DESC:FIELD OF THE DISCLOSURE:

The present disclosure relates to a process for the separation of aromatic impurities from hydrocarbon feed stocks.

DEFINITION:

The term raffinate used in the present disclosure refers to a stream which contains hydrocarbon oil, rich in saturated hydrocarbon and low in aromatics.

BACKGROUND OF THE INVENTION:

Hydrocarbon feedstock typically, contains hydrocarbons such as parafins, naphthenes along with impurities of aromatics, heavy asphaltic material, paraffin waxes and non-hydrocarbon material such as nitrogen compounds, sulfur compounds and oxygen compounds.

The impurities of the heavy asphaltic material and paraffin waxes, can be effectively removed by precipitation or by filtration at reduced temperatures, while the impurities of aromatics, coloring pigments and non-hydrocarbon compounds are separated using techniques such as azeotropic distillation, extractive distillation, liquid-liquid extraction, crystallization by freezing, adsorption on solids and the like. Amongst these techniques liquid-liquid extraction is the most widely used process for separating aromatics from hydrocarbon feedstock.

For instance, US4013549 discloses a process for upgrading lubricating oil stocks. The process involves separation of aromatic, sulfur and nitrogen-containing impurities using a mixture of n-methyl-2-pyrrolidone (NMP) and phenol. The mixture disclosed in the US4013549 may further contain minor amount of water.
US3415743 discloses a process for the extraction of heavy aromatics and heavy aliphatics present in the cycle oil using a solution containing dimethylformamide and water.
US3929617 discloses a process for the production of high Viscosity Index, UV stable lubricating oil. The process includes first contacting a hydrocarbon feedstock with hydrogen in the presence of a hydrocracking catalyst, at mild hydrocracking conditions, to obtain a hydrocrackate product. In the second step, at least a portion of the hydrocrackate is then extracted using a mixture of solvent having preferential solubility for aromatics. The solvents used in accordance with the process of US3929617 include furfural, phenol, NMP and dimethyl formamide.
US4273645 discloses a liquid-liquid solvent extraction process for producing lubricating oils. The solvents used in the US 4,273,645 include furfural, phenol, cresylic acid and sulfur dioxide. Further, about 0.002%-0.2% by weight of water soluble polyethylene oxide resin is added into the solvent to facilitate the phase separation and to increase the raffinate yield.
US4909927 discloses a process for the separation of aromatics present in hydrocarbon oils using a combination of solvents such as NMP, phenol, furfural, ethyl benzene and morpholine.
US5922193 discloses a process for the extraction of aromatics from gas oils and lube distillates. The solvent used in the process of US 5922193 is a mixture of furfural and ethers and/or aldehydes.
US6866772 discloses a furfural extraction process for lube oil base-stock production from hydrocarbon oils containing aromatic material. The extraction process disclosed in US 6,866,772 highlights the use of various amide based co-solvents along with furfural in order to increase the raffinate yield.
US20100243533 discloses a process for extraction of an aromatic material from hydrocarbon oil using a mixture of N-Methyl-2-Pyrrolidone (NMP) and a co-solvent along with varying water content.
From the foregoing; it is clear that the use of organic solvents with or without co-solvent, water and additives for separation of impurities from hydrocarbon feedstock are highly preferred. However, the use of such organic solvents cause serious environmental issues, therefore recently ‘green’ solvent systems are suggested, particularly using ionic liquids.

For instance, US 7019188 discloses a process for the separation of olefins, diolefins and lower aromatics from the mixed streams of hydrocarbons using ionic liquids in the absence of metal compounds. The ionic liquid used in the process of the US 7019188 includes butyl-3-methylimidazolium tetrafluoroborate and 4-methyl-N-butylpyridinium tetrafluoroborate.
EP 2292572 discloses a process for the separation of aromatic compounds from a mixture comprising aromatic and aliphatic compounds. The process involves the method step of contacting the mixture with an ionic liquid in an extraction zone to yield an aromatics rich ionic liquid stream and an aromatics-depleted aliphatic stream. The aromatics rich ionic liquid is then stripped using a non-aqueous stripping gas to obtain an aromatics-rich hydrocarbon stream and a purified ionic liquid stream.
US20130153470 discloses a process for removing one or more polycyclic aromatic hydrocarbon compounds from a vacuum gas oil. The process involves the method step of contacting the vacuum gas oil with a vacuum gas oil-immiscible phosphonium ionic liquid to produce a mixture comprising the vacuum gas oil and the vacuum gas oil-immiscible phosphonium ionic liquid. The mixture so obtained is then separated to obtain a vacuum gas oil effluent containing the polycyclic aromatic hydrocarbon compound.
Although, the use of ionic liquids as an alternative to less desirable organic solvents is under intensive research, it is observed that the use of ionic liquids for the separation of impurities further requires certain stringent operational conditions such as the use of a stripping media, vacuum, temperature, which results the process uneconomical.
Till now, NMP & co-solvent based processes and ionic liquid based extraction processes have been disclosed for aromatic extraction.
However, the processes are less efficient as far as removal of aromatics is concerned. Further, the problems incurred due the use of stringent operating conditions for ionic liquid based processes required to be resolved. The present disclosure is focused on resolving the aforesaid drawbacks and providing a hitherto novel solvent system which is capable of selectively extracting aromatic/s or impurities in an efficient manner from the hydrocarbon feedstock.
OBJECTS:
Some of the objects of the present disclosure which at least one embodiment is adapted to provide, are described herein below:
It is an object of the present disclosure to provide a novel solvent system for the separation of impurities from hydrocarbon feedstock.
It is another object of the present disclosure to provide a solvent system which is ecofriendly.
It is still another object of the present disclosure to provide a simple and economic process for the selective extraction of aromatics from hydrocarbon feed stocks.
It is yet another object of the present disclosure to provide a process for the selective extraction of aromatics from hydrocarbon feed stocks which is ecofriendly.
It is yet another object of the present disclosure to provide a process for the selective extraction of aromatics from hydrocarbon feed stocks which improves the raffinate yield by 3-4 wt%.
It is yet another object of the present disclosure to provide an energy efficient process for the selective extraction of aromatics from hydrocarbon feed stocks.
It is yet another object of the present disclosure to provide hydrocarbon oil which is low in aromatics and high in saturated hydrocarbons.
It is a further object of the present disclosure to provide pure hydrocarbon oil having improved viscosity index.
Other objects and advantages of the present disclosure will be more apparent from the following description and the accompanying drawings, which are not intended to limit the scope of the present disclosure.

BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS:
A process for the selective extraction of aromatics from hydrocarbon feed stocks of the present disclosure will now be explained in relation to the accompanying drawings, in which:
FIGURE 1 illustrates raffinate yields in a single stage extraction, using 150N as feed and the solvent systems comprising N-methyl-2 pyrrolidone (NMP), water and co-solvents (CS) at varied proportions; and
FIGURE 2 illustrates raffinate yields in a single stage extraction, using 500N as feed and the solvent systems comprising N-methyl-2 pyrrolidone (NMP), water and co-solvents (CS) at varied proportions; and
FIGURE 3 illustrates final raffinate yields in 3-stage extraction, using 500N as feed and the solvent systems comprising N-methyl-2 pyrrolidone (NMP), water and co-solvents (CS) at varied proportions.
SUMMARY
In accordance with the present disclosure there is provided a solvent system for the separation of aromatic compounds from hydrocarbon feedstock; said system comprises:
a) 60 to 90 wt. % of N-methyl-2 pyrrolidone (NMP),
b) 10 to 40 wt. % of at least one co-solvent (CS),
c) 0.1 to 1 wt. % of at least one ionic liquid (IL) and
d) 1 to 5 wt. % of water.
The present disclosure also provides a process for the selective separation of aromatic compounds from hydrocarbon feed stocks; said process comprising the following steps:
- preparing a solvent system containing 60 to 90 wt. % of N-methyl-2 pyrrolidone (NMP), 10 to 40 wt. % of at least one co-solvent (CS), 0.1 to 1 wt. % of at least one ionic liquid (IL) and 1 to 5 wt. % of water;
- contacting hydrocarbon feedstock with said solvent system at predetermined temperature and agitation conditions to obtain a biphasic system containing a raffinate phase and an extract phase; and
- separating the raffinate phase from the extract phase to obtain purified hydrocarbon oil which is low in aromatic compounds and high in saturated hydrocarbons.
DETAILED DESCRIPTION OF THE INVENTION:
In accordance with the present disclosure there is provided a novel solvent system comprising N-methyl-2 pyrrolidone (NMP), at least one co-solvent (CS), at least one ionic liquid (IL) and water for the separation of impurities/aromatic compounds from hydrocarbon feedstock. The solvent system of the present disclosure is capable of reducing the amount of aromatic compounds at least by 25 wt.%.
In the solvent system 60 to 90 wt. % of N-methyl-2 pyrrolidone (NMP) is used. The co-solvent is employed in the composition in an amount of 10 to 40 wt %, whereas the Ionic liquid is used in an amount of 0.1 to1.0 wt %. In one embodiment the amount of said ionic liquid (IL) is 0.5 wt. %.
Non limiting examples of co-solvents include amides, glycol and paraffinic hydrocarbons and the like.
The ionic liquid comprises an anion and a cation. Non-limiting examples of anion includes tetrafluoroborat, Acetate, methylsulfate, p-toluene-4-sulfonate, bis(trifluoromethylsulfonyl)imide and the like. Non-limiting examples of cation include different groups based on imidazolium, pyridinium, pyrrolidinium and the like.
The solvent system of the present disclosure also contains water in order to increase the selectivity of the system for aromatics. Water is used in an amount of 1 to 5 wt.%, preferably, 3 wt.%.
In accordance with the present disclosure there is also provided a process for the selective separation of aromatic compounds from hydrocarbon feed stocks.
The process of the present disclosure includes the following steps:
In the first step, a solvent system containing 60 to 90 wt. % of N-methyl-2 pyrrolidone (NMP), 10-40 wt. % of co-solvent (CS) and 0.1-1 wt % of ionic liquid (IL) and 1 to 5 wt. % water is prepared.
The solvent system of the present disclosure has low boiling point which makes the process of the present disclosure more energy efficient.
Non limiting examples of co-solvent include amides, glycol and paraffinic hydrocarbons. In an embodiment of the present invention, the co-solvent used in the process is amide based.
In another embodiment of the present invention, the Ionic liquid used in the process is imidazolium based.
In the second step, hydrocarbon feedstock is contacted with the solvent system of the present disclosure, at a predetermined temperature and agitation conditions to obtain a biphasic system containing a raffinate phase and an extract phase.
The raffinate phase contains hydrocarbon oil rich in saturated hydrocarbons and low in aromatic compounds while the extract phase contains the hydrocarbon oil which substantially contains aromatic compounds.
The process of the present disclosure is highly flexible to handle wide range of hydrocarbon feedstock which includes but is not limited to lube oil distillate, naphtha oil, deasphalted oil (DAO) and the like.
Further, the hydrocarbon feedstock used in accordance with the present disclosure is characterized by a boiling point ranging from 150 to 650oC.
In another embodiment of the present invention, the hydrocarbon feed stock is lube oil distillate comprising 30 wt% to 70 wt% of aromatic compounds.
The ratio of hydrocarbon feedstock to the solvent system ranges between 1:1 and 2.5:1.
In the third step, the raffinate phase is separated from the extract phase to obtain purified hydrocarbon oil which is low in aromatic compounds and high in saturated hydrocarbons.
The solvent system present in the extract phase and/ or the purified hydrocarbon oil is then recovered using a distillation technique.
The present disclosure is further described in light of the following examples which is set forth for illustration purpose only and not to be construed for limiting the scope of the disclosure.
EXAMPLES:
Example 1:
Liquid-Liquid extraction experiments were performed in single stage batch extraction equipment using NMP and water as a base solvent mixture (control). The feed Arab Mix, 150 neutral (150N) distillate was preheated. Initially, 200 gm of feed, whose properties are given in table 1, was mixed with solvent system, with solvent/Feed ratio of 1.4 (Vol/Vol) for 2 hours in a single stage glass extraction apparatus. The temperature of the equilibrium set up was kept at 70oC with stirrer rotational speed of 500 rpm. After mixing the content, it was kept for 3 hours to settle for phase separation. After settling of phases, the raffinate phase and extract phase were collected separately. The raffinate and extract phases were weighed accurately to ensure the material balance. The solvent was removed from both the phases by water wash and/or nitrogen stripping under vacuum conditions to obtain purified raffinate which is low in aromatics (aromatic compounds) and high in saturated hydrocarbons.
The refractive index of the raffinate sample was measured using refractometer, which is indication of quality of hydrocarbon oil.
Table No. 1:
S.No. Properties Result
1 Density@15oC, gm/ml 0.9134
2 Refractive index @60oC 1.4948
3 Kinematic viscosity, cSt @100oC 43
4 Distillation (ASTM-1160), oC
5 Vol% recovery 402
50/90 440/477
95 490
5 Sulphur, wt% 2.483
6 Saturates, wt% 52.0
7 Aromatics, wt% 48.0

Example 2:
The process of example 1 was repeated using NMP, water and at least one co-solvent (System I). The co-solvents and their properties are given in table 2.

Table 2
S. No. Name of Co-solvent Melting Point (oC) Boiling Point(oC) Refractive Index @ 20 oC Density@ 20oC gm/ml
1 Ehthylene Glycol -13.0 197.6 1.4385 1.1088
2 Diethylene Glycol -8.0 245.8 1.4470 1.12
3 Propylene Glycol -59 188.2 1.4470 1.036
4 N,N-Di Methyl Formamide -61.0 153 1.4305 0.949
5 N,N-Di Methyl Acetamide -18.6 163 1.4375 0.943
6 N,N-Dimethyl propionamide -45 175 1.4400 0.920
7 N-Decane -27.9 174.1 1.4110 0.730
8 N-Hexane -95.0 69.0 1.3750 0.660

The comparative results from the Liquid-Liquid equilibrium studies on 150N distillate of example 1 and example 2 are shown in the Figure 1.
Analysis of the data in the Figure 1 shows that extraction conducted with 20 % co-solvent along with NMP and water was more effective compared to control (NMP and water) in terms of raffinate yield improvement of 2 wt%. Further, the quality of raffinate in terms of RI measured at 60oC is also better.

Example 3:
The process of example 1 was repeated using NMP, water, co-solvent and at least one Ionic liquid. The ionic liquids employed and their properties are provided in table 3.

Table 3
S. No. Name of Ionic liquid Refractive Index @ 20 oC Density@ 20oC gm/ml
1 1-Butyl-3-Methylimidazolium tetrafluoroborate 1.520 1.21
2 1-Ethyl-3-Methylimidazolium Acetate 1.502 1.102
3 1-Butyl-3-Methylimidazolium Bis(trifluoro methylsulfonyl)imide 1.428 1.44
4 1-Butyl-3-MethylPyridinium tetrafluoroborate 1.400 1.204
5 1-Ethyl-3-MethylPyridinium Bis(trifluoro methylsulfonyl)imide 1.412 1.5236
6 1-Butyl-1-MethylPyrrolidinium Bis(trifluoro methylsulfonyl)imide 1.422 1.401

The comparative results from the Liquid-Liquid equilibrium studies on 150N distillate of example 1, example 2 and example 3 are shown in the Table 5.

Table 5
S. No. Case Yield RI Sulfur, wt% Saturates, wt% Aromatics, wt%
1 NMP+Water (Control) 75.4 1.4795 1.713 63.2 36.8
2 NMP+20% CS+Water (System I) 76.8 1.4794 1.704 65.5 34.5
3 NMP+20% CS+water+0.1%IL (present disclosure) 77.0 1.4789 1.696 65.9 34.1
4 NMP+20% CS+water+0.25%IL
(present disclosure) 77.3 1.4792 1.692 66.4 33.6
5 NMP+20% CS+water+0.5%IL
(present disclosure) 77.6 1.4794 1.635 66.7 33.3
6 NMP+20% CS+water+0.75%IL
(present disclosure) 78.1 1.4800 1.691 66.8 33.2
7 NMP+20% CS+water+1.0%IL
(present disclosure) 78.5 1.4810 1.701 65.0 35.0

Analysis of the data in the Table 5 shows that extraction conducted with mixed solvent system comprising 0.5 % Ionic liquid along with NMP, water and co-solvent was more effective compared to control (NMP and water) and system I (NMP, water and co-solvent) in terms of raffinate yield improvement. It is found that solvent system of the present disclosure which comprises 0.5 % Ionic liquid along with NMP, water and co-solvent of provides 3 wt% improvement in raffinate yield compared to control.
Example 4:
Liquid-Liquid extraction experiments were performed in single stage batch extraction equipment using NMP and water as base solvent mixture (control). The feed Arab Mix, 500 neutral (500N) distillate was preheated. Initially, 200 gm of feed, whose properties are given in table 4, was mixed with solvent system, with solvent/Feed ratio of 1.65 (Vol/Vol) for 2 hours in a single stage glass extraction apparatus. The temperature of the equilibrium set up was kept at 90oC with stirrer rotational speed of 500 rpm. After mixing the content, it was kept for 3 hours to settle for good phase separation. After settling of phases, the raffinate phase and extract phase were collected separately. The raffinate and extract phases were weighed accurately to ensure the material balance. The solvent was removed from both the phases by water wash and/or nitrogen stripping under vacuum conditions to obtain purified raffinate which is low in aromatics and high in saturated hydrocarbons.
The refractive index of the raffinate sample was measured using refractometer, which is indication of quality of hydrocarbon oil.
Table 4
S. No. Properties Result
1 Density@15oC, gm/ml 0.9390
2 Refractive index @60oC 1.5095
3 Viscosity, ssu @100oC 73
4 Distillation (ASTM-1160), oC
5 Vol% recovery 466
50/90 516/574
95 584
5 Sulphur, wt% 2.716
6 Saturates, wt% 42.17
7 Aromatics, wt% 58.83

Example 5:
The process of example 4 was performed with NMP, water and at least one co-solvent. The co-solvents and their properties are shown in table no. 2.
The comparative results from the Liquid-Liquid equilibrium studies on 500N distillate of example 4 and example 5 are shown in the Figure 2.
Analysis of the data in the Figure 2 shows that extraction conducted with 20 % CS along with NMP and water was more effective compared to control (NMP and water) in terms of raffinate yield improvement of 3 wt%.

Example 6:
The process of example 4 was performed with the solvent system of the present dislcosure (NMP, water, co-solvent and at least one Ionic liquid). Ionic liquids and their properties are given in table 3.
The comparative results from the Liquid-Liquid equilibrium studies on 500N distillate of example 4, example 5 and example 6 are shown in the Table 6.
Table 6
S.No. Case Yield RI Sulfur, wt% Saturates, wt% Aromatics, wt%
1 NMP+Water 68.3 1.4828 1.673 50.57 49.43
2 NMP+20% CS+Water 71.8 1.4825 1.637 52.12 47.88
3 NMP+20% CS+water+0.1%IL 72.0 1.4821 1.606 53.68 46.32
4 NMP+20% CS+water+0.25%IL 72.5 1.4819 1.568 56.72 43.28
5 NMP+20% CS+water+0.5%IL 73.4 1.4815 1.521 58.01 41.99
6 NMP+20% CS+water+0.75%IL 73.5 1.4823 1.541 57.25 42.75
7 NMP+20% CS+water+1.0%IL 73.8 1.4832 1.604 56.14 43.86

Analysis of the data in the Table 6 shows that extraction conducted with mixed solvent system comprising 0.5 % ionic liquid along with NMP, water and co-solvent was more effective compared to control (NMP and water) and system I (NMP, water and co-solvent) in terms of raffinate yield.
It is found that solvent system of the present disclosure which comprises 0.5 % Ionic liquid along with NMP, water and co-solvent of provides 4 wt% improvement in raffinate yield compared to control.

Example 7:
3-stage Liquid-Liquid extraction experiments were performed in a batch extraction equipment using NMP and water as a control (base solvent mixture) to match the experimental data of raffinate yields and quality with the refinery data. The feed Arab Mix, 500 neutral (500N) distillate was preheated. Initially, the first stage of Liquid-Liquid extraction was carried out using 200 gm of 500N feed, and the operating conditions and procedure followed was same as in example 4.
The second stage of Liquid-Liquid extraction was performed using the raffinate from the first stage of extraction as feed and it was mixed with solvent system (NMP+water), with solvent/Feed ratio of 1.65 (Vol/Vol) for 2 hours in a single stage glass extraction apparatus. The temperature of the equilibrium set up was kept at 90oC with stirrer rotational speed of 500 rpm. After mixing the content, it was kept for 3 hours to settle for good phase separation. After settling of phases, the raffinate phase and extract phase were collected separately. The raffinate and extract phases were weighed accurately to ensure the material balance. The solvent was removed from both the phases by water wash and/or nitrogen stripping under vacuum conditions to obtain purified raffinate which is low in aromatics and high in saturated hydrocarbons.
The third stage of Liquid-Liquid extraction was carried out using the raffinate from the second stage of extraction as a feed and it was mixed with solvent system (NMP+water), with solvent/Feed ratio of 1.65 (Vol/Vol) for 2 hours in a single stage glass extraction apparatus. The temperature of the equilibrium set up was kept at 90oC with stirrer rotational speed of 500 rpm. After mixing the content, it was kept for 3 hours to settle and for good phase separation. After settling of phases, the raffinate phase and extract phase are collected separately. The raffinate and extract phases were weighed accurately to ensure the material balance. The solvent was removed from both the phases by water wash and/or nitrogen stripping under vacuum conditions to obtain final purified raffinate which is low in aromatics and high in saturated hydrocarbons.

Example 8:
The process of example 7 was performed with NMP, water and at least one co-solvent.
The comparative results from the 3- stage Liquid-Liquid equilibrium studies on 500N distillate of example 7 and example 8 are shown in the Figure 3.
Analysis of the data in the Figure 3 shows that extraction conducted with 20 % CS along with NMP and water was more effective compared to control (NMP and water) in terms of raffinate yield improvement of 2.0 wt%.
Example 9:
The process of example 8 was performed with the solvent system of the present disclosure (NMP, water, co-solvent and at least one Ionic liquid).
The comparative results from the 3-stage Liquid-Liquid equilibrium studies on 500N distillate of example 7, example 8 and example 9 are shown in the Table 7.
Table 7
S.No. Case Yield RI Sulfur, wt% Saturates, wt% Aromatics, wt%
1 NMP+Water 58.4 1.4742 1.32 61.0 39.0
1 NMP+20% CS+Water 60.2 1.4748 1.29 63.01 36.99
2 NMP+20% CS+water+0.1%IL 60.5 1.4739 1.26 63.45 36.55
3 NMP+20% CS+water+0.25%IL 60.7 1.4744 1.23 66.52 33.48
4 NMP+20% CS+water+0.5%IL 61.1 1.4747 1.18 69.87 30.13
5 NMP+20% CS+water+0.75%IL 61.5 1.4750 1.22 68.79 31.21
6 NMP+20% CS+water+1.0%IL 61.2 1.4755 1.24 68.41 31.59

Analysis of the data in the Table 7 shows that 3-stage extraction studies conducted with mixed solvent system comprising of 0.5 % Ionic liquid along with NMP, water and co-solvent was more effective compared to control (NMP and water) and system I (NMP, water and co-solvent) in terms of raffinate yield.
It is found that solvent system of the present disclosure which comprises 0.5 % Ionic liquid along with NMP, water and co-solvent of provides 2.5 wt% improvement in raffinate yield compared to control.

TECHNICAL ADVANCEMENTS AND ECONOMIC SIGNIFICANCE
The solvent system used in the present disclosure has low boiling point which makes the process energy efficient by decreasing the recovery column temperatures.
Yield of the hydrocarbon oil obtained from the process of the present disclosure based on mixed solvent system containing Ionic liquids is higher by 3 to 4 wt% compared to control (NMP+ water) and system I (NMP+water+atleast one co-solvent) which makes the process of the present disclosure cost effective.

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.
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 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 in the process or compound or formulation or combination 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. ,CLAIMS:1. A solvent system for the separation of aromatic compounds from hydrocarbon feedstock; said system comprises:
a) 60 to 90 wt. % of N-methyl-2 pyrrolidone (NMP),
b) 10 to 40 wt. % of at least one co-solvent (CS),
c) 0.1 to 1 wt. % of at least one ionic liquid (IL), and
d) 1 to 5 wt. % of water.

2. The system as claimed in claim 1, wherein the co-solvent is selected from the group consisting of amides, glycols and paraffinic hydrocarbons.

3. The system as claimed in claim 1, wherein the ionic liquid comprises an anion and a cation, said anion is selected from the group consisting of tetrafluoroborat, acetate, methylsulfate, p-toluene-4-sulfonate, and bis(trifluoromethylsulfonyl)imide; and said cation is selected from the group consisting of imidazolium, pyridinium and pyrrolidinium.

4. The system as claimed in claim 1, wherein the amount of said ionic liquid (IL) is 0.5 wt. %.

5. The system as claimed in claim 1, wherein the amount water is 3 wt.%.

6. The system as claimed in claim 1, characterized in that said system is capable of reducing the amount of aromatic compounds at least by 25 wt.%.

7. A process for the selective separation of aromatic compounds from hydrocarbon feed stocks; said process comprising the following steps:
- preparing a solvent system containing 60 to 90 wt. % of N-methyl-2 pyrrolidone (NMP), 10 to 40 wt. % of at least one co-solvent (CS), 0.1 to 1 wt. % of at least one ionic liquid (IL) and 1 to 5 wt. % of water;
- contacting hydrocarbon feedstock with said solvent system at predetermined temperature and agitation conditions to obtain a biphasic system containing a raffinate phase and an extract phase; and
- separating the raffinate phase from the extract phase to obtain purified hydrocarbon oil which is low in aromatic compounds and high in saturated hydrocarbons.

8. The process as claimed in claim 7, wherein the extract phase contains the hydrocarbon oil which substantially contains in aromatic compounds.

9. The process as claimed in claim 7, wherein the hydrocarbon feedstock is selected from the group consisting of lube oil distillate, naphtha oil and deasphalted oil (DAO).

10. The process as claimed in claim 7, wherein the hydrocarbon feedstock is characterized by a boiling point ranging from 150 and 650oC.

11. The process as claimed in claim 7, wherein the hydrocarbon feed stock is lube oil distillate comprising 30 wt% to 70 wt% of aromatic compounds.

12. The process as claimed in claim 7, wherein the ratio of hydrocarbon feedstock to the solvent system ranges from 1:1 to 2.5:1.

13. The process as claimed in claim 7, further comprises a step of recovering the solvent system using a distillation technique.