Acetonitrile separation process
View Patent ↗Provided herein are processes for the separation of acetonitrile from low-purity feedstock streams. The provided processes are particularly useful for isolating acetonitrile at high purity from chemical manufacturing waste streams that include methanol, water, and allyl alcohol.
1 . A process for producing acetonitrile, the process comprising:
distilling a feedstock stream in a dehydration distillation column to yield a dehydration distillate stream and a dehydration bottoms stream, wherein the feedstock stream comprises acetonitrile, acrylonitrile, allyl alcohol, and water and the dehydration distillate stream is collected as the top stream from the dehydration distillation column;
extracting the dehydration distillate stream with a caustic to hydrolyze acrylonitrile and yield an extract stream comprising water and from 0.01 wt % to 5.0 wt % of hydroxypropionitrile and a raffinate stream comprising allyl alcohol and less than 1 wt % water;
reacting allyl alcohol in the raffinate stream with a strong acid in a reactor to yield a reactor output stream;
distilling the reactor output stream in a lights removal distillation column to yield a lights removal distillate stream and a lights removal bottoms stream; and
distilling the lights removal bottoms stream in a heavies removal distillation column to yield a product acetonitrile stream containing more than 98 wt % acetonitrile.
2 . The process of claim 1 , wherein the feedstock stream comprises more than 0.02 wt % allyl alcohol, and wherein the reactor output stream comprises less than 7 ppm allyl alcohol.
3 . The process of claim 1 , wherein allyl alcohol in the raffinate stream reacts with the strong acid to form a protonated salt species.
4 . The process of claim 1 , wherein the raffinate stream further comprises oxazole, wherein oxazole in the raffinate stream reacts with the strong acid to form oxazole sulfate.
5 . The process of claim 4 , wherein the reactor output stream comprises greater than 0.01 wt % protonated salt species and/or greater than 0.1 wt % oxazole sulfate.
6 . The process of claim 1 , wherein the feedstock stream comprises more than 38 wt % water and wherein the raffinate stream comprises less than 0.4 wt % water.
7 . The process of claim 1 , wherein the strong acid comprises sulfuric acid.
8 . The process of claim 1 , wherein the mass ratio of the acetonitrile to the water in the raffinate stream is greater than 60:1.
9 . The process of claim 1 , wherein the mass ratio of the acetonitrile to allyl alcohol in the reactor output stream is greater than 100,000:1.
10 . The process of claim 1 , wherein the dehydration distillation column is operated at a pressure less than 85 kPa.
11 . The process of claim 1 , wherein the raffinate stream comprises more than 0.08 wt % allyl alcohol and/or more than 0.4 wt % oxazole.
12 . The process of claim 1 , wherein the feedstock stream and the lights removal distillate stream comprise methanol.
13 . The process of claim 1 , wherein the lights removal distillate stream comprises more than 15 wt % methanol.
14 . A process for producing acetonitrile, the process comprising:
distilling a feedstock stream comprising acetonitrile, acrylonitrile, allyl alcohol, and water in a dehydration distillation column to yield a dehydration distillate stream and a dehydration bottoms stream, the dehydration distillate stream being collected as the top stream from the dehydration distillation column;
extracting the dehydration distillate stream with a caustic to hydrolyze acrylonitrile to yield an extract stream comprising water and from 0.01 wt % to 5.0 wt % of hydroxypropionitrile and a raffinate stream comprising allyl alcohol and less than 1 wt % water;
distilling the raffinate stream in a lights removal distillation column to yield a lights removal distillate stream and a lights removal bottoms stream comprising allyl alcohol and less than 1 wt % water;
reacting allyl alcohol from the lights removal bottoms stream with a strong acid in a reactor to yield a reactor output stream comprising less than 7 ppm allyl alcohol;
and distilling the reactor output stream in a heavies removal distillation column purifying the reactor output stream to yield a product acetonitrile stream comprising greater than 98 wt % acetonitrile.
15 . The process of claim 14 , further comprising:
treating an intermediate stream comprising acetonitrile, hydrogen cyanide, and water in a digester to remove hydrogen cyanide and produce the feedstock stream.
16 . The process of claim 1 , wherein the distilling of the feedstock stream in the dehydration distillation column comprises distilling the feedstock at temperatures ranging from 60° C. to 85° C.