FIELD OF THE INVENTION

[001] The present disclosure generally relates to the field of heat storage and heat transfer, and in particular to a stable heat transfer nanofluid composition.

BACKGROUND OF THE INVENTION

[002] Among the various energy sources available to man, very few are renewable, while having minimal carbon footprint. Solar energy represents the most underutilized clean energy resource available to man at present. Though it has received widespread attention, several challenges persist. The planetary rotation of earth leads to diurnal cycling of light. This represents a situation where we have access to this abundant energy source for only 12 hours a day. As a result, the effective utilization of solar energy requires a two-pronged approach involving the development of: a) solar energy conversion devices, and b) energy transfer and storage devices.

[003] Solar- to-electrical energy conversion efficiency at present seldom achieves its optimum potential in commercial devices, due to losses associated with heat transfer and storage among others. Heat transfer fluids (HTF) are used in solar power plants for the efficient transfer of heat or thermal energy. Organic oil-based heat transfer agents are attractive choices due to their low cost and a wide working-temperature range.

However, most organic oils suffer from drawbacks of poor specific heat capacity and high viscosity. Higher viscosity leads to a higher cost of pumping the fluid through the heat-exchanger, hence lowering the cost-effectiveness of the thermal energy storage system.

[004] In recent years, an increased understanding of semi-conductor technology has led to a race to produce highly efficient solar-based energy conversion devices. Hence, the development of an efficient heat transfer fluid capable of assimilating and dissipating heat with minimum loss is pivotal for sustaining this rapid growth of the solar energy sector.

SUMMARY OF THE INVENTION

[005] In an aspect of the present invention, there is provided a process for the extraction of at least one oil extract from at least one petroleum-based oil, comprising the steps of: (a) contacting at least one petroleum-based oil with at least one first solvent to obtain a first mixture; (b) contacting the first mixture with at least one second solvent to obtain a biphasic liquid system; (c) separating the biphasic liquid system into: (i) phase comprising the at least one first solvent; and (ii) phase comprising the at least one second solvent; (d) contacting the phase comprising the at least one second solvent with an aqueous salt solution to obtain a second mixture; (e) contacting the second mixture with the at least one first solvent to obtain a biphasic system comprising: (i) phase comprising the at least one first solvent and the at least one oil extract; and (ii) phase comprising the second mixture; and (fjisolating the at least one oil extract from the at least one first solvent, to obtain the at least one oil extract.

[006] In another aspect of present disclosure, there is provided a composition comprising: (a) at least one base fluid; and (b) at least one oil extract extracted using process as described herein, wherein the at least one oil extract has a weight percentage in the range of 5 - 20 % with respect to the composition.

[007] In yet another aspect of present invention, there is provided a process for the preparation of a composition, comprising: (a) at least one base fluid; and (b) at least one oil extract extracted using process as described herein, said process comprising the steps of: (a) contacting at least one base fluid with the at least one oil extract to obtain mixture A; (b) homogenizing mixture A by sonication to obtain the composition, wherein the at least one oil extract has a weight percentage in the range of 5 - 20 % with respect to the composition.

[008] These and other features, aspects, and advantages of the present subject matter will be better understood with reference to the following description and appended claims. This summary is provided to introduce a selection of concepts in a simplified form. This summary is not intended to identify key features or essential features of the claimed subject matter, nor is it intended to be used to limit the scope of the claimed subject matter.

BRIEF DESCRIPTION OF THE DRAWINGS [009] The detailed description is described with reference to the accompanying figures. In the figures, the left-most digit(s) of a reference number identifies the figure in which the reference number first appears. The same numbers are used throughout the drawings to reference like features and components.

[0010] Figure 1 depicts the thermal gravimetric analysis (TGA) of pure base fluid and that of compositions comprising (a) at least one base fluid and (b)at least one oil extract. The effect of increasing weight percentage of oil extract on the thermal stability of the composition is depicted. The compositions comprising of 5, 10, 20 and 40 % of oil extract with respect to the composition were tested.

DETAILED DESCRIPTION OF THE INVENTION

[0011] Those skilled in the art will be aware that the present disclosure is subject to variations and modifications other than those specifically described. It is to be understood that the present disclosure includes all such variations and modifications. The disclosure also includes all such steps, features, compositions and compounds referred to or indicated in this specification, individually or collectively, and any and all combinations of any or more of such steps or features.

Definitions:

[0012] For convenience, before further description of the present disclosure, certain terms employed in the specification, and examples are collected here. These definitions should be read in the light of the remainder of the disclosure and understood as by a person of skill in the art. The terms used herein have the meanings recognized and known to those of skill in the art, however, for convenience and completeness, particular terms and their meanings are set forth below.

[0013] The articles "a", "an" and "the" are used to refer to one or to more than one (i.e., to at least one) of the grammatical object of the article.

[0014] The terms "comprise" and "comprising" are used in the inclusive, open sense, meaning that additional elements may be included. It is not intended to be construed as "consists of only".

[0015] Throughout this specification, unless the context requires otherwise the word "comprise", and variations such as "comprises" and "comprising", will be understood to imply the inclusion of a stated element or step or group of element or steps but not the exclusion of any other element or steps.

[0016] The term "including" is used to mean "including but not limited to", "including" and "including but not limited to" are used interchangeably.

[0017] Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood to one of ordinary skill in the art to which this disclosure belongs. Although methods and materials similar or equivalent to those described herein can be used in the practice or testing of the disclosure, the preferred methods, and materials are now described. All publications mentioned herein are incorporated herein by reference.

[0018] Ratios, concentrations, amounts, and other numerical data may be presented herein in a range format. It is to be understood that such range format is used merely for convenience and brevity and should be interpreted flexibly to include not only the numerical values explicitly recited as the limits of the range, but also to include all the individual numerical values or sub-ranges encompassed within that range as if each numerical value and sub-range is explicitly recited. For example, a weight range of about 70 wt % to about 95 wt % should be interpreted to include not only the explicitly recited limits of about 70 wt% to about 95 wt%, but also to include sub-ranges, such as 70.05 wt % to 91 wt %, 70 wt % to 85 wt %, and so forth, as well as individual amounts, including fractional amounts, within the specified ranges, such as 70.5 wt %, 81.1 wt %, and 92.9 wt %, for example.

[0019] The present disclosure is not to be limited in scope by the specific embodiments described herein, which are intended for the purposes of exemplification only. Functionally equivalent products, compositions, and methods are clearly within scope of the disclosure, as described herein.

[0020] To address the problem of low thermal conductivity and low specific heat capacity of known heat transfer fluids, as discussed above, the present disclosure provides a superior oil extract-based heat transfer fluid composition exhibiting enhanced thermal conductivity and specific heat capacity along with improvement of other thermo-physical properties like viscosity, thermal stability and flash point. [0021] Additionally, petroleum-based oils suffer from toxicity owing to high polycyclic aromatic hydrocarbon (PAH) content. The stipulated limit is specifically restricted to 3% in the case of rubber processing oil. The extraction of petroleum based oils for the removal of oil extracts is hence important as it reduces their PAH content. For the purpose, several DMSO-based methods exist for the process of extraction of oil. However, the present disclosure provides a process for the effective extraction of PAH from petroleum-based oil extract. In an embodiment of present disclosure, there is provided a process for the extraction of at least one oil extract from at least one petroleum-based oil, comprising the steps of: (a) contacting at least one petroleum- based oil with at least one first solvent to obtain a first mixture; (b) contacting the first mixture with at least one second solvent to obtain a biphasic liquid system; (c) separating the biphasic liquid system into: (i) phase comprising the at least one first solvent; and (ii) phase comprising the at least one second solvent; (d)contacting the phase comprising the at least one second solvent with an aqueous salt solution to obtain a second mixture; (e) contacting the second mixture with the at least one first solvent to obtain a biphasic system comprising: (i) phase comprising the at least one first solvent and the at least one oil extract; and (ii) phase comprising the second mixture; and (f) isolating the at least one oil extract from the at least one first solvent, to obtain the at least one oil extract.

[0022] In an embodiment of the present disclosure, there is provided a process for extraction of the at least one oil extract from the at least one petroleum-based oil, as described herein, wherein the first mixture is obtained by contacting at least one petroleum-based oil with the at least one solvent at a temperature in the range of 20-35 °C. In another embodiment of the present disclosure, the first mixture can be obtained by contacting at least one petroleum-based oil with at least one solvent at a temperature of 25 °C.

[0023] In an embodiment of the present disclosure, there is provided a process for extraction of the at least oil extract from the at least one petroleum-based oil, as described herein, wherein the first mixture is contacted with a second solvent at a temperature in the range of 35-60 °C to obtain a biphasic liquid system. In another embodiment of the present disclosure, the biphasic liquid system is obtained by contacting the first mixture with a second solvent at a temperature of 55 °C.

[0024] In an embodiment of the present disclosure, there is provided a process for extraction of the at least one oil extract from the at least one petroleum-based oil, as described herein, wherein the biphasic system is separated into (i) a phase containing first solvent; and (ii) a phase containing a second solvent, is carried out using a separating funnel at a temperature in the range of 20-35 °C. In another embodiment of the present disclosure, the biphasic system is separated into (i) a phase containing first solvent; and (ii) a phase containing a second solvent, is carried out using a separating funnel at a temperature of 30 °C.

[0025] In an embodiment of the present disclosure, there is provided a process for extraction of the at least oil extract from the at least one petroleum-based oil, as described herein, wherein contacting the phase comprising the at least one second solvent with an aqueous salt solution at a temperature in the range of 20-35 °C results in a second mixture. In another, embodiment of the present disclosure, contacting the phase comprising the at least one second solvent with an aqueous salt solution at a temperature of 30 °C results in a second mixture

[0026] In an embodiment of the present disclosure, there is provided a process for extraction of the at least oil extract from the at least one petroleum-based oil, as described herein, wherein contacting the second mixture with the at least one first solvent to obtain a biphasic system comprising: (i) phase comprising the at least one first solvent and the at least one oil extract; and (ii) phase comprising the second mixture, is carried out at a temperature in the range of 20-35 °C. In another embodiment of the present disclosure, contacting the second mixture with the at least one first solvent to obtain a biphasic system comprising: (i) phase comprising the at least one first solvent and the at least one oil extract; and (ii) phase comprising the second mixture, is carried out at a temperature in the range of 30 °C.

[0027] In an embodiment of the present disclosure, there is provided a process for extraction of the at least oil extract from the at least one petroleum-based oil, as described herein, wherein isolating the at least one oil extract from the at least one first solvent, to obtain the at least one oil extract, is carried out using a process selected from the group consisting of evaporation, distillation, fractional distillation, and lyophilization. In another embodiment of the present disclosure, isolating the at least one oil extract from the at least one first solvent, to obtain the at least one oil extract, is carried out using evaporation.

[0028] In an embodiment of present disclosure, there is provided a process for the extraction of at least one oil extract from at least one petroleum-based oil, comprising the steps of: (a) contacting at least one petroleum based oil with at least one first solvent to obtain the first mixture at a temperature in the range of 20-35 °C; (b) contacting the first mixture with at least one second solvent to obtain a biphasic liquid system at a temperature in the range of 35 - 60 °C; (c) separating the biphasic liquid system into: (i) phase comprising the at least one first solvent; and (ii) phase comprising the at least one second solvent, using a separating funnel at a temperature in the range of 20-35 °C; (d) contacting the phase comprising the at least one second solvent with an aqueous salt solution to obtain a second mixture at a temperature in the range of 20-35 °C; (e) contacting the second mixture with the at least one first solvent to obtain a biphasic system comprising: (i) phase comprising the at least one first solvent and the at least one oil extract; and (ii) phase comprising the second mixture, at a temperature in the range of 20-35 °C; (f) isolation of the at least one oil extract from the at least one first solvent, using a process selected from the group consisting of evaporation, distillation, fractional distillation, and lyophilization.

[0029] In an embodiment of the present disclosure, there is provided a process for extraction of the at least oil extract from the at least one petroleum-based oil, as described herein, wherein the at least one petroleum-based oil can be selected from the group consisting of rubber processing oil (RPO), clarified oil (CLO), vacuum gas oil (VGO), deasphalted oil (DAO), 150 N extract, 500 N extract, and combinations thereof.

[0030] In an embodiment of the present disclosure, there is provided a process for extraction of the at least oil extract from the at least one petroleum-based oil, as described herein, wherein the at least one second solvent is immiscible with the at least one first solvent.

[0031] In an embodiment of the present disclosure, there is provided a process for extraction of the at least oil extract from the at least one petroleum-based oil, as described herein, wherein the aqueous salt solution is a saturated solution.

[0032] In an embodiment of present disclosure, there is provided a process for the extraction of at least one oil extract from at least one petroleum-based oil selected from the group consisting of rubber processing oil (RPO), clarified oil (CLO), vacuum gas oil (VGO), deasphalted oil (DAO), 150 N extract, 500 N extract, and combinations thereof, comprising the steps of: (a) contacting at least one petroleum based oil with at least one first solvent to obtain the first mixture at a temperature in the range of 20-35 °C; (b) contacting the first mixture with at least one second solvent to obtain a biphasic liquid system at a temperature in the range of 35 - 60 °C, wherein the at least one second solvent is immiscible with the at least one first solvent; (c) separating the biphasic liquid system into: (i) phase comprising the at least one first solvent; and (ii) phase comprising the at least one second solvent, using a separating funnel at a temperature in the range of 20-35 °C; (d) contacting the phase comprising the at least one second solvent with an aqueous salt solution to obtain a second mixture at a temperature in the range of 20-35 °C, wherein the aqueous salt solution is a saturated solution; (e) contacting the second mixture with the at least one first solvent to obtain a biphasic system comprising: (i) phase comprising the at least one first solvent and the at least one oil extract; and (ii) phase comprising the second mixture, at a temperature in the range of 20-35 °C, wherein the at least one second solvent is immiscible with the at least one first solvent; (f) isolation of the at least one oil extract from the at least one first solvent, using a process selected from the group consisting of evaporation, distillation, fractional distillation, and lyophilization.

[0033] In an embodiment of the present disclosure, there is provided a process for extraction of the at least oil extract from the at least one petroleum-based oil, as described herein, wherein the at least one petroleum-based oil to the at least one first solvent w/v ratio is in the range of 1: 10 - 1 :50. In another embodiment of the present disclosure, the at least one petroleum-based oil to the at least one first solvent w/v ratio is 1:20.

[0034] In an embodiment of the present disclosure, there is provided a process for extraction of the at least oil extract from the at least one petroleum-based oil, as described herein, wherein the first mixture to the at least one second solvent volume ratio is in the range of 1:5 - 1 : 10. In another embodiment of the present disclosure, the first mixture to the at least one second solvent volume ratio is 1 : 15.

[0035] In an embodiment of the present disclosure, there is provided a process for extraction of the at least oil extract from the at least one petroleum-based oil, as described herein, wherein the phase comprising the at least one second solvent to the aqueous salt solution volume ratio is in the range of 1:20 - 1:50. In another embodiment of the present disclosure, the phase comprising the at least one second solvent to the aqueous salt solution volume ratio is 1:30.

[0036] In an embodiment of the present disclosure, there is provided a process for extraction of the at least oil extract from the at least one petroleum-based oil, as described herein, wherein the second mixture to the at least one first solvent volume ratio is in the range of 1 : 10 - 1:50. In another embodiment of the present disclosure, the second mixture to the at least one first solvent volume ratio is in the range of 1:30.

[0037] In an embodiment of present disclosure, there is provided a process for the extraction of at least one oil extract from at least one petroleum-based oil selected from the group consisting of rubber processing oil (RPO), clarified oil (CLO), vacuum gas oil (VGO), deasphalted oil (DAO), 150 N extract, 500 N extract, and combinations thereof, comprising the steps of: (a) contacting at least one petroleum based oil with at least one first solvent to obtain the first mixture at a temperature in the range of 20-35 °C, wherein the at least one petroleum-based oil to the at least one first solvent w/v ratio is in the range of 1: 10 - 1:50; (b) contacting the first mixture with at least one second solvent to obtain a biphasic liquid system at a temperature in the range of 35 - 60 °C, wherein the at least one second solvent is immiscible with the at least one first solvent and the first mixture to the at least one second solvent volume ratio is in the range of 1 :5 - 1 : 10; (c) separating the biphasic liquid system into: (i) phase comprising the at least one first solvent; and (ii) phase comprising the at least one second solvent, using a separating funnel at a temperature in the range of 20-35 °C; (d) contacting the phase comprising the at least one second solvent with an aqueous salt solution to obtain a second mixture at a temperature in the range of 20-35 °C, wherein the aqueous salt solution is a saturated solution and the phase comprising the at least one second solvent to the aqueous salt solution volume ratio is in the range of 1 :20 - 1:50; (e) contacting the second mixture with the at least one first solvent to obtain a biphasic system comprising: (i) phase comprising the at least one first solvent and the at least one oil extract; and (ii) phase comprising the second mixture, at a temperature in the range of 20-35 °C, wherein the at least one second solvent is immiscible with the at least one first solvent and the second mixture to the at least one first solvent volume ratio is in the range of 1: 10 - 1:50; (f) isolation of the at least one oil extract from the at least one first solvent, using a process selected from the group consisting of evaporation, distillation, fractional distillation, and lyophilization.

[0038] In an embodiment of the present disclosure, there is provided a process for extraction of the at least oil extract from the at least one petroleum-based oil, as described herein, wherein the at least one petroleum-based oil comprises aromatics having a weight percentage in the range of 10 - 85 %. In another embodiment of the present disclosure, the at least one petroleum-based oil comprises aromatics having a weight percentage of 65 %.

[0039] In an embodiment of the present disclosure, there is provided a process for extraction of the at least oil extract from the at least one petroleum-based oil, as described herein, wherein the first solvent is cyclohexane.

[0040] In an embodiment of the present disclosure, there is provided a process for extraction of the at least oil extract from the at least one petroleum-based oil, as described herein, wherein the second solvent is N-methyl-2-pyrrolidone (NMP).

[0041] In an embodiment of the present disclosure, there is provided a process for extraction of the at least oil extract from the at least one petroleum-based oil, as described herein, wherein the aqueous salt solution is selected from the group consisting of aqueous solution of sodium chloride, aqueous solution of potassium chloride, and combinations thereof.

[0042] In an embodiment of the present disclosure, there is provided a process for extraction of the at least oil extract from the at least one petroleum-based oil, as described herein, wherein the at least one oil extract comprises at least 80% aromatics. In another embodiment of the present disclosure, the at least one oil extract comprises 90% aromatics.

[0043] In an embodiment of present disclosure, there is provided a process for the extraction of the at least one oil extract from the at least one petroleum-based oil, as described herein, wherein the at least one petroleum-based oil comprises aromatics having a weight percentage in the range of 10- 85 % and can be selected from the group consisting of rubber processing oil (RPO), clarified oil (CLO), vacuum gas oil (VGO), deasphalted oil (DAO), 150 N extract, 500 N extract, and combinations thereof, comprising the steps of: (a) contacting at least one petroleum based oil with cyclohexane to obtain the first mixture is carried out at a temperature in the range of 20-35 °C, wherein the at least one petroleum-based oil to cyclohexane w/v ratio is in the range of 1 : 10 - 1 :50; (b) contacting the first mixture with NMP to obtain a biphasic liquid system is carried out at a temperature in the range of 35 - 60 °C, wherein the NMP is immiscible with the cyclohexane and the cyclohexane to the NMP volume ratio is in the range of 1:5 - 1: 10; (c) separating the biphasic liquid system into: (i) phase comprising the cyclohexane; and (ii) phase comprising the NMP, is carried out using a separating funnel at a temperature in the range of 20-35 °C; (d) contacting the phase comprising the NMP with an aqueous salt solution to obtain a second mixture is carried out at a temperature in the range of 20-35 °C, wherein the aqueous salt solution is a saturated solution selected from the group consisting of aqueous solution of sodium chloride, aqueous solution of potassium chloride, and combinations thereof and the phase comprising the NMP to the aqueous salt solution volume ratio is in the range of 1:20 - 1:50; (e) contacting the second mixture with cyclohexane to obtain a biphasic system comprising: (i) phase comprising the cyclohexane and the at least one oil extract; and (ii) phase comprising the second mixture, is carried out at a temperature in the range of 20-35 °C, wherein the NMP is immiscible with the cyclohexane and the second mixture to the at least one first solvent volume ratio is in the range of 1: 10 - 1 :50.; (f) isolation of the at least one oil extract from the at least one first solvent, is carried out using a process selected from the group consisting of evaporation, distillation, fractional distillation, and lyophilization, wherein the at least one oil extract comprises at least 80% aromatics.

[0044] In an embodiment of present disclosure, there is provided a composition comprising: (a) at least one base fluid; and (b) at least one oil extract, extracted using a process as described herein, having a weight percentage in the range of 5 - 20 % with respect to the composition. In another embodiment of present disclosure, there is provided a composition comprising: (a) at least one base fluid; and (b) at least one oil extract having a weight percentage in the range of 8 - 12 % with respect to the composition. In yet another embodiment of present disclosure, there is provided a composition comprising: (a) at least one base fluid; and (b) at least one oil extract having a weight percentage of 10 % with respect to the composition.

[0045] In an embodiment of present disclosure, there is provided a composition comprising: (a) at least one base fluid; and (b) at least one oil extract, extracted using a process for the extraction of the at least one oil extract from at least one petroleum- based oil, comprising the steps of: (a) contacting at least one petroleum-based oil with at least one first solvent to obtain a first mixture; (b) contacting the first mixture with at least one second solvent to obtain a biphasic liquid system; (c) separating the biphasic liquid system into: (i) phase comprising the at least one first solvent; and (ii) phase comprising the at least one second solvent; (d) contacting the phase comprising the at least one second solvent with an aqueous salt solution to obtain a second mixture; (e) contacting the second mixture with the at least one first solvent to obtain a biphasic system comprising: (i) phase comprising the at least one first solvent and the at least one oil extract; and (ii) phase comprising the second mixture; and (f) isolating the at least one oil extract from the at least one first solvent, to obtain the at least one oil extract, wherein the oil extract has a weight percentage in the range of 5 - 20 % with respect to the composition. [0046] In an embodiment of present disclosure, there is provided a composition comprising: (a) at least one base fluid selected from the group diphenyl oxide (DPO), Hytherm 500, and Hytherm 600, and combinations thereof; and (b) at least one oil extract, extracted using a process as described herein, having a weight percentage in the range of 5 - 20 % with respect to the composition.

[0047] In an embodiment of present disclosure, there is provided a composition comprising: (a) at least one base fluid selected from the group diphenyl oxide (DPO), Hytherm 500, and Hytherm 600, and combinations thereof; and (b) at least one oil extract, extracted using a process for the extraction of the at least one oil extract from at least one petroleum-based oil, comprising the steps of: (a) contacting at least one petroleum-based oil with at least one first solvent to obtain a first mixture; (b) contacting the first mixture with at least one second solvent to obtain a biphasic liquid system; (c) separating the biphasic liquid system into: (i) phase comprising the at least one first solvent; and (ii) phase comprising the at least one second solvent; (d) contacting the phase comprising the at least one second solvent with an aqueous salt solution to obtain a second mixture; (e) contacting the second mixture with the at least one first solvent to obtain a biphasic system comprising: (i) phase comprising the at least one first solvent and the at least one oil extract; and (ii) phase comprising the second mixture; and (f) isolating the at least one oil extract from the at least one first solvent, to obtain the at least one oil extract, wherein the oil extract is having a weight percentage in the range of 5 - 20 % with respect to the composition.

[0048] In an embodiment of present disclosure, there is provided a composition comprising: (a) at least one base fluid selected from the group diphenyl oxide (DPO), Hytherm 500, and Hytherm 600, and combinations thereof; and (b) at least one oil extract, extracted using a process for the extraction of the at least one oil extract from at least one petroleum-based oil, wherein the at least one petroleum-based oil comprises aromatics having a weight percentage in the range of 10- 85 % and can be selected from the group consisting of rubber processing oil (RPO), clarified oil (CLO), vacuum gas oil (VGO), deasphalted oil (DAO), 150 N extract, 500 N extract, and combinations thereof, comprising the steps of: (a) contacting at least one petroleum based oil with cyclohexane to obtain the first mixture at a temperature in the range of 20-35 °C, wherein the at least one petroleum-based oil to cyclohexane w/v ratio is in the range of 1 : 10 - 1 :50; (b) contacting the first mixture with NMP to obtain a biphasic liquid system at a temperature in the range of 35 - 60 °C, wherein the NMP is immiscible with the cyclohexane and the cyclohexane to the NMP volume ratio is in the range of 1 :5 - 1: 10; (c) separating the biphasic liquid system into: (i) phase comprising the cyclohexane; and (ii) phase comprising the NMP, using a separating funnel at a temperature in the range of 20-35 °C; (d) contacting the phase comprising the NMP with an aqueous salt solution to obtain a second mixture at a temperature in the range of 20-35 °C, wherein the aqueous salt solution is a saturated solution selected from the group consisting of aqueous solution of sodium chloride, aqueous solution of potassium chloride, and combinations thereof and the phase comprising the NMP to the aqueous salt solution volume ratio is in the range of 1 :20 - 1 :50; (e) contacting the second mixture with cyclohexane to obtain a biphasic system comprising: (i) phase comprising the cyclohexane and the at least one oil extract; and (ii) phase comprising the second mixture, at a temperature in the range of 20-35 °C, wherein the NMP is immiscible with the cyclohexane and the second mixture to the at least one first solvent volume ratio is in the range of 1: 10 - 1:50; (f) isolation of the at least one oil extract from the at least one first solvent, using a process selected from the group consisting of evaporation, distillation, fractional distillation, and lyophilization, wherein the at least one oil extract comprises at least 80% aromatics and the oil extract is having a weight percentage in the range of 5 - 20 % with respect to the composition.

[0049] In an embodiment of present disclosure, there is provided a composition comprising: (a) Hytherm 500, which includes: (i) saturates having weight percentage in the range of 70 - 95%; (ii) aromatics having weight percentage in the range of 0- 25%; (iii) resins having weight percentage in the range of 0-3%; and (iv) asphalts having weight percentage in the range of 0.5 - 2%; and (b) at least one oil extract, extracted using a process as described herein, having a weight percentage in the range of 5 - 20 % with respect to the composition. In another embodiment of present disclosure, there is provided a composition comprising: (a) Hytherm 500, which includes (i) saturates having weight percentage of 80 %; (ii) aromatics having weight percentage of 10 %; (iii) resins having weight percentage of 2 %; and (iv) asphalts having weight percentage of 1 %; and (b) at least one oil extract, extracted using a process as described herein, having a weight percentage in the range of 5 - 20 % with respect to the composition. In yet another embodiment of present disclosure, there is provided a composition comprising: (a) Hytherm 500, which includes (i) saturates having weight percentage of 80 %; (ii) aromatics having weight percentage of 10 %; (iii) resins having weight percentage of 2 %; and (iv) asphalts having weight percentage of 1 % ; and (b) RPO extract, extracted using a process as described herein, having a weight percentage of 20 % with respect to the composition.

[0050] In an embodiment of present disclosure, there is provided a composition comprising: (a) Hytherm 600, which includes (i) saturates having weight percentage in the range of 90 - 95%; (ii) aromatics having weight percentage in the range of 0 - 5%; (iii) resins having weight percentage in the range of 0 - 1 %; and (iv) asphalts having weight percentage in the range of 0.1 - 1%; and (b) at least one oil extract, extracted using a process as described herein, having a weight percentage in the range of 5 - 20 % with respect to the composition. In another embodiment of present disclosure, there is provided a composition comprising: (a) Hytherm 600, which includes (i) saturates having weight percentage of 92 %; (ii) aromatics having weight percentage of 2 %; (iii) resins having weight percentage of 0.5 %; and (iv) asphalts having weight percentage of 0.5 %; and (b) at least one oil extract, extracted using a process as described herein, having a weight percentage in the range of 5 - 20 % with respect to the composition. In yet another embodiment of present disclosure, there is provided a composition comprising: (a) Hytherm 600, which includes (i) saturates having weight percentage of 92 %; (ii) aromatics having weight percentage of 2 %; (iii) resins having weight percentage of 0.5 %; and (iv) asphalts having weight percentage of 0.5 %; and (b) RPO extract, extracted using a process as described herein, having a weight percentage of 20 % with respect to the composition.

[0051] In an embodiment of present disclosure, there is provided a composition comprising: (a) DPO; and (b) at least one oil extract, extracted using a process as described herein, having a weight percentage in the range of 5 - 20 % with respect to the composition. In another embodiment of present disclosure, there is provided a composition comprising: (a) DPO; and (b) RPO extract, extracted using a process as described herein, having a weight percentage of 5 % with respect to the composition. In yet another embodiment of present disclosure, there is provided a composition comprising: (a) DPO; and (b) RPO extract, extracted using a process as described herein, having a weight percentage of 10 % with respect to the composition. In another embodiment of present disclosure, there is provided a composition comprising: (a) DPO; and (b) RPO extract, extracted using a process as described herein, having a weight percentage of 20 % with respect to the composition.

[0052] In an embodiment of present disclosure, there is provided a composition comprising: (a) DPO; and (b) at least one oil extract, extracted using a process as described herein, having a weight percentage in the range of 5 - 20 % with respect to the composition. In another embodiment of present disclosure, there is provided a composition comprising: (a) DPO; and (b) 150N extract, extracted using a process as described herein, having a weight percentage of 5 % with respect to the composition. In yet another embodiment of present disclosure, there is provided a composition comprising: (a) DPO; and (b) 150N extract, extracted using a process as described herein, having a weight percentage of 10 % with respect to the composition. In another embodiment of present disclosure, there is provided a composition comprising: (a) DPO; and (b) 150N extract, extracted using a process as described herein, having a weight percentage of 20 % with respect to the composition.

[0053] In an embodiment of present disclosure, there is provided a composition comprising: (a) DPO; and (b) at least one oil extract, extracted using a process as described herein, having a weight percentage in the range of 5 - 20 % with respect to the composition. In another embodiment of present disclosure, there is provided a composition comprising: (a) DPO; and (b) 500N extract, extracted using a process as described herein, having a weight percentage of 5 % with respect to the composition. In yet another embodiment of present disclosure, there is provided a composition comprising: (a) DPO; and (b) 500N extract, extracted using a process as described herein, having a weight percentage of 10 % with respect to the composition. In another embodiment of present disclosure, there is provided a composition comprising: (a) DPO; and (b) 500N extract, extracted using a process as described herein, having a weight percentage of 20 % with respect to the composition.

[0054] In an embodiment of present disclosure, there is provided a composition comprising: (a) DPO; and (b) at least one oil extract, extracted using a process as described herein, having a weight percentage in the range of 5 - 20 % with respect to the composition. In another embodiment of present disclosure, there is provided a composition comprising: (a) DPO; and (b) VGO extract, extracted using a process as described herein, having a weight percentage of 5 % with respect to the composition. In yet another embodiment of present disclosure, there is provided a composition comprising: (a) DPO; and (b) VGO extract, extracted using a process as described herein, having a weight percentage of 10 % with respect to the composition. In another embodiment of present disclosure, there is provided a composition comprising: (a) DPO; and (b) VGO extract, extracted using a process as described herein, having a weight percentage of 20 % with respect to the composition.

[0055] In an embodiment of present disclosure, there is provided a composition comprising: (a) DPO; and (b) at least one oil extract, extracted using a process as described herein, having a weight percentage in the range of 5 - 20 % with respect to the composition. In another embodiment of present disclosure, there is provided a composition comprising: (a) DPO; and (b) DAO extract, extracted using a process as described herein, having a weight percentage of 5 % with respect to the composition. In yet another embodiment of present disclosure, there is provided a composition comprising: (a) DPO; and (b) DAO extract, extracted using a process as described herein, having a weight percentage of 10 % with respect to the composition. In another embodiment of present disclosure, there is provided a composition comprising: (a) DPO; and (b) DAO extract, extracted using a process as described herein, having a weight percentage of 20 % with respect to the composition.

[0056] In an embodiment of present disclosure, there is provided a composition comprising: (a) at least one base fluid; and (b) at least one oil extract, extracted using a process as described herein, having the weight percentage in the range of 5 - 20 % with respect to the composition. The composition exhibits an enhanced thermal conductivity with an enhancement of up to 104%, compared to the thermal conductivity of base fluid alone. In another embodiment, the composition exhibits an enhanced thermal conductivity with an enhancement of 37.1%, compared to the thermal conductivity of base fluid alone. The heat transfer fluids with the oil extract additives obtained using the described NMP-based extraction method were found to have higher thermal conductivity as compared to the extracts obtained using the existing DMSO-based methods.

[0057] In an embodiment of the present disclosure, a heat exchange test is conducted using a high temperature solar loop test fabricated as described in the patent application (Indian Patent, App. No: 7104/CHE/2015) to study the cyclic stability of prepared compositions.

[0058] In an embodiment of present disclosure, there is provided a composition comprising: (a) at least one base fluid; and (b) at least one oil extract, extracted using a process as described herein, having the weight percentage in the range of 5 - 20 % with respect to the composition. The composition exhibits substantially the same thermal conductivity after 10 cycles of loop operations, as it shows during the first cycle.

[0059] In an embodiment of present disclosure, there is provided a process for the preparation of a composition, comprising: (a) at least one base fluid; and (b) at least one oil extract, extracted using a process as described herein, wherein the at least one oil extract has a weight percentage in the range of 5 - 20 % with respect to the composition. The process comprising the steps of: (a) contacting at least one base fluid with the at least one oil extract to obtain mixture A; (b) homogenizing the mixture A by sonication to obtain the composition,

[0060] In an embodiment of present disclosure, there is provided a process for the preparation of a composition, comprising: (a) at least one base fluid; and (b) at least one oil extract, extracted using a process as described herein, wherein the at least one oil extract has a weight percentage in the range of 5 - 20 % with respect to the composition, the process comprises,contacting at least one base fluid with the at least one oil extract at a temperature in the range of 20 - 35 °C, to obtain the mixture A. In another embodiment of present disclosure, there is provided a process for the preparation of a composition, wherein the at least one base fluid and the at least one oil extract were contacted at a temperature of 25 °Cto obtain mixture A. In yet another embodiment of the present disclosure, the at least one base fluid can be DPO and the at least one oil extract can be RPO extract which are contacted at a temperature of 25 °Cto obtain mixture A, wherein the RPO extract has a weight percentage of 20 % with respect to the composition.

[0061] In an embodiment of present disclosure, there is provided a process for the preparation of a composition, comprising: (a) at least one base fluid; and (b) at least one oil extract, extracted using a process as described herein, wherein the at least one oil extract has a weight percentage in the range of 5 - 20 % with respect to the composition, the process comprises,homogenizing the mixture A by sonication extract at a temperature in the range of 30 -60 °C for a period in the range of 1 - 4 hours, to obtain the composition. In another embodiment of the present disclosure, homogenizing the mixture A by sonication to obtain the composition is carried out at a temperature of 45 °C for a period of 3 hours.

[0062] In an embodiment of present disclosure, there is provided a process for the preparation of a composition, comprising: (a) at least one base fluid; and (b) at least one oil extract, extracted using a process as described herein, wherein the at least one oil extract has a weight percentage in the range of 5 - 20 % with respect to the composition. The composition can be used as a heat transfer fluid for heat storage and heat transfer applications.

[0063] Although the subject matter has been described in considerable detail with reference to certain preferred embodiments thereof, other embodiments are possible.

EXAMPLES

[0064] The disclosure will now be illustrated with working examples, which is intended to illustrate the working of disclosure and not intended to take restrictively to imply any limitations on the scope of the present disclosure. Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood to one of ordinary skill in the art to which this disclosure belongs. Although methods and materials similar or equivalent to those described herein can be used in the practice of the disclosed methods and compositions, the exemplary methods, devices and materials are described herein. It is to be understood that this disclosure is not limited to particular methods, and experimental conditions described, as such methods and conditions may apply. Example 1

Material and Methods

[0065] The base fluids used for the preparation of the heat transfer fluid composition were selected from the group consisting of DPO, Hytherm 500 and Hytherm 600. The latter two base fluids comprise various components in differing weight percentages. Broadly, Hytherm 500 contemplated by the instant disclosure can comprise: (i) saturates having weight percentage in the range 70 - 75%; (ii) aromatics having weight percentage in the range of 20-25%; (iii) resins having weight percentage in the range of 1-3%; and (iv) asphalts having weight percentage in the range of 1 - 2%. Similarly, Hytherm 600 contemplated by the instant disclosure can comprise: (i) saturates having weight percentage in the range 90 - 95%; (ii) aromatics having weight percentage in the range of 0-5%; (iii) resins having weight percentage in the range of 0-1%; and (iv) asphalts having weight percentage in the range of 0.1 - 1%.

[0066] Hytherm-500 used for the preparation of heat transfer fluid composition had the following characteristics and composition. It was a yellowish coloured base fluid (lube oil) for applications around 285 °C having a viscosity index of 93.9. It mainly contains saturates, and the SARA (saturate, aromatics, resins, and asphalts) analysis results showed that it contains 73.9 % saturates, 22.2% aromatics, 2.2 % resins, and 1.7 % asphalts.

[0067] Similarly, Hytherm 600 used for the preparation of heat transfer fluid composition had the following characteristics and composition. It was a blackish coloured base fluid (lube oil) for applications around 305 °C having a viscosity index of 111.8. It mainly contains saturates, and the SARA (saturate, aromatics, resins, and asphalts) analysis results showed that it contains 92.2 % saturates, 0.0% aromatics, 0.0 % resins, and 0.8 % asphalts.

Example 2

Extraction of polyaromatic hydrocarbon from Rubber Processing Oil

[0068] The extraction of rubber processing oil was carried out using N-methyl-2- pyrrolidone (NMP) and cyclohexane. Rubber processing oil known as HP-Elasto 710 having a high aromatic content (-66 %) was employed. Initially 50 ml of rubber processing oil was completely dissolved in 200 ml of cyclohexane and taken into a separating funnel. Extraction of aromatics was done using 3 x25 ml of NMP, whereby the aliphatics were preferentially separated into the cyclohexane layer. NMP layers were combined and treated with 100 ml of saturated brine solution and the precipitate formed was back extracted with 3 x 25 ml of cyclohexane. The extraction process was carried out at temperature in the range of20-60 °C for the effective extraction of RPO. The cyclohexane portion was dried over anhydrous magnesium sulphate. Then the cyclohexane fraction was collected and the solvent was evaporated using rotary evaporator under reduced pressure.

[0069] The obtained polyaromatic hydrocarbon containing extract was used as an additive to improve the thermal conductivity and specific heat capacity of the base fluid. Example 3

Preparation of heat transfer fluid composition

[0070] Synthesis of oil extract-based heat transfer fluids was done by adding 10 gm of RPO to 90 gm of DPO. The mixture was homogenized using an ultra-sonication bath. The sonication was carried out at a temperature in the range of 30-60 °C for a time duration in the range of 1-4 h. The compositions were thoroughly characterized by thermo-physicochemical methods.

Example 4

Study of thermal conductivity of NMP-based extract containing heat transfer fluids

[0071] Thermal conductivity is an important parameter in determining the heat transfer capacity of prepared oil-based heat transfer fluids. Various compositions were prepared to optimize the concentration of oil (RPO) extract in the base fluid to obtain maximum enhancement in thermal conductivity. As the extract itself is highly viscous, base fluids with low viscosity, such as diphenyl oxide (DPO)were preferred. Also, it was found that the addition of the oil extract to the viscous thermic fluids such as Hytherm-500 and Hytherm-600 introduced undesirable characteristics such as decreased thermal conductivity and increased viscosity.

[0072] The thermal conductivity of the compositions at different temperatures was measured using transient plane source method and the results are recorded in Table 1 below, along with the percentage enhancement in thermal conductivity with respect to the parent base fluid composition (DPO). Results in Table 1 involve RPO extract obtained using the NMP-based extraction process described in this disclosure.

Table 1

DPO + 10 % RPO 0.15132 0.15967 0.17172 0.22541 0.24112

Enhancement of k (%) 31.3% 24.4% 17.7% 43.0% 82.1%

DPO + 20 % RPO 0.15799 0.16120 0.18198 0.23886 0.27048

Enhancement of k (%) 37.1% 25.6% 24.7% 51.5% 104.2%

DPO + 30 % RPO 0.14521 0.15132 0.16212 0.21541 0.23121

Enhancement of k (%) 26.0% 18.0% 11.1% 36.6% 74.6%

DPO + 40 % RPO 0.13922 0.14942 0.14928 0.12013 0.21222

Enhancement of k (%) 20.8% 16.5% 2.3% -23.8% 60.3%

RT refers to room temperature, typically taken as 20 °C.

[0073] The results provided in Table 1 clearly indicate the findings of the study that at a given temperature there was significant increase in thermal conductivity of parent base fluid, i.e., DPO with the addition of up to 20 wt. % of RPO extract. The thermal conductivity was found to achieve a maximum upon addition of20 wt. % of RPO extract, 104% at 200 °C, beyond which further addition of oil extract to the base fluid was found to be detrimental. The enhancement in thermal conductivity was seen to drop from a high of 104% to 60.3% upon addition of 40 wt. % of RPO extract.

[0074] The NMP -based method has wide-applicability and is applicable to a range of petroleum-based oils. The Table 3 lists the thermal enhancement of parent base fluid composition (DPO) upon addition of various oil extracts- vacuum gas oil (VGO), deasphalted oil (DAO), 150 N extract, and 500 N extract.

[0075] The thermal conductivity of the compositions at different temperatures was measured using transient plane source method and the results are recorded in Table 2 below, along with the percentage enhancement in thermal conductivity with respect to the parent base fluid composition (DPO). Results in Table 2 involve various oil extracts obtained using the NMP-based extraction process described in this disclosure.

Table 2

Enhancement of k 27.8 20.2 15.7

(%)*

DPO+VGO 0.14812 0.14931 0.1492

Enhancement of k 28.5 29.6 29.5

(%)*

DPO+DAO 0.14710 0.14911 0.14913

Enhancement of k 27.7 29.4 29.4

(%)*

""calculated based on the k for pure DPO at RT (from Tables 1 and 2).

[0076] Significant enhancement in thermal conductivity can be seen upon addition of the various oil extracts. The VGO extract was seen to produce the highest enhancement after RPO extract. A maximum of 29.6% was seen upon the addition of 10 wt % of VGO in to the DPO (base fluid).

Example 5

Study of thermal conductivity of DMSO-based extract containing heat transfer fluids

[0077] Similar to Example 4, the RPO extract was incrementally added into DPO to check the thermal performance of the composition. Results in Table 3 involve RPO extract obtained using the DMSO-based extraction process described previously in the literature as compared to the NMP -based process employed in Example 4.

[0078] The thermal conductivity of the compositions at different temperatures was measured using transient plane source method and the results are recorded in Table 3 below along with the percentage enhancement in thermal conductivity with respect to the parent base fluid composition (DPO).

Table 3

Thermal Conductivity, k (W/mK)

Compositions RT 50 °C 100 °C 150 °C 200 °C

DPO 0.11523 0.12831 0.14593 0.15766 0.13243

DPO + 5 % RPO 0.12840 0.13010 0.14897 0.18990 0.20021

Enhancement of k (%) 11.4% 1.4% 2.1% 20.5% 51.2%

DPO + 10 % RPO 0.13220 0.13960 0.16230 0.20120 0.21340

Enhancement of k (%) 14.7% 8.8% 11.2% 27.6% 61.1% DPO + 20 % RPO 0.14110 0.15030 0.17130 0.22710 0.23050

Enhancement of k (%) 22.5% 17.1% 17.4% 44.0% 74.1%

[0079] As is clear from the results provided in Table 3, there is enhancement seen upon addition of the DMSO-based RPO extract to the DPO base fluid. However, on comparison with Table 1, the usefulness of the NMP-based oil extraction process outlined in this disclosure is clear. The enhancement observed with the NMP-based RPO additive is significantly higher when compared with the DMSO-based extract. A maximum of 104.2% was observed for the composition comprising DPO+20% RPO at 200 °C. Example 6

Study of thermal conductivity of NMP-based extract containing heat transfer fluids

[0080] Any fluid used as heat-exchanger should not only be able to transfer heat with minimal loss, but also should have a wide temperature range within which it can work reliably. Hence, the measurement of thermal stability is also an important parameter while determining the heat transfer capacity of prepared oil-based heat transfer fluids. The measurements were done using thermal gravimetric analysis of various compositions prepared using a process as described in Examples 2 and 3. Example 7

Thermal stability study of various oil extract containing heat transfer fluids:

[0081] Any fluid used as heat-exchanger should not only be able to transfer heat with minimal loss, but also should have a wide temperature range within which it can work reliably. Hence, the measurement of thermal stability is also an important parameter while determining the heat transfer capacity of prepared oil-based heat transfer fluids. The measurements were done using thermal gravimetric analysis of various compositions prepared using a process as described in Examples 2 and 3. [0082] Figure 1 shows an increase in the thermal stability of the base fluid (DPO) with the incremental addition of RPO extract. The increased stability observed is in good correlation with the thermal conductivity enhancement seen in Table 1.

[0083] The composition comprising DPO+40% RPO showed highest thermal stability. However, upon comparison with the thermal conductivity data from Table 1 , it is clear that the composition comprising DPO+20% RPO had the best thermal parameters for use as heat transfer fluid.

[0084] Although the subject matter has been described in considerable detail with reference to certain examples and implementations thereof, other implementations are possible.