream, treating the adiponitrile process stream in a wiped film evaporator, and/or treating the adiponitrile process stream in a falling film evaporator to form a first overhead lights stream comprising low-boiling components and high-boiling components, and a first bottoms heavies stream comprising high-boiling components and solid impurities;
b) distilling the first overhead lights stream to form a second overhead lights stream comprising low-boiling components, and a second bottoms heavies stream comprising TCH and heavies;
c) distilling the second bottoms heavies stream to form a third distillate comprising TCH and impurities, and a third bottoms heavies stream comprising heavies; and
d) distilling the third distillate to form a fourth overhead lights stream comprising low-boiling components, and a fourth bottoms heavies stream comprising TCH and less than 5 wt. % impurities;
wherein the step b), step c), or step d) comprises distilling in a low pressure distillation column.

18. A process for purifying TCH, the process comprising:
a) separating an adiponitrile process stream to form a first overhead lights stream comprising low-boiling components and high-boiling components, and a first bottoms heavies stream comprising high-boiling components and solid impurities;
b) distilling the first overhead lights stream to form a second overhead lights stream comprising low-boiling components, and a second bottoms heavies stream comprising TCH and heavies;
c) distilling the second bottoms heavies stream to form a third distillate comprising TCH and impurities, and a third bottoms heavies stream comprising heavies; and
d) separating the third distillate in a flash vessel to form a fourth overhead lights stream comprising low-boiling components, and a fourth bottoms heavies stream comprising TCH and less than 5 wt. % impurities;
wherein step b) or step c) comprises distilling in a low pressure distillation column.

Assignees

• Ascend Performance Mat Operations Llc

Inventors

• Dube Sanjay
• Haseltine Benjamin
• Ebert Jefferson Thomas
• Elmore Darrick

Classifications

• C07C253/34 Primary

  Separation; Purification · CPC title

• C07C255/04

  containing two cyano groups bound to the carbon skeleton · CPC title

• C07C255/05

  containing at least three cyano groups bound to the carbon skeleton · CPC title