Organic compounds -- part of the class 532-570 series – Organic compounds – Halogen containing
Reexamination Certificate
2003-04-01
2004-08-10
Price, Elvis O. (Department: 1621)
Organic compounds -- part of the class 532-570 series
Organic compounds
Halogen containing
C570S175000, C570S177000, C570S190000, C570S191000, C570S200000, C570S216000, C570S234000, C570S236000, C564S001500, C564S248000, C564S281000, C564S444000, C564S445000, C564S463000, C564S497000, C564S509000, C564S510000
Reexamination Certificate
active
06774270
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to a process for removal of hexafluoropropylene dimers and other oligomeric contaminants from fluids.
BACKGROUND OF THE INVENTION
Fluorinated fluids derived from hexafluoropropylene have many industrial uses, such as coolants for electronic devices (e.g., supercomputers), inert solvents and fluids, fire-extinguishing agents and as heat transfer agents. However, in the processes used in their preparation, or upon transient heating, many of these fluorinated fluids form oligomeric byproducts such as dimers. These dimers may be hazardous to persons handling the liquid or operating equipment containing the contaminated liquid, or may be reactive, and therefore undesirable, under conditions of use.
U.S. Pat. No. 3,696,156 describes a method of removing perfluoroolefin and perfluorochloroolefin impurities from saturated fluoroperhalocarbon compounds having two to six carbon atoms, by contacting the impure fluoroperhalocarbon in the vapor phase at about 180 to 250° C. with alumina containing a basic alkali metal or alkaline earth metal hydroxide or oxide.
U.S. Pat. No. 5,233,107 describes a process for removing olefinic impurities from hydrogen-containing chlorofluorocarbons in the gas phase at 200 to 400° C. over a zeolite. The contaminated higher boiling chlorofluorocarbons are preheated to convert the liquid to the gas phase in advance. The addition of 0.5 to 10% air or oxygen by volume to the process stream is recommended to keep coking at a very low level. One of the disadvantages of processes utilizing elevated temperatures is that they require handling hot gases contaminated with hazardous compounds. In addition, certain fluorocarbons are unstable and generate a variety of olefinic and aliphatic impurities at elevated temperatures especially in the presence of catalytic surfaces.
A system and method for purifying saturated fluoroperhalocarbon liquids by removing olefinic impurities therefrom has been disclosed in U.S. Pat. Nos. 5,300,714 and 5,507,941. Inorganic oxide, hydroxide, carbonate, or phosphate particles are used in the method.
England et al.,
J Fluorine Chem.
1981, 17, 265-288, describe reactions of amines with a dimer of hexafluoropropene and a perfluorovinyl sulfide prepared from hexafluoropropene. Anhydrous ammonia was added to a solution of hexafluoropropene dimer to form (1-amino-2,2,3,3,3-pentafluoropropylidene)propanedinitrile.
An organic amine-impregnated activated carbon composition, which preferably has been pre-treated, has been used in breathing gas filters to enhance removal of various toxic perfluorocarbons as is disclosed in U.S. Pat. No. 5,462,908. There is no disclosure as to the composition of the treated material or the nature of the nucleophile used to form a stable immobilized adduct with fluoroalkenes.
U.S. Pat. No. 6,521,461 (Mueller et al.) describes a method for removing one or more fluorinated alkenes from a fluid by contacting the fluid with an N-, S-, or P-containing nucleophile for a time sufficient to form an N-, S-, or P-containing nucleophile-fluoroalkene adduct. The nucleophile, and therefore the adduct, can be covalently bonded, coated or adsorbed to a particulate support which can be enmeshed in a porous, fibrous web.
SUMMARY OF THE INVENTION
Hexafluoropropylene (HFP) has been used in the preparation of a wide variety of useful fluorinated compounds and polymers, which are prepared by the fluoride-catalyzed addition of hexafluoropropylene to an electrophile. However, these methods invariably lead to the HFP dimeric and other oligomeric byproducts which can contaminate the desired product, may cause health or exposure risks, and are difficult to remove. Known means to remove the oligomeric byproducts are often expensive, time-consuming or involved the use of hazardous reagents. Simple distillation is often difficult due to the similar boiling points between the desired product and the undesired dimers. Distillation may also concentrate the toxic dimers and dimer hydrides. More particularly, many of the current methods are reactive with the desired reaction product as well as the undesired dimer byproduct and can reduce the yield of the desired, valuable products.
Briefly, the present invention provides a method of removing hexafluoropropylene dimers (“HFP dimers”), dimer hydrides and other oligomers from a fluid by heating the fluid to isomerize the HFP dimers to the thermodynamic isomer, and contacting the fluid with a tertiary amine (or salts thereof, preferably HF salts thereof) to form a hexafluoropropylene dimer—tertiary amine adduct. The method may further comprise the step of separating the dimer adducts from the reaction mixture.
The present invention provides a simple method of removing the undesired oligomeric byproducts using readily available materials and equipment. Advantageously, the method does not involve potentially hazardous reagents or reaction conditions, and the reagents do not substantially reduce the yields of the desired HFP-derived products.
The method is particularly useful in removing HFP dimers from fluorinated compounds derived from hexafluoropropylene, such as fluorinated ketones, HFP trimers and fluorinated aromatic compounds. Thus, the invention further provides a method of producing a fluorinated compound derived from hexafluoropropylene comprising the steps of contacting HFP with an electrophile in the presence of fluoride ion, optionally separating the crude reaction product, heating the crude reaction product to isomerize the HFP dimers, and treating the isomerized dimers with a tertiary amine (or salts thereof).
If desired, the tertiary amine may be adsorbed on, or coated on, or bonded to a support such as a porous on nonporous support. Useful supports may include a particulate support, a porous on nonporous film or web, or a foam.
As used in this application:
“Adduct” or “dimer-amine adduct,” means the addition product of a tertiary amine and an HFP dimer with or without the elimination of a byproduct;
“fluid” refers to a material that is a liquid at 25° C. and 760 mm Hg pressure, i.e., standard conditions;
“HFP dimer” refers to unsaturated compounds of the formula C
6
F
12
, formed by the dimerization of hexafluoropropylene.
“HFP dimer hydride” or “hydrides of HFP dimer” refers to compounds of the formula C
6
F
13
H, formed by the addition of HF to an HFP dimer.
“HFP oligomer” refers to dimers, trimers and tetramers of hexafluoropropylene;
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patent: 5233107 (1993-08-01), Jansen
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patent: 6521461 (2003-02-01), Mueller et al.
patent: WO 99/37598 (1999-07-01), None
England et al., Reactions of Amines with a Dimer of Hexafluoropropene and with a Perfluorovinyl Sulfide Prepared with Hexafluoropropene, Journal of Fluorine Chemistry, (1981), pp. 265-288, vol. 17.
Probst et al., Synthesis and Chemistry of Perfluoro-2-lodo-2-Methyl-Alkanes, Journal of Fluorine Chemistry, (1987), pp. 223-245, vol. 37.
Chambers et al., “‘Naked Fluoride Ion’ from Elemental Fluorine”, Journal of Fluorine Chemistry, (1999), pp. 213-215, vol. 94.
Brunskill et al., “Anionic Oligomerisation of Hexafluoropropene: Fission of a Carbon-Carbon Bond by Fluoride Ion”, Chemical Communications, (1970), pp. 444-446.
Snegirev et al., “Reaction of Secondary Amines with Hexafluoropropylene Dimers”, Bulletin of the Academy of Sciences of the USSR, Division of Chemical Science, (Nov., 1983), pp. 2305-2312, vol. 32, No. 11, Part 2.
Ishikawa et al., “Chemistry of Hexafluoroprene Oligomers”, Dept. of Chemical Technology, Tokyo Institute of Technology (Ookayama, Meguro-ku, Tokyo 152), (1981), pp. 51-62, 39 (1) (translation included).
Smith et al., “The Chemistry of Carbonyl Fluoride. II. Synthesis of Perfluoroisopropyl Ketones”, Journal of American Chemical Society, (Nov. 20, 1962), pp. 42
Flynn Richard M.
Qiu Zai-Ming
Vitcak Daniel R.
Zhang Zhongxing
Kokko Kent S.
Price Elvis O.
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