Anhydrosugar synthesis
Improved methods of making anhydrosugars by pyrolysis of a substrate sugar to remove at least one water molecule thereby producing a desired anhydrosugar and side products, the improvement being either 1) protecting one hydroxyl group of the substrate sugar before pyrolysis; or (2) pretreating the substrate sugar with a metal salt and optional acid before pyrolysis, wherein lower amounts of said side products are produced by said improved method.
1. A method of making an anhydrosugar, comprising:
a) dissolving a carbohydrate substrate in a solvent;
b) performing a Fischer glycosidation on the C1 carbon of said carbohydrate substrate by reacting said dissolved sugar substrate with an alcohol in the presence of a solid acid catalyst, wherein said Fischer glycosidation adds the alcohol on said C1 carbon as an ether;
c) removing said solid acid catalyst and said solvent to form a solid sample; and,
d) performing heat treatment on said solid sample to produce a desired anhydrosugar.
2. The method of claim 1 , wherein said heat treatment occurs at about 350° C. to 600° C.
3. The method of claim 1 , wherein said alcohol is alkane or aryl based.
4. The method of claim 1 , wherein said solid acid catalyst is Amberlyst-15.
5. The method of claim 1 , wherein said ether has a methyl or phenyl group.
6. The method of claim 1 , wherein said carbohydrate substrate is one or more of the following: mannose, galactose, allose, talose, glucose, pentose, hexose, sucrose, maltose, lactose, cellobiose, maltodextrins, starches, cellulose, lignocellulose, and derivatives thereof.
7. The method of claim 1 , wherein said carbohydrate substrate is a polymeric sugar and where the method is preceded by a step converting said polymeric sugar to one or more simple sugars.
8. The method of claim 1 , wherein the desired anhydrosugar is levoglucosan (C 6 H 10 O 5 ), mannosan (C 6 H 10 O 5 ), galactosan (C 6 H 10 O 5 ), levoglucosone (C 6 H 6 O 3 ) or 5-hydroxymethylfurfural (C 6 H 6 O 3 ), furfural, 1,4;3,6-Dianhydroglucose, anhydroglucofuranose or combinations thereof.