Tricyanohexane purification methods
View Patent ↗Provided herein are processes for purifying TCH in a feed stream, such as an adiponitrile process stream. The processes include a first separating step of separating the adiponitrile process stream to form a first overhead stream comprising low-boiling components and high-boiling components and a first bottoms stream comprising high-boiling components. The processes also include a second separating step of separating the first overhead stream in one or more distillation columns to form a lights stream comprising low-boiling components, a heavies stream comprising high-boiling components, and a TCH stream.
1. A process for purifying TCH, the process comprising:
a first separating step of separating a feed stream to form a first overhead stream comprising low-boiling components and high-boiling components and a first bottoms stream comprising high-boiling components and solid impurities; and
a second separating step of separating the first overhead stream in one or more distillation columns to form a lights stream comprising low-boiling components, a heavies stream comprising high-boiling components, and a TCH stream comprising TCH, from 0 wt. % to 0.05 wt. % adiponitrile, from 0 wt. % to 0.1 wt. % di(2-cyanoethyl) amine, from 0 wt. % to 0.05 wt. % cyanovaleramide, and from 0 wt. % to 0.05 wt. % tri(2-cyanoethyl) amine, and less than 10 wt. % additional impurities; and
wherein the residence time of the first overhead stream in temperatures above 230° C. in any column at any step in the process is less than 8 hours.
2. The process of claim 1 , wherein the first overhead stream comprises less than 20 wt. % heavies.
3. The process of claim 1 , wherein the TCH stream comprises less than 1 wt. % additional impurities.
4. The process of claim 1 , wherein the residence time of the first overhead stream in pressures above 50 torr is less than 8 hours.
5. The process of claim 1 , further comprising recycling at least a portion of the heavies stream.
6. The process of claim 1 , wherein the second separating step further comprises:
separating the first overhead stream in a distillation column to form the lights stream as a second overhead stream and a second bottoms stream; and
separating the second bottoms stream in a distillation column to form the heavies stream as a third bottoms stream and the TCH stream as a third overhead stream.
7. The process of claim 6 , further comprising recycling at least a portion of the third bottoms stream.
8. The process of claim 7 , wherein the recycling comprises recycling at least a portion of the third bottoms stream to the second bottoms stream and/or to the first overhead stream.
9. The process of claim 7 , wherein the recycled stream comprises from 0 wt. % to 40 wt. % high-boiling components.
10. The process of claim 7 , wherein the recycling controls the concentration of high-boiling components in the first overhead stream to be from 0 wt. % to 10 wt. %.
11. The process of claim 1 , further comprising a treating step of treating the TCH stream to form a purified TCH stream.
12. The process of claim 11 , wherein the treating step comprises nitrogen stripping or treating with a molecular sieve.
13. The process of claim 11 , wherein the purified TCH stream comprises less than 0.1 wt. % impurities, less than 20 ppm water, and/or less than 5 ppm metals.
14. The process of claim 1 , wherein the first separating step comprises flashing the feed stream or treating the feed stream in a wiped film evaporator.
15. The process of claim 1 , wherein less than 50 wt. % of high-boiling components in the first overhead stream decompose into low-boiling components during the second separating step.
16. The process of claim 1 , wherein the feed stream is a co-product stream produced by an adiponitrile production and/or an adiponitrile purification process.
17. The process of claim 16 , wherein the first bottoms stream and/or the lights stream is recycled to the adiponitrile production and/or the adiponitrile purification process.