Method for producing sugar anhydride and saccharide
A method for producing sugar anhydride, comprising: (1) first heat treatment step of heating polysaccharide having reducing end group at 130-350° C. in the presence of C1-C10 alcohol compound free of an acetal structure; (2) second heat treatment step of heating the first heat treated polysaccharide for pyrolysis to form a gaseous sugar anhydride, the second heat treatment forming no char or only filmy char and forming no carbon monoxide or some carbon monoxide such that the amount of carbon monoxide formed is not more than 5 parts by weight per 100 parts by weight of the absolute dry weight of the polysaccharide; and (3) recovery step of cooling the gaseous sugar anhydride to a temperature not higher than the boiling point thereof. According to this method, sugar anhydride can be easily produced at a high yield.
1 . A method for producing a sugar anhydride, comprising:
(1) a first heat treatment step of heating a raw material, polysaccharide having a reducing end-group at a temperature of from 280° C. to 350° C. in the presence of an alcohol compound of 1 to 10 carbon atoms free of an acetal structure,
(2) a second heat treatment step of heating the first heat treated polysaccharide for pyrolysis to form a gaseous sugar anhydride, the second heat treatment forming no char or only filmy char and forming no carbon monoxide or some carbon monoxide such that the amount of carbon monoxide formed is not more than 5 parts by weight per 100 parts by weight of the absolute dry weight of the second heat treated polysaccharide, and
(3) a recovery step of cooling the gaseous sugar anhydride to a temperature not higher than the boiling point thereof and recovering the sugar anhydride.
2 . The method of claim 1 wherein the second heat treatment step includes irradiating infrared radiation for heating.
3 . The method of claim 1 wherein in the second heat treatment step, the first heat treated polysaccharide is heated for 60 seconds at the longest.
4 . The method of claim 1 wherein in the second heat treatment step, the bulk temperature of the second heat treated polysaccharide itself is 400 to 500° C.
5 . The method of claim 1 wherein the alcohol compound of 1 to 10 carbon atoms free of an acetal structure is at least one compound selected from monohydric aliphatic alcohols of 1 to 3 carbon atoms, alkylene glycols of 2 or 3 carbon atoms, and glycerin.
6 . The method of claim 1 wherein the raw material, polysaccharide having the reducing end-group is cellulose.
7 . The method of claim 1 wherein the sugar anhydride is levoglucosan.
8 . The method of claim 1 wherein the raw material, polysaccharide is in sheet, powder, fiber, or particle form.
9 . The method of claim 1 wherein the raw material, polysaccharide is a raw material consisting essentially of polysaccharide having a reducing end-group.