DESC:FIELD
The present disclosure relates to a process for the synthesis of isopropyl glycol acetate.
BACKGROUND
The background information herein below relates to the present disclosure but is not necessarily prior art.
Isopropyl glycol acetate is an organic compound having the following structural formula,

Isopropyl glycol acetate
Isopropyl glycol acetate is a clear, colourless liquid with a characteristic fruity odour, acts as a solvent and has a wide range of application, including printing inks. It is miscible with most of the other organic solvents, and moderately soluble in water.
Various methods for the synthesis of isopropyl glycol acetate are known in the art, however the conventionally known methods employ costly and harmful reagents which makes the process costly and hazardous. Further, the conventional processes provide the product with low yield and low purity.
Therefore, there is felt a need to provide a process for the synthesis of isopropyl glycol acetate that mitigates the aforestated drawbacks or at least provides a suitable alternative.

OBJECTS
Some of the objects of the present disclosure, which at least one embodiment herein satisfies, are as follows:
It is an object of the present disclosure to ameliorate one or more problems of the background or to at least provide a useful alternative.
Another object of the present disclosure is to provide a process for the synthesis of isopropyl glycol acetate.
Still another object of the present disclosure is to provide a process for the synthesis of isopropyl glycol acetate, which is simple, efficient and environment friendly.
Yet another object of the present disclosure is to provide a process for the synthesis of isopropyl glycol acetate from isopropyl glycol.
Yet another object of the present disclosure is to provide a process for the synthesis of isopropyl glycol acetate with a comparatively high purity and high yield.
Still another object of the present disclosure is to provide a process for the synthesis of isopropyl glycol from isopropyl alcohol.
Other objects and advantages of the present disclosure will be more apparent from the following description, which is not intended to limit the scope of the present disclosure.
SUMMARY
The present disclosure relates to a process for the synthesis of isopropyl glycol acetate. The process comprises mixing a predetermined amount of isopropyl alcohol with a predetermined amount of ethylene oxide in the presence of a first catalyst under stirring to obtain a first mixture. The first mixture is heated under stirring at a first predetermined temperature for a first predetermined time period to obtain isopropyl glycol. A predetermined amount of an acylating agent is mixed with a predetermined amount of the isopropyl glycol and adding a second catalyst under stirring to obtain a second mixture. The second mixture is heated at a second predetermined temperature for a second predetermined time period to obtain isopropyl glycol acetate.
In an embodiment of the present disclosure, the first catalyst is at least one selected from the group consisting of BF3.ether, sodium hydroxide and potassium hydroxide.
The first predetermined temperature is in the range of 60 °C to 100 °C.
The first predetermined time period is in the range of 1 hour to 4 hours.
In an embodiment of the present disclosure, a weight ratio of isopropyl alcohol to ethylene oxide is in the range of 1:0.1 to 1:1.
The acylating agent is acetic acid.
The second catalyst is selected from the group consisting of sulphuric acid, and sulphuric acid adsorbed on silica gel (SiO2-H2SO4).
The second predetermined temperature is in the range of 60 °C to 120 oC.
The second predetermined time period is in the range of 2 hours to 8 hours.
In an embodiment of the present disclosure, a weight ratio of isopropyl glycol to the acylating agent is in the range of 1: 0.5 to 1:2.
BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWING
The present disclosure will now be described with the help of the accompanying drawing, in which:
Figure 1a illustrates 1H NMR spectrum of isopropyl glycol synthesized in accordance with the present disclosure;
Figure 1b illustrates 13C NMR spectrum of isopropyl glycol synthesized in accordance with the present disclosure;
Figure 2a illustrates 1H NMR spectrum of isopropyl glycol acetate synthesized in accordance with the present disclosure;
Figure 2b illustrates 13C NMR spectrum of isopropyl glycol acetate synthesized in accordance with the present disclosure;
Figure 2c illustrates IR spectrum of isopropyl glycol acetate synthesized in accordance with the present disclosure; and
Figure 2d illustrates mass spectrum of isopropyl glycol acetate synthesized in accordance with the present disclosure.
DETAILED DESCRIPTION
The present disclosure relates to a process for the synthesis of isopropyl glycol acetate.
Embodiments, of the present disclosure, will now be described with reference to the accompanying drawing.
Embodiments are provided so as to thoroughly and fully convey the scope of the present disclosure to the person skilled in the art. Numerous details are set forth, relating to specific components, and methods, to provide a complete understanding of embodiments of the present disclosure. It will be apparent to the person skilled in the art that the details provided in the embodiments should not be construed to limit the scope of the present disclosure. In some embodiments, well-known processes, well-known apparatus structures, and well-known techniques are not described in detail.
The terminology used, in the present disclosure, is only for the purpose of explaining a particular embodiment and such terminology shall not be considered to limit the scope of the present disclosure. As used in the present disclosure, the forms "a,” "an," and "the" may be intended to include the plural forms as well, unless the context clearly suggests otherwise. The terms "comprises," "comprising," “including,” and “having,” are open ended transitional phrases and therefore specify the presence of stated features, integers, steps, operations, elements, modules, units and/or components, but do not forbid the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups thereof. The particular order of steps disclosed in the method and process of the present disclosure is not to be construed as necessarily requiring their performance as described or illustrated. It is also to be understood that additional or alternative steps may be employed.
As used herein, the term "and/or" includes any and all combinations of one or more of the associated listed elements.
The terms first, second, third, etc., should not be construed to limit the scope of the present disclosure as the aforementioned terms may be only used to distinguish one element, component, region, layer or section from another component, region, layer or section. Terms such as first, second, third etc., when used herein do not imply a specific sequence or order unless clearly suggested by the present disclosure.
Isopropyl glycol acetate is an organic compound that is a clear, colourless liquid with a characteristic fruity odour. Isopropyl glycol acetate has a wide variety of applications including printing inks. It is miscible with most of the organic solvents, and moderately soluble in water.
Various methods for the synthesis of isopropyl glycol acetate are known in the art, however the conventionally known methods employ costly and harmful reagents which makes the process costly and hazardous. Further, the conventional processes provide the product with low yield and low purity.
The present disclosure provides a process for the synthesis of isopropyl glycol acetate.
The process comprises the following steps:
(i) mixing a predetermined amount of isopropyl alcohol with a predetermined amount of ethylene oxide in the presence of a first catalyst under stirring to obtain a first mixture;
(ii) heating the first mixture under stirring at a first predetermined temperature for a first predetermined time period to obtain isopropyl glycol;
(iii) mixing a predetermined amount of an acylating agent with a predetermined amount of the isopropyl glycol adding a second catalyst under stirring to obtain a second mixture; and
(iv) heating the second mixture at a second predetermined temperature for a second predetermined time period to obtain isopropyl glycol acetate.
A schematic representation of the process for the synthesis of isopropyl glycol from isopropyl alcohol is given below as Scheme I.

Scheme I
A schematic representation of the process for the synthesis of isopropyl glycol acetate from isopropyl glycol is given below as Scheme II.


Scheme II
In accordance with the present disclosure, the first catalyst is at least one selected from the group consisting of BF3.ether, sodium hydroxide and potassium hydroxide. In an exemplary embodiment of the present disclosure, the first catalyst is a combination of BF3.ether and sodium hydroxide.
In accordance with the present disclosure, the first predetermined temperature is in the range of 60 °C to 100 °C. In an embodiment of the present disclosure, the first predetermined temperature is in the range of 80 °C to 95 °C.
The first predetermined time period is in the range of 1 hour to 4 hours. In an exemplary embodiment of the present disclosure, the first predetermined time period is 2 hours.
In accordance with the present disclosure, a weight ratio of isopropyl alcohol to ethylene oxide is in the range of 1:0.1 to 1:1. In an embodiment of the present disclosure, the weight ratio of isopropyl alcohol to ethylene oxide is in the range of 1: 0.3 to 1:0.5.
In accordance with the present disclosure, the acylating agent is acetic acid.
Conventionally, acetyl chloride is known to be used as an acylating agent. However, acetyl chloride is costly and hazardous which makes it unfit to be used at a commercial/industrial scale. Therefore, the inventors of the present disclosure have developed a process for the acetylation of alcohols by using acetic acid as the acylating agent (which is much cheaper and non-hazardous as compared to acetyl chloride) in the presence of a catalyst which acts as a protonating agent.
In an embodiment of the present disclosure, the second catalyst also acts as a protonating agent and is selected from the group consisting of sulphuric acid, and sulphuric acid adsorbed on silica gel (SiO2-H2SO4). In an exemplary embodiment of the present disclosure, the second catalyst is sulphuric acid. In another exemplary embodiment of the present disclosure, the second catalyst is sulphuric acid adsorbed on silica gel (SiO2-H2SO4).
Conventionally, various catalysts such as homogeneous transition-metal-based catalysts or organocatalysts have been developed for the acetylation of alcohols, however, the acetylation conversion by using such catalysts results in low yield of isopropyl glycol acetate (IPGA). Moreover, the homogeneous transition-metal-based catalysts such as RuCl3 are very costly.
Further, the other known conventional catalysts such as cobalt (II) salen complex, ZnAl2O¬-SiO2 nanocomposite, BiFeO3, anhydrous NiCl2 and thallium (III) chloride are associated with several disadvantages such as use of additives or surfactants or co-catalysts are required essentially during the process along with the catalyst. In addition, the use of the conventional catalysts such as CeCl3, ZrCl4, La(NO3)·6H2O, Al(OTf)3 which are known for the acetylation of isopropyl glycol (IPG) are found to have many disadvantages in reaction procedures such as tedious work up, require more reaction time for conversion, high catalyst loading and the like.
In accordance with the present disclosure, the second predetermined temperature is in the range of 60 °C to 120 °C. In an exemplary embodiment, the second predetermined temperature is 80 °C. In another exemplary embodiment, the second predetermined temperature is 100 °C.
The second predetermined time period is in the range of 2 hours to 8 hours. In an exemplary embodiment of the present disclosure, the second predetermined time period is 4 hours.
In accordance with the present disclosure, a weight ratio of isopropyl glycol to the acylating agent is in the range of 1: 0.5 to 1:2. In an exemplary embodiment of the present disclosure, the weight ratio of isopropyl glycol to the acylating agent is 1:1.
In an exemplary embodiment of the present disclosure, the synthesis of isopropyl glycol from isopropyl alcohol is given below as:

In an exemplary embodiment of the present disclosure, the synthesis of isopropyl glycol acetate from isopropyl glycol is given below as:

In another exemplary embodiment of the present disclosure, the synthesis of isopropyl glycol acetate from isopropyl glycol is given below as:

The preparation of isopropyl glycol from isopropyl alcohol in accordance with the present disclosure is simple and efficient.
The present disclosure provides a simple process for the synthesis of isopropyl glycol acetate, which provides a higher yield of the product with greater purity.
The process of the present disclosure employs cheaper and non-hazardous reagents and hence, the process is cost-efficient and environment friendly.
The foregoing description of the embodiments has been provided for purposes of illustration and not intended to limit the scope of the present disclosure. Individual components of a particular embodiment are generally not limited to that particular embodiment, but, are interchangeable. Such variations are not to be regarded as a departure from the present disclosure, and all such modifications are considered to be within the scope of the present disclosure.
The present disclosure is further described in light of the following experiments which are set forth for illustration purpose only and not to be construed for limiting the scope of the disclosure. The following experiments are scalable to industrial/commercial process.
EXPERIMENTAL DETAILS
Synthesis of isopropyl glycol acetate in accordance with the present disclosure
Step-1: Synthesis of Isopropyl glycol in accordance with the present disclosure
General procedure: A predetermined amount of isopropyl alcohol (IPA) was taken in an autoclave reactor followed by adding a predetermined amount of ethylene oxide (EO) and a predetermined amount of BF3.ether under stirring to obtain a first mixture. The first mixture was heated in the autoclave reactor at a pressure in the range of 0.8 mmHg to1 mmHg at a first predetermined temperature for a first predetermined time period to obtain isopropyl glycol. The resulting isopropyl glycol was distilled by fractional distillation and isopropyl carbitol was separated out as a by-product.
The isopropyl glycol was characterized by using 1H NMR (Figure 1a) and 13C NMR (Figure 1b).
Examples 1 to 5: The examples 1 to 5 were carried out by following the general procedure as disclosed herein above, with variable amounts of the reactants/reagents and variable process parameters as summarized in Table 1 herein below:
Table 1: The variable amounts of the reactants/reagents and variable process parameters used in Examples 1 to 5 for the synthesis of Isopropyl glycol.
Example 1 2 3 4 5
IPA (kg) 27.08 20 20 28 28
Net IPA
Consumption (kg) 3.71 10.561 9.37 11.03 6.4
Ethylene Oxide (EO) (kg) 9.93 9.8 9.8 10.26 8.9
Weight ratio of IPA:EO 1:0.35 1:0.5 1:0.5 1:0.4 1:0.3
BF3.ether (kg) 0.06 0.06 0.06 0.06 0.06
KOH (kg) 0.06 - - - -
NaOH (kg) - 0.06 0.06 0.06 0.06
First predetermined temperature (°C) 90 95 80 85 85
First predetermined time period (hours) 2 2 2 2 2
Chromatographic purity by GC (% Area) 98.38 96.221 98.021 97.834 98.431
Cellosolve (Isopropyl Glycol-IPG) 9.984 33.82 33.66 33.03 25.67
Carbitol 7.5 17.49 17.32 13.91 9.25
Recycle IPA (kg) 23.37 9.439 10.63 16.97 21.6
Yield of Cellosolve (IPG) kg 3.52 (56.8%) 9.439
(65.5%) 9.556. (66.04%) 12.04. (70.4%) 9.027 (73.3%)
Yield of carbitol (kg) 2.64 (43.2%) 4.971 (34.5%) 4.92 (33.96%) 5.07 (29.6%) 3.25 (26.7%)
EO conversion. % 34.74 74.60% 65.61 % 83.05% 67.75. %
From the above table, it is concluded that the BF3.ether catalyst with the above mentioned reaction conditions was found to be an efficient catalyst for the conversion of isopropyl alcohol to isopropyl glycol (IPG) with excellent yield and high purity.
Step-2: Synthesis of isopropyl glycol acetate in accordance with the present disclosure
Example (i): Synthesis of isopropyl glycol acetate by using Acetic acid (in presence of H2SO4 as a catalyst)
5 mmol of isopropyl glycol obtained in step-1 (Example 5) was taken in a reaction vessel followed by adding 5 mmol acetic acid dropwise and 10 ml of H2SO4 as a second catalyst to obtain a second mixture. The second mixture was gently heated with stirring at 100 °C (oil-bath) for 4 hours to obtain a product mixture comprising isopropyl glycol acetate. The reaction was monitored by IR.
The so obtained isopropyl glycol acetate was distilled out directly from the reactor vessel under reduced pressure (yield 99.2%, and 99.5% purity).
The isopropyl glycol acetate (IPGA) was characterized by, 1H NMR (Figure 2a) 13C NMR (Figure 2b), IR (Figure 2c) and mass spectral data (Figure 2d).
Example (ii): Synthesis of isopropyl glycol acetate by using Acetic acid (in presence of SiO2-H2SO4 as a catalyst)
Preparation of Sulphuric acid adsorbed on silica gel (SiO2-H2SO4):
29.5 g of silica gel having 230–400 mesh size was mixed in 70 ml of EtOAc, followed by adding 0.8 ml of 98% aq. solution of H2SO4 under magnetic stirring (magnetically) for 30 minutes to obtain slurry. EtOAc was removed from the slurry under reduced pressure using a rotary evaporator and dried at 100 °C for 72 hours under vacuum to obtain SiO2-H2SO4 as a free-flowing powder.
Preparation of Isopropyl glycol acetate in the presence of SiO2-H2SO4
5 mmol of isopropyl glycol obtained in step-1 (Example 5) was taken in a reaction vessel followed by adding 5 mmol of acetic acid dropwise and 2 g of SiO2-H2SO4 catalyst to obtain a mixture. The mixture was gently heated with stirring at 100 °C (oil-bath) for 4 hours to obtain a product mixture comprising isopropyl glycol acetate. The reaction was monitored by IR.
The so obtained isopropyl glycol acetate was distilled out directly from the reaction vessel under reduced pressure (yield 97.8%, and 98.3% purity). The catalyst was separated from the reaction by simple filtration method by Whatman filter paper (pore size 20 micrometer).
From the above two synthetic routes for the synthesis of Isopropyl glycol acetate i.e., Example (i) by using acetic acid with H2SO4 (yield 99.2%, and 99.5% purity), and Example (ii) by using SiO2.H2SO4 Catalyst (yield 97.8%, and 98.37% purity), the synthetic route of Example (i) was found to be efficient for acetylation of IPA by using H2SO4 as catalyst and commercialised to get the excellent yield with short time of period at large scale and its cost-effective method.
Comparative examples:
Comparative example 1: Synthesis of isopropyl glycol acetate by using Acetic acid (in presence of RuCl3 as a catalyst)
The same procedure of Example (ii) was followed except RuCl3 was used as a second catalyst to obtain isopropyl glycol acetate (yield 85%). When the catalyst RuCl3 (costly catalyst) was used, the time required for completion of the reaction was 6 hours which was comparatively high.
Comparative examples 2 to 5: Synthesis of isopropyl glycol acetate by using Acetic acid in presence of the catalyst as listed below
The isopropyl glycol acetate was prepared by following the same procedure of Comparative Example 1 by using different transition metal catalysts such as CeCl3, ZrCl4, La(NO3)·6H2O and Al(OTf)3. However, the yield of isopropyl glycol acetate obtained was not more than 95% and it was found that these catalysts were associated with many disadvantages in reaction procedures such as tedious work up and required more reaction time for conversion.
TECHNICAL ADVANCEMENT
The present disclosure described herein above has several technical advantages including, but not limited to, the realization of a process for the synthesis of isopropyl glycol acetate, that
• is simple and economical;
• results in higher yield and purity of the product; and
• is commercially scalable and environment friendly.
The embodiments herein and the various features and advantageous details thereof are explained with reference to the non-limiting embodiments in the following description. Descriptions of well-known components and processing techniques are omitted so as to not unnecessarily obscure the embodiments herein. The examples used herein are intended merely to facilitate an understanding of ways in which the embodiments herein may be practiced and to further enable those of skill in the art to practice the embodiments herein. Accordingly, the examples should not be construed as limiting the scope of the embodiments herein.
The foregoing description of the specific embodiments so fully reveal the general nature of the embodiments herein that others can, by applying current knowledge, readily modify and/or adapt for various applications such specific embodiments without departing from the generic concept, and, therefore, such adaptations and modifications should and are intended to be comprehended within the meaning and range of equivalents of the disclosed embodiments. It is to be understood that the phraseology or terminology employed herein is for the purpose of description and not of limitation. Therefore, while the embodiments herein have been described in terms of preferred embodiments, those skilled in the art will recognize that the embodiments herein can be practiced with modification within the spirit and scope of the embodiments as described herein.
The use of the expression “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 invention to achieve one or more of the desired objects or results. While certain embodiments of the inventions have been described, these embodiments have been presented by way of example only, and are not intended to limit the scope of the inventions. Variations or modifications to the formulation of this invention, within the scope of the invention, may occur to those skilled in the art upon reviewing the disclosure herein. Such variations or modifications are well within the spirit of this invention.
Any discussion of documents, acts, materials, devices, articles or the like that has been included in this specification is solely for the purpose of providing a context for the disclosure. It is not to be taken as an admission that any or all of these matters form a part of the prior art base or were common general knowledge in the field relevant to the disclosure as it existed anywhere before the priority date of this application.
The numerical values given for various physical parameters, dimensions, and quantities are only approximate values and it is envisaged that the values higher than the numerical value assigned to the physical parameters, dimensions and quantities fall within the scope of the invention unless there is a statement in the specification to the contrary.
While considerable emphasis has been placed herein on the specific features of the preferred embodiment, it will be appreciated that many additional features can be added and that many changes can be made in the preferred embodiment without departing from the principles of the disclosure. These and other changes in the preferred embodiment of the disclosure will be apparent to those skilled in the art from the disclosure herein, whereby it is to be distinctly understood that the foregoing descriptive matter is to be interpreted merely as illustrative of the disclosure and not as a limitation. ,CLAIMS:WE CLAIM:
1. A process for the synthesis of isopropyl glycol acetate, said process comprising the following steps:
(i) mixing a predetermined amount of isopropyl alcohol with a predetermined amount of ethylene oxide in the presence of a first catalyst under stirring to obtain a first mixture;
(ii) heating the first mixture under stirring at a first predetermined temperature for a first predetermined time period to obtain isopropyl glycol;
(iii) mixing a predetermined amount of an acylating agent with a predetermined amount of the isopropyl glycol and adding a second catalyst under stirring to obtain a second mixture; and
(iv) heating the second mixture at a second predetermined temperature for a second predetermined time period to obtain isopropyl glycol acetate.
2. The process as claimed in claim 1, wherein said first catalyst is at least one selected from the group consisting of BF3.ether, sodium hydroxide and potassium hydroxide.
3. The process as claimed in claim 1, wherein said first predetermined temperature is in the range of 60 °C to 100°C.
4. The process as claimed in claim 1, wherein said first predetermined time period is in the range of 1 hour to 4 hours.
5. The process as claimed in claim 1, wherein a weight ratio of isopropyl alcohol to ethylene oxide is in the range of 1:0.1 to 1:1.
6. The process as claimed in claim 1, wherein said acylating agent is acetic acid.
7. The process as claimed in claim 1, wherein said second catalyst is selected from the group consisting of sulphuric acid, and sulphuric acid adsorbed on silica gel (SiO2-H2SO4).
8. The process as claimed in claim 1, wherein said second predetermined temperature is in the range of 60 °C to 120 °C.
9. The process as claimed in claim 1, wherein said second predetermined time period is in the range of 2 hours to 8 hours.
10. The process as claimed in claim 1, wherein a weight ratio of isopropyl glycol to the acylating agent is in the range of 1:0.5 to 1:2.

Dated this 02nd day of November, 2023

_______________________________
MOHAN RAJKUMAR DEWAN, IN/PA – 25
of R.K.DEWAN & CO.
Authorized Agent of Applicant

TO,
THE CONTROLLER OF PATENTS
THE PATENT OFFICE, AT MUMBAI