A process of preparation of high purity fluoroethylene carbonate (FEC)

Abstract

The present invention relates to an improved process for the preparation of colorless and high purity fluoroethylene carbonate (FEC), which is cost-effective and industrially scalable. More particularly, the process comprising the steps of: admixing the potassium fluoride in a polar aprotic solvent, adding catalyst, a polymerization inhibitor; chloroethylene carbonate (CEC) to obtain the crude fluoroethylene carbonate (FEC); purifying crude FEC in the presence of a stabilizing agent, by flash distillation, followed by fractional distillation to obtain pure fluoroethylene carbonate (FEC) with purity of greater than 99.00 % and APHA color value less than 25. Further purified by melt crystallization to obtain highly pure fluoroethylene carbonate (FEC) with purity greater than 99.90 % and APHA color value of less than 15.

Description

[0001] A PROCESS OF PREPARATION OF HIGH PURITY FLUOROETHYLENE CARBONATE (FEC)

[0002] FIELD OF THE INVENTION:

[0003]

[0001] The present invention relates to a process for preparation of fluoroethylene carbonate (FEC). More particularly, the present invention relates to a process for preparation of colorless fluoroethylene carbonate (FEC) having high yield and high purity, which is cost-effective and industrially scalable.

[0004] BACKGROUND OF THE INVENTION:

[0005]

[0002] Fluoroethylene carbonate (FEC) is having a chemical structure of Formula-I as given below:

[0006] Formula-I

[0007]

[0003] Fluoroethylene carbonate (FEC) is chemically known as 4-fluoro- 1 ,3-dioxolan- 2-one. It is one of the major electrolyte additives that can be used in the fabrication of lithium-ion batteries. It not only enables the formation of thin, smooth and stable passive solid electrolyte interphase (SEI) layer, which helps in increasing the cycling efficiency and discharge capacity retention of the secondary battery but also helps to enhance battery performance especially under demanding circumstances like high voltages and low temperatures. It not only suppresses the decomposition of the electrolyte but also lowers the impedance of the battery.

[0008]

[0004] Fluoroethylene carbonate or 4-Fluoro-l,3-dioxolan-2-one herein after may be referred as fluoroethylene carbonate (FEC). Various processes for the preparation of fluoroethylene carbonate (FEC) and its purification are known in the prior-art.

[0005] Kobayashi Masafumi et al in Japanese patent number 4531153 (herein after JP ‘153) discloses the process for the preparation of fluoroethylene carbonate by reaction of ethylene carbonate with fluorine gas. The major drawback of this process is direct fluorination reactions are very highly exothermic and unless suitable means and equipment of capabilities were not utilized, it shall pose serious threats of risk and hazard. Therefore, the process for preparation of fluoroethylene carbonate as disclosed in JP ‘ 153 appears to be not viable for industrial scale.

[0009]

[0006] Boese et al in US patent number 7745648 (hereinafter US ‘648) discloses process for preparation of 4-fluoro-l,3-dioxolan-2-one comprising reacting ethylene carbonate with elemental fluorine, said process comprising: mixing ethylene carbonate in a reaction vessel with 3 to 20% by weight 4-fluoro-l,3-dioxolan-2-one relative to the ethylene carbonate as a solvent for the ethylene carbonate, whereby a solution of ethylene carbonate in 4-fluoro-l,3-dioxolan-2-one is formed, and thereafter introducing fluorine gas or a mixture containing fluorine in an inert gas into the resulting solution at a temperature of 15 °C to 45 °C to obtain fluoroethylene carbonate having 63.9% yield. One or more drawbacks of this process are the fluoroethylene carbonate product obtained is in very low yield, silent about purity of fluoroethylene carbonate and requires multiple distillation. Therefore, the process for preparation of fluoroethylene carbonate as disclosed in US ‘648, is not a viable and not cost-effective process for large scale industrial production.

[0010]

[0007] Lambert et al. in US patent publication 20120157695 (herein after US ‘695) discloses process for purification of fluoroethylene carbonate comprising distilling a reaction mixture comprising fluoroethylene carbonate, ethylene carbonate, higher fluorinated carbonates and HF in at least two distillations. However, said process provides the total yield of isolated fine product was about 36% by weight after the two distillation steps, which is very low. Therefore, the process for preparation of fluoroethylene carbonate as disclosed in US ‘695, is not a viable and not cost-effective process for large scale industrial production.

[0011]

[0008] Xiaolong et al in Chinese patent number 101597275 (herein after CN ‘275) discloses process for preparation of fluoroethylene carbonate comprising reacting ethylene carbonate with fluorine gas to obtain crude fluoroethylene carbonate having 52.30% yield. Further, resulting crude fluoroethylene carbonate was recrystallized using mixture of toluene and n-hexane at -10 °C followed by distillation under vacuum to obtain pure Fluoroethylene carbonate. The drawback of this process is direct fluorination reactions are very highly exothermic, and product obtained after purification in very low yield i.e. 52.30 %. Therefore, the process for preparation of fluoroethylene carbonate as disclosed CN ‘275 is not suitable for large scale industrial production.

[0012]

[0009] To overcome the above prior art problems, Xianlin et al in Chinese patent number CN 100558721 (herein after CN ‘721) discloses process for preparation of fluoroethylene carbonate comprising reacting 4-chloro-l,3-dioxolane-2-one with potassium fluoride in presence of dimethyl carbonate, tetrabutylammonium bromide and heating at 90 °C followed by purification using vacuum distillation to obtain Fluoroethylene carbonate. The drawbacks of this process are it requires high reaction temperature and final product obtained which is yellow in color. Therefore, the process for preparation of fluoroethylene carbonate as disclosed CN ‘721 is not suitable for large scale industrial production.

[0013]

[0010] Liu Hongguang et al in Chinese patent number 102875521 (herein after CN ‘521) discloses process for preparation of fluoroethylene carbonate comprising reacting chloroethylene carbonate with solid potassium fluoride in presence of diethyl carbonate and p-tert-butylcalix[6]arene as a catalyst followed by heating at 110 °C for 10 hours to obtain Fluoroethylene carbonate. The drawbacks of this process are it requires high reaction temperature, longer reaction time and silent about purity of the final product. Therefore, the process for preparation of fluoroethylene carbonate as disclosed CN ‘521 is not suitable for large scale industrial production.

[0014] [Oi l] Zhou Lishan et al in Chinese patent number 103467436 (herein after CN ‘436) discloses process for preparation of Fluoroethylene carbonate comprising reacting chloroethylene carbonate with solid potassium fluoride in presence of diethyl carbonate and tetraphenylphosphonium difluoride as a catalyst followed by heating at 110 °C for 10 hours to obtain fluoroethylene carbonate. The drawbacks of this process are it requires high reaction temperature, longer reaction time and silent about purity of the final product. Therefore, the process for preparation of fluoroethylene carbonate as disclosed CN ‘436 is not suitable for large scale industrial production.

[0015]

[0012] An Feng et al in “Guangzhou Huagong (2014), 42(2), 71-72 ” discloses process for preparation of fluoroethylene carbonate comprising reacting chloroethylene carbonate with anhydrous potassium fluoride in presence of diethyl carbonate and 18 -crown ether-6 as a catalyst to obtain fluoroethylene carbonate. The drawback of this process is less quality material obtained which is in yellow / brown color. Therefore, the process for preparation of fluoroethylene carbonate as disclosed above journal article is not suitable for large scale industrial production.

[0016]

[0013] While various processes for the synthesis and purification are known in the art, they suffer from one or more drawbacks such as low yield, presence of contaminants, coloration of the product etc.

[0017]

[0014] Therefore, still there exist a need in the prior art to develop improved, economically viable and safe process for preparation of fluoroethylene carbonate in higher yield, having higher purity, colorless product and free from contaminants, which may overcome drawbacks of the prior-art. OBJECT OF THE INVENTION:

[0018]

[0015] The main objective of the present invention is to provide a process of preparation of colorless fluoroethylene carbonate (FEC), which is simple, economical and commercially scalable.

[0019]

[0016] Another objective of the present invention is to provide fluoroethylene carbonate (FEC) in higher yield and having high purity of greater than 99.90 %.

[0020]

[0017] One more objective of the present invention is to provide a colorless fluoroethylene carbonate (FEC) having improved quality with an APHA value less than 15.

[0021] SUMMARY OF THE INVENTION:

[0022]

[0018] The present invention relates to an improved process for the preparation of colorless fluoroethylene carbonate (FEC), which is simple, environmental, economic and commercially viable.

[0023]

[0019] The first aspect of the present invention relates to a process for the preparation of pure fluoroethylene carbonate (FEC), comprising the steps of: a) admixing the potassium fluoride in a polar aprotic solvent; b) adding catalyst and a polymerization inhibitor to step (a); c) adding chloroethylene carbonate (CEC) to the above step (b) reaction mixture; d) maintain the step c) reaction mixture at temperature ranging between 20 °C to 80 °C to obtain the crude fluoroethylene carbonate (FEC); e) treating the step (d) fluoroethylene carbonate (FEC) with a stabilizing agent ranging between 0.01 to 0.5% w / w with respect to crude FEC; f) purifying the reaction mixture of step (e) by flash distillation followed by fractional distillation to obtain pure fluoroethylene carbonate (FEC) with purity of greater than 99.00 %; and g) optionally, step (f) is further purified by melt crystallization to obtain highly pure fluoroethylene carbonate (FEC) with purity of greater than 99.90 % and APHA color value less than 15.

[0024]

[0020] The second aspect of the present invention relates to a process for purification of fluoroethylene carbonate (FEC), comprising the steps of: a) treating the crude fluoroethylene carbonate (FEC) with a stabilizing agent ranging between 0.01 to 0.5 % w / w with respect to crude FEC; b) purifying the step (a) by flash distillation and followed by fractional distillation to obtain pure fluoroethylene carbonate (FEC) with purity greater than 99.00 %; and c) optionally, step (b) is further purified by melt crystallization to obtain highly pure fluoroethylene carbonate (FEC) with purity of greater than 99.90% and APHA color value of less than 15.

[0025] DETAILED DESCRIPTION OF INVENTION:

[0026]

[0021] In order to provide a clear and consistent understanding of the terms used in the present specification, a number of definitions are provided below. Moreover, unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this disclosure belongs. Methods and materials are described herein for use in the present disclosure; other, suitable methods and materials known in the art can also be used. The materials, methods, and examples are illustrative only and not intended to be limiting. All publications, patent applications, patents, sequences, database entries, and other references mentioned herein are incorporated by reference in their entirety. In case of conflict, the present specification, including definitions, will control.

[0022] The use of the word “a” or “an” when used in conjunction with the term “comprising” in the claims and / or the specification may not only mean “one”, but also encompasses the meaning of “one or more”, “at least one”, and “one or more than one”. Similarly, the word “another” may mean at least a second or more.

[0027]

[0023] As used in this specification the words “comprising” (and any form of comprising, such as “comprise” and “comprises”), “consisting” (and any form of consisting, such as “consists”), “having” (and any form of having, such as “have” and “has”), “including” (and any form of including, such as “include” and “includes”) or “containing” (and any form of containing, such as “contain” and “contains”), are inclusive or open-ended and do not exclude additional, unrecited elements or process steps.

[0028]

[0024] The expression of various quantities in terms of “%” or “% w / w” means the percentage by weight of the total solution or composition unless otherwise specified.

[0029]

[0025] The invention will now be described in detail in connection with certain preferred embodiments, so that various aspects thereof may be fully understood and appreciated.

[0030]

[0026] While the following specification concludes with claims particularly pointing out and distinctly claiming the invention, it is anticipated that the invention can be more readily understood through reading the following detailed description and by studying the included examples.

[0031]

[0027] The best methods and materials of performing the present invention are described here.

[0032]

[0028] According to first embodiment, the present invention provides a process for the preparation of pure fluoroethylene carbonate (FEC), comprising the steps of: a) admixing the potassium fluoride in a polar aprotic solvent; b) adding catalyst and a polymerization inhibitor to step (a); c) adding chloroethylene carbonate (CEC) to the above step (b) reaction mixture; d) maintain the step c) reaction mixture at temperature ranging between 20 °C to 80 °C to obtain the crude fluoroethylene carbonate (FEC); e) treating the step (d) fluoroethylene carbonate (FEC) with a stabilizing agent ranging between 0.01 to 0.5% w / w with respect to crude FEC; f) purifying the reaction mixture of step (e) by flash distillation followed by fractional distillation to obtain pure fluoroethylene carbonate (FEC) with purity greater than 99.00 %; and g) optionally, step (f) is further purified by melt crystallization to obtain highly pure fluoroethylene carbonate (FEC) with purity greater than 99.90 % and APHA color value less than 15.

[0033]

[0029] In the first embodiment of step a), the polar aprotic solvent in step a) is selected from dimethyl carbonate, methyl ethyl carbonate, diethyl carbonate, ethylene carbonate, methyl isobutyl ketone (MIBK), acetonitrile, dimethylformamide, A,A-dimethyl acetamide tetramethylurea, dimethylpropyleneurea (DMPU), dimethyl sulfoxide (DMSO), sulfolane, tetraethylene glycol dimethyl ether, polyethylene glycol dimethyl ether or mixture(s) thereof.

[0034]

[0030] In the first embodiment of step a), after admixing the potassium fluoride in a polar aprotic solvent, the reaction mixture can be heated to 90 °C to 110 °C to distill out water azeotropically along with solvent. The reaction mixture can be heated till the moisture content less than 0.05% in the reaction mixture.

[0035]

[0031] In the first embodiment of step b), the term ‘catalyst’ refers to a substance that expedites chemical reactions by lowering the activation energy required for the transformation of reactants into products, without being consumed itself in the process.

[0032] In the first embodiment of step b), the catalyst can be selected from 18-crown- 6-ether, PEG400, tetrabutylammonium bromide, tetrabutylammonium chloride or tetraphenylphosphonium bromide. Preferably, the catalyst used is 18-crown-6-ether.

[0036]

[0033] In the first embodiment of step b), the term ‘polymerization inhibitor’ refers to a chemical compound that can be added to a reaction mixture to prevent the unwarranted self-polymerization of reactive monomers. It is added to ensure that the chemical transformations proceed smoothly yielding desired products.

[0037]

[0034] In the first embodiment of step b), the polymerization inhibitor can be selected from butylated hydroxytoluene (BHT), succinonitrile, 4-methoxyphenol, hydroquinone, 2,2,6,6-tetramethylpiperidin-l-yl)oxyl (TEMPO), phenothiazine, 4-tert butyl catechol and 2,5-di-tert butylhydroquinone. Preferably, the polymerization inhibitor used is butylated hydroxytoluene (BHT).

[0038]

[0035] In the first embodiment of step b), the catalyst and polymerization inhibitor can be added to step (a), after cooling the reaction mixture below 60 °C.

[0039]

[0036] In the first embodiment of step b), the catalyst and polymerization inhibitor can be added in any order, either concurrently, separately, or in combination thereof.

[0040]

[0037] In the first embodiment of step b), the catalyst can be added to step a) 0.10 to 0.20 % w / w with respect to chloroethylene carbonate.

[0041]

[0038] In the first embodiment of step b), the polymerization inhibitor can be added to step a) 0.10 to 0.20% w / w with respect to chloroethylene carbonate.

[0042]

[0039] In the first embodiment of step c), the chloroethylene carbonate (CEC) can be prepared by process known in the prior-art or it can be available in commercial scale.

[0040] In the first embodiment of step c), the chloroethylene carbonate (CEC) and potassium fluoride can be added in the molar ratio of 1: 1 to 1: 1.5; Preferably the molar ratio of 1: 1 to 1: 1.3.

[0043]

[0041] In the first embodiment of step c), the chloroethylene carbonate (CEC) can be added gradually to a step b) reaction mixture at temperature of 30 °C to 60 °C over a period of 20 minutes to 2 hours.

[0044]

[0042] In the first embodiment of step d), the reaction mixture can be maintained at temperature of 20 °C to 80 °C; preferably at temperature of 30 °C to 40 °C.

[0045]

[0043] In the first embodiment of step d), the reaction mixture can be maintained for 30 minutes to 8 hours; preferably 1 hour to 5 hours.

[0046]

[0044] In the first embodiment, preferably the step a) to step d) can be carried out under nitrogen atmosphere.

[0047]

[0045] After completion of reaction, resulting reaction mixture can be cooled at room temperature and insoluble solid (KF / KC1 salt) can be filtered out under vacuum and resulting wet cake can be washed with solvent as mentioned above step (a). Further, all the filtrates can be combined and distilled under vacuum at less than 40 °C to recover solvent and to obtain crude fluoroethylene carbonate (FEC).

[0048]

[0046] In the first embodiment of step d), the crude fluoroethylene carbonate (FEC) may have yield greater than 90.00 %.

[0049]

[0047] In the first embodiment of step d), the crude fluoroethylene carbonate (FEC) may have purity greater than 92.00 % by Gas Chromatography (GC).

[0050]

[0048] In the first embodiment of step d), the crude fluoroethylene carbonate (FEC) may have APHA color value greater than 500.

[0049] The APHA color value, also called as Hazen or Platinum Cobalt (Pt-Co) scale is a standard for colour measurement of liquids and is used to measure chromaticity. It is a measure of the gradients of yellow hues in liquids in comparison to a platinum cobalt reference solution and has a range of 0 to 500 wherein a value of 0 corresponds to achromatic color (of distilled water) and a value of 500 corresponds to a yellow color.

[0051]

[0050] In the first embodiment of step e), the treating can be admixing or adding the stabilizing agent to the crude FEC of step d) while stirring.

[0052]

[0051] In the first embodiment of step e), the stabilizing agent can be selected from butylated hydroxytoluene (BHT), succinonitrile and calcium hydroxide.

[0053]

[0052] In the first embodiment of step e), the stabilizing agent can be used in ranging between 0.01 to 0.5 % w / w with respect to crude FEC.

[0054]

[0053] In the first embodiment of step e), the stabilizing agent can be used as stabilizing the product and improving the quality of the product like preventing degradation and color impairment.

[0055]

[0054] In the first embodiment of step f), after addition of stabilizing agent to the crude fluoroethylene carbonate (FEC), the resulting reaction mixture can be distilled by flash distillation under vacuum followed by fractional distillation under vacuum to obtain pure fluoroethylene carbonate (FEC).

[0056]

[0055] In the first embodiment of step f), by employing flash distillation, followed by fractional distillation in the process of the present invention has proved to be effective in obtaining pure FEC with high yield and purity. The flash distillation process efficiently separates components based on boiling points, ensuring heightened purity by eliminating impurities and lower boiling point substances. The subsequent fractional distillation further concentrates the product, increasing overall yield and purity. This iterative approach ensures the final product meets strict specifications, such as high GC purity (more than 99.90%) and specified APHA color value (less than 15) range, while minimizing contamination.

[0057]

[0056] In the first embodiment of step f), the obtained pure fluoroethylene carbonate (FEC) may have overall yield greater than 80.00 %; preferably greater than 85 %.

[0058]

[0057] In the first embodiment of step f), the obtained pure fluoroethylene carbonate (FEC) may have purity greater than 99.00 % by Gas Chromatography (GC).

[0059]

[0058] In the first embodiment of step f), the obtained pure fluoroethylene carbonate (FEC) has colorless in appearance having APHA color value less than 50; preferably less than 25.

[0060]

[0059] In the first embodiment of step g), the melt crystallization can be carried out any known method by person skilled in the art.

[0061]

[0060] The above general process for melt crystallization can be varied by one skilled in the art to achieve maximum equipment productivity, product purity or yield by carefully adjusting the crystallization and sweating temperatures, and by adjusting the rate of cooling during crystallization and the rate of heating during sweating. Alternatively, the sequence of melting, partially crystallizing to form a liquid and a solid phase, optionally sweating the solid phase, and separating the solid and liquid phases can be repeated until the desired degree of purity is attained. The liquid phase resulting from the initial crystallization step may be subjected to various processes for recovery of valuable materials or to enable partial recycle to the crystallization process to increase yield.

[0062]

[0061] In the first embodiment of step g), the obtained pure fluoroethylene carbonate (FEC) may have overall yield greater than 75.00 %; preferably greater than 80.00 %.

[0062] In the first embodiment of step g), the obtained pure fluoroethylene carbonate (FEC) may have purity greater than 99.90 % by Gas Chromatography (GC).

[0063]

[0063] In the first embodiment of step g), the obtained pure fluoroethylene carbonate (FEC) has colorless in appearance having APHA color value less than 50; preferably less than 25; more preferably less than 15.

[0064]

[0064] In the first embodiment of step g), the obtained pure fluoroethylene carbonate (FEC) has free fluoride (less than 30 ppm), chloride (less than 5 ppm) and sulphate (less than 10 ppm).

[0065]

[0065] According to second embodiment, the present invention provides a process for purification of the fluoroethylene carbonate (FEC) further comprising the steps of: a) treating the crude fluoroethylene carbonate (FEC) with a stabilizing agent ranging between 0.01 to 0.5 % w / w with respect to crude FEC; b) purifying the step (a) by flash distillation and followed by fractional distillation to obtain pure fluoroethylene carbonate (FEC) with purity of greater than 99.00 %; and c) optionally, step (b) is further purified by melt crystallization to obtain highly pure fluoroethylene carbonate (FEC) with purity greater than 99.90% and APHA color value of less than 15.

[0066]

[0066] In the second embodiment of step a), the treating can be admixing or adding the stabilizing agent to the crude FEC while stirring.

[0067]

[0067] In the second embodiment of step a), the stabilizing agent can be selected from butylated hydroxytoluene (BHT), succinonitrile and calcium hydroxide.

[0068]

[0068] In the second embodiment of step a), the stabilizing agent ranging between 0.01 to 0.5 % w / w with respect to crude FEC.

[0069] In the second embodiment of step a), the stabilizing agent can be used for stabilizing the product and improving the quality of the product by preventing degradation and color impairment.

[0069]

[0070] In the second embodiment of step a), the stabilizing agent can be preventing degradation of crude fluoroethylene carbonate (FEC).

[0070]

[0071] In the second embodiment of step b), after addition of stabilizing agent to the crude fluoroethylene carbonate (FEC), the resulting reaction mixture can be distilled by flash distillation under vacuum followed by fractional distillation under vacuum to obtain pure fluoroethylene carbonate (FEC).

[0071]

[0072] In the second embodiment of step b), by employing flash distillation, followed by fractional distillation in the process of the present invention has proved to be effective in obtaining pure FEC with high yield and purity. The flash distillation process efficiently separates components based on boiling points, ensuring heightened purity by eliminating impurities and lower boiling point substances. The subsequent fractional distillation further concentrates the product, increasing overall yield and purity. This iterative approach ensures the final product meets strict specifications, such as high GC purity and specified APHA color value range, while minimizing contamination.

[0072]

[0073] In the second embodiment of step c), the melt crystallization can be carried out any known method by person skilled in the art.

[0073]

[0074] In the second embodiment of step c), the obtained pure fluoroethylene carbonate (FEC) may have overall yield greater than 75.00%; preferably greater than 80.00%.

[0074]

[0075] In the second embodiment of step c), the obtained pure fluoroethylene carbonate (FEC) may have purity greater than 99.90% by Gas Chromatography (GC).

[0076] In the second embodiment of step c), the obtained pure fluoroethylene carbonate (FEC) has colorless in appearance having APHA color value less than 50; preferably less than 25; more preferably less than 15.

[0075]

[0077] In the second embodiment of step c), the obtained pure fluoroethylene carbonate (FEC) has free fluoride (less than 30 ppm), chloride (less than 5 ppm) and sulphate (less than 10 ppm).

[0076]

[0078] Addition of both a polymerization inhibitor and stabilizing agent are required to obtain a consistently colorless product and higher yield. However, without the addition of the polymerization inhibitor and stabilizing agent; the process provided colored Fluoroethylene carbonate (FEC), even after flash and / or fractional distillation, with an APHA color value greater than of 500.

[0077]

[0079] In accordance to the present invention, when polymerization inhibitor was added during the reaction and stabilizing agent during the purification, the product obtained had an APHA color value of less than 50; preferably less than 25; more preferably less than 15. Further any individual metal (Na, K, Cu, Fe, Pb, Ca, Zn, Ni, Cr, Mg and Ba etc.) content will be less than 1 ppm; preferably less than 0.5 ppm.

[0078]

[0080] The present invention is more particularly described in the following examples that are intended as illustration only, since numerous modifications and variations within the scope of the present invention will be apparent to those skilled in the art. Unless otherwise noted, all reagents used in the examples were obtained or are available from the chemical suppliers.

[0079]

[0081] The following examples illustrate the basic methodology and versatility of the present invention. EXAMPLE(S):

[0080] Example-01:

[0081]

[0082] Anhydrous potassium fluoride (308.21 g) was added into anhydrous dimethyl carbonate (1250 g) under nitrogen atmosphere with stirring. The mixture was heated to distill out water azeotropically along with dimethyl carbonate till moisture content was reduced to less than 0.05%. The reaction mixture was then cooled to ~50 °C and 18-crown- 6-ether (0.75 g) and butylated hydroxy toluene (BHT) (0.75 g) were added. Chloroethylene carbonate (530 g) was slowly added at 45 °C to 60 °C to the above reaction mixture over a period of 40 minute to 60 minutes under nitrogen atmosphere. Then temperature of the reaction mixture was gradually increased to 70 °C to 75 °C and maintained at the same temperature for 3 hours under nitrogen atmosphere. After completion of the reaction, the reaction mixture was cooled to room temperature and insoluble solids (KF / KC1 salt) were filtered out under vacuum and wet cake was washed with dimethyl carbonate (in 1: 1 ratio with respect to chloroethylene carbonate). The combined filtrate was distilled under vacuum to recover dimethyl carbonate and to obtain crude fluoroethylene carbonate (90.40% yield) with 94.48% GC purity.

[0082]

[0083] Butylated hydroxytoluene (0.5 g) was added to the above crude product. The reaction mixture was purified by flash distillation under vacuum followed by fractional distillation under vacuum to obtain pure fluoroethylene carbonate.

[0083] Yield: 81.41%

[0084] Purity: 99.31% by Gas Chromatography

[0085] APHA color value (Appearance): 15 (colorless)

[0086] Acidity (as HF): 15 ppm; Chloride (Cl ): 3.20 ppm; Sulfate (SO4‘): 2.99 ppm; Na: 0.28 ppm; Fe: 0.13 ppm; Ca: 0.02 ppm; Zn: 0.02 ppm; Ni: 0.03 ppm; Cr: 0.05 ppm Individual metal (Cu, Pb, Mg, Ba): Not detected. Example-02:

[0087]

[0084] Anhydrous potassium fluoride (308.21 g) was added into anhydrous dimethyl carbonate (1250 g) under nitrogen atmosphere with stirring. The mixture was heated to distill out water azeotropically along with dimethyl carbonate till moisture content was reduced to less than 0.05%. The reaction mixture was then cooled to ~50 °C and 18-crown- 6-Ether (0.75 g) and butylated hydroxytoluene (0.75 g) were added. Chloroethylene carbonate (530 g) was then slowly added at 45 °C to 60 °C to the above reaction mixture over a period of 40 minute to 60 minutes under nitrogen atmosphere. Then temperature of the reaction mixture was gradually increased 70 °C to 75 °C and maintained at the same temperature for 3 hours under nitrogen atmosphere. After completion of the reaction, the reaction mixture was cooled to room temperature and insoluble solids (KF / KC1 salt) were filtered out under vacuum and wet cake was washed with dimethyl carbonate (in 1: 1 ratio with respect to chloroethylene carbonate). The combined filtrate was distilled under vacuum at less than 40 °C to recover dimethyl carbonate and to obtain crude fluoroethylene carbonate with 92.47% GC purity.

[0088]

[0085] Succinonitrile (0.75 g) was added to the above crude product. Further, the reaction mixture was purified by flash distillation under vacuum to obtain a light yellow to colorless product (APHA color value 50-150). It was then further purified by fractional distillation under vacuum to obtain colorless pure fluoroethylene carbonate (FEC).

[0089] Yield: 81.3%

[0090] Purity: 99.26% by Gas Chromatography

[0091] APHA color value (Appearance): 14 (colorless)

[0092] Acidity (as HF): 15 ppm

[0093] Chloride (Cl ): 3.0 ppm

[0094] Sulfate (SO4‘): 8 ppm

[0095] Na: 0.02 ppm; Ca: 0.08 ppm; Ba: 0.14 ppm; Individual metal (K, Cu, Fe, Pb, Zn, Ni, Cr, Mg): Not detected. Example-03:

[0096]

[0086] Anhydrous potassium fluoride (308.21 g) was added into anhydrous dimethyl carbonate (1250 g) under nitrogen atmosphere with stirring. The mixture was heated to distill out water azeotropically along with dimethyl carbonate till moisture content in the reaction mixture was reduced to less than 0.05 %. The reaction mixture was then cooled to ~50 °C and 18-crown-6-ether (0.75g) and butylated hydroxytoluene (0.75g) were added. Chloroethylene carbonate (530 g) was then slowly added at 45 °C to 60 °C to the above reaction mixture over a period of 40 minute to 60 minutes under nitrogen atmosphere. Then temperature of the reaction mixture was gradually increased to 70 °C to 75 °C and maintained at same temperature for 3 hours under nitrogen atmosphere. After completion of the reaction, the reaction mixture was cooled to room temperature and insoluble solids (KF / KC1 salt) were filtered out under vacuum and washed with dimethyl carbonate (in 1: 1 ratio with respect to chloroethylene carbonate). The combined filtrate was distilled under vacuum to recover dimethyl carbonate and to obtain crude fluoroethylene carbonate (92.60 % yield) with 92.69 % GC purity.

[0097]

[0087] Calcium hydroxide (2.5 g) was added to the above crude product, further the reaction mixture was purified by flash distillation under vacuum to obtain a light yellow to colourless product (APHA 50-150). It was then further purified by fractional distillation under vacuum at 90 °C to 115 °C to obtain colorless pure fluoroethylene carbonate (FEC).

[0098] Yield: 80.75%

[0099] Purity: 99.26% by Gas Chromatography

[0100] APHA color value (Appearance): 12 (colorless)

[0101] Acidity (as HF): 14 ppm

[0102] Chloride (Cl ): 2.0 ppm

[0103] Sulfate (SO4‘): 6 ppm

[0104] Na: 0.05 ppm; Ca: 0.09 ppm; Ba: 0.57 ppm; Individual metal (K, Cu, Fe, Pb, Zn, Ni,

[0105] Cr, Mg): Not detected Example-04:

[0106]

[0088] Anhydrous potassium fluoride (273 g) was added into anhydrous dimethyl carbonate (1250 g) under nitrogen atmosphere with stirring. The mixture was heated to distill out water azeotropically along with dimethyl carbonate (495 g) till moisture content in reaction mixture was reduced to less than 0.035%. The reaction mixture was cooled to 30°C to 35 °C. Further, 18-crown-6-ether (0.90 g) and butylated hydroxytoluene (BHT) (0.75 g) were added. Chloroethylene carbonate (530 g) was slowly added to the above reaction mixture over the period of 40 minutes to 90 minutes at 30 °C to 40 °C under nitrogen atmosphere and maintained at 35 °C to 40 °C for 5 hours under nitrogen atmosphere. After completion of the reaction, the reaction mixture was cooled at room temperature and insoluble solids (KF / KC1 salt) were filtered out under the vacuum and wet cake was washed with dimethyl carbonate (in 1:1 ratio with respect to Chloroethylene carbonate). The combined filtrate was distilled under vacuum to recover dimethyl carbonate and to obtain a crude fluoroethylene carbonate (94.46% yield) with 94.4% GC purity.

[0107]

[0089] Butylated hydroxytoluene (0.73 g) was added to the above crude product. Further, the reaction mixture was purified by flash distillation under vacuum followed by fractional distillation under vacuum to obtain pure fluoroethylene carbonate (FEC).

[0108] Yield: 90.0%

[0109] Purity: 99.34% by Gas Chromatography.

[0110] APHA color value (Appearance): 22 (colorless)

[0111] Chloride (CF) (Argentometric method): <2 ppm Sulfate (SOT) (Turbidimetry method): <10 ppm Na: 0.70 ppm; Ca: 0.09 ppm; K: 0.50 ppm; Cu: 0.01 ppm; Zn: 0.01 ppm; Cr: 0.01; ppm; Mg: 0.01 ppm; Individual metal (Fe, Pb, Ni, Ba): Not detected. Example-05:

[0112]

[0090] Anhydrous potassium fluoride (164 g) was added into anhydrous dimethyl carbonate (750 g) under nitrogen atmosphere with stirring. The mixture was heated to distill out water azeotropically along with dimethyl carbonate (265 g) till moisture content in reaction mixture was reduced to less than is 0.038%. The reaction mixture was cooled to 30 °C to 35 °C. Further, 18-crown-6-ether (0.54 g) and butylated hydroxytoluene (0.45 g) were added to the reaction mixture, chloroethylene carbonate (316 g) was slowly added to the above reaction mixture over the period of 40 minute to 90 minutes at 30 °C to 40 °C under nitrogen atmosphere and maintained at 35 °C to 40 °C for 5 hours under nitrogen atmosphere. After completion of the reaction, the reaction mixture was cooled to room temperature and insoluble solids (KF / KC1 salt) were filtered out under the vacuum and wet cake was washed with dimethyl carbonate (in 1 : 1 ratio with respect to CEC). The combined filtrate was distilled under vacuum to recover dimethyl carbonate and to obtain a crude fluoroethylene carbonate (92.53% yield) with 92.15 % GC purity.

[0113]

[0091] Succinonitrile (0.45g) was added to the above crude product. Further, the reaction mixture was purified by flash distillation under vacuum followed by fractional distillation under vacuum to obtain pure fluoroethylene carbonate (FEC).

[0114] Yield: 87.07%.

[0115] Purity: 99.17% by Gas Chromatography

[0116] APHA color value (Appearance): 18 (colorless)

[0117] Chloride (CF) (Argentometric method): <2ppm Sulfate (SO4-) (Turbidimetry method): <10ppm Na: 0.50 ppm; K: 0.01 ppm; Cu: 0.01 ppm; Zn: 0.01 ppm; Cr: 0.01 ppm; Mg: 0.01 ppm;

[0118] Individual metal (Ca, Ba, Fe, Pb, Ni): Not detected.

[0119] Example-06:

[0120]

[0092] Anhydrous potassium fluoride (185.21 g) was added into anhydrous acetonitrile (901 g) under nitrogen atmosphere with stirring. The mixture was heated to distill out water azeotropically along with acetonitrile till moisture content was reduced to less than 0.05%. The reaction mixture was then cooled to ~50 °C and 18-crown-6-ether (0.3 g) and butylated hydroxytoluene (0.3 g) were added, chloroethylene carbonate (322 g) was slowly added at 45 °C to 60 °C to the above reaction mixture over a period of 40 minute to 60 minutes under nitrogen atmosphere. Then temperature of the reaction mixture was gradually increased to 70 °C to 75 °C and maintained at same temperature for Ih under nitrogen atmosphere. After completion of the reaction, the reaction mixture was cooled to room temperature and insoluble solids (KF / KC1 salt) were filtered out under vacuum and wet cake was washed with acetonitrile (in 1:1 ratio with respect to chloroethylene carbonate). The combined filtrate was distilled under vacuum to recover acetonitrile and to obtain crude fluoroethylene carbonate (90.79% yield) with 92.97% GC purity.

[0121]

[0093] Butylated hydroxytoluene (0.5 g) was added to the above crude product. The reaction mixture was purified by flash distillation under vacuum followed by fractional distillation under vacuum to obtain pure fluoroethylene carbonate.

[0122] Yield: 80.49%

[0123] Purity: 99.14% by Gas Chromatography

[0124] APHA color value (Appearance): 23 (colorless)

[0125] Chloride (C1‘) (Argentometric method): <2 ppm

[0126] Sulfate (SO4-) (Turbidimetry method): <10 ppm

[0127] Na: 0.11 ppm; Ca: 0.15 ppm; Ba: 0.05 ppm; Cu: 0.01 ppm; Fe: 0.07 ppm; Pb: 0.01 ppm; Zn: 0.01 ppm; Ni: 0.03 ppm; Mg: 0.01 ppm; Individual metal (K, Ni, Cr): Not detected.

[0128] Example-07:

[0129]

[0094] Fluoroethylene carbonate obtained in example 1-6 (705 g) is taken into the melt crystallizer and gradually cooled to 10-15 °C. The impure liquid material is drained out in another tank. Raise the temperature of the melt crystallizer slowly to 30-40 °C. Purity of the melted material is monitored continuously and pure fractions are collected separately into the collection tank to obtain 670 g of fluoroethylene carbonate having GC purity of 99.95% with APHA color value of 8 (colorless).

[0130] Chloride (CP) (Argentometric method): <1 ppm

[0131] Sulfate (SO4-) (Turbidimetry method): <5 ppm

[0132] Na metal content: 0.4 ppm.

[0133] Individual metal (K, Cu, Fe, Pb, Ca, Zn, Ni, Cr, Mg, Ba) content: Not detected.

[0134]

[0095] Various modifications of the embodiments, in addition to those described herein, will be apparent to those skilled in the art from the foregoing description. Such modifications are also intended to fall within the scope of the appended claims. Each reference, including all patent, patent applications, and publications, cited in the present application is incorporated herein by reference in its entirety.

Claims

CLAIMS:

1. A process for the preparation of pure fluoroethylene carbonate (FEC), comprising the steps of: a) admixing the potassium fluoride in a polar aprotic solvent; b) adding catalyst and a polymerization inhibitor to step (a); c) adding chloroethylene carbonate (CEC) to the above step (b) reaction mixture; d) maintain the step c) reaction mixture at temperature ranging between 20 °C to 80 °C to obtain the crude fluoroethylene carbonate (FEC); e) treating the step (d) of crude fluoroethylene carbonate (FEC) with a stabilizing agent ranging between 0.01 to 0.5% w / w with respect to crude FEC; f) purifying the reaction mixture of step (e) by flash distillation followed by fractional distillation to obtain pure fluoroethylene carbonate (FEC) with purity greater than 99.00 %; and g) optionally, step (f) is further purified by melt crystallization to obtain highly pure fluoroethylene carbonate (FEC) with purity greater than 99.90 % and APHA color value less than 15.

2. The process as claimed in claim 1 , wherein the polar aprotic solvent in step a) is selected from dimethyl carbonate, methyl ethyl carbonate, diethyl carbonate, ethylene carbonate, methyl isobutyl ketone (MIBK), acetonitrile, dimethylformamide, A,A-dimethyl acetamide tetramethylurea, dimethylpropyleneurea (DMPU), dimethyl sulfoxide (DMSO), sulfolane, tetraethylene glycol dimethyl ether, polyethylene glycol dimethyl ether or mixture(s) thereof.

3. The process as claimed in claim 1, wherein the catalyst used in step (b) is selected from 18-crown-6-ether, PEG400, tetrabutylammonium bromide, tetrabutylammonium chloride or tetraphenylphosphonium bromide or mixture(s) of thereof.

4. The process as claimed in claim 1, wherein the polymerization inhibitor in step (b) is selected from butylated hydroxytoluene (BHT), succinonitrile, 4-methoxyphenol, hydroquinone, 2,2,6,6-tetramethylpiperidin-l-yl)oxyl (TEMPO), phenothiazine, 4-tert butyl catechol, 2,5-di-tert butylhydroquinone or mixture(s) of thereof.

5. The process as claimed in claim 1, wherein in step (b) reaction mixture maintained for time duration ranging between 1 hour to 5 hours to obtain the crude Fluoroethylene carbonate (FEC).

6. The process as claimed in claim 1, wherein in step (b) the catalyst and polymerization inhibitor are added in any order, either concurrently, separately, or in combination thereof.

7. The process as claimed in claim 1, wherein purification of the fluoroethylene carbonate (FEC) is further comprising the steps of: a) treating the crude fluoroethylene carbonate (FEC) with a stabilizing agent ranging between 0.01 to 0.5 % w / w with respect to crude FEC; b) purifying the step (a) by flash distillation and followed by fractional distillation to obtain pure fluoroethylene carbonate (FEC) with purity greater than 99.00 %; and c) optionally, step (b) is further purified by melt crystallization to obtain highly pure fluoroethylene carbonate (FEC) with purity greater than 99.90% and APHA color value of less than 15.

8. The process as claimed in claim 1 in step (e) or claim 7 in step (a), wherein the stabilizing agent is selected from butylated hydroxytoluene (BHT), succinonitrile, calcium hydroxide or mixture of thereof.

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