Method of oxidizing glycolaldehyde using nitric acid
The present invention relates to a method of synthesizing at least one organic acid comprising oxidizing glycolaldehyde with nitric acid in the presence of a solvent. Advantageously, it is an industrially applicable process, which prepares organic acid, notably glycolic acid and/or glyoxylic acid in a high yield based on bio-based feedstocks.
1. A method of synthesizing at least one organic acid comprising oxidizing glycolaldehyde with nitric acid in the presence of a solvent, selected from the list consisting of water, ether, methanol and ethanol, and wherein the organic acid is glycolic acid, glyoxylic acid or a mixture thereof.
2. The method according to claim 1 , wherein glycolaldehyde is oxidized with nitric acid in the presence of an initiator.
3. The method according to claim 2 , wherein the initiator is a nitrite salt.
4. The method according to claim 3 , wherein the initiator nitrite salt is selected from the group consisting of ammonium nitrite, sodium nitrite, potassium nitrite, lithium nitrite or a mixture thereof.
5. The method according to any one of claim 1 , wherein the organic acid is or comprises glycolic acid and glycolaldehyde is oxidized into glycolic acid according to reaction Scheme 1:
wherein the concentration of nitric acid in the solvent is higher than 20 wt. %.
6. The method according to claim 5 , wherein the selectivity to glycolic acid is of at least 70% and the yield to glycolic acid is of at least 70%.
7. The method according to claim 5 , wherein the concentration of nitric acid in the solvent is from 30 wt. % to 60 wt. %.
8. The method according to any one of claim 1 , wherein the organic acid is or comprises glyoxylic acid and glycolaldehyde is oxidized into glyoxylic acid according to reaction Scheme 2:
wherein the concentration of nitric acid in the solvent is equal to or lower than 30 wt. %.
9. The method according to claim 8 , wherein the selectivity to glyoxylic acid is of at least 45% and the yield to glyoxylic acid is higher than 20%.
10. The method according to claim 8 , wherein the concentration of nitric acid in the solvent is from 5 wt. % to 30 wt. %.
11. A mixture comprising glycolaldehyde, nitric acid and a solvent selected from the list consisting of water, ether, methanol and ethanol.
12. The mixture according to claim 11 , which further comprises an initiator.
13. The mixture according to claim 12 , wherein the initiator is a nitrite salt.
14. The mixture according to claim 13 , wherein the nitrite is a nitrite salt selected from the group consisting of ammonium nitrite, sodium nitrite, potassium nitrite, lithium nitrite and mixtures thereof.