Method for preparing anhydrous sugar alcohol
The present invention relates to a method for preparing anhydrous sugar alcohol, and more particularly, to a cheap and highly efficient method for preparing anhydrous sugar alcohol having a high final purity of at least 99%, and having good ion content, pH, conductivity, and color properties. According to the method, a hydrogenated sugar is dehydrated so as to be transformed into anhydrous sugar alcohol, and a series of processes including distillation, crystallization, decoloration, and ion exchange resin treatment are conducted.
1. A method for preparation of anhydrosugar alcohol comprising the steps of:
(1) converting hydrogenated sugar to anhydrosugar alcohol by dehydration reaction;
(2) distilling the resulting liquid of the reaction of said step (1) by using a thin-film evaporator;
(3) crystallizing the resulting distillate of said step (2);
(4) decolorizing the resulting crystallite of said step (3);
(5) treating the resulting product of said step (4) with cationic ion exchange resin; and
(6) treating the resulting product of said step (5) with anionic ion exchange resin,
wherein no decolorizing is conducted after step (6),
wherein the decolorization is conducted by using active carbon and wherein the active carbon has an average particle size of from 0.25 mm to 0.75 mm, and
wherein the prepared anhydrosugar alcohol has as purity of 99% or higher, an on content of 10 ppm or less, a pH of 6 to 8, a conductivity of 10 pS/cm or less, and a YI value of 0.1 or less.
2. The method for preparation of anhydrosugar alcohol according to claim 1 , wherein the hydrogenated sugar is hexitol and the anhydrosugar alcohol is dianhydrohexitol.
3. The method for preparation of anhydrosugar alcohol according to claim 1 , wherein an acid catalyst is used in the step of converting hydrogenated sugar to anhydrosugar alcohol by dehydration reaction.
4. The method for preparation of anhydrosugar alcohol according to claim 3 , wherein the acid catalyst is a single acid catalyst selected from sulfuric acid, nitric acid, hydrochloric acid, p-toluenesulfonic acid and phosphoric acid.
5. The method for preparation of anhydrosugar alcohol according to claim 3 , wherein the acid catalyst is an acid mixture of a first acid and a second acid, where the first acid is sulfuric acid and the second acid is one or more sulfur-containing acid materials selected from the group consisting of p-toluenesulfonic acid, methanesulfonic acid, ethanesulfonic acid, benzenesulfonic acid, naphthalenesulfonic acid and aluminum sulfate.
6. The method for preparation of anhydrosugar alcohol according to claim 1 , wherein the distillation is conducted two or more times.
7. The method for preparation of anhydrosugar alcohol according to claim 1 , wherein the crystallization is conducted by using a solvent.
8. The method for preparation of anhydrosugar alcohol according to claim 1 , wherein the crystallization is conducted by a method of melt crystallization.
9. The method for preparation of anhydrosugar alcohol according to claim 1 , wherein the cationic ion exchange resin is a strong cationic ion exchange resin.
10. The method for preparation of anhydrosugar alcohol according to claim 1 , wherein the anionic ion exchange resin is a strong anionic ion exchange resin.
11. The method for preparation of anhydrosugar alcohol according to claim 1 , further comprising the step:
(7) concentrating or solidifying the resulting product of said step (6).