Method for preparing high-purity anhydrosugar alcohol using sequential combination of thin film distillation and short path distillation
The present invention relates to a technique for preparing an anhydrosugar alcohol using hydrogenated sugar as a raw material and, more specifically, to a technique for preparing a high-purity anhydrosugar alcohol (in particular, isosorbide, isomannide, isoidide, and the like) having a purity of 98% or higher and containing less than 0.1% of sorbitol and a sorbitan isomer, which are impurities, in a high total distillation yield of 94% or higher (more preferably, 95% or higher) by adding an acid to hydrogenated sugar (for example, hexitol) to convert same to an anhydrosugar alcohol, and then distilling the converted liquid over two or more stages by sequentially using a combination of an external condenser type wiped film evaporator and an internal condenser type short path evaporator.
1. A method for producing anhydrosugar alcohol comprising the steps of:
converting hydrogenated sugar to anhydrosugar alcohol by dehydration reaction, and
distilling the resulting liquid of the converting step in two or more stages by sequential use of a combination of an external condenser type, wiped-film evaporator and an internal condenser type, short-path evaporator.
2. The method for producing anhydrosugar alcohol according to claim 1 , wherein the internal condenser type, short-path evaporator comprises an internal condenser, an input line for raw material, an output line for distillation residue, a vacuum line and an output line for distillate.
3. The method for producing anhydrosugar alcohol according to claim 2 , wherein when the distilling step is conducted with using the internal condenser type, short-path evaporator, the inside of the evaporator is depressurized by pressure reduction through the vacuum line and additionally through the output line for distillation residue.
4. The method for producing anhydrosugar alcohol according to claim 2 , wherein when the distilling step is conducted with using the internal condenser type, short-path evaporator, the degree of vacuum of the vacuum line is the same as the degree of vacuum of the output line for distillation residue.
5. The method for producing anhydrosugar alcohol according to claim 1 , wherein the hydrogenated sugar is hexitol and the anhydrosugar alcohol is dianhydrohexitol.
6. The method for producing 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.
7. The method for producing anhydrosugar alcohol according to claim 1 , wherein the resulting liquid of the step of converting hydrogenated sugar to anhydrosugar alcohol is pre-treated to remove moisture and low-boiling-point substance before being fed to the first distilling step.
8. The method for producing anhydrosugar alcohol according to claim 1 , wherein the distillation using the external condenser type, wiped-film evaporator is conducted under a temperature condition of from 120 to 250° C.
9. The method for producing anhydrosugar alcohol according to claim 1 , wherein the distillation using the external condenser type, wiped-film evaporator is conducted under a pressure condition of 10 mmHg or less.
10. The method for producing anhydrosugar alcohol according to claim 1 , wherein the distillation using the internal condenser type, short-path evaporator is conducted under a temperature condition of from 100 to 250° C.
11. The method for producing anhydrosugar alcohol according to claim 1 , wherein the distillation using the internal condenser type, short-path evaporator is conducted under a pressure condition of 10 mmHg or less.
12. The method for producing anhydrosugar alcohol according to claim 1 , wherein the distillate after the distilling step of two or more stages has an anhydrosugar alcohol purity of 98% or higher, a content of sorbitol and sorbitan isomer as impurities of less than 0.1%, and a distillation yield of 94% or higher.
13. The method for producing anhydrosugar alcohol according to claim 1 , wherein after the distilling step of two or more stages, a step of post-treatment is further conducted for the anhydrosugar alcohol resulting from the distillation, and wherein the post-treatment is selected from crystallization, adsorbent treatment, ion purification, and a combination thereof.