Organic compounds -- part of the class 532-570 series – Organic compounds – Halogen containing
Reexamination Certificate
1997-08-28
2001-05-08
Siegel, Alan (Department: 1621)
Organic compounds -- part of the class 532-570 series
Organic compounds
Halogen containing
C570S135000, C570S137000
Reexamination Certificate
active
06229058
ABSTRACT:
FIELD OF THE INVENTION
The instant invention relates to producing fluorinated propanes and pentanes. More particularly it relates to producing perhalofluoropropanes and pentanes by reacting dihalodifluoromethanes with polyfluoroethylenes, notably tetrafluoroethylene (TFE) and chlorotrifluoroethylene (CFFE) while in the presence of an aluminum chlorofluoride catalyst.
In another aspect, the instant invention relates to preparing novel perbromofluoroalkanes containing three, or five carbon atoms.
In still another aspect, the instant invention relates to a process for converting the perhalofluorocarbons to hydrofluorocarbons(HFCs) by reaction with a source of active hydrogen effective to convert one or more carbon-nonfluorohalogen bonds to carbon-hydrogen bonds.
Thus, the perhalofluoropropanes and pentanes, products of the inventive process, are potentially useful for manufacturing hydrofluorocarbons which, in turn, in view of their inherently low ozone depletion potentials, are environmentally attractive alternatives for perchlorofluorocarbons (CFC's) in such established uses as refrigerants, expansion agents, aerosol, propellants, fire extinguishing agents, power cycle working fluids, polymerization media, heat transfer media, solvents, carrier fluids, cleaning and drying agents, gaseous dielectrics, among other applications.
BACKGROUND OF THE INVENTION
Joyce, U.S. Pat. No. 2,462,402 (Feb. 22, 1949) discloses a process for the production of highly halogenated fluoroalkanes which comprises contacting TFE with a polyhalogenated alkane,preferably a methane, containing at least one chlorine atom and no more than two fluorine atoms, in the presence of a polyvalent metal halide catalyst, preferably aluminum chloride.
U.S. Pat. No. 2,462,402, to Coffman, et. al., is referenced in the Journal of the American Chemical Society, Vol. 71, pages 979-980 (1949) which discloses that reacting CHClF2 (chlorodifluoromethane) while in the presence of aluminum chloride with TFE produces CHCl2F5 having one less F atom than the sum of fluorine atoms in the reactants. Likewise, CHClF2 reacting with CTFE yields CHCl3F4.
Paleta, in a review article “Fluorine Chemistry Reviews”, Vol. 8, page 51 (1977) states: “The ionic addition reactions of fluoromethanes in the presence of aluminum chloride are limited to the monofluoro derivatives only. When in contact with aluminum chloride, both difluorodichloromethane and difluorochloromethane were found to undergo a rapid disproportionation with the formation of monofluorochloromethanes (along with some further compounds) that are able to add to fluoroethylenes.”
The disclosure of each of the previously identified references is hereby incorporated by reference.
SUMMARY OF THE INVENTION
One aspect of this invention relates to a process for producing valuable perhalopolyfluoropropanes and pentanes from known dihalodifluoromethanes, particularly dichlorodifluoromethane, and polyfluoroethylenes, such as tetrafluoroethylene (hereinafter referred to as “TFE”) and chlorotrifluoroethylene (hereinafter referred to as “CTFE”).
Another aspect of the invention provides such a process that produces propanes and pentanes wherein the total number of fluorine atoms is equal to the sum of the number of fluorine atoms in the dihalodffluoromethane reactant and the number of fluorine atoms in the polyfluoroethylene reactant.
Still another aspect of the invention relates to novel perbromofluoropropanes and pentanes.
A still further aspect of the invention relates to a process for obtaining hydropolyfluoropropanes and pentanes having relatively low ozone depletion potentials wherein carbon-nonfluorohalogen bonds, e.g., C—Cl or C—Br bonds, of the perhalofluoropropanes and pentanes are converted to carbon-hydrogen bonds.
Notwithstanding conventional beliefs as described in Paleta, the instant invention can react dihalodifluoromethanes, wherein the halo corresponds to non-fluoro halogens, with TFE and/or CTFE to produce perhalofluoropropanes and/or pentanes, wherein the total number of fluorines in said propanes and pentanes is equal to the sum of the fluorines in the methanes and fluoroolefins being reacted.
The process of the invention comprises producing perhalofluoropropanes and/or pentanes by:
(i) contacting (a) a dihalodifluoromethane, CXYF2, wherein X and Y are independently Cl or Br, with (b) at least one of tetrafluoroethylene and chlorotrifluoroethylene while in the presence of (c) a catalytic amount of an effective aluminum chlorofluoride, at a temperature and pressure effective to result in the formation of (d) at least one of a perhalofluoropropane having 5 to 6 fluorine atoms and 2 to 3 nonfluorohalogen atoms, e.g., bromine and/or chlorine atoms, and a perhalofluoropentane having 8 to 10 fluorine atoms and 2 to 4 nonfluorohalogen atoms, e.g., bromine and/or chlorine atoms; the total number of fluorine atoms in said propane and/or pentane products being the sum of the number of fluorine atoms in the dihalodifluoromethane and the number of fluorine atoms in the TFE and/or CTFE, and;
(ii) recovering at least one of said propanes and pentanes.
In one aspect of the invention, the dihalodifluoromethane comprises CCl2F2 (CFC-12), the fluoroethylene comprises TFE and the aluminum chlorofluoride contains about 3 to about 64% F by weight, normally about 16 to 61 % F by weight. Such aluminum chlorofluorides, which correspond to AlCl3-xFx, wherein x is typically about 1.0 to about 2.8, are hereinafter referred to as “modified aluminum chlorides”. Modified aluminum chlorides are conveniently prepared by reacting commerically available anhydrous AlCl3 with one or more chlorofluorocarbons, hydrochlorofluorocarbons, or hydrofluorocarbons as disclosed in U.S. Pat. No. 5,157,171 to Sievert, et. al. at column 4 line 2 through column 5 line 4, the entire disclosure of which is hereby incorporated herein by reference.
In one embodiment of the invention, the reaction conditions, e.g., the mole ratios of reactants, their feed rates, and temperature and pressure, are controlled so as to favor a one-to-one reaction of the dihalodifluoromethane with the fluoroolefin, while in the presence of a modified aluminum chloride catalyst, and result in the formation of halofluoropropanes as the predominant products as illustrated by equation (1).
CCl2F2+CF2═CF2—>C3Cl2F6, e.g., CCl2FCF2CF3. (1)
In another embodiment, the reaction conditions are adjusted for promoting production of halofluoropentanes as the predominant products via a one-to-two reaction stoichiometry, while in the presence of a modified aluminum chloride catalyst, as illustrated in equation (2).
CCl2F2+2 CF2═CF2—>C5Cl2F10, e.g., C2F5CCl2C2F5. (2)
In still another aspect of the invention, the reaction products, as perhalofluoropropanes and/or as perhalofluoropentanes are treated with one or more reducing means under conditions effective for converting the non-fluorohalide groups of the propanes and pentanes, i.e., the —CXY— groups, wherein X and Y are independently Cl or Br, to —CHX— or —CH2— groups, usually the latter. The reducing means include photochemical reducing means, chemical reducing means, catalytic hydrogenation reducing means, among other suitable means.
DETAILED DESCRIPTION
In accordance with the present invention one or more perhalofluoropropanes comprising (A) C3XYF6, when produced from TFE, (B) C3ClXYF5, when produced from CTFE, and perhalofluoropentanes having the formula C5XYF10, when produced from TFE, (C) C5Cl2XYF8, when derived from a mixture of TFE and CTFE; wherein X and Y stand for Cl or Br as defined above, can be prepared by reacting CXYF2, e.g., CCl2F2, with TFE and/or CTFE in the presence of a modified aluminum chloride catalyst. The reactions may be represented by equations (1) and (2) above, illustrated with CCl2F2 and TFE as the reactants.
The CXYF2 starting materials for the process of this invention can be selected from at least one member selected from the group of CCl2F2, CBrCIF2, and CBr2F2. The fluoroolefin starting materials for the process of this inve
Nappa Mario Joseph
Sievert Allen Capron
E. I. Du Pont de Nemours and Company
Shipley James E.
Siegel Alan
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