Process for the synthesis of glycolonitrile
A process to prepare substantially pure glycolonitrile in an aqueous medium is provided by reacting hydrogen cyanide and formaldehyde. The formaldehyde feed stream is heated prior to reacting with hydrogen cyanide, resulting in an aqueous glycolonitrile solution with fewer impurities, especially less unreacted formaldehyde, than is obtained by other methods. The process enables production of an aqueous glycolonitrile solution that requires less post-reaction purification (if any at all) prior to enzymatically converting the glycolonitrile into glycolic acid.
1. A method for preparing glycolonitrile comprising:
a) providing an aqueous formaldehyde feed stream that is heated to a temperature of about 90° C. to about 150° C. for a determinable period of time; and
b) reacting the heated aqueous feed stream of (a) with hydrogen cyanide at a temperature suitable for glycolonitrile synthesis, whereby glycolonitrile is produced.
2. The method of claim 1 , further comprising recovering the glycolonitrile produced in step (b).
3. The method of claim 1 wherein an amount sodium hydroxide is added to the aqueous formaldehyde feed stream prior to heating the aqueous formaldehyde feed stream wherein the molar ratio of sodium hydroxide to formaldehyde is about 1:50 to about 1:2000.
4. The method of claims 1 , 2 , or 3 further comprising adding an acid to the glycolonitrile produced in step (b) to form a stabilized glycolonitrile solution.
5. The method of claim 4 , wherein the acid is glycolic acid.
6. The method of claim 4 or claim 5 wherein the stabilized glycolonitrile solution has a pH of less than 7.
7. The method of claim 6 wherein the stabilized glycolonitrile solution has a pH of less than about 4.
8. The method of claim 1 wherein the molar ratio of hydrogen cyanide to formaldehyde is at least 1.01:1.
9. The method of claim 8 wherien the molar ratio of hydrogen cyanide to formaldehyde is at least 1.01:1 to about 1.15:1.
10. The method of claim 1 wherein the aqueous formaldehyde feed stream further comprises about 0.1 wt % to about 15 wt % methanol.
11. The method according to claim 1 wherein the aqueous formaldehyde feed stream further comprises about 3 wt % to about 8 wt % methanol.
12. The method according to claim 1 wherein said temperature suitable for glycolonitrile synthesis is about 0° C. to about 70° C.
13. The method according to claim 12 wherein said temperature suitable for glycolonitrile synthesis is about 10° C. to about 30° C.
14. The method according to claim 1 wherein the aqueous formaldehyde feed stream is heated for a period of time from about 10 seconds to about 24 hours.
15. The method according to claim 14 wherein the period of time is about 10 seconds to about 20 minutes.
16. The method according to claim 15 wherein the aqueous formaldehyde feed stream is heated for a period of time from about 2 minutes to about 10 minutes.
17. The method of claim 1 wherein the resulting aqueous solution of glycolonitrile comprises less unreated formaldehyde compared to a reaction product obtained without heating the aqueous formaldehyde feed stream prior to reacting with hydrogen cyanide.
18. The method of claim 1 , wherein the glycolonitrile produced may be used for enzymatic conversion to ammonium glycolate without purification.