Claims:1. An ionic liquid comprising at least one nitrogen containing Lewis base, at least one Bronsted acid, and at least one metal salt; wherein the at least one nitrogen containing Lewis base is selected from the group consisting of urea, amides, cyclic 5-membered-ring amides, cyclic 6-membered-ring amides, amines, cyclic 5-membered-ring amines, and cyclic 6-membered-ring amines.

2. The ionic liquid as claimed in claim 1, wherein the at least one nitrogen containing Lewis base is selected from the group consisting of urea, acetamide, methyl-2-pyrrolidone, triethylamine, diethylisopropylamine, and triisopropylamine.

3. The ionic liquid as claimed in claim 1, wherein the at least one Bronsted acid is selected from the group consisting of HF, HCl, H2SO4, HBr, H3PO4, and HClO4.

4. The ionic liquid as claimed in claim 1, wherein the metal in the at least one metal salt is selected from the group consisting of Al, Mg, Cr, Mn, Fe, Co, Ni, Cu, Zn, Ga, Ge, In, Sn, Ti, Pb, Cd, and Hg; and the salt is at least one selected from the group consisting of chloride, bromide, iodide, sulfate, acetate, and chromate.
5. The ionic liquid as claimed in claim 1, wherein the molar ratio of the at least one nitrogen containing Lewis base and the at least one Bronsted acid is in the range of 4:1 to 1:4.

6. The ionic liquid as claimed in claim 1, wherein the molar ratio of the at least one nitrogen containing Lewis base and the at least one metal salt is in the range of 10:1 to 1:10.

7. The ionic liquid as claimed in claim 1, further comprises at least one fluid medium selected from the group consisting of benzene, toluene, xylene, chlorobenzene, nitrobenzene, substituted benzene compounds, dichloromethane, and dichloroethane.

8. A process for the preparation of the ionic liquid as claimed in claim 1, said process comprises the following steps:
? contacting the at least one nitrogen containing Lewis base and the at least one Bronsted acid to form an adduct; and
? reacting the adduct with the at least one metal salt and stirring the resultant mixture at a temperature in the range of 10 ?C to 100 ?C for a time period of 1 hour to 10 hours, to form the ionic liquid.
9. A process for the preparation of the ionic liquid as claimed in claim 1, said process comprising stirring a mixture of the at least one nitrogen containing Lewis base and the at least one metal salt at a temperature in the range of 10 ?C to 100 ?C for a time period of 1 hour to 10 hours, followed by adding the at least one Bronsted acid and stirring the resultant mixture at a temperature in the range of 10 ?C to 100 ?C for a time period of 1 hour to 10 hours, to obtain the ionic liquid. , Description:FIELD
The present disclosure relates to ionic liquids.
BACKGROUND
Ionic liquids comprise anionic components and cationic components that interact with each other. The ionic liquids exhibit low vapor pressure, have high ionic conductivity and have low flammability.
Conventional ionic liquids may be associated with one or more problems such as high cost, poor biodegradability, and low ‘recovery and reuse’ potential. Further, the preparation of ionic liquids is complex, and time consuming. Still further, ionic liquids derived from Lewis base may undergo decomposition at high temperature.
There is, therefore, a need to provide cost-effective and environment-friendly ionic liquids having desired activity. Further, it is desired that the ionic liquids that can be prepared by a simple process.
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 prior art or to at least provide a useful alternative.
An object of the present disclosure is to provide an ionic liquid.
Another object of the present disclosure is to provide cost-effective and environment-friendly ionic liquids.
Another object of the present disclosure is to provide an ionic liquid prepared by a simple process.
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
In an aspect, the present disclosure provides an ionic liquid comprising at least one nitrogen containing Lewis base, at least one Bronsted acid and at least one metal salt. The at least one nitrogen containing Lewis base is selected from the group consisting of urea, amides, cyclic 5-membered-ring amides, cyclic 6-membered-ring amides, amines, cyclic 5-membered-ring amines, and cyclic 6-membered-ring amines. The at least one Bronsted acid can be selected from the group consisting of HF, HCl, H2SO4, HBr, H3PO4, and HClO4. The metal in the at least one metal salt can be selected from the group consisting of Al, Mg, Cr, Mn, Fe, Co, Ni, Cu, Zn, Ga, Ge, In, Sn, Ti, Pb, Cd, and Hg. The salt can be at least one selected from the group consisting of chloride, bromide, iodide, sulfate, acetate, and chromate.
In another aspect, the present disclosure provides a process for preparing the ionic liquids of the present disclosure.
The ionic liquids of the present application are cost-effective, environment friendly and can be used for various reactions such as alkylation, trans-alkylation, acylation, Diel-Alder reaction, Friedel-Crafts reaction, and oligomerization.

DETAILED DESCRIPTION
An environment-friendly and cost-effective catalyst having desired activity is preferred for carrying out reactions at industrial scale. The present disclosure envisages ionic liquids prepared from inexpensive and environment-friendly starting materials, using a simple process. Particularly, ionic liquids that can be recycled and reused easily are envisaged.
In an aspect, the present disclosure provides an ionic liquid comprising at least one nitrogen containing Lewis base, at least one Bronsted acid and at least one metal salt. The at least one nitrogen containing Lewis base is selected from the group consisting of urea, amides, cyclic 5-membered-ring amides, cyclic 6-membered-ring amides, amines, cyclic 5-membered-ring amines, and cyclic 6-membered-ring amines.
In accordance with the embodiments of the present disclosure, the at least one nitrogen containing Lewis base can be selected from the group consisting of urea, N-methyl-2-pyrilidone, acetamide, triethylamine, diethylisopropylamine, and triisopropylamine.
In accordance with one embodiment of the present disclosure, the at least one nitrogen containing Lewis base is urea.
In accordance with another embodiment of the present disclosure, the at least one nitrogen containing Lewis base is triethylamine.
In accordance with another embodiment of the present disclosure, the at least one nitrogen containing Lewis base is N-methyl-2-pyrrolidone.
In accordance with the embodiments of the present disclosure, the at least one Bronsted acid can be selected from the group consisting of HF, HCl, H2SO4, HBr, H3PO4, and HClO4.
In accordance with one embodiment of the present disclosure, the at least one Bronsted acid is H2SO4.
In accordance with another embodiment of the present disclosure, the at least one Bronsted acid is HCl.
In accordance with the embodiments of the present disclosure, the metal in the at least one metal salt can be selected from the group consisting of Al, Mg, Cr, Mn, Fe, Co, Ni, Cu, Zn, Ga, Ge, In, Sn, Ti, Pb, Cd, and Hg.
In accordance with the embodiments of the present disclosure, the salt can be at least one selected from the group consisting of chloride, bromide, iodide, sulfate, acetate, and chromate.
In accordance with one exemplary embodiment of the present disclosure, the metal salt is aluminum trichloride (AlCl3).
In accordance with another embodiment of the present disclosure, the metal salt is ferric chloride (FeCl3).
In accordance with yet another embodiment of the present disclosure, the metal salt is copper chloride (CuCl2).
In accordance with still another embodiment of the present disclosure, the metal salt is Nickel chloride (NiCl2).
The metals salts of metals such as Al, Mg, Cr, Mn, Fe, Co, Ni, Cu, Zn, Ga, Ge, In, Sn, Ti, Pb, Cd, and Hg, that interact in a way similar to AlCl3, FeCl3, CuCl2, and NiCl2; and form ionic liquids, are envisioned in accordance with the disclosure.
In accordance with the embodiments of the present disclosure, the molar ratio of the at least one nitrogen containing Lewis base and the at least one Bronsted acid can be in the range of 4:1 to 1:4.
In accordance with one embodiment of the present disclosure, the molar ratio of the at least one nitrogen containing Lewis base and the at least one Bronsted acid is 2:1.
In accordance with another embodiment of the present disclosure, the molar ratio of the at least one nitrogen containing Lewis base and the at least one Bronsted acid is 1:1.
In accordance with the embodiments of the present disclosure, the molar ratio of the at least one nitrogen containing Lewis base and the at least one metal salt can be in the range of 10:1 to 1:10.
In accordance with one embodiment of the present disclosure, the molar ratio of the at least one nitrogen containing Lewis base and the at least one metal salt is 1:4.
In accordance with another embodiment of the present disclosure, the molar ratio of the at least one nitrogen containing Lewis base and the at least one metal salt is 1:2.
The at least one nitrogen containing Lewis base, the at least one Bronsted acid and the at least one metal salt used for the preparation of the ionic liquids of the present disclosure are inexpensive and environment-friendly. Therefore, the ionic liquids of the present disclosure are also inexpensive and environment-friendly.
The catalytic activity of the ionic liquids of the present disclosure depends upon the at least one Lewis base, the at least one Bronsted acid and the at least one metal salt; and their relative amounts. Further, the ionic liquids of the disclosure have tunable acidity. The desired acidity can be achieved by selection of appropriate Bronsted acid. Further, the metal salt and its amount can also influence the acidity of the ionic liquids of the present disclosure.
Ionic liquids of the present disclosure exhibit a low vapor pressure, and low flammability. Due to these characteristics, the ionic liquids of the present disclosure are safer and environmentally friendly.
In accordance with the embodiments of the present disclosure, the ionic liquid further comprises at least one fluid medium selected from the group consisting of benzene, toluene, xylene, chlorobenzene, nitrobenzene, substituted benzene compounds, dichloromethane, and dichloroethane.
In accordance with one embodiment of the present disclosure, the ionic liquid comprises benzene as a fluid medium.
In second aspect, the present disclosure provides a process for the preparation of the ionic liquids of the present disclosure. The process involves the following steps: First, at least one nitrogen containing Lewis base is contacted with at least one Bronsted acid to form an adduct. The adduct is reacted with at least one metal salt and the resultant mixture is stirred at a temperature in the range of 10 ?C to 100 ?C for a time period of 1 hour to 10 hours, to obtain the ionic liquid.
The step of adduct formation can be carried out without the use of a fluid medium.
The step of adduct formation can be carried out in the presence of at least one fluid medium. In accordance with one embodiment of the present disclosure, the step of adduct formation is carried out in benzene as a fluid medium.
The step of reacting the adduct with at least one metal salt can be carried out in the presence of at least one fluid medium. In accordance with one embodiment of the present disclosure, the step of reacting the adduct with at least one metal salt is carried out in benzene as a fluid medium.
The ionic liquid of the present disclosure can also be prepared by a process involving the following steps. A mixture of the at least one nitrogen containing Lewis base and the at least one metal salt is stirred at a temperature in the range of 10 ?C to 100 ?C for a time period of 1 hour to 10 hours. Then, at least one Bronsted acid is added and the resultant mixture is stirred at a temperature in the range of 10 ?C to 100 ?C for a time period of 1 hour to 10 hours, to obtain the ionic liquid.
Thus, the ionic liquids of the process of the present disclosure are prepared using a simple process.
The ionic liquid of the present disclosure can be used for various reactions such as alkylation, trans-alkylation, acylation, Diel-Alder reaction, Friedel-Crafts reaction, and oligomerization. These reactions can be carried out using 0.1% to 10% w/w of the ionic liquids of the present disclosure, as a catalyst.
After completion of the reaction, the ionic liquid of the present disclosure can be easily recovered. The recovered ionic liquids can be reused for the next cycle without processing. Thus, the recovery and reuse of the ionic liquids is simple.
The alkylation of benzene with olefins in the presence of the ionic liquid of the present disclosure provides an excellent yield of linear alkyl benzenes (LABs).
Further, the trans-alkylation of heavier alkyl benzene (HAB) with benzene can be carried out using the ionic liquid of the present disclosure, as a catalyst.
The disclosure will now be described with reference to the following laboratory experiments, which do not limit the scope and ambit of the disclosure. The description provided is purely by way of example and illustration.
The laboratory scale experiments provided herein can be scaled up to industrial or commercial scale.
EXPERIMENTS
Experiment 1: Preparation of Urea-H2SO4 adduct with benzene as a fluid medium
Dried urea (9.9 g) was added to a reactor followed by benzene (15 g) and concentrated (98% w/w) sulphuric acid (8.08 g) and the resultant mixture was stirred for 30 min at room temperature, during which a white precipitate formed. The supernatant was decanted and the white solid precipitate was separated, and dried to obtain a Urea-H2SO4 adduct in benzene.

Experiment 2: Preparation of Urea-H2SO4 adduct without the use of a fluid medium
Concentrated (98% w/w) sulphuric acid (8.08 g) was added dropwise to dried urea (9.9 g) and the resultant mixture was stirred for 30 min at room temperature. The white solid precipitate was dried to obtain a Urea-H2SO4 adduct.

Experiment 3: Preparation of Urea-H2SO4-AlCl3 ionic liquid with benzene as a fluid medium
The Urea-H2SO4 adduct (18.29 g) obtained in experiment-1 was mixed with AlCl3 (33.5 g) and benzene (20 g) in a reactor under nitrogen atmosphere at 30 0C. The resultant mixture was stirred for 3 h to obtain Urea-H2SO4-AlCl3 ionic liquid.
Experiment 4: Preparation of Urea-H2SO4-AlCl3 ionic liquid with benzene as a fluid medium
To a mixture of urea (6g) and benzene (20 g), was slowly added AlCl3 (20 g) in a reactor under nitrogen atmosphere at 30 0C. The resultant mixture was stirred for 3 h followed by slow addition of H2SO4 (9.8g) and stirring for 3 h to obtain Urea- AlCl3- H2SO4 ionic liquid with benzene as a fluid medium.
This experiment can also be performed without the use of a fluid medium to obtain Urea- AlCl3- H2SO4 ionic liquid in the form of a eutectic liquid.

Experiment 5: Preparation of TEA-H2SO4 adduct without using a fluid medium
Triethylamine (TEA) (10 g) was added to a reactor at 5 ?C, followed by dropwise addition of H2SO4 (9.7 g) while the reaction mass was continuously stirred. A white solid mass was obtained. The white solid mass was washed with dichloromethane (DCM) and dried to provide TEA-H2SO4 adduct. The TEA-H2SO4 adduct was stored under inert atmosphere.

Experiment 6: Preparation of TEA-H2SO4-AlCl3 ionic liquid in the form of a eutectic liquid
To a reactor maintained under nitrogen atmosphere was added TEA-H2SO4 adduct (5 g) obtained in the Experiment-5 and AlCl3 (6.7 g). The resultant mixture was stirred for 1 hour to obtain TEA-H2SO4-AlCl3 ionic liquid in the form of a pale yellow coloured eutectic liquid.

Experiment 7: NMP-HCl adduct formation with benzene as a fluid medium
Hydrogen chloride (HCl) gas was purged through a reactor containing a solution of N-Methyl-2-pyrrolidone (NMP) (10 g, 1 mol) in benzene (5 g). The gas stream exiting the reactor was passed through water and pH of water was checked continuously. When the pH of water was 1, the purging of HCl gas was stopped. A precipitate comprising adduct in the form of colorless crystals was obtained. The precipitate was separated and dried to provide NMP-HCl adduct.

Experiment 8: Preparation of NMP-HCl-AlCl3 ionic liquid with benzene as a fluid medium
To a reactor, maintained under nitrogen atmosphere, were charged the adduct (5 g) obtained in Experiment 7, anhydrous AlCl3 (4.9 g, 1.5 mol) and benzene (5 g) at room temperature. The resultant mixture was stirred for 3.5 hours at room temperature to obtain NMP-HCl-AlCl3 ionic liquid in benzene.

Experiment 9: NMP-HCl adduct formation without a fluid medium
Hydrogen chloride (HCl) gas was purged through a reactor containing N-Methyl-2-pyrrolidone (NMP) (10 g, 1 mol). The gas stream exiting the reactor was passed through water and pH of water was checked continuously. When the pH of water was 1, the purging of HCl gas was stopped. The resultant product was dried to obtain NMP-HCl adduct in the form of colorless crystals.

Experiment 10: Preparation of NMP-HCl-AlCl3 ionic liquid as a eutectic liquid
To a reactor, maintained under nitrogen atmosphere, were charged the adduct (5 g) obtained in Experiment 9, and anhydrous AlCl3 (4.9 g, 1.5 mol) at room temperature. The resultant mixture was stirred at room temperature for 3.5 hours to obtain NMP-HCl-AlCl3 ionic liquid in the form of a eutectic liquid.

Experiment 11: Preparation of NMP-HCl-FeCl3 ionic liquid with benzene as a fluid medium
To a reactor, maintained under nitrogen atmosphere, were charged the NMP-HCl adduct (2.7 g) obtained in Experiment 7, anhydrous FeCl3 (6.48 g) and benzene (20 g) at 65oC. The resultant mixture was stirred for 2 hours at 65oC followed by cooling to obtain NMP-HCl-FeCl3 ionic liquid in benzene in the form of a brown colored semi-viscous liquid.

Experiment 12: Preparation of NMP-HCl-CuCl2 ionic liquid with benzene as a fluid medium
To a reactor, maintained under nitrogen atmosphere, were charged the NMP-HCl adduct (2.7 g) obtained in Experiment 7, anhydrous CuCl2 (5.36 g) and benzene (20 g) at 65oC. The resultant mixture was stirred for 2 hours at 65oC followed by cooling to obtain NMP-HCl-CuCl2 ionic liquid in benzene in the form of a dark greenish brown colored semi-viscous liquid.

Experiment 13: Preparation of NMP-HCl-NiCl2 ionic liquid with benzene as a fluid medium
To a reactor, maintained under nitrogen atmosphere, were charged the NMP-HCl adduct (2.7 g) obtained in Experiment 7, anhydrous NiCl2 (5.16 g) and benzene (20 g) at 65oC. The resultant mixture was stirred for 2 hours at 65oC followed by cooling to obtain NMP-HCl- NiCl2 ionic liquid in benzene in the form of a brown colored viscous liquid.

Experiment 14: Alkylation of benzene with a hydrocarbon feed in the presence of Urea-H2SO4-AlCl3 ionic liquid
To a reactor maintained under nitrogen atmosphere, were charged a hydrocarbon fraction (72 g) containing 80% paraffin and 20% olefin, and benzene (28 g) and the resultant mixture was heated to 45 oC. Urea-H2SO4-AlCl3 ionic liquid (1.6 g) obtained in the experiment-3 was added to the mixture and the reaction mixture was stirred at 45oC for 10 min. After the completion of the reaction, the hydrocarbon layer and ionic liquid layer were allowed to separate. The hydrocarbon layer showed 88% conversion of the olefin initially present in the hydrocarbon fraction to produce linear alkyl benzene (LAB).
The separated ionic liquid layer was reused.

Experiment 15: Alkylation of benzene with a hydrocarbon feed in the presence of TEA-H2SO4-AlCl3 ionic liquid
To a reactor maintained under nitrogen atmosphere were charged a hydrocarbon fraction (72 g) containing 80% paraffin and 20% olefin, and benzene (28 g), and the resultant mixture was heated to 45oC. TEA-H2SO4-AlCl3 ionic liquid (1g) obtained in the experiment-6 was added to the mixture and the reaction mixture was stirred at 45oC for 10 min. After the completion of the reaction, the hydrocarbon layer and ionic liquid layer were allowed to separate. The hydrocarbon layer showed 96% conversion of the olefin initially present in the hydrocarbon fraction to form linear alkyl benzene (LAB).
The separated ionic liquid layer was reused.

Experiment 16: Alkylation of benzene with a hydrocarbon feed in the presence of NMP-HCl-AlCl3 ionic liquid
A hydrocarbon feed containing paraffin and olefins was used as an alkylating agent for the alkylation of benzene. The product of the alkyaltion of benzene was linear alkyl benzene (LAB).
To a reactor maintained under nitrogen atmosphere, was charged benzene (23.4 g) and a hydrocarbon feed containing 20% olefin (72.0g) and 80% paraffins, and heated to 45 ?C. The NMP-HCl-AlCl3 ionic liquid (1.2 g) obtained in Experiment-8 was added to the mixture and the reaction mixture was stirred for 10 minutes.
Heating and stirring was stopped and the reaction mass is allowed to settle. The hydrocarbon layer was separated, analyzed for bromine index to get olefin content. The conversion of olefins to LAB was found to be 99.5%.
The ionic liquid layer was separated and reused.

Experiment 17: Trans-alkylation reaction of higher alkyl benzenes in the presence of NMP-HCl-AlCl3 ionic liquid
11.7 ml (10.0 gm) of heavier alkyl benzene stream, containing 10 % linear alkyl benzene and 90 % heaviers such as dilakylbenzenes and oligomers, was added to a reactor maintained under nitrogen atmosphere. The content of the reactor was heated to 85 oC and benzene (60 gm) was added to the reactor. The resultant mixture was heated to 80 oC and stirred for 15 mins, followed by addition of NMP-HCl-AlCl3 (11 gm) ionic liquid obtained in Experiment-8. The reaction mixture was stirred for 2 hours. The reaction mixture was cooled and allowed to settle and the hydrocarbon layer and ionic liquid layer were separated. The upper layer was the hydrocarbon layer and the lower layer was catalyst layer. The upper layer was analyzed by gas chromatography. The conversion of the heaviers was 25%.
The ionic liquid layer was separated and reused.

TECHNICAL ADVANCEMENTS
The present disclosure described herein above has several technical advantages including, but not limited to, the realization of ionic liquids:
? prepared from inexpensive and environment-friendly components;
? having tunable catalytic activity;
? that can be easily recovered and reused; and
? prepared by a simple process.

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 “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.
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.