KR20140059904A - Method for producing highly pure anhydrosugar alcohols with improved yield by using redistillate of waste generated from crystallization procedure - Google Patents

Abstract

The present invention relates to a method for producing anhydrosugar alcohol using a sugar hydride as a raw material, and more specifically, to a method for producing a high purity anhydrosugar alcohol by adding an acid in a sugar hydride (i.e. hexitol) to convert into an anhydrosugar alcohol followed by distilling a resulting liquid of the conversion reaction and crystallizing the result liquid of the distillation reaction in a solvent. The method comprises: removing the distillation solvent from a crystallization mother liquor generated from the crystallization process, distilling a result of the removal to obtain a redistillate, and putting the redistillate (1) in a distillation process of distilling the result liquid of the conversion reaction, or (2) in a crystallization process of the result liquid of the distillation reaction (3) in a post purification process after independently recrystallizing the same, or (4) right in a post purification process, to raise a total yield of the anhydrosugar alcohol, further to reduce the amount of waste generation and the costs of processing so that the technique of the present invention can produce a high purity anhydrosugar alcohol with low costs and high efficiency.

Description

FIELD OF THE INVENTION [0001] The present invention relates to a method for producing a high purity, free alcohol free from anhydrous anhydrous alcohols by using a re-distillate of a crystallization process waste,

The present invention relates to a process for preparing anhydrosugar alcohol from a hydrogenated sugar as a raw material, and more particularly, to a process for producing anhydrosugar alcohol by converting anhydride sugar (for example, hexitol) A method for producing a high purity, free alcohol without distillation by distilling a liquid resulting from the conversion reaction and crystallizing the resulting liquid in a solvent, the method comprising: removing a crystallization solvent from a crystallization mother liquor generated in a crystallization step, (1) introducing the distillate into a distillation stage of the liquid resulting from the conversion reaction, (2) introducing the distillate into a crystallization stage of the distillation result liquid, (3) independently recrystallizing the same, (4) immediately after completion of the purification step, the total yield of alcohol-free alcohol can be improved, and further, the amount of waste generated and the cost of treatment can be reduced There, low cost, to a technique capable of producing the anhydrosugar alcohol of high purity with high efficiency.

Hydrogenated sugar (also referred to as " sugar alcohol ") refers to a compound obtained by adding hydrogen to a reducing end group of a saccharide, generally HOCH ₂ (CHOH) _n CH ₂ OH (where n is an integer of 2 to 5 ), And classified into tetritol, pentitol, hexitol and heptitol (C 4, 5, 6 and 7, respectively), depending on the number of carbon atoms. Among them, hexitol having 6 carbon atoms includes sorbitol, mannitol, iditol, galactitol and the like, and sorbitol and mannitol are particularly useful substances.

Anhydrosugar alcohol has a diol form with two hydroxyl groups in the molecule and can be prepared by utilizing hexitol derived from starch (for example, Korean Patent No. 10-1079518, Korean Patent Laid- -2012-0066904). Since alcohol-free alcohol is an eco-friendly substance derived from renewable natural resources, there has been much interest for a long time and studies on the manufacturing method have been carried out. Among these alcohol-free alcohols, isosorbide prepared from sorbitol has the widest industrial application currently.

The use of anhydrous alcohol is widely used in the treatment of cardiovascular diseases, patches, adhesives, oral cleansers and the like, solvents for compositions in the cosmetics industry, and emulsifiers in the food industry. In addition, it is possible to increase the glass transition temperature of a polymer substance such as polyester, PET, polycarbonate, polyurethane, and epoxy resin, to improve the strength of these materials, and to be an environmentally friendly material derived from natural materials. useful. It is also known to be used as an environmentally friendly solvent for adhesives, environmentally friendly plasticizers, biodegradable polymers, and water-soluble lacquers.

As such, alcohol-free alcohol has attracted a great deal of attention due to its versatility and its use in real industry is increasing. However, the conventional method of producing an alcohol-free alcohol has a high catalyst cost for dehydration and low conversion, distillation and purification yield. In addition, when crystallizing a nonaqueous alcohol by using a solvent, the loss of the target material is significant and a large amount of waste is generated, which is economically and environmentally problematic.

DISCLOSURE OF THE INVENTION An object of the present invention is to solve the problems of the prior art described above, and it is an object of the present invention to provide a process for producing a highly pure alcohol free alcohol by converting a hydrogenated sugar to an alcohol free alcohol after distillation, It is possible to improve the total yield of the alcohol without sugar, improve the distillation efficiency by improving the flowability of the distillate in some cases, further reduce the amount of waste generated and the cost of the treatment, The present invention also provides a process for producing a high-purity alcohol-free alcohol.

In order to solve the above-mentioned technical problems, the present invention provides a process for producing a polyhydric alcohol, comprising the steps of: dehydrating a hydrogenated sugar to convert it into a dihydric alcohol; Distilling the liquid resulting from the conversion reaction; And crystallizing the resultant solution in a solvent, wherein the crystallization solvent is removed from the crystallization mother liquor generated in the crystallization step, and the resultant is distilled to remove the re-distillate (1) introducing the distillate into the distillation stage of the liquid resulting from the conversion reaction, (2) introducing the distillate into the crystallization stage of the distillation liquid, (3) independently recrystallizing and then introducing the distillate into a subsequent purification step , And (4) directly into a subsequent purification step.

According to the present invention, the total yield of alcohol-free alcohol can be improved, and when the re-distillate of the mother liquor is fed to the distillation step of the liquid resulting from the conversion reaction, the flowability of the distillate can be improved, Waste generation amount and treatment cost can also be reduced. Therefore, the process for producing an alcohol-free alcohol of the present invention can be particularly useful for a large-scale commercial alcohol-free alcohol production process employing distillation and solvent crystallization.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic view showing one preferred embodiment of a condenser built-in thin film still structure which can be used in the method for producing alcohol-free alcohol of the present invention. FIG.

Hereinafter, the present invention will be described in detail.

The method for producing an alcohol-free alcohol of the present invention includes a step of dehydrating a hydrogenated sugar to convert it to an alcohol-free alcohol.

The hydrogenated sugar is generally referred to as sugar alcohol and means a compound obtained by adding hydrogen to the reducing end group of the saccharide. Hydrogenated sugars are classified into tetritol, pentitol, hexitol and heptitol (C 4, 5, 6 and 7, respectively) depending on the number of carbon atoms. Among them, hexitol having 6 carbon atoms includes sorbitol, mannitol, iditol, galactitol and the like, and sorbitol and mannitol are particularly useful substances.

As used herein, the expression ' anhydrous alcohol ' refers to any material obtained by removing one or more water molecules from the original internal structure of the hydrogenated sugar (or sugar alcohol) in one or more steps in any manner.

In the present invention, hexitol is preferably used as the hydrogenating sugar, more preferably hydrogenated sugar selected from sorbitol, mannitol, editol, and mixtures thereof.

Therefore, in the present invention, dianhydrohexitol, which is a dehydrate of hexitol, is obtained as the above-mentioned alcohol without sugar, more preferably isosorbide (1,4-3,6-dianhydrosorbitol), iso Anhydrous alcohol selected from mannide (1,4-3,6-dianhydro mannitol), isodide (1,4-3,6-dianhydride) and mixtures thereof is obtained. Of these, isosorbide is particularly high in industrial and medicinal applications.

The hydrogenated sugar is converted to a dihydric alcohol by dehydration reaction. There is no particular limitation on the method of dehydrogenating the hydrogenated sugar, and known methods known in the art can be used as it is or modified appropriately.

The acid catalyst is preferably used for dehydrating the hydrogenated sugar and converting it into anhydrosugar alcohol. More preferably, a mixed acid of the first acid and the second acid can be used. As the acid catalyst, sulfuric acid, hydrochloric acid, phosphoric acid and the like can be used in the case of a single acid catalyst, and sulfuric acid as a primary acid and p-toluenesulfonic acid, methanesulfonic acid, ethanesulfonic acid, benzene At least one sulfur-containing acid salt selected from the group consisting of sulfonic acid, naphthalenesulfonic acid and aluminum sulfate can be used. The amount of the acid catalyst to be used is preferably 0.5 to 10 parts by weight per 100 parts by weight of hydrogenated sugar (e.g., hexitol). If the amount of the acid catalyst is excessively smaller than this range, the conversion time to the alcohol without sugar alcohol may become too long, whereas if the amount of the acid catalyst is excessively larger than this range, the production of the saccharide polymer increases, have.

According to one embodiment of the present invention, the step of converting the hydrogenated sugar into anhydrosugar alcohol is carried out in the presence of an acid catalyst as described above at a temperature of 105-200 占 폚 (more preferably 110-150 占 폚) and 1 to 100 mmHg (More preferably, 1 to 50 mmHg) for 1 to 10 hours (more preferably, 2 to 5 hours), but the present invention is not limited thereto.

In the case of using an acid catalyst in the dehydrogenation reaction of the hydrogenated sugar, it is preferable that the reaction liquid is neutralized. Neutralization can be performed by lowering the temperature of the reaction liquid after completion of the dehydration reaction (for example, 100 ° C or less) and adding a known alkali such as sodium hydroxide. The pH of the solution is preferably 6 to 8 as a result of the neutralization reaction.

According to one preferred embodiment of the process for preparing anhydrosugar alcohol of the present invention, the liquid resulting from the conversion of the hydrogenated sugar to the anhydride alcohol can be pretreated prior to introduction into the distillation stage. This pretreatment is intended to remove moisture and low boiling matter remaining in the liquid resulting from the conversion step, and the resulting liquid is subjected to a conversion step at a temperature of 90 ° C. to 110 ° C. and a pressure of 10 mmHg to 100 mmHg for 1 hour or more , 1 to 4 hours), but is not limited thereto.

The result of the conversion reaction (preferably the resultant solution as described above) is then subjected to a distillation, preferably a thin-film distillation step.

Preferably, the distillation step is carried out in a condenser built-in thin film still containing a built-in condenser, a feed line, a distillation residue discharge line, a vacuum line and a distillate discharge line.

More preferably, the distillation is further depressurized through the distillation residue discharge line together with the depressurization through the vacuum line during the distillation using the condenser built-in thin film still.

A preferred embodiment of the condenser built-in thin film still structure that can be used in the method for producing an alcohol-free alcohol of the present invention is schematically shown in Fig. The condenser built-in thin film still 1 according to Fig. 1 comprises an internal condenser 5, a raw material input line 6, a distillation residue discharge line 7, a vacuum forming side branch line 7-1, a vacuum line 8, And a distillate discharge line 9 and a heating jacket 2, a wiper 3, a condenser guard 4 and cooling water inlet / outlet lines (10 and 11, respectively) . The condenser built-in type thin film still that can be used in the present invention is not limited to the structure shown in FIG. 1, and may further include additional components as needed in addition to the above-described components.

In a preferred embodiment of the present invention, there is no particular limitation on the method of further depressurizing the inside of the still through the distillation residue discharge line. For example, a vacuum pump connected to a vacuum line may be connected to the side line for vacuum formation of the residue discharge line so that the same degree of vacuum is applied to the distillation residue discharge line and the vacuum line, or alternatively, the vacuum formation of the distillation residue discharge line A separate vacuum pump may be connected to the side branch line to provide a degree of vacuum independent of the vacuum line.

The distillation step can be effectively carried out under temperature conditions of preferably 100 to 250 DEG C, more preferably 100 to 200 DEG C, and still more preferably 110 to 170 DEG C. [ If the distillation temperature is less than 100 ° C, the distillation of alcohol without sugar can not be effected effectively. On the other hand, when the distillation temperature is higher than 250 ° C, the alcohol without sugar is carbonized, a polymer substance is formed, the color becomes dark due to the formation of a coloring material, By-products such as furfural and the like are formed. This leads to lowering of the purity and pH of the liquid resulting from distillation, which is not preferable from an industrial viewpoint.

(For example, 0.0001 to 10 mmHg, more specifically 0.0001 to 8 mmHg) and preferably 5 mmHg or less (for example, 0.001 to 10 mmHg) in the distillation step under the above- 5 mmHg), more preferably 1 mmHg or less (for example, 0.01 to 1 mmHg, more specifically 0.01 to 0.8 mmHg). If the distillation pressure is higher than 10 mmHg, the distillation temperature must be increased in order to distill the alcohol without alcohol, and the above-described problems may arise. On the other hand, in order to lower the distillation pressure, a high vacuum apparatus cost is further required, and distillation purity is lowered, so that an excessively low distillation pressure is not preferable.

The distillate obtained as a result of the distillation step is then subjected to a crystallization step using a solvent.

As the solvent used for crystallization, for example, one or more organic solvents such as acetone, ethyl acetate, toluene, benzene, xylene, and alcohol (for example, isopropyl alcohol) may be used. According to a preferred embodiment of the present invention, acetone or an alcohol (for example, isopropyl alcohol) is used as a crystallization solvent.

There are no particular restrictions on the crystallization method and apparatus, and methods and apparatuses that have been known in the art for a long time can be used as is or modified appropriately. Specifically, for example, when the distillate obtained as a result of the distillation step is dissolved in a solvent such as acetone, ethyl acetate, toluene, benzene, xylene, alcohol or the like according to need, and the temperature of the solution is lowered, Precipitation can be used. The amount of the solvent used and the temperature for raising / lowering the cooling rate can be appropriately determined according to the throughput and the specific equipment conditions. According to a preferred embodiment of the present invention, acetone is used as a solvent, the weight ratio of the solvent to the distillate free alcohol alcohol solution is adjusted to 10: 1 to 1: 1, and then the temperature of the solution is raised to 30 ° C or higher Followed by cooling to 10 ° C or lower to precipitate an alcohol-free alcohol crystal.

The precipitated alcohol-free alcohol crystals are separated from the crystallization mother liquor through filtration or the like and, if necessary, are subjected to a further additional purification step.

On the other hand, in the present invention, the crystallization solvent is removed from the crystallization mother liquor generated in the crystallization step.

There is no particular limitation on the method and apparatus for removing the solvent from the crystallization mother liquor, and methods and apparatuses that have been known in the art for a long time can be used as is or modified appropriately. There is no particular limitation on the solvent removal conditions. When a rotary evaporator is used, it is preferable to use a rotary evaporator under reduced pressure (for example, under a pressure of 250 torr or less The solvent may be removed by treating the crystallization mother liquor for an appropriate period of time (e.g., 30 minutes to 3 hours). When a thin film still is used, the solvent can be continuously removed.

The purity of alcohol-free alcohol in the resultant product after removing the solvent is preferably 75% or more. If the purity is less than 75%, the total yield improvement effect may be insufficient.

In the present invention, the resultant product obtained by removing the crystallization solvent from the crystallization mother liquor (hereinafter also referred to as " concentrated crystallization mother liquor ") is distilled to obtain a redistilled product. The distillation for obtaining such a re-distillation can be preferably carried out using a batch distiller or a thin film still, and the thin film still can be a wiped type evaporator (external condenser type) A condenser built-in type short-tube evaporator (internal condenser type) may be used. The distiller for obtaining the re-distillate is preferably equipped with two or more stages of multi-stage (more specifically, 2 to 15 stages) packing columns, more preferably 3 to 10 stages of packing columns. The temperature and pressure conditions of the distillation step for obtaining the re-distillate may be appropriately selected according to the given equipment and process conditions, and may be selected, for example, from 100 to 250 ° C (more specifically, from 100 to 220 ° C, (For example, 0.001 to 10 mmHg), more specifically, 5 mmHg or less (for example, 0.01 to 5 mmHg ) (Pressure inside the distiller) may be selected but not limited thereto.

The purity of alcohol-free alcohol in the thus-obtained crystallization mother liquor distillate is preferably 95% or higher, more preferably 98% or higher, and still more preferably 99% or higher. If the purity is less than 95%, the total yield improvement effect may be insufficient.

The re-distillate is then fed into the distillation stage of the liquid resulting from the conversion reaction, (2) into the crystallization stage of the distillation liquid, (3) independently recrystallized and then introduced into the subsequent purification stage, (4) immediately into the subsequent purification step. Hereinafter, specific examples will be described.

When the crystallization mother liquor distillate is fed into the distillation stage of the liquid resulting from the conversion reaction [the above (1)], it may be fed alone or, if necessary, fed with the distillation result liquid not fed into the crystallization stage after the distillation stage . When it is added together with the distillation result liquid, the weight ratio of the crystallization mother liquor distillate: distillation resultant is not particularly limited and may be appropriately selected within the range of, for example, 9: 1 to 1: 9. There is also no particular limitation on the amount of the crystallization mother liquor distillate (or a mixture of the crystallization mother liquor distillate and the distillation result liquid) charged in the distillation step. For example, 100 parts by weight of the conversion reaction distilled in the same step Can be appropriately selected within a range of 5 to 50 parts by weight (more specifically, 5 to 40 parts by weight).

There is no particular limitation on the method of introducing the concentrated crystallization mother liquor distillate (or a mixture thereof) into the distillation step together with the liquid resulting from the conversion reaction. For example, before starting the distillation step, the crystallization mother liquor distillate (Or a mixture containing the same) and the result of the conversion reaction may be mixed, and then the resultant mixture may be added to the still, or alternatively, the line of transferring the solution to the still can be added to the distillation column ) And the distillation result, the components may be mixed into the distillation column while they are being conveyed.

The amount of the crystallization mother liquor distillate to be added to the crystallization step of the distillation result liquid (above (2)) is not particularly limited. For example, when 100 parts by weight of the distillation result liquid added in the same step May be appropriately selected within a range of 1 to 50 parts by weight (more specifically, 5 to 40 parts by weight).

There is also no particular limitation to the method of introducing the crystallization mother liquor distillate into the crystallization step together with the distillation resultant liquid. For example, before starting the crystallization step, the re-distillate and the distillation result liquid are mixed in a separate vessel in advance, Alternatively, the re-distillation line may be connected to the line for transferring the distillation result liquid to the crystallization vessel so that the components are mixed into the crystallization vessel immediately while being transferred.

When the crystallization mother liquor distillate is independently recrystallized and then introduced into a subsequent purification step [3], the solvent, recrystallization method, apparatus and conditions used for recrystallization are as described in the crystallization step And preferably the same solvent as that used in the preceding crystallization step is used. According to one preferred embodiment of the present invention, acetone is used as a solvent and the weight ratio of the concentrated crystallization mother liquid: solvent is set to 10: 1 to 1: 1 (more preferably, 5: 1 to 1: 1) After the mixture is mixed, the temperature of the solution is raised to 30 ° C or higher and then cooled to 10 ° C or lower to precipitate a recrystallized product of alcohol-free alcohol. The precipitated alcohol-free alcohol recrystallized product is recovered through filtration and the like, if necessary, washed with the same solvent as the recrystallization solvent, and then put in a subsequent purification step (for example, a post treatment selected from adsorbent treatment, ion purification and a combination thereof) do.

Alternatively, the crystallization mother liquor distillate is introduced into the subsequent purification step as described above without going through the recrystallization treatment and the like (see (4) above). For example, when the purity of the alcohol free alcohol in the crystallization mother liquor distillate is 99% or more, it is possible to immediately enter the subsequent purification step.

In addition, the method for producing an alcohol-free alcohol of the present invention may further include performing a post-treatment on the anhydrous alcohol crystals obtained in the crystallization step, the adsorbent treatment, ion purification and a combination thereof.

The adsorbent treatment is for decolorization and can be carried out according to a conventional adsorbent treatment method using a known adsorbent such as activated carbon. As the activated carbon, there may be used one or more selected from the group consisting of plant raw materials such as wood and coconut, activated carbon obtained by activating mineral raw materials such as lignite, bituminous coal, bituminous coal and anthracite.

The ion purification is for removing ions that may be present in an alcohol free alcohol. Depending on the kinds of ions that can be present, ion exchange resins selected from the group of cationic, weakly cationic, strongly anionic and weakly anionic ion exchange resins May be carried out one or more times.

Hereinafter, the present invention will be described in more detail with reference to examples and comparative examples. However, the following examples are intended to assist the understanding of the present invention, and the scope of the present invention is not limited thereto.

[ Example ]

Manufacturing example

100 g of sulfuric acid (Duksan Chemical Co.) and 40 g of methanesulfonic acid (Duksan Chemical Co., Ltd.) were added to the flask, and the flask was charged with 100 g of sorbitol powder (D-sorbitol, manufactured by Samyang Genex Co., Ltd.) in a batch reactor equipped with a stirrer. And the temperature of the reactor was raised to about 140 캜. The dehydration reaction was carried out under reduced pressure of about 30 mmHg to convert it to alcohol without sugar. After completion of the dehydration reaction, the temperature of the reaction mixture was lowered to 110 占 폚, and about 300 g of 50% sodium hydroxide solution (Samseon Pure Chemical Co., Ltd.) was added to neutralize the resultant solution. After neutralization, the temperature of the resulting solution was adjusted to 100 ° C. and concentrated under a pressure of 40 mmHg or less for 1 hour or more to remove water and low boiling point substances in the resultant liquid.

Comparative Example  One

The result of the conversion reaction obtained in the above Production Example was distilled using a condenser built-in thin film still as shown in Fig. 1 under the conditions of a distillation temperature of 140 DEG C and a distiller internal pressure of 5 mmHg or less. The purity of the anhydrous alcohol obtained through distillation was 98.0% and the distillation yield was 92%.

1,889 g of the resultant distillation result liquid and 940 g of acetone were placed in a jacket-equipped crystallization apparatus, and the temperature was raised to 40 DEG C and then to 10 DEG C to form crystals. This process was repeated three times, and the resulting crystals were filtered and washed with 470 g of acetone to give an anhydrous alcohol crystals having a purity of 99.7%. The crystallization yield was 88.0%, and the overall process yield was 62.3%.

Gas chromatograph (GC) was used for the analysis.

Example  One

The crystallized mother liquor remaining after the crystal filtration in the crystallization step of Comparative Example 1 was collected and placed in a rotary evaporator (Heidloph, Germany), and the temperature was raised to 50 ° C. Then, the acetone was removed under a vacuum of 250 torr or less, A mother liquor was obtained. The free alcohol purity of the concentrated crystallization mother liquor was 84%.

810 g of the concentrated crystallization mother liquor was placed in a batch distillator equipped with a 5-stage packing column, and the temperature was raised to 200 ° C under a pressure of 5 mmHg or lower in the distiller and re-distilled. The purity of the obtained re-distillate was 98.4% and the distillation yield was 88%.

199 g of the obtained crystallization mother liquor distillate was mixed with 1,889 g of the distillation result liquid prepared in the same manner as in Comparative Example 1 and then crystallized in the same manner as in Comparative Example 1 using 1,040 g of acetone. The resulting crystals were filtered and washed with 520 g of acetone to give anhydrous alcohol. The purity of the alcohol-free alcohol obtained was 99.8%, the crystallization yield was 92.1%, and the overall process yield was 71.0%.

Example  2

810 g of the concentrated crystallization mother liquor obtained in Example 1 was placed in a condenser external thin film evaporator (external condenser type) equipped with a 3-stage packing column and subjected to re-distillation under the conditions of a distillation temperature of 180 ° C and a distiller internal pressure of 5 mmHg or less Respectively. The purity of the obtained re-distillate was 98.0%, and the distillation yield was 92%.

208 g of the obtained crystallization mother liquor distillate was mixed with 1,889 g of the distillation result liquid prepared in the same manner as in Comparative Example 1 and then crystallized in the same manner as in Comparative Example 1 using 1,040 g of acetone. The resulting crystals were filtered and washed with 520 g of acetone to give anhydrous alcohol. The purity of the alcohol without anhydride was 99.7%, the crystallization yield was 91.2%, and the yield of the whole process was 71.7%.

Example  3

A mixture of 199 g of the crystallization mother liquor distillate obtained in Example 1 and 2,733 g of the result of the conversion reaction obtained in the above Preparation Example was distilled at a distillation temperature of 140 캜 using a condenser built-in thin film evaporator (internal condenser type) And distilled under a pressure of 5 mmHg or less. The purity of the anhydrous alcohol obtained through distillation was 98.2% and the distillation yield was 94%.

1,985 g of the resultant distillation resultant and 990 g of acetone were placed in a jacket-equipped crystallization apparatus, and the temperature was raised to 40 ° C and then decreased to 10 ° C to produce crystals. The obtained crystals were filtered and washed with 490 g of acetone to obtain an anhydrous alcohol crystals having a purity of 99.7%. The yield of crystallization was 88.9% and the yield of the whole process was 66.2%.

Example  4

681 g of the concentrated crystallization mother liquor obtained in Example 1 was placed in a batch distillator equipped with a 10-stage packing column and the temperature was raised to 180 ° C under the pressure of the internal pressure of the distiller of 5 mmHg or less and re-distilled. The purity of alcohol-free alcohol in the obtained re-distillate was 99.5%, the distillation yield was 61%, and the overall yield of the process was 67.5%. The purity of alcohol-free alcohol in the re-distillate obtained in this Example was just enough to be fed into the subsequent purification process.

1: Thin film still
2: heating jacket
3: wiper
4: Condenser guard
5: Built-in condenser
6: Feed line
7: Distillation residue discharge line
7-1: Side branch line for vacuum forming
8: Vacuum line
9: Distillate discharge line
10: Cooling water inflow line
11: Cooling water outflow line

Claims (15)

Dehydrogenating the hydrogenated sugar to convert it to an alcohol-free alcohol; Distilling the liquid resulting from the conversion reaction; And crystallizing the resultant solution in a solvent, the method comprising the steps of:
(1) introducing the re-distillate into the distillation step of the liquid resulting from the conversion reaction, or (2) introducing the distillate into the distillation column to remove the crystallization solvent from the crystallization mother liquor resulting from the crystallization step, (3) independently recrystallized and then introduced into a subsequent purification step, or (4) immediately introduced into a subsequent purification step. The method for producing an alcohol-free alcohol according to claim 1, wherein the solvent used for crystallization is at least one selected from acetone, ethyl acetate, toluene, benzene, xylene and alcohol. The process for producing an alcohol-free alcohol according to claim 1, wherein distillation for obtaining a redistillation product is carried out using a batch distiller or a thin film still. 4. The process for producing an alcohol-free alcohol according to claim 3, wherein the distiller for obtaining the redistilled product is equipped with a multi-stage packing column of two or more stages. The process for producing an alcohol-free alcohol according to claim 1, wherein the purity of alcohol-free alcohol in the redistilled product is 95% or more. The process for producing an alcohol-free alcohol according to claim 1, wherein the solvent used in the recrystallization of the redistillation product is the same as that used in the preceding crystallization step. The process for producing an alcohol-free alcohol according to claim 1, wherein the purity of alcohol-free alcohol in the re-distillate is 99% or more, and the re-distillate is directly fed to the subsequent purification step. The process according to claim 1, wherein the distillation step is carried out in a condenser built-in thin film still containing an internal condenser, a feed line, a distillation residue discharge line, a vacuum line and a distillate discharge line . 9. The process according to claim 8, wherein during the distillation, the interior of the still is further depressurized through a distillation residue discharge line, together with a reduced pressure through a vacuum line. The process according to claim 1, wherein the hydrogenated saccharide is hexitol and the anhydrous alcohol is dianhydrohexitol. The process for producing an alcohol-free alcohol according to claim 1, wherein an acid catalyst is used in the step of dehydrating the hydrogenated sugar to convert it to an alcohol-free alcohol. The process according to claim 1, wherein the conversion step of the hydrogenated sugar to the anhydride alcohol is pre-treated to remove water and low boiling point substances before the distillation step. The process for producing an alcohol-free alcohol according to claim 1, wherein the distillation is carried out at a temperature of 100 to 250 ° C. The process for producing an alcohol-free alcohol according to claim 1, wherein the distillation is carried out under a pressure of 10 mmHg or less. The process for producing an alcohol-free alcohol according to claim 1, further comprising a step of performing a post-treatment on the anhydrous alcohol crystals obtained in the crystallization step, selected from adsorbent treatment, ion purification and a combination thereof.

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