FORM 2
THE PATENTS ACT, 1970
(39 OF 1970)
&
THE PATENTS RULES, 2003
COMPLETE SPECIFICATION
(See Section 10 and Rule 13)
A PROCESS FOR THE PREPARATION OF DIANHYDROSUGAR
ALCOHOLS
RELIANCE INDUSTRIES LIMITED
an Indian Company
of Maker Chambers IV,
Nariman Point, Mumbai- 400021,
Maharashtra, India
INVENTORS:
1. GOKHALEUDAY
2. SAKHALKAR MANGESH
3. UPPARA PARASU VEERA
4. ADURI PAVAN KUMAR
THE FOLLOWING SPECIFICATION PARTICULARLY DESCRIBES THE INVENTION AND THE MANNER IN WHICH IT IS TO BE PERFORMED.

Field:
The present disclosure relates to a process for the preparation of a dianhydrosugar alcohol.
Background:
Dianhydrosugar alcohol such as isosorbide is a versatile ingredient having wide range of applications. It is used as a co-monomer in polyester, as a plasticizer in PVC, in pharmaceutical product and as an additive in personal care and consumer product.
It can be used in the production of other polymers such as polyurethane, polycarbonates and the like. Polyester with increased glass transition temperature and improved crystallinity can be obtained by addition of low to moderate proportions of isosorbide. Further, by addition of isosorbide to polyester, PTA consumption can be reduced along with improved Tg.
Various processes for the production of anhydrosugar alcohols such as isosorbide are known, e.g. anhydro sugars are produced by dehydration of the corresponding sugar alcohols by the action of dehydration catalysts. The dehydration catalysts used in these processes are mineral acids. One of the most commonly used mineral acids is sulphuric Acid. Hydrochloric acid can also be used in place of sulfuric acid. However, there are certain drawbacks associated with use of HC1 such as it distills off at high vacuum and temperature and thereby decreasing the initial acidity and rate of reaction.
US4408061 discloses a process for the preparation of 1,4-3,6-dianhydro-hexitols from hexitols by elimination of water, characterized in that gaseous hydrogen halide is used as an acid dehydrating agent optionally with carboxylic acids, carboxylic acid halides and/or carboxylic acid anhydrides, as cocatalysts.

US7649099 discloses a method for producing a dianhydrosugar alcohol comprising: in a first reactor, reacting a polyol in the presence of a first catalyst to form a monocyclic sugar, the first catalyst being a solid acid catalyst selected from the group consisting of a heteropoly acid, an anion exchange resin, an acidic clay, a molecular sieve material and a sulfated zirconia; transferring the monocyclic sugar to a second reactor; and in a second reactor, converting the monocyclic sugar to a dianhydrosugar alcohol in the presence of a second catalyst selected from the group consisting of sulfuric acid, phosphoric acid, hydrochloric acid and p-toluenesulfonic acid.
US7772412 discloses a method of dehydration of a sugar or sugar alcohol, comprising: providing a dehydration catalyst within a reactor, the dehydration catalyst being selected from the group consisting of solid acid catalysts and mineral acid catalysts; providing a co-catalyst comprising a support material and a metal within the reactor; introducing a sugar or sugar alcohol to the reactor in the absence of any solvent; flowing H2 through the reactor; and exposing the sugar or sugar alcohol to the catalyst in the presence of the co-catalyst at a H2 pressure of less than or equal to about 300 psig to convert at least some of the sugar or sugar alcohol into a bicyclic ether anhydrosugar product.
US20090259057 discloses a process for the production of a dianhydrosugar from a sugar alcohol via the sugar alcohol anhydride intermediary, comprising the steps of: (a) combining a sugar alcohol with an acid catalyst to create a reaction mixture; (b) heating the reaction mixture under ambient pressure conditions to a temperature between about 130 and 170°C; (c) holding the reaction mixture at a temperature between about 130 and 170°C until less than a preselected amount of the sugar alcohol anhydride intermediary remains. The acid catalyst is selected from the group consisting of sulfuric acid, phosphoric acid; alkyl, aryl, and arylalkylsulfonic acids; polymer bound sulfonic acids; trifluoromethanesulfonic acid; strong acid resins; acid forms of perfluorinated membranes; heteropoly acids and their acidic salts; zeolites; and acid clays. The invention disclosed in US20090259057 particularly relates to the preparation of dianhydrosugar using sorbitol and sulphuric acid as an acid catalyst.

These known processes are inefficient and expensive. Additionally, these processes are environmentally unfriendly due to the involvement of highly corrosive catalysts thus necessitating the use of only specific acid-resistant materials of construction for the manufacture related equipment. Further, the use of conventional catalyst leads to formation of excessive unwanted - side products/polymers in the process. Accordingly, there is felt a need to find out alternative acid catalysts which can overcome the disadvantages associated with the known conventional catalysts.
Objects:
Some of the objects of the present disclosure are discussed herein below.
• It is an object of the present disclosure to provide a simple process for the preparation of dehydrated sugar alcohol using a phosphonate based catalyst.
• It is another object of the present disclosure to provide a process for preparing dehydrated sugar alcohol which is fast, selective and high yielding.
• It is still another object of the present disclosure to provide a process for preparing dehydrated sugar alcohol in a highly pure form.
• It is yet another object of the present disclosure to provide a process for preparing dehydrated sugar alcohol which reduces the formation of undesirable oligomeric and colored polymer compounds.
• It is a further object of the present disclosure to provide an environment friendly process for preparing dehydrated sugar alcohol.
Other objects and advantages of the present disclosure will be more apparent from the following description when read in conjunction with the accompanying figures which are not intended to limit the scope of the present disclosure.

Summary:
In accordance with the present disclosure there is provided a process for the preparation a dianhydrosugar alcohol; said process comprising the following steps:
i. dehydrating a sugar alcohol in the presence of at least one phosphonate based acid catalyst with simultaneous removal of water to obtain a reaction mixture; ii. removing residual water from the reaction mixture; and iii. obtaining the dianhydrosugar alcohol by subjecting the reaction mixture to fractional distillation. In accordance with one embodiment of the present disclosure the process further comprises a step of neutralizing the reaction mixture by an alkali.
In accordance with another embodiment of the present disclosure the process further comprises a step of decolorizing the reaction mixture by contacting said mixture with an activated carbon.
Typically, the method step of dehydration is carried out under continuous stirring at a temperature of 100 to 150°C and a pressure of 200 to 250 mmHg.
Typically, the method step of distillation is carried out at a temperature of 150 to 200°C and at a pressure of 5 to lOmmHg.
Typically, the phosphonate based acid catalyst is at least one catalyst selected from the group consisting of 2-aminoethylphosphonic acid (AEPn), dimethyl methylphosphonate (DMMP), 1-hydroxy ethylidene-l,l-diphosphonic acid (HEDP), amino tris(methylene phosphonic acid) (ATMP), ethylenediamine tetra(methylene phosphonic acid) (EDTMP), tetramethylenediamine tetra(methylene phosphonic acid) (TDTMP), hexamethylenediamine tetra(methylene phosphonic acid) (HDTMP), phosphonobutane-tricarboxylic acid (PBTC), N-(phosphonomethyl)iminodiacetic acid (PMIDA), 2-carboxyethyl phosphonic acid (CEPA), 2-hydroxyphosphonocarboxylic

acid (HPAA), amino-tris-(methylene-phosphonic acid) (AMP) and diethylene triamine pentamethylene phosphonate (DTPMP/DETMP).
In one of the exemplary embodiments of the present disclosure the acid catalyst is 1-hydroxy ethylidene-l,l-diphosphonic acid (HEDP).
Typically, the amount of the acid catalyst is between 0.1 and 5 wt. % with respect to the weight of the sugar alcohol.
Typically, the sugar alcohol is at least one selected from the group consisting of sorbitol manitol and iditol.
In accordance with one embodiment of the present disclosure the sugar alcohol is sorbitol.
In accordance with one embodiment of the present disclosure the dianhydrosugar alcohol is isosorbide.
In one of the exemplary embodiment of the present disclosure the sugar alcohol is sorbitol, the phosphonate based acid catalyst is 1-hydroxy ethylidene-1.1-diphosphonic acid (HEDP) and the dianhydrosugar alcohol is isosorbide.
Typically, the purity of the dianhydrosugar alcohol is at least 99 %.
Typically, the yield of the dianhydrosugar alcohol is at least 65 %.
Typically, the formation of unwanted side products/polymers is less than 1 %.
In accordance with another aspect of the present disclosure there is also provided use of an acid catalyst selected from the group consisting of 2-aminoethylphosphonic acid (AEPn), dimethyl methylphosphonate (DMMP), 1 -hydroxy ethylidene-1,1-

diphosphonic acid (HEDP), amino tris(methylene phosphonic acid) (ATMP), ethylenediamine tetra(methylene phosphonic acid) (EDTMP), tetramethylenediamine tetra(methylene phosphonic acid) (TDTMP), hexamethylenediamine tetra(methylene phosphonic acid) (HDTMP), phosphonobutane-tricarboxylic acid (PBTC), N-(phosphonomethyl)iminodiacetic acid (PMIDA), 2-carboxyethyl phosphonic acid (CEPA), 2-hydroxyphosphonocarboxylic acid (HPAA), amino-tris-(methyIene-phosphonic acid) (AMP) and diethylene triamine pentamethylene phosphonate (DTPMP/DETMP) for the preparation of dianhydrosugar alcohol from a sugar alcohol.
Description:
The inventors of the present disclosure focused on the problems associated with the use of acid catalysts such as sulphuric acid, hydrochloric acid and the like for making dehydrated sugars. The inventors of the present disclosure after conducting various experiments found that dianhydrosugar alcohols such as isosorbide can be produced by dehydrative cyclization of sugar alcohol (sorbitol) in the presence of a phosphonate based catalyst. It is also found that the catalysts of the present disclosure give higher selectivity thereby reducing the formation of undesirable oligomeric or colored polymer compounds during the reaction. The reaction of the present disclosure thus employs phosphonate based catalysts which in turn makes the process environment friendly.
In accordance with the present disclosure there is provided a process for the preparation a dianhydrosugar alcohol. The process involves the following steps:
In the first step, a sugar alcohol which includes but is not limited to sorbitol, manitol and iditol is dehydrated in the presence of at least one phosphonate based acid catalyst with simultaneous removal of water to obtain a reaction mixture. The dehydration is carried out under continuous stirring at a temperature of 100 to 150°C and a pressure of200 to 250 mmHg.

In accordance with the present disclosure the amount of the acid catalyst is maintained between 0.1 and 5 wt. % with respect to the weight of the sugar alcohol. In accordance with one embodiment of the present disclosure the sugar alcohol is sorbitol.
In accordance with the present disclosure the phosphonate based acid catalyst employed is at least one catalyst selected from the group consisting of 2-aminoethylphosphonic acid (AEPn), dimethyl methylphosphonate (DMMP), 1-hydroxy ethylidene-l,l-diphosphonic acid (HEDP), amino tris(methylene phosphonic acid) (ATMP), ethylenediamine tetra(methylene phosphonic acid) (EDTMP), tetramethylenediamine tetra(methylene phosphonic acid) (TDTMP), hexamethylenediamine tetra(methylene phosphonic acid) (HDTMP), phosphonobutane-tricarboxylic acid (PBTC), N-(phosphonomethyl)iminodiacetic acid (PMIDA), 2-carboxyethyl phosphonic acid (CEPA), 2-hydroxyphosphonocarboxylic acid (HPAA), amino-tris-(methylene-phosphonic acid) (AMP) and diethylene triamine pentamethylene phosphonate (DTPMP/DETMP). In one of the exemplary embodiments of the present disclosure the acid catalyst is 1-hydroxy ethylidene-1,1-diphosphonic acid (HEDP).
In the next step, residual water from the reaction mixture is removed. Finally, the dianhydrosugar is obtained by subjecting the reaction mixture to fractional distillation. The distillation is carried out at a temperature of 150 to 200°C and at a pressure of 5 to lOmmHg. In accordance with one embodiment of the present disclosure the dianhydrosugar alcohol is isosorbide.
The process of the present disclosure also involves the method steps, if required, such as neutralizing the reaction mixture by an alkali and/or decolorizing the reaction mixture by contacting said mixture with an activated carbon. .

In one of the exemplary embodiment of the present disclosure the sugar alcohol is sorbitol, the phosphonate based acid catalyst is 1 -hydroxy ethylidene-1,1-diphosphonic acid (HEDP) and the dianhydrosugar alcohol is isosorbide.
The reaction scheme of acid catalyzed dehydrative cyclization of sorbitol to Isosorbide is provided herein below.

The process of the present disclosure provides a dianhydrosugar alcohol having purity of at least 99 %. Further, the yield of a dianhydrosugar alcohol obtained by the present process is at least 65 %. Still further, in the process of the present disclosure the formation of unwanted side products/polymers is less than 1 %.
In accordance with another aspect of the present disclosure there is also provided use of an acid catalyst selected from the group consisting of 2-aminoethylphosphonic acid (AEPn), dimethyl methylphosphonate (DMMP), 1-hydroxy ethylidene-1,1-diphosphonic acid (HEDP), amino tris(methylene phosphonic acid) (ATMP), ethylenediamine tetra(methylene phosphonic acid) (EDTMP), tetramethylenediamine tetra(methylene phosphonic acid) (TDTMP), hexamethylenediamine tetra(methylene phosphonic acid) (HDTMP), phosphonobutane-tricarboxylic acid (PBTC), N-(phosphonomethyl)iminodiacetic acid (PMIDA), 2-carboxyethyl phosphonic acid (CEPA), 2-hydroxyphosphonocarboxylic acid (HPAA), amino-tris-(methylene-phosphonic acid) (AMP) and diethylene triamine pentamethylene phosphonate (DTPMP/DETMP) for the preparation of dianhydrosugar alcohol from a sugar alcohol.

Hereinafter, the present disclosure will be described in more detail with reference to the following Examples, but the scope of the present disclosure is not limited thereto.
Example 1:
100 grams of sorbitol was taken in a 250 ml flask connected to a distillation assembly and 1.0 grams of 1-Hydroxy Ethylidene-l,l-Diphosphonic (HEDP) acid catalyst was added to it. The mass was heated to 180 °C in 3 hours with simultaneous distillation of the water of reaction at reduced pressure (200-250 mm Hg). The reaction mass was then distilled at 6 mm Hg at about 165°C to obtain distillate of isosorbide. Product was analysed by GC and HPLC. Purity and isolated yield were 99 and 75 % respectively.
Example 2:
The procedure as described for Example 1 was repeated except Phosphono butane tricarboxylic acid was used instead of 1-Hydroxy Ethylidene-1,1-Diphosphonic Acid. Product was analysed by GC and HPLC. Purity and isolated yield were 99% and 69 % respectively.
Example 3:
The procedure as described for Example 1 was repeated except Amino Tris methylene Phosphonate was used instead of 1-Hydroxy Ethylidene-1,1-Diphosphonic Acid. Product was analysed by GC and HPLC. Purity and isolated yield were 99% and 69 % respectively.
Example 4:
The procedure as described for Example 1 was repeated except Diethylene Triamine Pentamethylene Phosphonate was used instead of 1-Hydroxy Ethylidene-1,1-Diphosphonic Acid. Product was analysed by GC and HPLC. Purity and isolated yield were 99% and 68 % respectively.

Example 5:
The procedure as described for example 1 was followed except conventional catalyst H2S04 was used and reaction was carried out for 1 hour.
In order to find out the un-wanted products or polymers, 400 grams of water was added to the reaction mass with vigorous stirring to obtain slurry which was then filtered to separate polymers. Dried polymer weight was measured. The comparative results are shown in table 1.
Table 1:

Catalyst Sorbit Catalyst Temp. Reaction Isolated Un wanted
ol
gm amt. (gm) °C time, hours Yield % products/ polymers (gm)
Example 1 HEDP 100 1.6 180 3 75 0.8
Example 5 H2S04 100 1.0 180 1 60 17.5
From the results as shown in table no. 1, it is clear that the process of the present disclosure yields isosorbide in higher amount. Further, the process of the present disclosure reduces the formation of un-wanted products/ polymers.
Throughout this specification the word "comprise", or variations such as "comprises" or "comprising", will be understood to imply the inclusion of a stated element, integer or step, or group of elements, integers or steps, but not the exclusion of any other element, integer or step, or group of elements, integers or steps.
The use of the expression "a", "at least" or "at least one" suggests the use of one or more elements or ingredients or quantities, as the use may be in the embodiment of the disclosure to achieve one or more of the desired objects or results.

The numerical values given for various physical parameters, dimensions and quantities are only approximate values and it is envisaged that the values higher or lower than the numerical value assigned to the physical parameters, dimensions and quantities fall within the scope of the disclosure and the claims unless there is a statement in the specification to the contrary.
While certain embodiments of the disclosure have been described, these embodiments have been presented by way of examples only, and are not intended to limit the scope of the disclosure. Variations or modifications in the process of this disclosure, within the scope of the disclosure, may occur to those skilled in the art upon reviewing the disclosure herein. Such variations or modifications are well within the spirit of this disclosure.

We claim:
1. A process for the preparation a dianhydrosugar alcohol; said process
comprising the following steps:
i. dehydrating a sugar alcohol in the presence of at least one phosphonate based acid catalyst with simultaneous removal of water to obtain a reaction mixture; ii. removing residual water from the reaction mixture; and iii. obtaining the dianhydrosugar alcohol by subjecting the reaction mixture to fractional distillation.
2. The process as claimed in claim 1, further comprises a step of neutralizing the
reaction mixture by an alkali.
3. The process as claimed in claim 1, further comprises a step of decolorizing the
reaction mixture by contacting said mixture with an activated carbon.
4. The process as claimed in claim 1, wherein the method step of dehydration is
carried out under continuous stirring at a temperature of 100 to 150°C and a
pressure of 200 to 250 mmHg.
5. The process as claimed in claim 1, wherein the method step of distillation is carried out at a temperature of 150 to 200°C and at a pressure of 5 to l0mmHg.
6. The process as claimed in claim 1, wherein the phosphonate based acid catalyst is at least one catalyst selected from the group consisting of 2-aminoethylphosphonic acid (AEPn), dimethyl methylphosphonate (DMMP), 1-hydroxy ethylidene-l,l-diphosphonic acid (HEDP), amino tris(methylene phosphonic acid) (ATMP), ethylenediamine tetra(methylene phosphonic acid) (EDTMP), tetramethylenediamine tetra(methylene phosphonic acid) (TDTMP),

hexamethylenediamine tetra(methylene phosphonic acid) (HDTMP),
phosphonobutane-tricarboxylic acid (PBTC), N-
(phosphonomethyl)iminodiacetic acid (PMIDA), 2-carboxyethyl phosphonic acid (CEPA), 2-hydroxyphosphonocarboxylic acid (HPAA), amino-tris-(methylene-phosphonic acid) (AMP) and diethylene triamine pentamethylene phosphonate (DTPMP/DETMP).
7. The process as claimed in claim 1, wherein the acid catalyst is 1-hydroxy ethylidene-l,l-diphosphonic acid (HEDP).
8. The process as claimed in claim 1, wherein the amount of the acid catalyst is between 0.1 and 5 wt. % with respect to the weight of the sugar alcohol.
9. The process as claimed in claim 1, wherein the sugar alcohol is at least one selected from the group consisting of sorbitol, manitol and iditol.
10. The process as claimed in claim 1, wherein the sugar alcohol is sorbitol.
11. The process as claimed in claim 1, wherein the dianhydrosugar alcohol is isosorbide.
12. The process as claimed in claim 1, wherein the sugar alcohol is sorbitol, the phosphonate based acid catalyst is 1-hydroxy ethyIidene-l,1-diphosphonic acid (HEDP) and the dianhydrosugar alcohol is isosorbide.
13. The process as claimed in claim 1, wherein the purity of the dianhydrosugar alcohol is at least 99 %.
14. The process as claimed in claim 1, wherein the yield of the dianhydrosugar alcohol is at least 65 %.

15.The process as claimed in claim 1, wherein the formation of unwanted side products/polymers is less than 1 %.
16. Use of an acid catalyst selected from the group consisting of 2-
aminoethylphosphonic acid (AEPn), dimethyl methylphosphonate (DMMP), 1-
hydroxy ethylidene-l,l-diphosphonic acid (HEDP), amino tris(methylene
phosphonic acid) (ATMP), ethylenediamine tetra(methylene phosphonic acid)
(EDTMP), tetramethylenediamine tetra(methylene phosphonic acid) (TDTMP),
hexamethylenediamine tetra(methylene phosphonic acid) (HDTMP),
phosphonobutane-tricarboxylic acid (PBTC), N-
(phosphonomethyl)iminodiacetic acid (PMIDA), 2-carboxyethyl phosphonic acid (CEPA), 2-hydroxyphosphonocarboxylic acid (HPAA), amino-tris-(methylene-phosphonic acid) (AMP) and diethylene triamine pentamethylene phosphonate (DTPMP/DETMP) for the preparation of dianhydrosugar alcohol from a sugar alcohol.