Production of glycolaldehyde by hydrous thermolysis of sugars
The present invention provides a method for the production of glycolaldehyde with high specificity. The hydrous thermolysis consists of the spraying of aqueous sugar solutions containing from 25 to 80% of water but preferably 30 to 60% water, as a fine mist into a reactor held at the between 500 and 600° C., but preferably between 520 and 560° C. and the condensation of the resulting vaporous product in a surface condenser with optional heat recovery. The residence time of the vaporous product in the reactor should be in the range 0.1–5 seconds, but preferably in the range 0.5 to 2 seconds. Aldose monomeric sugars, preferably glucose (also known as dextrose), are preferred for use in the aqueous solution. The yield of glycolaldehyde in the condensed liquid is minimum 50% by weight of the sugar fed for glucose solutions.
1. A method for the production of glycolaldehyde by hydrous thermolysis comprising the steps of:
a) preparing an aqueous sugar solution, from an aldose-containing sugar selected from the group consisting of glucose and sucrose;
b) atomizing said aqueous sugar solution;
c) injecting said atomized aqueous sugar solution into a reactor heated between 500 and 600° C., creating a vaporous pyrolysis product;
d) cooling said vapourous pyrolysis product in a condenser, obtaining a liquid condensate;
e) collecting said liquid condensate into a holding tank to yield a glycolaldehyde-rich liquid; and
f) filtering the glycolaldehyderich liquid, wherein the resulting yield of glycolaldehyde is at least 30% by weight of the sugar used in the aqueous solution.
2. The method of claim 1 , including an additional step (g), wherein said glycolaldehyde-rich liquid is contacted by activated carbon to remove coloured organic components.
3. The method of claim 1 , wherein said aqueous sugar solution contains water in the range of 25% to 99% by weight.
4. The method of claim 1 , wherein said aqueous sugar solution contains water in the range of 30% to 70% by weight.
5. The method of claim 1 , wherein said atomized aqueous sugar solution has droplets of a diameter less than 200 microns.
6. The method of claim 1 , wherein said atomized aqueous sugar solution has droplets of a diameter less than 50 microns.
7. The method of claim 1 , wherein said reactor is heated to a temperature in the range of 520 to 560° C.
8. The method of claim 1 , including filtering said liquid LO condensate after said cooling step and before collecting in said holding tank.
9. The method according to claim 1 , wherein the glycolaldehyde-rich liquid of step (e) has a glycolaldehyde percentage by weight to °Brix ratio greater than 0.5.
10. The method according to claim 2 , wherein the glycolaldehyde-rich liquid of step (e) has a glycolaldehyde percentage by weight to °Brix ratio greater than 0.5.
11. A method for the production of glycolaldehyde by hydrous thermolysis comprising the steps of:
a) preparing an aqueous sugar solution from glucose containing water in the range of 30% to 70% by weight;
b) atomizing said aqueous sugar solution into droplets of a diameter of less than 50 microns;
c) injecting said atomized aqueous sugar solution into a reactor heated between 520 and 560° C., creating a vapourous pyrolysis product;
d) cooling said vapourous pyrolysis product in a condenser, obtaining a liquid condensate;
e) collecting said liquid condensate into a holding tank to yield a glycolaldehyde-rich liquid; and
f) filtering said glycolaldehyde-rich liquid, wherein the resulting yield of glycolaldehyde is at least 50% by weight of the glucose used in the aqueous solution.
12. The method of claim 11 , including an additional step (g), wherein said glycolaldehyde-rich liquid is contacted by activated carbon to remove coloured organic components.