Chemistry: analytical and immunological testing – Halogen containing
Reexamination Certificate
2001-06-14
2003-02-18
Warden, Jill (Department: 1743)
Chemistry: analytical and immunological testing
Halogen containing
C436S125000, C570S179000, C570S177000
Reexamination Certificate
active
06521461
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to fluoroalkene-nucleophile adduct formation for removal, immobilization, or quantification of fluoroalkenes from fluids.
BACKGROUND OF THE INVENTION
Perfluoroalkane fluids have many industrial uses, such as coolants for electronic devices (e.g., supercomputers) and as heat transfer media in vapor-phase soldering processes. However, upon transient heating many of these perfluorinated liquids at high temperatures, toxic impurities may form, such as certain fluoroalkenes, for example perfluoroisobutene (PFIB). These impurities may be hazardous to persons handling the liquid or operating equipment containing the contaminated liquid. Analytical procedures for the identification and quantification of the highly volatile low molecular weight fluorocarbons generally require chromatographic separation and reference standards for calibration. The more toxic perfluoroolefins such as PFIB are not readily available to be used as reference standards and transportation is a serious problem. Marhevka et al.,
Anal. Chem.,
1982, 54, 2607-2610, describe a method to generate a reference standard and suggest the use of an analytical surrogate, perfluorocyclopentene (PFCP), for calibration purposes.
Various methods have been suggested for reducing the hazard of PFIB exposure of operators of equipment that might inadvertently produce PFIB (Turbini, L. J., Zado, F. M., “Chemical and Environmental Aspects of Condensation Reflow Soldering”,
Electronic Packaging and Production,
January 1980, 49-59 and “Fluorinert Liquids”, 3M Publication No. 98-0211-4411-2(78.2)R1 XY, June 1988). Some of these methods include techniques of operating and maintaining vapor-phase soldering equipment to avoid localized super-heating of perfluorinated liquids, thus reducing the amount of PFIB produced, and standards of designing work areas to provide sufficient ventilation to maintain PFIB levels at less than hazardous levels.
U.S. Defensive Publication T983,009 (June, 1979) describes a method of converting PFIB in a mixture of fluorine-containing compounds into a relatively nontoxic ether by contacting the mixture with a solution of methanol and a selected hydrogen halide. While this method does produce products which are generally less toxic than PFIB, it has disadvantages, including 1) being complex to perform in a continuous mode, since various feed streams of reactants must be controlled, 2) using hazardous hydrogen halides (e.g., HF and HCl) as reactants, and 3) yielding products which may create a disposal problem.
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 degrees 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 degrees 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.
Hall et al.
Chemistry and Industry
, Mar. 6, 1989, 145-146, describe activated carbon filters to provide protection against exposure to PFIB and note that some of the PFIB is hydrolysed to produce 2H-perfluoroisobutyric acid and hydrogen fluoride. After storage and reuse of the exposed filter, 1,1,3,3,3-pentafluoropropene and 1,1,1,3,3,3-hexafluoropropane were found in the effluent stream.
A system and method for purifying saturated fluoroperhalocarbon liquids by removing olefinic impurities, such as PFIB, therefrom have 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.
Coffman et al.,
J Org. Chem.,
1949, 14, 747-753, reported that ammonia reacted with tetrafluoroethylene forms an amine which splits out HF to form difluoroacetonitrile which then forms a trimer.
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.
An exhaustive review of one of the fluoroalkenes is presented in “The Chemistry of Perfluoroisobutene,” by Y. V. Zeifinan, et al.,
Russian Chemical Reviews,
1984, 53 (March), 256-273. Reactions of PFIB with numerous N, O, S, and P nucleophiles are discussed, without reference to their quantitative analytical application or the ability of these nucleophiles to react with other fluoroalkenes.
SUMMARY OF THE INVENTION
Briefly, this invention provides a method for removing one or more highly fluorinated or perfluorinated alkenes (also referred to hereinbelow as a “fluoroalkene”) from a fluid, comprising the step of contacting the fluid with ammonium hydroxide or an organic nitrogen-, sulfur-, or phosphorus-containing nucleophile wherein the nucleophilic atom is N, S, or P (hereinafter sometimes referred to as N-, S-, or P-nucleophiles) for a time sufficient to form a nitrogen-, sulfur-, or phosphorus-containing nucleophile-fluoroalkene adduct. Preferably, the N-, S-, or P-nucleophile is sorbed on, or coated on, or bonded to, or itself can be, a support and can be used in a bed or cartridge. More preferably, the N-, S-, or P-nucleophile which can be sorbed on, or coated on, or bonded to a support is enmeshed in or forms a fibrous matrix, preferably a nonwoven matrix, which provides an essentially homogeneous, porous material. Alternatively the N-, S-, or P-nucleophile can be sorbed on, coated onto, or bonded directly to a porous matrix. Preferably, the nucleophile is ammonia or it comprises a nitrogen, sulfur or phosphorus nucleophile compound.
The optimum amount of nucleophile that can be loaded on a support varies with the nature of the support. In general, it is preferred to load the nucleophile in an amount in the range of 0.1 to 10 weight percent, more preferably 0.1 to 5 weight percent, based on the weight of the support.
In another aspect, the present invention provides a method for quantifying a highly fluorinated or perfluorinated alkene, for example PFIB, comprising the steps of
a) providing a stable or unstable N-, S-, or P-containing nucleophile-fluoroalkene adduct, which may be sorbed to a support, and
b) quantifying for highly fluorinated or perfluorinated alkenes in a fluid by either
1) measuring highly fluorinated or perfluorinated alkenes when the N-, S-, or P-containing nucleophile-fluoroalkene adduct is stable, displacing the adduct from the support when necessary, or
2) measuring the fluoride ion for indirect quantification of highly fluorinated or perfluorinated alkenes, when the N-, S-, or P-containing nucleophile-fluoroalkene is unstable and produces fluoride ion.
In yet another aspect, the present invention describes a method for preparing an adduct comprising the step of contacting an immobilized N-, S-, or P-containing nucleophile with a fluid comprising a fluoroalkene for a time su
Cheburkov Yuri
DeRoos Fred Lynn
Hagen Donald Frederick
Johnson Glenn Delmont
Marhevka John Stephen
3M Innovative Properties Company
Dahl Philip Y.
Siefke Sam P.
Warden Jill
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