WO2024013757A1

WO2024013757A1 - A thermic fluid composition and a process for preparing the same

Info

Publication number: WO2024013757A1
Application number: PCT/IN2022/051117
Authority: WO
Inventors: Kanaparthi Ramesh; Atmakuri RAJASEKHAR; Kottari NARESH; Aradhana TRIPATHI; Gnanasekaran VALAVARASU
Original assignee: Hindustan Petroleum Corporation Limited
Priority date: 2022-07-13
Filing date: 2022-12-22
Publication date: 2024-01-18

Abstract

The present invention discloses a thermic fluid composition made up of a base oil, a polyalphaolefin, an antioxidant, a corrosion inhibitor. The thermic fluid composition thermic fluid composition which is in liquid form at room temperature and exhibit high heat resistance and stability at higher temperatures from 25 to 270 °C. The thermic fluid composition contains 65-95 wt.% of the base oil, 5-34 wt.% of polyalphaolefin, 0.01-0.2 wt.% of an antioxidant, and 0.01-0.2 wt.% of a corrosion inhibitor.

Description

A THERMIC FLUID COMPOSITION AND A PROCESS FOR PREPARING THE

SAME

FIELD OF THE INVENTION:

The present invention relates to the field of heat transfer from one system to another. Specifically, the present invention relates to a mineral oil thermic fluid composition useful in solar thermal applications and process heat applications. Further, the present invention relates to a process for preparing the said thermic fluid composition.

BACKGROUND OF THE INVENTION:

The industrial development requires energy in various forms such as heat energy, mechanical energy and/or electrical energy. However, environmental loss of heat energy is a very common problem in various industries. To stop the environmental loss of heat energy many methods are employed, and the very common method is heat transfer from one system to another via thermic fluid. Some of such known methods and the fluid compositions are disclosed here in below.

US11180709B2 discloses a functional fluid such as automotive engine transmission fluids, clutch fluids, gearbox fluids, electric motor fluids, and/or battery packing cooling fluids comprising a low viscosity, low-volatility polyalpha-olefin base stock, and processes for lubricating and/or cooling an engine transmission, an electric motor, and/or a battery packing using such functional fluids.

US11162046B2 discloses a lubricating oil composition for automobile transmission that includes low-viscosity base oils i.e., (i) between 45 and 95 mass % of a Fischer-Tropsch synthetic low- viscosity base oil with a 100 °C. kinematic viscosity of between 1 mm²/s and 2 mm²/s, and between 0 and 25 mass % of other than a Fischer-Tropsch synthetic low- viscosity base oil with a 100 °C. kinematic viscosity of between 1 mm²/s and 2 mm²/s, and (ii) between 0 and 35 mass % of a base oil wherein the 100 °C. kinematic viscosity is greater than 2 mm²/s and no greater than 5 mm²/s; and (iii) between 5 and 55 mass % of an olefin polymer or copolymer, as a high- viscosity base oil, wherein the 100 °C. kinematic viscosity is between 100 and 800 mm²/s. A lubricating oil composition for an automatic transmission wherein the 100 °C. kinematic viscosity of this composition is between 3.8 and 5.5 mm² /s, the viscosity index is no less than 190, the flashpoint is no less than 140 °C, and the reduction ratio of the 100 °C. kinematic viscosity after shear stability testing, at 60 °C. for 20 hours, is maintained at no greater than 3%. US20210040369A1 discloses heat transfer fluids for use in an apparatus having a heat transfer system. In one embodiment, the heat transfer fluids have at least one Group IV base oil, as a major component; at least one phenolic antioxidant, as a minor component; and optionally an aminic antioxidant in an amount less than about 0.25 weight percent, based on the total weight of the heat transfer fluid. In another embodiment, the heat transfer fluids have at least one Group V base oil, as a major component; and a mixture of at least two antioxidants, as a minor component. The at least one Group IV base oil and the at least one Group V base oil have a kinematic viscosity (Kinematic viscocity 100) from about 0.5 cSt to about 12 cSt at 100 °C. The mixture of at least two antioxidants has a phenolic antioxidant and an aminic antioxidant. This disclosure further relates to methods for improving thermal-oxidative stability of a heat transfer fluid used in an apparatus having a heat transfer system.

US20070078070A1 discloses compositions comprising a blend of Group II basestocks and low volatility, low viscosity PAO basestocks. The blend is particularly useful for preparing finished lubricants that meet or even exceed the criteria for SAE Grade 0W multi-grade engine oils. The combination of these low volatility, low viscosity PAOs with Group II basestocks provide, in embodiments, the necessary performance criteria in automatic transmission fluids, automotive or industrial gear oils, hydraulic fluids, or any other high-performance lubricant requiring a combination of excellent low fluidity and low volatility.

US20120316094A1 discloses a novel lubricant composition having admixture of a first base stock component comprising one or more base stocks each having a viscosity of at least 40 cSt, Kinematic viscosity at 100 °C and a molecular weight distribution (MWD) as a function of viscosity at least 10 percent less than algorithm: MWD=0.2223+1.0232*log (Kv at 100 °C. in cSt); and a second base stock component comprising one or more base stocks each having a viscosity less than 10 cSt, Kv at 100 °C.

These known heat transfer fluids have many drawbacks such as they are limited to engine/automobile heat transmission and are not useful in heat transfer in processing industry. However, in food processing industry, there is very high demand for heat transfer solutions and wherein, the said solution should be of high purity i.e., free from metals, lead and having low aromatic compounds, low sulphur content nature.

Accordingly, there is need of a thermic fluid composition which have broader thermal stability with high purity and have medium vapor pressure.

OBJECTIVES OF THE PRESENT INVENTION:

The primary objective of the present invention is to provide a thermic fluid composition and a process for preparing the said thermic fluid composition.

Further objective of the present invention is to provide an organic thermic fluid composition which has good oxidation stability.

Further objective of the present invention is to provide a thermic fluid composition which can be used in process heating applications in food industry.

It is further objective of the present invention is to provide a thermic fluid composition which have broader thermal stability from 25 to 270 °C and have medium vapor pressure.

Further objective of the present invention is to provide a thermic fluid composition to be used in solar thermal applications, food processing industry and in process heat applications.

SUMMARY OF THE PRESENT INVENTION:

The present invention provides a thermic fluid composition consisting of a base oil, a polyalphaolefin, an antioxidant and a corrosion inhibitor. Specifically, the thermic fluid composition includes 55 to 95 wt.% of the base oil, 5 to 45 wt.% of the polyalphaolefin, 0.01 to 0.2 wt.% of the antioxidant, and 0.01 to 0.2 wt.% of the corrosion inhibitor.

More specifically, the base oil is 65 to 95 wt.% and the base oil is a hydro treated group-II base oil obtained from a petroleum refinery. Wherein, the base oil is selected from a hydro treated base oil-0 having viscosity 72-75 mm²/s at 40 °C, a hydro treated base oil-1 having viscosity 10- 12 mm²/s at 40 °C and a hydro treated base oil-2 having viscosity 27-29 mm²/s at 40 °C. The polyalphaolefin is 5 to 34 wt.% and the polyalphaolefin is formed by oligomerization of a- olefin. The a-olefin is selected from 1 -propene, 1 -butene, 1 -pentene, 1 -hexene, 1 -heptene, 1- octene, 1 -nonene, 1 -decene, 1 -undecane, 1 -dodecene, 1 -tridecene, 1 -tetradecene, 1 -hexadecene, 1 -octadecene, 1- eicosane or a combination thereof.

The antioxidant is selected from Hexamethylene bis, N-Phenyl Benzenamine, phenyl- [alpha] - napthalamine, phenyl- [beta] -napthalamine, or a combination thereof. The corrosion inhibitor is sodium nitrite.

The thermic fluid composition has a thermal stability from 25 to 270 °C and have medium vapor pressure. The thermic fluid composition as disclosed herein is used in solar thermal applications and in process heat applications.

Further, the present invention provides a process for preparing the thermic fluid composition, wherein, the process includes preparing a reaction solution by mixing at least 55 to 95 wt.% of a base oil, 5 to 45 wt.% of a polyalphaolefin, 0.01 to 0.2 wt.% of an antioxidant, and 0.01 to 0.2 wt.% of a corrosion inhibitor. Wherein, the base oil is a hydro treated group-II base oil obtained from a petroleum refinery. Then sonicating the reaction solution for 20 to 40 minutes, followed by stirring at 500 rpm at 45 to 50 °C for 20 to 40 minutes. Then ultra-sonicating the reaction solution at 20 KHz for 15 minutes using a probe ultrasonicator.

Wherein, the base oil is selected from a hydro treated base oil-0 having viscosity 72-75 mm²/s at 40 °C, a hydro treated base oil-1 having viscosity 10-12 mm²/s at 40 °C and a hydro treated base oil-2 having viscosity 27-29 mm²/s at 40 °C.

The process includes preparing the reaction solution by preparing a first mixture by mixing at least 90 to 99.55 wt.% of a hydro treated group-II base oil, 0.02 to 0.45 wt.% of the antioxidant, or 0.05 to 0.2 wt.% of the corrosion inhibitor. Then mixing 90 wt.% of the first mixture, 10 wt.% of the polyalphaolefin and/or the hydro treated group-II base oil to obtain the reaction solution. Further, sonicating the reaction solution for 20 to 40 minutes and stirring at 500 rpm at 45 to 50 °C for 20 to 40 minutes. Then ultra-sonicating the reaction solution at 20 KHz for 15 minutes using a probe ultrasonicator.

BRIEF DESCRIPTION OF THE DRAWING:

To further clarify advantages and aspects of the present thermic fluid composition, a more particular description of the said thermic fluid composition will be rendered by reference to specific embodiments thereof, which is illustrated in the appended drawing(s). It is appreciated that the drawing(s) depicts only typical embodiments of the invention and are therefore not to be considered limiting of its scope.

Figure 1: illustrates a schematic flow diagram of the natural circulation loop.

Figure 2: illustrates UV-Absorbance of SI composition, S2 composition, and Trimethylpentane solution.

DESCRIPTION OF THE INVENTION:

The heat transfer mediums are widely used for applications such as heat removal from exothermic reactions, and concentrated solar power. Further, the heat transfer mediums are also used in heat storage applications in preferred temperature ranges. As such the heat transfer mediums mainly consist of polyalphaolefin based homogeneous solution with excellent stability and heat transfer characteristics.

Accordingly, the present invention provides the thermic fluid composition which acts as a heat transfer medium and the said composition contains a base oil, a polyalphaolefin, an anti-oxidant, and a corrosion inhibitor.

According to the specific embodiment, the present invention provides a thermic fluid composition, wherein, the said composition includes a base oil, a polyalphaolefin, an antioxidant and a corrosion inhibitor. Specifically, the thermic fluid composition includes 55 to 95 wt.% of the base oil, 5 to 45 wt.% of the polyalphaolefin, 0.01 to 0.2 wt.% of the antioxidant, and 0.01 to 0.2 wt.% of the corrosion inhibitor.

More specifically, the base oil is 65 to 95 wt.% and the base oil is a hydro treated group-II base oil obtained from a petroleum refinery. Wherein, the base oil is selected from a hydro treated base oil-0 having viscosity 72-75 mm²/s at 40 °C, a hydro treated base oil-1 having viscosity 10- 12 mm²/s at 40 °C and a hydro treated base oil-2 having viscosity 27-29 mm²/s at 40 °C.

The polyalphaolefin is 5 to 34 wt.% and the polyalphaolefin is formed by oligomorisation of a- olefin. The a-olefin is selected from 1 -propene, 1 -butene, 1 -pentene, 1 -hexene, 1 -heptene, 1- octene, 1 -nonene, 1 -decene, 1 -undecane, 1 -dodecene, 1 -tridecene, 1 -tetradecene, 1 -hexadecene, 1 -octadecene, 1- eicosane or a combination thereof.

The said thermic fluid composition has a thermal stability from 25 to 270 °C and have medium vapor pressure. The thermic fluid composition as disclosed herein is used in solar thermal applications, food processing industry and in process heat applications.

Further, the present invention provides a process for preparing the thermic fluid composition, wherein, the process includes preparing a reaction solution by mixing 55 to 95 wt.% of a base oil, 5 to 45 wt.% of a polyalphaolefin, 0.01 to 0.2 wt.% of an antioxidant, and 0.01 to 0.2 wt.% of a corrosion inhibitor. Wherein, the base oil is a hydro treated group-II base oil obtained from a petroleum refinery. Then sonicating the reaction solution for 20 to 40 minutes, followed by stirring at 500 rpm at 45 to 50 °C for 20 to 40 minutes. Then ultrasonicating the reaction solution at 20 KHz for 15 minutes using a probe ultrasonicator.

The base oil is a hydro treated group-II base oil obtained from a petroleum refinery. Wherein, the base oil is selected from a hydro treated base oil-0 having viscosity 72-75 mm²/s at 40 °C, a hydro treated base oil-1 having viscosity 10-12 mm²/s at 40 °C and a hydro treated base oil-2 having viscosity 27-29 mm²/s at 40 °C.

In an embodiment, the polyalphaolefin is 5 to 34 wt.% and the polyalphaolefin is formed by oligomorisation of a-olefin. The a-olefin is selected from 1 -propene, 1 -butene, 1 -pentene, 1- hexene, 1 -heptene, 1 -octene, 1 -nonene, 1 -decene, 1 -undecane, 1 -dodecene, 1 -tridecene, 1- tetradecene, 1 -hexadecene, 1 -octadecene, 1- eicosane or a combination thereof. The process includes preparing the reaction solution by preparing a first mixture by mixing at least 90 to 99.55 wt.% of a hydro treated group-II base oil, 0.02 to 0.45 wt.% of the antioxidant, or 0.05 to 0.2 wt.% of the corrosion inhibitor. Then mixing 90 wt.% of the first mixture, 10 wt.% of the polyalphaolefin and/or the hydro treated group-II base oil to obtain the reaction solution. Further, sonicating the reaction solution for 20 to 40 minutes and stirring at 500 rpm at 45 to 50 °C for 20 to 40 minutes. Then ultra-sonicating the reaction solution at 20 KHz for 15 minutes using a probe ultrasonicator.

In an embodiment, the process includes steps of preparing the reaction solution by preparing a first mixture by mixing at least one of 90 to 99.55 wt.% of the hydro treated base oil-0, 0.02 to 0.45 wt.% of the antioxidant, or 0.05 to 0.2 wt.% of the corrosion inhibitor. Then mixing 90 wt.% of the first mixture and 10 wt.% of the polyalphaolefin to obtain the reaction solution. Further, sonicating the reaction solution for 20 to 40 minutes and stirring at 500 rpm at 45 to 50 °C for 20 to 40 minutes. Then, ultra-sonicating the reaction solution at 20 KHz for 15 minutes using a probe ultrasonicator.

In an embodiment, the process includes steps of preparing the reaction solution by preparing a first mixture by mixing at least one of 90 to 99.55 wt.% of the hydro treated base oil-1, 0.02 to 0.45 wt.% of the antioxidant, or 0.05 to 0.2 wt.% of the corrosion inhibitor. Then mixing 90 wt.% of the first mixture and 10 wt.% of the hydro treated base oil-1 to obtain the reaction solution. Further, sonicating the reaction solution for 20 to 40 minutes and stirring at 500 rpm at 45 to 50 °C for 20 to 40 minutes. Then, ultrasonicating the reaction solution at 20 KHz for 15 minutes using a probe ultrasonicator.

In the present process, the polyalphaolefin is formed by oligomerization of a-olefin, wherein, the a-olefin is selected from 1 -propene, 1 -butene, 1 -pentene, 1 -hexene, 1 -heptene, 1 -octene, 1- nonene, 1 -decene, 1 -undecane, 1 -dodecene, 1 -tridecene, 1 -tetradecene, 1 -hexadecene, 1- octadecene, 1- eicosane or a combination thereof. The antioxidant is selected from Hexamethylene bis, N-Phenyl Benzenamine, phenyl- [alpha] -napthalamine, phenyl- [beta] - napthalamine, or a combination thereof. The corrosion inhibitor is sodium nitrite. In another embodiment, in the thermic fluid composition of present invention, the other petrochemical olefin produced by synthesizing oligomers of either 1 -decene or 1 -dodecene can be used. Since petrochemical olefins are free from waxy, sulphur and nitrogen compounds and having good viscosity index, oxidation stability and flow properties, homogeneous solution of these compounds shows good antioxidant and stability characteristics.

Hydro treated group-II base oil:

Hydro treated group-II base oil are obtained from petroleum refinery with high purity after refining at various stages from Hydro treating, Hydro isomerization, dewaxing and Hydro finishing operations. Depending upon their properties, various hydro treated group-II base oils are referred as Base Oil -0, Base Oil -1, Base Oil -2.

Polyalphaolefin (PAO) compound:

Olefins are alkenes with at least one double or triple bond between carbon and hydrogen. Alpha olefins are family of alkenes with a chemical formula CxH2x and double bond at the primary or alpha position as shown below.

H / CH2-CH2-CH2-CH2 -CH3

C = C iF H

The term Polyalphaolefin used here refers to hydrocarbon formed by oligomerization of olefin. Specifically, in the present invention the Polyalphaolefin compounds are hydrogenated and produced from oligomorisation of a-olefin.

CH2 = CHR

Wherein R can be Hydrocarbyl group such as aryl, alkyl or arylalkyl.

Specifically, herein the polyalphaolefin are prepared by the oligomorisation of petrochemical alpha olefins (C6-C20) or simple alkene monomer such as 1 -Decene, or 1 -Octene. Olefin oligomorisation is a process of forming heavy carbon alpha olefin with the cationic oligomorisation in the presence of lewis acids such as AICI3, BF3, FeCk and results in olefin oligomer. Feed contains olefin monomers and unsaturated compounds with oligomorisation results in formation of olefin oligomer and non-reacted compounds so upon separation and hydrogenation of product under catalyst, saturated polyalphaolefins will be formed.

Petrochemical olefins are wax free, with high oxidation stability and good flow properties.

AICI3 FeCh , - l-(Ci₀)4 (Olef _r. , Non reacted Compounds

1 Decene - '■ in Oligomer) - ► Olefin Compound separation

Poly Alpha Olefin

In an embodiment, the Polyalphaolefin are derived from olefin monomers and are selected from a group consisting of aromatic olefins, aliphatic olefins and cyclic olefins. As specific examples of preferred alpha olefins include but are not limited to 1 -propene, 1 -butene, 1 -pentene, 1- hexene, 1 -heptene, 1 -octene, 1 -nonene, 1 -decene, 1 -undecane, 1 -dodecene, 1 -tridecene, 1- tetradecene, 1 -hexadecene, 1 -octadecene, 1-eicosene.

In accordance with another embodiment of present invention there is provided synthetic organic thermic fluid with good oxidation stability and thermal stability up to 270 °C, consists of saturated polyalphaolefin (5-34%), base oil (65-95%), Antioxidant (0-0.2%) and corrosion inhibitor (0-0.2%).

In accordance with another embodiment of present invention there is provided synthetic organic thermic fluid with good oxidation stability and thermal stability up to 270 °C, consists of saturated polyalphaolefin (5-34%), base oil (65-95%), Antioxidant (0.01-0.2%) and corrosion inhibitor (0.01-0.2%).

In a preferred embodiment, the present invention provides a stable organic thermic fluid which can be used as heat transfer fluid medium for primary and secondary heating in process heating application up to 270 °C.

Preparation of Polyalphaolefin (PAO):

Example- 1:

To a stirred solution of 1 -octene (30 mL), AlCh (6 g) followed by catalytic amount of de-ionized water (100 pL) is added. This flask is quickly set-up with condenser and the reaction was continued at 50 °C for 16 hours. After the reaction stopped, reaction solution is cooled to room temperature and reaction contents are transferred into a separating funnel which is then quenched with water (20 mL). The separated water-layer (bottom layer) from the separating funnel is collected and discarded. The top layer in the separating funnel is washed again with water (2 X 20 mL) and the separated water layer is discarded. Top layer is then collected and dried over anhydrous sodium sulfate and then filtered. Collected filtrate was concentrated using rotary evaporator to afford polyalphaolefin product- 1 (PAO-1) for which the viscosity and pour point properties are given below.

Viscosity of PAO-1 at 40 °C: 35.279 cSt

Viscosity of PAO-1 at 100 °C: 6.4363 cSt Pour point of PAO-1 : -66 °C

Example-2:

To a stirred solution of olefin-rich refinery stream (delayed coker naphtha) (400 mL), AlCh (6 g) followed by catalytic amount of de-ionized water (200 pL) is added. This flask is quickly set-up with condenser and the reaction was continued at 50 °C for 16 hours. After the reaction stopped, reaction is cooled to room temperature and reaction contents are transferred into separating funnel which is then quenched with water (200 mL). The separated water-layer (bottom layer) from the separating funnel is collected and discarded. The top layer in the separating funnel is washed again with water (2 X 100 mL) and the separated water layer is discarded. Top layer is then collected and dried over anhydrous sodium sulfate and then filtered. Collected filtrate was concentrated using rotary evaporator to afford polyalphaolefin product-2 (PAO-2) for which the viscosity and pour point properties are given below.

Viscosity of PAO-2 at 40 °C: 9.614 cSt Viscosity of PAO-2 at 100 °C: 2.542 cSt Pour point of PAO-2: -71 °C

Thermic fluid composition and proportion of individual compounds: Below Table 1 provides the constituents and their WAV percentage. Table 1

Thermic fluid composition preparation (SI) (stable up to 270 °C):

A 300 mL flask with magnetic stir bar was cleaned with acetone and dried in oven at 90 °C after thoroughly evacuated by purging with dry compressed air to eliminate contaminants. The flask was charged with hydro treated base oil-0, antioxidant and corrosion inhibitor (99.55:0.225:0.225) by weight and the mixture is labeled as a first feed of SI. Take the PAO feed to the reaction flask with the weight ratio of (first feed of SI: Polyalphaolefin) (90: 10) by weight and sonicate the solution for half an hour. Keep the reaction flask with above formulation on hot plate and using magnetic stir, continue mechanical stirring at 500 rpm and temperature maintained at 45 to 50 °C for about half an hour. Ultrasonicate the formed solution at 20 KHz for 15 minutes using Probe ultrasonicator for uniform mixing of the two compounds. Analysis of prepared thermic fluid by Rapid small scale oxidation test shows significant improvement in oxidation stability as comparable to commercial synthetic thermic fluids. Further, various examples of the said thermic fluid composition (SI) are provided herein below i.e., example 1-5.

EXAMPLE 1:

The procedure was essentially same as above, except there is antioxidant (0.25%) from group of methyl and phenyl based such as but not limited to Hexamethylene bis, N-Phenyl Benzenamine, Phenyl- [alpha] -napthalamine and/or phenyl- [beta] -napthalamine and sodium nitrite as corrosion inhibitor (0.2%) in first feed of SI.

EXAMPLE 2:

The procedure was essentially same as Example 1, except there is antioxidant (0.45%) from group of methyl and phenyl based such as but not limited to Hexamethylene bis, N-Phenyl Benzenamine, Phenyl- [alpha] -napthalamine and/or phenyl- [beta] -napthalamine and without corrosion inhibitor in first feed of S 1.

EXAMPLE 3:

The procedure was essentially same as Example 1, except there is antioxidant (0.025%) from group of methyl and phenyl based such as but not limited to Hexamethylene bis, N-Phenyl Benzenamine, Phenyl- [alpha] -napthalamine and/or phenyl- [beta] -napthalamine and without corrosion inhibitor in first feed of S 1.

EXAMPLE 4:

The procedure was essentially same as Example 1, except there is antioxidant (0.4%) from group of methyl and phenyl based such as but not limited to Hexamethylene bis, N-Phenyl Benzenamine, Phenyl- [alpha] -napthalamine and/or phenyl- [beta] -napthalamine and sodium nitrite as corrosion inhibitor (0.05%) in first feed of SI.

EXAMPLE 5:

The procedure was essentially same as Examplel, except there is no antioxidant from group of methyl and phenyl based such as but not limited to Hexamethylene bis, N-Phenyl Benzenamine, Phenyl- [alpha] -napthalamine and/or phenyl- [beta] -napthalamine and no corrosion inhibitor in first feed of SI.

Thermic fluid composition preparation (S2) (stable up to 230 °C):

A 300 mL flask with magnetic stir bar was cleaned with acetone and dried in oven at 90 °C after thoroughly evacuated by purging with dry compressed air to eliminate contaminants. The flask was charged with hydro treated base oil-1, antioxidant and corrosion inhibitor (99.55:0.225:0.225) by weight and the mixture is labeled as a first feed of S2. Take the Hydro treated base oil-2 feed to the reaction flask with the weight ratio of (first feed of S2: Hydro treated base oil-2) (90:10) by weight and sonicate the solution for half an hour. Keep the reaction flask with above formulation on hot plate and using magnetic stir, continue mechanical stirring at 500 rpm and temperature maintained at 45 to 50 °C for about half an hour. Ultrasonicate the formed solution at 20 KHz for 15 minutes using Probe ultrasonicator for uniform mixing of the two compounds. Analysis of prepared thermic fluid by Rapid small scale oxidation test shows significant improvement in oxidation stability as comparable to commercial synthetic thermic fluids. Further, various examples of the said thermic fluid composition (S2) are provided herein below i.e., example 1-5.

EXAMPLE 1:

The procedure was essentially same as above, except there is antioxidant (0.25%) from group of methyl and phenyl based such as but not limited to Hexamethylene bis, N-Phenyl Benzenamine, Phenyl-[alpha]-and/or phenyl- [beta] -napthalamine and Corrosion inhibitor (0.2%) in first feed of S2.

EXAMPLE 2:

The procedure was essentially same as Examplel, except there is antioxidant (0.45%) from group of methyl and phenyl based such as but not limited to Hexamethylene bis, N-Phenyl Benzenamine, Phenyl- [alpha] -and/or phenyl- [beta] -napthalamine and without corrosion inhibitor in first feed of S2.

EXAMPLE 3:

The procedure was essentially same as Examplel, except there is antioxidant (0.025%) from group of methyl and phenyl based such as but not limited to Hexamethylene bis, N-Phenyl Benzenamine, Phenyl- [alpha] -and/or phenyl- [beta] -napthalamine and without Corrosion inhibitor in first feed of S2.

EXAMPLE 4:

The procedure was essentially same as Examplel, except there is antioxidant (0.4%) from group of methyl and phenyl based such as but not limited to Hexamethylene bis, N-Phenyl Benzenamine, Phenyl-[alpha]-and/or phenyl- [beta] -napthalamine and corrosion inhibitor (0.05%) sodium nitrite in first feed of S2.

EXAMPLE 5:

The procedure was essentially same as Examplel, except there is no antioxidant from group of methyl and phenyl based such as but not limited to Hexamethylene bis, N-Phenyl Benzenamine, Phenyl- [alpha] -and/or phenyl- [beta] -napthalamine and no corrosion inhibitor in first feed of S2. Thermophysical Properties (Significance and Measurement):

Heat transfer coefficient (OHTC)

The heat transfer coefficient is the proportionality constant between the heat flux and the thermodynamic driving force for the flow of heat. Heat transfer performance is generally quantified by heat transfer coefficient, heat-transfer coefficient is a function of the Reynolds number, the Prandtl number, and the tube diameter. These can be further broken down into the following fundamental parameters: physical properties (namely viscosity, thermal conductivity, and specific heat), tube diameter and mass velocity. Unlike other parameters ‘h (overall heat transfer coefficient, W/(m².K)) is a cumulative function of other physical properties hence this can be used to quantify the overall performance of thermic fluid or heat transfer fluid (HTF). The parameter ‘h’ refers to overall heat transfer coefficient for heat exchange. A high value of ‘h’ indicates that HTF has properties which boosts the heat transfer performance and vice-versa. Here overall heat transfer coefficient ‘U’ is estimated in-place of ‘h’ by using high temperature solar loop as shown in Figure- 1.

Overall heat transfer coefficient is used to express the overall heat transfer rate from hot fluid at average bulk temperature Thot to cold fluid at average bulk temperature Tcoia given by below expression.

Heat transfer rate from Hot fluid to cold fluid given by:

Q= (Uo*Ao*LMTD = (Thot-T cold))/ (Resistance term includes conduction and convection)

Thermal stability studies:

Since most of the organic thermic fluid or heat transfer fluid (HTF) undergo boiling before thermal decomposition it becomes inappropriate to measure decomposition temperature by using Thermo Gravimetric analysis (TGA). Hence decomposition studies were carried out in autoclave in batch mode. The fluid is initially taken in the autoclave and is then subjected to leak test at 30 bar for 45 minutes. Once no leak was observed the chamber is pressurized with nitrogen to about 5 bar and is then heated, once the set temperature is reached the chamber is maintained in isothermal condition at 230 to 270 °C for 72 hours. The heater is then switched off and is allowed to reach equilibrium with ambient. Once the temperature reaches desired value the autoclave is vented to remove the gases, the sample is then collected from the autoclave and is weighed. Further studies on physical properties carried out on the HTF.

Below Table 2 describes physical property analysis before and after thermal stability studies with antioxidant.

Table 2

AO1 * - Antioxidant (0-0.2 W/W %)from variety of group listed hereinabove in example 1-5.

AO2* - Antioxidant (0-0.2 W/W %) from variety of group listed hereinabove in example 1-5.

Cyclic stability studies:

Cycling stability studies were carried out on the sample SI and S2 formulations in a designed natural circulation loop as shown in Figure 1. Developed SI and S2 formulations circulated in closed loop with temperature range 100 - 230 - 270 °C with 1 to 3 °C/min. Schematic of the natural circulation loop shown in Figure 1. Property variation of the formulation over 100 cycles as shown in below Table 3(a) - Table 3(b). Table 3(a) Property Variation over 100 cycles on Natural Circulation Loop

Table 3(b) Property Variation over 100 cycles on Natural Circulation Loop

Property Set:

The below Table 4 demonstrate various properties of the present disclosed thermic fluid compositions (as named as SI and S2)

Table 4

The composed of saturated polyalphaolefin, antioxidant shows excellent heat resistance. Since the thermic fluid composition of the present invention exhibits good stability characteristics from 25 °C to high temperatures (up to 230 °C for S2 and up to 270 °C for SI) and medium vapor pressure. Hence, the thermic fluid composition can be used in process heat applications with maximum film temperatures of 270 °C and 230 °C respectively.

Accordingly, the thermic fluid compositions of the present invention can be used for heat transfer applications with maximum film temperature of 270 and 230 °C. Thermal stability of heat medium composition evaluated under nitrogen pressure at 2 to 5 bar with bulk fluid temperature maintained at 270 ^and 230 °C for about 72 hours. Thus, the thermic fluid composition can be used in solar thermal applications and process heat applications.

As per laboratory study, the developed thermic fluid composition meets the purity test requirement as per 21 CFR 172.878 for the following tests.

Further, the Table 5 provides purity details of the major components of the thermic fluid composition (SI and S2). The Table 6 provides purity tests performed on thermic fluid composition (SI) and on Trimethylpentane solution. Table 5: Purity details of the major components of the thermic fluid composition (SI and S2)

Table 6: Purity tests performed thermic fluid composition (SI) and Trimethylpentane

Wherein, the chloride solution is a mixture of 3ml ferric chloride, 1.5 ml cobaltous chloride and 0.5 ml cupric sulfate and 5 ml oil under test. The Trimethylpentane solution is a mixture of Trimethylpentance with concentration of 7 mg of naphthalene in 1 liter. The developed thermic fluid composition meets the test requirements of readily carbonizable substances as per United States Pharmacopeia XX (1980). The developed thermic fluid composition meets the Specifications prescribed in the “Journal of the Association of Official Analytical Chemists," Volume 45, page 66 (1962), which is incorporated by reference, after correction of the ultraviolet absorbance for any absorbance due to added antioxidants.

Further, the Table 7 provides various properties, their unit and methods.

Table 7

The thermic fluid composition provides many advantages such as low cost due to presence of low/ zero synthetic content and with less carbon forms, high thermal and oxidation stability. Laboratory tests confirms that the disclosed formulations show good thermal and oxidation stability, low coke forming tendency, good heat transfer characteristics.

Claims

We Claim:

1. A thermic fluid composition, wherein, the said composition comprises 55 to 95 wt.% of a base oil, 0.01 to 0.2 wt.% of an antioxidant, and 0.01 to 0.2 wt.% of a corrosion inhibitor.

2. The thermic fluid composition as claimed in claim 1, wherein, the base oil is 65 to 95 wt.% and the base oil is selected from a hydro treated base oil-0 having viscosity 72-75 mm²/s at 40 °C, a hydro treated base oil-1 having viscosity 10-12 mm²/s at 40 °C and a hydro treated base oil-2 having viscosity 27-29 mm²/s at 40 °C.

3. The thermic fluid composition as claimed in claim 1 consist of 5 to 45 wt.% of a polyalphaolefin.

4. The thermic fluid composition as claimed in claim 3, wherein, the polyalphaolefin is 5 to 34 wt.% and the polyalphaolefin is formed by oligomerization of a-olefin, wherein, the a- olefin is selected from 1 -propene, 1 -butene, 1 -pentene, 1 -hexene, 1 -heptene, 1 -octene, 1- nonene, 1 -decene, 1 -undecane, 1 -dodecene, 1 -tridecene, 1 -tetradecene, 1 -hexadecene, 1- octadecene, 1- eicosane, or a combination thereof.

5. The thermic fluid composition as claimed in claim 1, wherein, the antioxidant is selected from Hexamethylene bis, N-Phenyl Benzenamine, phenyl- [alpha] -napthalamine, phenyl- [beta]-napthalamine, or a combination thereof.

6. The thermic fluid composition as claimed in claim 1, wherein, the corrosion inhibitor is sodium nitrite.

7. The thermic fluid composition as claimed in claim 1, wherein, the said composition has a thermal stability from 25 to 270 °C and have medium vapor pressure.

8. The thermic fluid composition as claimed in claim 1, wherein, the said composition is used in solar thermal applications, or in process heat applications. A process for preparing a thermic fluid composition, wherein, the process comprises steps of: preparing a reaction solution by mixing at least 55 to 95 wt.% of a base oil, 5 to 45 wt.% of a polyalphaolefin, 0.01 to 0.2 wt.% of an antioxidant, and 0.01 to 0.2 wt.% of a corrosion inhibitor; sonicating the reaction solution for 20 to 40 minutes; stirring at 500 rpm at 45 to 50 °C for 20 to 40 minutes; and ultrasonicating the reaction solution at 20 KHz for 15 minutes using a probe ultrasonicator. The process as claimed in claim 9, wherein, the base oil is selected from a hydro treated base oil-0 having viscosity72-75 mm²/s at 40 °C, a hydro treated base oil-1 having viscosity 10-12 mm²/s at 40 °C and a hydro treated base oil-2 having viscosity 27-29 mm²/s at 40 °C. The process as claimed in claim 9 to claim 10, wherein, the process comprises steps of: preparing the reaction solution by preparing a first mixture by mixing at least one of 90 to 99.55 wt.% of the hydro treated base oil-0, 0.02 to 0.45 wt.% of the antioxidant, or 0.05 to 0.2 wt.% of the corrosion inhibitor, mixing 90 wt.% of the first mixture and 10 wt.% of the polyalphaolefin to obtain the reaction solution; sonicating the reaction solution for 20 to 40 minutes; stirring at 500 rpm at 45 °C to 50 °C for 20 to 40 minutes; and ultrasonicating the reaction solution at 20 KHz for 15 minutes using a probe ultrasonicator. The process as claimed in claim 9 to claim 10, wherein, the process comprises steps of: preparing the reaction solution by preparing a first mixture by mixing at least one of 90 to 99.55 wt.% of the hydro treated base oil-1, 0.02 to 0.45 wt.% of the antioxidant, or 0.05 to 0.2 wt.% of the corrosion inhibitor, mixing 90 wt.% of the first mixture and 10 wt.% of the hydro treated base oil-2 to obtain the reaction solution; sonicating the reaction solution for 20 to 40 minutes; stirring at 500 rpm at 45 °C to 50 °C for 20 to 40 minutes; and ultrasonicating the reaction solution at 20 KHz for 15 minutes using a probe ultrasonicator. The process as claimed in claim 9 to claim 12, wherein, the polyalphaolefin is formed by oligomerization of a-olefin, wherein, the a-olefin is selected from 1 -propene, 1 -butene, 1- pentene, 1 -hexene, 1 -heptene, 1 -octene, 1 -nonene, 1 -decene, 1 -undecane, 1 -dodecene, 1- tri decene, 1 -tetradecene, 1 -hexadecene, 1 -octadecene, 1- eicosane or a combination thereof. The process as claimed in claim 9 to claim 12, wherein, the antioxidant is selected from Hexamethylene bis, N-Phenyl Benzenamine, phenyl- [alpha] -napthalamine, phenyl- [beta]-napthalamine, or a combination thereof. The process as claimed in claim 9 to claim 12, wherein, the corrosion inhibitor is sodium nitrite.