Process for recovering acetonitrile from acrylonitrile waste streams
A process for producing a high-purity acetonitrile product from a low-purity acetonitrile feedstock streams. In particular, the present disclosure relates to a process for producing a sales-grade, high purity acetonitrile by (a) distilling the feedstock stream in a to yield a crude acetonitrile stream, (b) treating the crude acetonitrile stream to produce an intermediate acetonitrile stream, (c) purifying the intermediate acetonitrile stream in a pressure swing distillation system to produce a recycle stream and an acetonitrile product stream, (d) recycling the recycle stream to the first distillation column, and (e) distilling the acetonitrile product stream to yield a purified acetonitrile product stream of at least 98 wt. % acetonitrile.
1. A process for recovering acetonitrile, comprising the steps of:
distilling a feedstock stream comprising methanol and acetonitrile present in an amount equal to or less than 10 wt % in a first distillation column to yield a crude acetonitrile stream comprising methanol,
treating the crude acetonitrile stream to remove hydrogen cyanide and produce an intermediate acetonitrile stream comprising less than 1 wt. % hydrogen cyanide,
purifying the intermediate acetonitrile stream in a pressure swing distillation system to produce an acetonitrile product stream and a recycle stream,
purifying the acetonitrile product stream to form a purified acetonitrile product stream comprising at least 98 wt. % acetonitrile,
wherein the first distillation column operates at a pressure greater than 0 psig.
2. The process of claim 1 , wherein the pressure swing distillation system comprises:
a low pressure distillation column and a high pressure distillation column and wherein the high pressure distillation column yields an overhead stream and a bottoms stream.
3. The process of claim 2 , wherein the recycle stream is the overhead stream of the high pressure distillation column.
4. The process of claim 2 , wherein the acetonitrile product stream is the bottoms stream of the high pressure distillation column.
5. The process of claim 1 , wherein the acetonitrile product stream comprises less than 1 wt. % methanol, wherein the feedstock stream further comprises oxazole and propionitrile, wherein the intermediate acetonitrile stream comprises less than 0.01 wt. % hydrogen cyanide, and wherein the purified acetonitrile product stream comprises at least 99.5 wt. % acetonitrile.
6. The process of claim 1 , further comprising the step of:
recycling the recycle stream, which comprises methanol, to the first distillation column.
7. The process of claim 1 , wherein the recycle stream comprises at least 0.01 wt. % methanol.
8. The process of claim 1 , wherein the recycle stream comprises from 0.01 wt. % to 5 wt. % methanol.
9. The process of claim 1 , wherein the purifying of the acetonitrile product stream comprises distilling the acetonitrile product stream to yield the purified acetonitrile product stream.
10. The process of claim 1 , wherein the feedstock stream comprises at least 0.05 wt. % methanol.
11. The process of claim 1 , wherein the feedstock stream comprises less than 5 wt. % acetonitrile.
12. The process of claim 1 , wherein the feedstock stream further comprises propionitrile.
13. The process of claim 1 , wherein the treating comprises reacting the crude acetonitrile stream with a caustic solution to react out hydrogen cyanide.
14. The process of claim 1 , wherein the crude acetonitrile stream comprises from 0.1 wt. % to 5 wt. % hydrogen cyanide.
15. The process of claim 1 , wherein the intermediate acetonitrile stream comprises less than 0.05 wt. % hydrogen cyanide.
16. The process of claim 1 , wherein the feedstock stream comprises one or more waste streams from acrylonitrile production processes.
17. The process of claim 2 , wherein the low pressure distillation column operates at a pressure less than −5 psig.
18. The process of claim 2 , wherein the high pressure distillation column operates at a pressure greater than 10 psig.
19. The process of claim 1 , wherein the purified acetonitrile product stream comprises at least 99.9 wt. % of acetonitrile.
20. The process of claim 1 , wherein the purified acetonitrile product stream comprises less than 0.1 wt. % of propionitrile.
21. A process for recovering acetonitrile, comprising the steps of:
distilling a feedstock stream comprising methanol and acetonitrile present in an amount equal to or less than 10 wt % in a first distillation column to yield a crude acetonitrile stream,
treating the crude acetonitrile stream to remove hydrogen cyanide and produce an intermediate acetonitrile stream comprising less than 1 wt. % hydrogen cyanide, and
purifying the intermediate acetonitrile stream in a pressure swing distillation system to produce a recycle stream and an acetontrile product stream comprising at least 90 wt. % acetonitrile,
wherein the first distillation column operates at a pressure greater than 0 psig.
22. The process of claim 1 , wherein the feedstock stream comprises from 0.01 wt. % to 1 wt. % methanol.
23. The process of claim 21 , wherein the feedstock stream comprises from 0.01 wt. % to 1 wt. % methanol.