United States Patent Office Patented June 28, 1966
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3,258,500 United States Patent Office Patented June 28, 1966 2 and simple and easy to operate and control, so as to obtain 3,258,500 high yields of the desired products. Still other objects PROCESS FOR FLUORNATING HALOHYDRO). will appear hereinafter. (CARBONS The above and other objects may be accomplished by Frederic W. Swamer, Boothwyn, and Benjamin W. Howk, 5 the process of this invention which comprises contacting West Chester, Pa., assignors to E. I. du Pont de Ne a vapor mixture of a halogenated aliphatic hydrocarbon nours and Company, Wilmington, Del, a corporation of 1 to 8 carbon atoms in which adjacent carbons are of Delaware No Drawing. Filed Aug. 17, 1959, Ser. No. 833,962 linked solely by 1 to 2 valence bonds and in which the 17 Clains. (C. 260-653.7) halogen atoms have an atomic weight of less than 80 10 and include at least one halogen atom having an atomic This invention relates to a process for catalytic vapor weight between 35 and 80 and at least a stoichiometric phase fluorination of halohydrocarbons and more particu proportion of anhydrous hydrogen fluoride with a catalyst larly to the substitution of fluorine for other halogens in which consists essentially of an activated anhydrous chro halohydrocarbons which contain halogens other than or mium (III) oxide at a temperature in the range of from in addition to fluorine, employing an improved catalyst about 150 C. to about 700° C. such that the principal for such reaction. reaction is the substitutioi, of fluorine for other halogen The process of this invention is applicable to the prep of the halogenated hydrocarbon, and separating the fluori aration of a large number of fluorinated compounds nated compound from the reaction mixture. which in general are well known and are valuable for a It has been found that the catalysts of the character wide variety of purposes such as refrigerants, propellents, 20 above specified are exceptionally active and efficient in dielectrics, general inert solvents, selective solvents in ex such process to cause the hydrogen fluoride to react with traction operations, and compounds characterized by sta the halogenated hydrocarbons of the specified class so that bility to high temperatures and chemical attack. Many fluorine is substituted for chlorine and bromine to produce of the lower boiling products such as dichlorodifluoro the desired fluorinated or more highly fluorinated products methane, chlorotrifluoromethane and trichlorofluoro 25 in unusually high yields and without requiring excessively methane are well known and have been widely used as high temperatures. The process is readily controlled to refrigerants and as propellents. More highly fluorinated produce any desired degree of fluorine substitution and or completely fluorinated compounds of the aliphatic is particularly effective for the complete replacement of series, such as carbon tetrafluoride, chloropentafluoro other halogens by fluorine, especially for the preparation ethane, hexafluoroethane, chloroheptafluoropropane, octa 30 of fluorocarbons from other completely halogenated hy fluoropropane, perfluorobutane, and perfluorocyclobutane drocarbons. are known and are recognized as being useful as refrig The process is simple and easily carried out by passing erants and propellents but they have not been readily avail a gaseous mixture of anhydrous hydrogen fluoride and able, particularly at low cost, because they have been diffi the halogenated hydrocarbon over or through the cata cult to make and have been obtainable only by complex lyst maintained at the desired temperature in a conven and expensive procedures. One procedure for producing tional reactor of the type commonly employed for reac carbon tetrafluoride, for example, comprises two steps: tions of this character. Usually, the gaseous mixture the conversion of dichlorodifluoromethane to chlorotri will be passed through a bed of the catalyst in a reaction fluoromethane over alumina and then the fluorination of tube. The reaction tube may be constructed of any chlorotrifluoromethane over chromium fluoride to pro 40 smetal or other material that is inert to anhydrous hydro duce carbon tetrafluoride. gen fluoride, hydrogen chloride and hydrogen bromide at The catalysts commonly used for replacing chlorine and temperatures up to 700° C. and is resistant to heat for bromine by fluorine in making fluoromethanes and fluoro extended periods of time. Suitable materials for con ethanes, have included antimony pentahalides, chromium struction of the reaction tube include Hastelloy C. nickel oxyfluorides, chromium fluoride, aluminum fluorides, ac alloy, Inconel nickel alloy, nickel, stainless steel, platinum, tivated carbon, and aluminum oxide impregnated with and fused refractory alumina such as Alundum. metal halides. While commercial processes have been The halogenated aliphatic hydrocarbons which may be developed for employing such catalysts, such processes fluorinated by the process of this invention are those have been quite limited in efficiency, in economy of oper which contain 1 to 8 carbon atoms and in which adjacent ation, and in the extent to which the fluorination of the 50 carbon atoms are linked solely by 1 to 2 valence bonds. halohydrocarbon could be induced to proceed. Usually These include the saturated compounds, such as halo complete fluorination is obtained with considerable diffi genated alkanes and halogenated cycloalkanes, and un culty and to only a limited extent, resulting in low yields saturated compounds, such as the halogenated alkenes of the desired product and high costs. and halogenate cycloalkenes. Preferably, the halo It is an object of this invention to provide a process genated hydrocarbons are the acyclic compounds, such as for fluorinating halohydrocarbons of the aliphatic series the halogenated alkanes and halogenated alkenes, and par which contain 1 or more halogen atoms other than or in ticularly the saturated acyclic halogenated hydrocarbons. addition to fluorine so as to partially or completely replace The halogen atoms in the halogenated hydrocarbons are such other halogen atoms by fluorine. Another object is those which have an atomic weight of less than 80, i.e., to provide a catalytic vapor phase process for reacting 60 fluorine, chlorine and bromine, and include at least one anhydrous hydrogen fluoride with halogenated aliphatic halogen atom having an atomic weight between 35 and hydrocarbons so as to replace halogen atoms therein other 80, i.e., chlorine and bromine. The halogenated hydro than fluorine in the presence of an improved and highly carbons may be partially or completely halogenated, active and efficient catalyst. A further object is to pro that is, from one to all of the hydrogen atoms will be vide such a process which is practical, efficient, economical replaced by halogen atoms, including at least one of chlo 3,258,500 3. 4. rine and bromine. The compounds that may be fluori Group IV.-Cyclicalkanes and cyclicalkenes containing nated by the process of this invention include the follow ing which for convenience are presented in groups having at least one halogen other than fluorine. members that are related in composition or in structure. 5c -c.c. -cF. crld F, Group I-Chloro- and bromoalkanes of the general CF2(CF)4CFBr- formula CHXy where m=1-8, n+y=2m+2, and --- X=C or Br. CF Cl(CIF)4CF Representatives: - --- --- CFC-CF C-(CF) -CF3 (Faccide c-cc-d; Cl CHC1 CHBr O CHCHCl CHCHBr CF-CFf Cl-CFC--- Cl=C Cl CHCHCHCHCl CHCHCHCHBr --- CHCl2 CHB I2 CHCIB r (F,CFBror BroFacF-F CHCHCl2 CHCHBr, CHCHCIBr - - CICHCHCl BFCHCHBr BrCHCHCl - CHCl CHBr3 CHClBra CF2CCCF ClCCl=C Cl CHCCl3 CH3CBrs CHClBr The process of this invention is also applicable to the CICHCHCl2 fluorination of phenyl, halophenyl and halomethylphenyl CC 20 substituted halomethanes such as CCl3CCl3 Group II.-Chloro-, bromo-, fluoroalkanes of the gen eral formula CHBr ClyF, where m=1-8, W -CCl3 Or Or Or n--x-y-z=2n-1-2 25 x--yRepresentatives: is at least one, and z is at least one. CFCl CF2Cl CFCl CFBr CFBr2 CFBr 30 Or Or Or Or CFBrC1 CFBrCl C CCl3 CFBrCl CHFBrC1 CHFCI CHFBr CICFCFCI BrCFCFBr ClCFCFBr CFCFCl CFCFBr CFCFBrC1 OrCl OrBr ClCFCF.Cl In the fluorination of these compounds, the halogens, BrCFCFCFCFBr CICFCFCFCFC1 other than fluorine, in the halomethyl groups are replaced BrCFCFCFCF-Cl Br(CF) Br by fluorine but the halogen substituents on the benzene 40 ring remain intact. CFCFBrCFCF CFCFCICFCF By the process of this invention the chlorine and/or CFCFBrCFCICF CFCCIFCCIFCF bromine of the halogenated hydrocarbons are partially or completely replaced by fluorine due to reaction with hy CF (CF)Br Br(CF) Br Cl(CF)3Cl drogen fluoride to provide halogenated hydrocarbons ClC(CF2)Cl. ClC(CF)6Cl Cl(CF2)6H 45 which contain a higher proportion of fluorine than the CICFCFCICF BrCFCFBrCF starting material. In some cases, compounds, other than the products of direct replacement, are obtained in minor Group III.-Chloro-, bromo-, and fluoroalkenes con proportions as the result of secondary disproportionation taining at least one halogen other than fluorine. reactions occurring in the process. Representatives: 50 The catalysts employed in this process consist essential CF=CFBr CF=CFC) ly of an activated anhydrous chromium (III) oxide. In BrCF-CFBr CCFECFC other words, except for diluents, carriers, and minor pro CF=CB r2 CFFCCl3 portions of impurities, they consist of CrO3 and have CFBr=CBr CFC=CCl been activated by heating in an inert atmosphere at a 55 temperature of from about 400° C. to about 600° C., CFBr-CHF CHC1-CBr preferably about 500 C. Inert atmospheres include ni CF=CHBr CHC-CF, trogen, air, steam, and anhydrous hydrogen fluoride, nitro CFBI-CHBr CHF-CHCI gen being preferred. The catalysts are practically inert ClCFCC CHFCCl3 toward gaseous anhydrous hydrogen fluoride, oxidation by ClCH=CC CHFCBra 60 air, and reduction by hydrogen at the temperatures em CCH-CHCI ployed in this process. Treatment of the catalysts with CH=CHCI gaseous anhydrous hydrogen fluoride for extended periods of time at such temperatures has not significantly affected CF=CFCFC1 CFCICF=CFCFC1 their activity as catalysts and does not convert the CrO CF=CCICFa to an oxyfluoride, i.e., a basic chromium fluoride.