Claims:WE CLAIM:
1. A solvent system for the separation of aromatic compounds from a hydrocarbon feedstock, said solvent system comprising:
• N-methyl-2-pyrrolidone (NMP) in an amount in the range of 91 wt% to 97 wt%;
• ethylene glycol in an amount in the range of 1 wt% to 5 wt%;
• at least one ionic liquid in an amount in the range of 0.1 wt% to 1 wt%; and
• water in an amount in the range of 1 wt% to 5 wt%
2. The solvent system as claimed in claim 1, wherein said ionic liquid comprises:
• an anion selected from the group consisting of tetrafluroborate, acetate, methylsulfate, p-toluene-4-sulfonate, and bis(trifluromethylsulfonyl)imide; and
• a cation selected from the group consisting of imidazolium, pyridinium, and pyrrolidinium.
3. The solvent system as claimed in claim 2, wherein said cation is imidazolium.
4. A solvent system for the separation of aromatic compounds from a hydrocarbon feedstock, said solvent system comprising:
• N-methyl-2-pyrrolidone (NMP) in an amount in the range of 93 wt% to 94 wt%;
• ethylene glycol in an amount of 3 wt%;
• at least one ionic liquid in an amount in the range of 0.1 wt% to 0.5 wt%; and
• water in an amount of 2 wt% to 4 wt%;
wherein, said at least one ionic liquid is selected from the group consisting of 1-Butyl-3-Methylimidazolium tetrafluoroborate, 1-Ethyl-3-Methylimidazolium Acetate, and 1-Butyl-3-Methylimidazolium Bis(trifluoromethylsulfonyl)imid.
5. The solvent system as claimed in claim 4, wherein the amount of water is 3 wt%.
6. A process for selective separation of aromatic compounds from a hydrocarbon feedstock, said process comprising the following steps:
a. preparing a solvent system comprising 91 wt% to 97 wt% of N-methyl-2 pyrrolidone (NMP), 1 wt% to 5 wt% of ethylene glycol, 0.1 wt% to 1 wt% of at least one ionic liquid and 1 wt% to 5 wt% of water;
b. contacting said hydrocarbon feedstock with said solvent system of step a, at a predetermined temperature under agitation to form a biphasic system containing a raffinate phase and an extract phase; and
c. separating said raffinate phase from said extract phase in said biphasic system, wherein said raffinate phase comprises substantially lower amount of aromatic compounds and higher amount of saturated hydrocarbons.
7. The process as claimed in claim 6, wherein said hydrocarbon feedstock is at least one selected from the group consisting of lube oil distillate, naphtha, and deasphalted oil (DAO).
8. The process as claimed in claim 6, wherein the ratio of said hydrocarbon feedstock to said solvent system is in the range of 1:1 to 2.5:1 (vol/vol).
9. The process as claimed in claim 6, wherein said predetermined temperature in step (b) is in the range of 60?C to 130?C.
10. The process as claimed in claim 6, further comprising a step of recovering the solvent system from said raffinate phase and said extract phase either by a process step of distillation and/or nitrogen stripping.
, Description:This is an application for a patent of addition to the Indian Patent Application No. 39/MUM/2014 filed on 06/01/2014 the entire contents of which are specifically incorporated herein by reference.
FIELD
The present disclosure relates to a solvent system for the separation of aromatic compounds from a hydrocarbon feedstock.
DEFINITIONS
As used in the present disclosure, the following terms are generally intended to have the meaning as set forth below, except to the extent that the context in which they are used indicate otherwise.
Raffinate: The term raffinate used in the present disclosure refers to a stream which contains hydrocarbon oil, rich in saturated hydrocarbons and low in aromatics.
BACKGROUND
Hydrocarbon feedstock typically contains hydrocarbons such as paraffins, 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 can be 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, wherein 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 organic solvents cause serious environmental issues, therefore recently ‘green’ solvent systems have been suggested, particularly ionic liquids.
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 makes the process uneconomical. Further, these processes are less efficient as far as removal of aromatics is concerned. Therefore, the problems incurred due to the use of stringent operating conditions for ionic liquid based processes are required to be resolved.
Therefore, there is felt a need to reduce the aforesaid drawbacks and provide a solvent system which is capable of selectively separating aromatic compounds in an efficient manner from the hydrocarbon feedstock.
OBJECTS:
Some of the objects of the present disclosure which at least one embodiment herein satisfies, are as follow:
An object of the present disclosure is to provide a solvent system for the separation of aromatic compounds from a hydrocarbon feedstock.
Another object of the present disclosure is to provide a solvent system which is ecofriendly.
Yet another object of the present disclosure is to provide a simple and economic process for the selective separation of aromatic compounds from a hydrocarbon feedstock.
Still another object of the present disclosure is to provide an ecofriendly process for the selective extraction of aromatic compounds from a hydrocarbon feedstock.
Yet another object of the present disclosure is to provide an energy efficient process for the selective separation of aromatics from a hydrocarbon feedstock.
Still another object of the present disclosure is to provide hydrocarbon oil which is low in aromatics and high in saturated hydrocarbons.
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.
SUMMARY
The present disclosure provides a solvent system for the separation of aromatic compounds from a hydrocarbon feedstock. The solvent system of the present disclosure comprises: N-methyl-2-pyrrolidone (NMP) in an amount in the range of 91 wt% to 97 wt%; ethylene glycol in an amount in the range of 1 wt% to 5 wt%; at least one ionic liquid in an amount in the range of 0.1 wt% to 1 wt%; and water in an amount in the range of 1 wt% to 5 wt%. The ionic liquid of the solvent system comprises an anion selected from the group consisting of tetrafluroborate, acetate, methylsulfate, p-toluene-4-sulfonate, and bis(trifluromethylsulfonyl)imide; and a cation selected from the group consisting of imidazolium, pyridinium, and pyrrolidinium. The solvent system of the present disclosure is characterized by an efficacy of separating at least 25 wt% of aromatic compounds present in the hydrocarbon feedstock.
Further, a process for the selective separation of aromatic compounds from a hydrocarbon feedstock is disclosed. The hydrocarbon feedstock that can be used for selective separation is at least one selected from the group consisting of lube oil distillate, naphtha, and deasphalted oil (DAO), and is characterized by a boiling point in the range of 150?C to 650?C. As per the process of the present disclosure, a solvent system comprising 91 wt% to 97 wt% of N-methyl-2 pyrrolidone (NMP), 1 wt% to 5 wt% of ethylene glycol, 0.1 wt% to 1 wt% of at least one ionic liquid and 1 wt% to 5 wt% of water is prepared. Thereafter, the hydrocarbon feedstock is contacted with the solvent system at a predetermined temperature in the range of 60?C to 130?C under stirring to form a biphasic system containing a raffinate phase and an extract phase. The ratio of the hydrocarbon feedstock to the solvent system is maintained in the range of 1:1 to 2.5:1 (vol/vol). From the biphasic system, the raffinate phase is separated, wherein the raffinate phase comprises hydrocarbon oil having substantially lower amount of aromatic compounds and higher amount of saturated hydrocarbons as compared to the hydrocarbon feedstock. The process of the present application may further comprise a step of recovering the solvent system from the raffinate phase and the extract phase using distillation and/or nitrogen stripping.
BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWING
The present disclosure will now be described with the help of the accompanying drawing, in which:
Figure 1 illustrates a graph plotted for the amount of aromatics present in the raffinate after the extraction/separation for single-stage liquid-liquid extraction using various solvent systems as provided in the experiments of set-1 of the present disclosure;
Figure 2 illustrates a graph plotted for the amount of aromatics present in the raffinate after the extraction/separation for single-stage liquid-liquid extraction using various solvent systems as provided in the experiments of set-2 of the present disclosure; and
Figure 3 illustrates a graph plotted for the amount of aromatics present in the raffinate after the extraction/separation for three-stage liquid-liquid extraction using various solvent systems as provided in the experiments of set-3 of the present disclosure; and
DETAILED DESCRIPTION
Hydrocarbon feedstock, typically, comprises aromatics as an impurity. The presence of aromatics in feedstock is undesirable for the performance and for environmental reasons. Removal of aromatics from the feedstock is more onerous as compared to other impurities. Various unit operations viz. azeotropic distillation, extractive distillation, liquid-liquid extraction, crystallization by freezing, adsorption on solids etc. have been used for the separation of aromatics. Among these, liquid-liquid extraction is widely used. In liquid-liquid extraction, a solvent is used to separate/remove/dissolve the aromatics from the feedstock. However, the solvent used for the extraction/removal of aromatics, as suggested in the liquid-liquid extraction, show serious environmental issues. Thus, there is a need for an alternative solvent, particularly green solvent, for the extraction/removal of aromatics from a hydrocarbon feedstock. The present disclosure, therefore, envisages an alternative/green solvent system for the extraction/removal of aromatics from a hydrocarbon feedstock.
In accordance with an aspect of the present disclosure, there is provided a solvent system for the separation of aromatic compounds from a hydrocarbon feedstock. The solvent system of the present disclosure comprises N-methyl-2 pyrrolidone (NMP), ethylene glycol, 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 characterized by an efficacy of removing/separating aromatic compounds in an amount of at least 25 wt% as present in the hydrocarbon feedstock.
In one embodiment, the solvent system of the present disclosure comprises N-methyl-2 pyrrolidone (NMP) in an amount in the range of 91 wt% to 97 wt%. The amount of ethylene glycol that can be used is in the range of 1 wt% to 5 wt%. The solvent system of the present disclosure comprises at least one ionic liquid to increase the selectivity of the solvent system for aromatics, thereby making the solvent system ecofriendly. The amount of at least one ionic liquid that can be used is in the range of 0.1 wt% to 1 wt%. The amount of water that can be used in the solvent system is in the range of 1 wt% to 5 wt%.
The ionic liquid of the solvent system of the present disclosure comprises an anion selected from the group consisting of tetrafluroborate, acetate, methylsulfate, p-toluene-4-sulfonate, and bis(trifluromethylsulfonyl)imide; and a cation selected from the group consisting of imidazolium, pyridinium, and pyrrolidinium.
In an embodiment of the present disclosure, the ionic liquid used in the process for the selective separation of aromatic compounds is imidazolium based.
Contacting a hydrocarbon feedstock with the solvent system of the present disclosure produces hydrocarbons with lower/reduced amount of aromatics as compared to the feedstock.
In accordance with the present disclosure, the solvent system is capable of separating/reducing the amount of aromatic compounds present in the feedstock by at least 25 wt%. The solvent system of the present disclosure comprises lower amount of ethylene glycol, however, it can efficiently reduce the amount of aromatic compounds present in the hydrocarbon feedstock.
In another embodiment, the solvent system of the present disclosure comprises N-methyl-2 pyrrolidone (NMP) in an amount in the range of 93 wt% to 94 wt%; ethylene glycol in an amount of 3 wt%; at least one ionic liquid in an amount in the range of 0.1 wt% to 0.5 wt%, wherein the at least one ionic liquid is selected from the group consisting of 1-Butyl-3-Methylimidazolium tetrafluoroborate, 1-Ethyl-3-Methylimidazolium Acetate, and 1-Butyl-3-Methylimidazolium Bis(trifluoromethylsulfonyl)imid; and water in an amount in the range of 2 wt% to 4 wt%. Preferably, the amount of water is 3 wt%.
In another aspect of the present disclosure, there is provided a process for the selective separation of aromatic compounds from a hydrocarbon feedstock. The process for the selective separation of aromatic compounds from the hydrocarbon feedstock is described herein below:
First, a solvent system comprising 91 wt% to 97 wt% of N-methyl-2 pyrrolidone (NMP), 1 wt% to 5 wt% of ethylene glycol, 0.1 wt% to 1 wt% of at least one ionic liquid and 1 wt% to 5 wt% of water is prepared. The solvent system of the present disclosure has a low boiling point and can be used at a low temperature for the separation/removal/extraction of aromatics from the feedstock. Thereby, making the process of the present disclosure energy efficient.
A hydrocarbon feedstock is then contacted with the solvent system under agitation/stirring at a predetermined temperature to produce a biphasic system containing a raffinate phase and an extract phase, wherein the predetermined temperature is in the range of 60?C to 130?C. The raffinate phase comprises hydrocarbon oil rich in saturated hydrocarbon and having substantially lower amount of aromatic compounds, whereas the extract phase comprises hydrocarbon oil having higher amount of aromatic compounds as compared to the raffinate phase. Thereafter, the raffinate phase is separated from the extract phase in the biphasic system to obtain a raffinate having substantially lower amount of aromatic compounds and higher amount of saturated hydrocarbons as compared to the feedstock.
Albeit, the solvent system of the present disclosure comprises lower amount of ethylene glycol, the solvent system gives a significant yield of raffinate with reduced amount of aromatic compounds.
In accordance with the present disclosure, the ratio of the hydrocarbon feedstock to the solvent system used for the process of separation of aromatics from the hydrocarbon feedstock is in the range of 1:1 to 2.5:1 (vol/vol).
The process of the present disclosure can be used to treat/handle hydrocarbon feedstock including, but not limited to, lube oil distillate, naphtha oil, deasphalted oil (DAO) and the like.
In accordance with an embodiment of the present disclosure, the feedstock is lube oil distillates comprising aromatic compounds in an amount in the range of 30 wt% to 70 wt%.
In accordance with the present disclosure, the hydrocarbon feedstock is characterized by a boiling point in the range of 150?C to 650?C.
Further, the process of separation of aromatic compounds of the present disclosure comprises a step of recovering the solvent system from the raffinate phase and the extract phase using distillation and/or nitrogen stripping.
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 can be scaled up to industrial/commercial scale and the results obtained can be extrapolated to industrial scale. In industrial/commercial scale operation, the feedstock is contacted with the solvent system of the present disclosure in a counter-current manner for a continuous extraction process. The feedstock enters an extraction tower from the bottom of the extraction tower and the solvent system of the present disclosure enters from the top of the extraction tower and is distributed/circulated uniformly within the extraction tower. After the extraction, a raffinate phase (aromatics lean phase) exits from the top of the extraction tower and an extract phase (aromatics rich phase) leaves from the bottom of the extraction tower.
Experiments:
Experiments Set-1
Experiment 1a: (Control) Extraction of aromatics from a feedstock using a solvent system containing NMP and water:
In a single-stage batch extraction equipment, liquid-liquid extraction experiment was performed using NMP and water as a base solvent mixture (control). First, the feedstock Arab Mix, 150 neutral (150N) distillate was preheated at a temperature of 70?C. In a single-stage glass extraction apparatus, 200 gm of the preheated feedstock, was mixed with a solvent system, wherein the feed/solvent ratio of 1.4 (vol/vol) was maintained for 2 hours. The characteristic properties of the feedstock Arab Mix, 150 neutral (150N) distillate, are tabulated herein table 1 below:
Table 1: Properties of the feedstock
S.No. Properties Value
1. Density at 15?C, gm/ml 0.9134
2. Refractive index at 60?C 1.4948
3. Kinematic viscosity (cSt) at 100?C 43

4. Distillation (ASTM-1160), ?C
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
The temperature of the extraction equipment was maintained at 70?C wherein, the contents were subjected to stirring at a speed of 500 rpm. After stirring, the content of the extraction equipment was kept for 3 hours for phase separation. After phase separation, two phases viz. a raffinate phase and an extract phase were obtained which were collected separately. The raffinate and the extract phases were weighed accurately to ensure the material balance of the contents. The solvent system was recovered from both the phases by water wash and nitrogen stripping under vacuum conditions to obtain raffinate having low aromatics (aromatic compounds) and high saturated hydrocarbons as compared to the feedstock.
Further, the refractive index of the raffinate phase was measured using refractometer, which is an indication of the quality of the hydrocarbon oil. The data so obtained is provided in table 4 hereinafter.
Experiments 1b: (Control) Extraction of aromatics from a feedstock using a solvent system containing Ethylene glycol, NMP, and water:
The process of experiment 1a was repeated using solvent systems containing 1%, 2%, 3%, 4%, and 5% ethylene glycol as a co-solvent along with varying amounts of NMP, and water. The characteristic properties of ethylene glycol are given in table 2 herein below.
Table 2: Characteristic properties of ethylene glycol
S.No. Glycol Melting point (?C) Boiling point (?C) R.I. at 20?C Density at 20?C (gm/ml)
1. Ethylene glycol -13.0 197.6 1.4385 1.1088
R.I.: refractive index
The feedstock 150 neutral (150N) distillate as used in experiment 1, and having the properties as provided in table 1 was used. The feedstock was contacted with the aforesaid solvent systems. The results of the experiments 1b for the extraction of aromatics were compared with the results of experiment 1a which is tabulated in table 4 hereinafter. The amount of aromatics (wt%) present in the raffinate after the extraction of aromatics is plotted in figure 1 which shows that the amount of aromatics present in the raffinate after the extraction using the aforesaid solvent systems is ranging from 36.5 wt% to 36.0 wt% which is a better extraction of aromatics as compared to the solvent system containing NMP+Water (36.8 wt% aromatics) of experiment 1a. The extraction of aromatics was the highest (36 wt% after extraction) when the solvent system containing 93% NMP + 4% EG + 3% water was used.
Experiments 1c: (Present disclosure) Extraction of aromatics from a feedstock using a solvent system containing Ethylene glycol, NMP, water, and an Ionic liquid:
Another liquid-liquid extraction experiment was conducted using the same feedstock and the process steps as disclosed in experiment 1a with solvent systems containing ethylene glycol, water along with 0.1%, 0.25% and 0.50% of an ionic liquid and varying amounts of NMP. The ionic liquids that can be used in the solvent system and their characteristic properties are provided in table 3 below:
Table 3: characteristic properties of the ionic liquid
S. No. Ionic liquid R.I. at 20?C Density (gm/ml)
at 20?C
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-3-MethylPyridinium tetrafluoroborate 1..422 1.401
R.I.: refractive index
The results of the experiments 1c for the amount of aromatics (wt%) present in the raffinate after the extraction of aromatics and the yield of raffinate were compared with the results of experiments 1b and experiment 1a which is tabulated in table 4 herein below.
Table 4:
Ex. No. Solvent System Yield R.I. Sulfur
(wt%) Saturates
(wt%) Aromatics
(wt%)
1a
(Control) 97% NMP+ 3%Water 75.4 1.4795 1.713 63.2 36.8

1b
(Control) 96% NMP+1% EG + 3%water 76.0 1.4788 1.701 63.6 36.4
95% NMP+2% EG + 3%water 76.8 1.4792 1.709 63.7 36.3
94% NMP+3% EG +3%water 77.3 1.4974 1.714 63.9 36.1
93% NMP+4% EG + 3%water 78.0 1.4798 1.720 64.0 36.0
92% NMP+5% EG + 3%water 79.6 1.4804 1.725 63.5 36.5

1c
(Present disclosure) 93.9% NMP+3% EG + 3%water +0.10% IL-1 78.2 1.4790 1.697 64.0 36.0
93.75% NMP+3% EG + 3%water +0.25% IL-2 78.9 1.4795 1.706 64.3 35.7
93.5% NMP+3% EG + 3%water +0.50% IL-3 79.5 1.4800 1.717 64.1 35.9
EG: ethylene glycol; R.I.: refractive index
IL-1: 1-Butyl-3-Methylimidazolium tetrafluoroborate;
IL-2: 1-Ethyl-3-Methylimidazolium Acetate;
IL-3: 1-Butyl-3-Methylimidazolium Bis(trifluoromethylsulfonyl)imide

These comparative data are plotted in figure 1 to compare the efficacy of the solvent systems of experiments 1c with that of experiments 1b and experiment 1a for the aromatic extraction. Some amount of NMP for the solvent system of experiment 1c was replaced with an equal amount of IL. The data shows that the solvent system of experiment 1c, containing lower amounts of NMP and ethylene glycol, when used for liquid-liquid extraction, resulted in better extraction of aromatics as compared to the solvent systems of experiments 1b containing higher amounts of NMP (up to 96%) and EG (up to 5%) and the solvent system of experiment 1a containing higher amount of NMP (97%) and water. Further, as the amount of NMP decreased and replaced with an equal amount of IL (from 0.1% to 0.5%), the amount of aromatics present in the raffinate after the extraction decreased (35.7 wt%) for the solvent system of experiment 1c. Therefore, it is evident from table 4 and figure 1 that the solvent systems of experiments 1c produce better extraction of aromatics as compared to the solvent systems of experiments 1b and the solvent system of experiment 1a.
Experiments Set-2
Experiment 2a: (Control) Extraction of aromatics from a feedstock using a solvent system containing NMP and water:
In a single-stage batch extraction equipment, liquid-liquid extraction experiment was performed using NMP and water as a base solvent mixture (control). First, the feedstock Arab Mix, 500 neutral (500N) distillate was preheated at a temperature of 90?C. In a single-stage glass extraction apparatus, 200 gm of the preheated feedstock, was mixed with a solvent system, wherein the feed/solvent ratio of 1.65 (vol/vol) was maintained for 2 hours. The characteristic properties of the feedstock Arab Mix, 150 neutral (150N) distillate, are tabulated herein table 5 below:
Table 5: Properties of the feedstock
S.No. Properties Value
1. Density at 15?C, gm/ml 0.9390
2. Refractive index at 60?C 1.5095
3. Kinematic viscosity (cSt) at 100?C 73

4. Distillation (ASTM-1160), ?C
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
The temperature of the extraction equipment was maintained at 90?C wherein, the contents were subjected to stirring at a speed of 500 rpm. After mixing, the content of the extraction equipment was kept for 3 hours for phase separation. After phase separation, two phases viz. a raffinate phase and an extract phase were obtained which were collected separately. The raffinate and the extract phases were weighed accurately to ensure the material balance of the contents. The solvent system was recovered from both the phases by water wash and nitrogen stripping under vacuum conditions to obtain raffinate having low aromatics (aromatic compounds) and high saturated hydrocarbons as compared to the feedstock.
Further, the refractive index of the raffinate phase was measured using refractometer, which is an indication of the quality of the hydrocarbon oil. The data so obtained is provided in table 6 hereinafter.
Experiments 2b: (Control) Extraction of aromatics from a feedstock using a solvent system containing Ethylene glycol, NMP, and water:
The process of experiment 2a was repeated using solvent systems containing 1%, 2%, 3%, 4%, and 5% ethylene glycol as a co-solvent along with varying amounts of NMP, and water. The characteristic properties of ethylene glycol are the same as provided in table 2.
The results of the experiments 2b for the extraction of aromatics were compared with the results of experiment 2a which is tabulated in table 6 hereinafter. The amount of aromatics (wt%) present in the raffinate after the extraction of aromatics is plotted in figure 2 which shows that the amount of aromatics present in the raffinate after the extraction using the solvent systems of experiments 2b is ranging from 49.24 wt% to 48.01 wt% which is a better separation as compared to the solvent system containing NMP+Water (49.43 wt% aromatics) of experiment 2a. The extraction of aromatics was the highest (48.01 wt% after extraction) when the solvent system containing 94% NMP + 3% EG + 3% water was used.
Experiments 2c: (Present disclosure) Extraction of aromatics from a feedstock using a solvent system containing Ethylene glycol, NMP, water, and an Ionic liquid:
Another, liquid-liquid extraction experiment was conducted using the same feedstock of experiment 2a and the same process steps with solvent systems containing ethylene glycol, water, along with 0.1%, 0.25% and 0.50% of an ionic liquid and varying amounts of NMP. The ionic liquids used and their characteristic properties are the same as provided in table 3.
The results of the experiments 2c for the amount of aromatics (wt%) present in the raffinate after the extraction of aromatics and the yield of raffinate were compared with the results of experiments 2b and experiment 2a. The data so obtained is tabulated in table 6 herein below.
Table 6:
Ex. No. Solvent System Yield R.I. Sulfur
(wt%) Saturates
(wt%) Aromatics
(wt%)
2a (Control) 97% NMP+ 3%Water (control) 68.3 1.4828 1.673 50.57 49.43

2b (Control) 96% NMP+1% EG + 3%water 69.5 1.4820 1.603 51.23 48.77
95% NMP+2% EG + 3%water 70.3 1.4824 1.635 51.57 48.43
94% NMP+3% EG +3%water 71.1 1.4827 1.679 51.99 48.01
93% NMP+4% EG + 3%water 72.9 1.4833 1.688 51.89 48.11
92% NMP+5% EG + 3%water 74.1 1.4837 1.701 50.76 49.24

2c
(Present disclosure) 93.9% NMP+3%EG + 3%water +0.10% IL-1 71.8 1.4819 1.598 52.17 47.83
93.75%NMP+3%EG+ 3%water+ 0.25% IL-2 72.6 1.4824 1.624 52.76 47.24
93.5% NMP +3%EG +3%water + 0.50% IL-3 73.7 1.4829 1.658 52.58 47.42
EG: ethylene glycol; R.I.: refractive index
IL-1: 1-Butyl-3-Methylimidazolium tetrafluoroborate;
IL-2: 1-Ethyl-3-Methylimidazolium Acetate;
IL-3: 1-Butyl-3-Methylimidazolium Bis(trifluoromethylsulfonyl)imide

These comparative results are plotted in figure 2 to compare the efficacy of the solvent systems of experiments 2c with that of experiments 2b and experiment 2a for the aromatic extraction. Some amount of NMP for the solvent system of experiment 2c was replaced with an equal amount of IL. The data shows that the solvent system of experiment 2c, containing lower amounts of NMP and ethylene glycol, when used for liquid-liquid extraction, resulted in better extraction of aromatics as compared to the solvent systems of experiments 2b containing higher amounts of NMP (up to 96%) and EG (up to 5%) and the solvent system of experiment 2a containing higher amount of NMP (97%) and water. Further, as the amount of NMP decreased and replaced with an equal amount of IL (from 0.1% to 0.5%), the amount of aromatics present in the raffinate after the extraction decreased (47.24 wt%) for the solvent system of experiment 2c. Therefore, it is evident from table 6 and figure 2 that the solvent systems of experiments 2c produce better extraction of aromatics as compared to the solvent systems of experiments 2b and the solvent system of experiment 2a.
Experiments Set-3
Experiment 3a: (Control) Three-stage Liquid-Liquid extraction of aromatics from a feedstock using a solvent system containing NMP and water:
A three-stage Liquid-Liquid extraction experiment was 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 first preheated. In the first stage, Liquid-Liquid extraction was performed using 200 gm of the preheated feed. The operating conditions and the process steps were similar to those employed in experiment 2a.
In the second stage, the raffinate obtained from the first stage was used as feed for the Liquid-Liquid extraction with solvent system containing NMP and water, wherein the feed/solvent ratio of 1.65 (vol/vol) was maintained for 2 hours in a single-stage glass extraction apparatus. The temperature of the equilibrium set up was kept at 90?C under stirring at a speed of 500 rpm. After stirring, the content of the extraction apparatus was kept for 3 hours to allow it to settle and thereby providing good phase separation. After settling, a biphasic system of a raffinate phase and an extract phase was obtained. The raffinate phase and extract phase were collected separately. The raffinate and extract phases were then weighed to ensure the material balance. The solvent system was recovered from both the phases by water wash and nitrogen stripping under vacuum conditions and a raffinate phase was obtained which had low aromatics and high saturated hydrocarbons as compared to the feedstock.
In the third stage, the raffinate from the second stage was used as a feed for the Liquid-Liquid extraction with a solvent system containing NMP and water. The feed/solvent ratio of 1.65 (Vol/Vol) was maintained for 2 hours in a single-stage glass extraction apparatus. The temperature of the equilibrium set up was kept at 90?C under stirring at a speed of 500 rpm. After stirring, the content of the extraction apparatus was kept for 3 hours to allow it to settle and thereby providing good phase separation. After settling, a biphasic system of a raffinate phase and an extract phase was obtained. The raffinate phase and extract phase were collected separately. The raffinate and extract phases were then weighed to ensure the material balance. The solvent system was recovered from both the phases by water wash and nitrogen stripping under vacuum conditions and a raffinate phase was obtained which had low aromatics and high saturated hydrocarbons as compared to the feedstock. The data so obtained is tabulated in table 7 hereinafter.
Experiments 3b: (Control) Three-stage Liquid-Liquid extraction of aromatics from a feedstock using a solvent system containing Ethylene glycol, NMP, and water:
The three-stage Liquid-Liquid extraction experiment of experiment 3a was performed with solvent systems containing 1%, 2%, 3%, 4%, and 5% ethylene glycol along with varying amounts of NMP and water. The characteristic properties of ethylene glycol are the same as provided in table 2.
The extraction results for the three-stage Liquid-Liquid extraction of experiments 3b were compared with the results of experiment 3a. The data so obtained is tabulated in table 7 hereinafter and plotted in figure 3 which shows that the aromatic extraction was more effective when the feedstock was contacted with the solvent systems of experiments 3b containing ethylene glycol along with NMP, and water as compared to the solvent system of experiment 3a i.e. NMP and water. The amount of aromatics (wt%) present in the raffinate after the separation using the solvent systems of experiments 3b containing ethylene glycol, NMP, and water is ranging from 38.4 wt% to 37.2 wt% which is a better extraction of aromatics as compared to the solvent system containing NMP+Water (39.0 wt% aromatics) of experiment 3a. The extraction of aromatics was the highest (37.2 wt% after extraction) when the solvent system containing 94% NMP + 3% EG + 3% water was used.
Experiments 3c: (Present disclosure) Three-stage Liquid-Liquid extraction of aromatics from a feedstock using a solvent system containing Ethylene glycol, NMP, water, and an Ionic liquid:
The three-stage Liquid-Liquid extraction experiment of experiment 3a was performed with solvent systems containing ethylene glycol, water, along with 0.1%, 0.25% and 0.50% of an Ionic liquid and varying amounts of NMP. The ionic liquids used and their characteristic properties are the same as provided in table 3.
The results of the three-stage Liquid-Liquid extraction process of experiments 3c, for the amount of aromatics (wt%) present in the raffinate after the extraction and the yield of raffinate were compared with the results of experiments 3b and experiment 3a. The comparative data/results so obtained are tabulated herein table 7 below:

Table 7:
Ex. No. Solvent System Yield R.I. Sulfur
(wt%) Saturates
(wt%) Aromatics
(wt%)
3a (Control) 97%NMP+3%Water (control) 58.4 1.4742 1.32 61.0 39.0

3b (Control) 96% NMP+1% EG + 3%water 59.2 1.4737 1.24 61.6 38.4
95% NMP+2% EG + 3%water 60.3 1.4740 1.29 62.3 37.7
94% NMP+3% EG +3%water 61.7 1.4743 1.34 62.8 37.2
93% NMP+4% EG + 3%water 62.5 1.4751 1.39 62.5 37.5
92% NMP+5% EG + 3%water 63.8 1.4758 1.43 62.1 37.9

3c (Present disclosure) 93.9% NMP+3% EG + 3%water +0.10% IL-1 62.3 1.4739 1.22 62.9 37.1
93.75% NMP+3% EG + 3%water+ 0.25% IL-2 62.9 1.4743 1.28 63.2 36.8
93.5% NMP+3%EG + 3%water+ 0.50% IL-3 63.9 1.4748 1.33 63.4 36.6
EG: ethylene glycol; R.I.: refractive index
IL-1: 1-Butyl-3-Methylimidazolium tetrafluoroborate;
IL-2: 1-Ethyl-3-Methylimidazolium Acetate;
IL-3: 1-Butyl-3-Methylimidazolium Bis(trifluoromethylsulfonyl)imide

These comparative data are plotted in figure 3 to compare the efficacy of the solvent systems of experiments 3c with that of experiments 3b and experiment 3a for the aromatic extraction for three-stage liquid-liquid extraction. Some amount of NMP for the solvent system of experiment 3c was replaced with an equal amount of IL. The data show that the solvent system of experiment 3c, containing lower amounts of NMP and ethylene glycol, when used for liquid-liquid extraction, resulted in better extraction of aromatics as compared to the solvent systems of experiments 3b containing higher amounts of NMP (up to 96%) and EG (up to 5%) and the solvent system of experiment 3a containing higher amount of NMP (97%) and water for the three-stage liquid-liquid extraction. Further, as the amount of NMP decreased and replaced with an equal amount of IL (from 0.1% to 0.5%), the amount of aromatics present in the raffinate after the extraction decreased (36.6 wt%) and the raffinate yield increased (63.9%) for the solvent system of experiment 3c. Therefore, it is evident from figure 3 and the table 7 that the solvent systems of experiments 3c produces better extraction of aromatics as compared to the solvent systems of experiments 3b and the solvent system of experiment 3a.
TECHNICAL ADVANCEMENTS
The present disclosure described herein above has several technical advantages including, but not limited to, the realization of:
? high separation of aromatics using low amount of ethylene glycol thereby making the separation/extraction economical;
? significant yield of the hydrocarbon oil along with high aromatics separation; and
? the solvent system used in the present disclosure has low boiling point which makes the process energy efficient by decreasing the recovery column temperatures.
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.