Acetonitrile separation process
A process for producing acetonitrile, the process comprising dehydrating a feedstock stream comprising acetonitrile, acrylonitrile, allyl alcohol, and water (and optionally methanol) in a dehydration (first) column to yield a dehydrated acetonitrile stream comprising acetonitrile and acrylonitrile, less than 1 wt % allyl alcohol, and less than 50 wt % water, and optionally hydrogen cyanide; distilling the dehydrated acetonitrile stream in a lights (second) column to yield a distillate stream comprising lights, and a bottoms stream comprising acetonitrile, acrylonitrile, water, and optionally hydrogen cyanide and acrylonitrile; extracting the distillation bottoms stream in an extraction (third) column to yield a raffinate stream comprising acetonitrile and less than 200 ppm acrylonitrile and an extract stream comprising water and acrylonitrile; purifying the raffinate stream to yield a product acetonitrile stream.
1 . A process for producing acetonitrile, the process comprising:
dehydrating a feedstock stream comprising acetonitrile, acrylonitrile, allyl alcohol, and water in a dehydration (first) column to yield a dehydrated acetonitrile stream comprising acetonitrile and acrylonitrile, less than 1 wt % allyl alcohol, and less than 50 wt % water, and optionally hydrogen cyanide;
distilling the dehydrated acetonitrile stream in a lights (second) column to yield a lights distillate stream comprising lights, and a bottoms stream comprising acetonitrile, water, and optionally hydrogen cyanide and acrylonitrile;
extracting the bottoms stream in an extraction (third) column to yield a raffinate stream comprising acetonitrile and less than 200 ppm acrylonitrile and an extract stream comprising water and acrylonitrile; and
purifying the raffinate stream to yield a product acetonitrile stream.
2 . The process of claim 1 , wherein the dehydration is conducted at a pressure less than 150 kPa.
3 . The process of claim 1 , wherein the feedstock stream comprises methanol.
4 . The process of claim 1 , wherein an accelerator is utilized during the extracting.
5 . The process of claim 1 , wherein the bottoms stream comprises from 0.1 wt % to 20 wt % methanol.
6 . The process of claim 1 , wherein the raffinate stream comprises less than 25 ppm acrylonitrile.
7 . The process of claim 1 , wherein the raffinate stream comprises less than 200 ppm hydrogen cyanide and less than 50 wt % water.
8 . The process of claim 1 , wherein the raffinate stream comprises less than 1 wt % metal cyanide.
9 . The process of claim 1 , wherein the dehydration yields a water stream comprising water, allyl alcohol, methanol, and heavies.
10 . The process of claim 1 , wherein the dehydrated acetonitrile stream comprises less than 20 wt % polymerized HCN.
11 . The process of claim 1 , wherein the dehydrated acetonitrile stream comprises less than 25 wt % heavies.
12 . The process of claim 1 , wherein the lights distillate stream comprises oxazole, methanol, and/or acrylonitrile.
13 . The process of claim 1 , wherein lights bottoms stream further comprises acetonitrile-water azeotrope composition.
14 . The process of claim 1 , wherein the extraction is conducted countercurrently.
15 . The process of claim 1 , wherein the raffinate stream comprises less than 25 wt % water and less than 50 ppm acrylonitrile.
16 . The process of claim 1 , wherein the purifying comprises distilling the raffinate stream in a drying (fourth) column to yield an overhead stream comprising acetonitrile-water azeotrope and a second bottoms stream comprising acetonitrile and less than 75 ppm water.
17 . The process of claim 16 , further comprising recycling the overhead stream to the dehydration column.
18 . The process of claim 16 , wherein the purifying further comprises distilling the second bottoms stream in a product (fifth) column to yield the product acetonitrile stream comprising greater than 99.99 wt % acetonitrile.
19 . The process of claim 18 , wherein the second bottoms stream comprises propionitrile and less than 5 wt % water and wherein the distilling in the product column yields the product acetonitrile stream as a second overhead stream and a third bottoms stream comprising propionitrile and optionally heavies.
20 . The process of claim 1 , wherein the dehydration is conducted at a pressure less than 100 kPa.