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United States Patent (19) 11) Patent Number: 4,705,904 Bonfield Et Al

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United States Patent (19) 11) Patent Number: 4,705,904 Bonfield Et Al United States Patent (19) 11) Patent Number: 4,705,904 Bonfield et al. 45) Date of Patent: Nov. 10, 1987 54 VAPOR PHASE SYNTHESIS OF which comprises contacting in the vapor phase in a HEXAFLUOROSOBUTYLENE catalyst zone, B, of a reactor hexafluoropropylene oxide 75 Inventors: John H. Bonfield, Basking Ridge; with a fluorinated catalyst such as fluorinated silica Harry E. Ulmer, Morristown, both of alumina at a temperature of about 400-600 C. for a N.J. residence time sufficient to form a vapor stream com prising hexafluoroacetone which is thereafter directly 73) Assignee: Allied Corporation, Morris contacted in a heating zone of the reactor with a vapor Township, Morris County, N.J. stream comprising a keytone-generating compound 21 Appl. No.: 820,896 such as acetic anhydride at a temperature of about 500-700' C. for a residence time sufficient to form a 22 Filed: Jan. 17, 1986 stream comprising hexafluoroisobutylene, substantially free of perfluoroisobutylene and recovering the hexa Related U.S. Application Data fluoroisobutylene product is disclosed. A direct one 63 Continuation of Ser. No. 580,083, Feb. 14, 1984, aban reactor vapor phase synthesis of hexafluoroisobutylene doned. which comprises (a) contacting, in the vapor phase, 51) Int, Cl. .............................................. CO7C 17/26 hexafluoropropene with less than a stoichiometric 52 U.S. C. ..................................... 570/142; 570/153 amount of oxygen required to convert substantially all 58 Field of Search .................. 580/83; 570/153, 142; the hexafluoroisopropene into hexafluoropropylene 568/399, 407, 400, 384; 549/523 oxide in the presence of a fluorinated catalyst such as (56) References Cited fluorinated silica-alumina at a temperature of about 400-600 C. for a time sufficient to form a vapor stream U.S. PATENT DOCUMENTS comprising hexafluoropropylene oxide substantially 3,332,965 7/1967 Fukui et al. ......................... 549/523 free of oxygen; (b) directly contacting said vapor 3,894,097 7/1975 Vanderkooi et al. ....... ... 570/142 stream, in a catalyst Zone, B, containing a fluorinated 3,946,081 3/1976 Wedemeyer et al. ... 0.568/400 catalyst which is preferably the same as used in catalyst 4,057,584 11/1977 Torizuka et al. ... ... 568/400 zone, A, at a temperature of about 400-650, preferably 4400.5468/1983 Rammeletal. .570/142 about 500-650 C. for a time sufficient to form a vapor FOREIGN PATENT DOCUMENTS stream comprising hexafluoroacetone; (c) directly con 62131 4/1983 Japan ................................... 568/384 tacting the vapor stream comprising hexafluroacetone 2119800 11/1983 United Kingdom ................ 570/153 with a vaporized compound such as acetic anhydride at a temperature of about 500-700 C., preferably about Primary Examiner-Donald B. Moyer 600 C. for a time sufficient to form a vapor stream Assistant Examiner-Joseph A. Boska comprising hexafluoroisobutylene, substantially-free of Attorney, Agent, or Firm-Richard C. Stewart; Gerhard perfluoroisobutylene; and (d) recovering hexa H. Fuchs fluoroisobutylene is also disclosed. 57 ABSTRACT A vapor phase synthesis of hexafluoroisobutylene, 4 Claims, No Drawings 4,705,904 1. 2 It is accordingly an object of the invention to provide VAPOR PHASE SYNTHESIS OF a new one stage route to hexafluoroisobutylene which utilizes cheaper and more readily accessible starting HEXAFLUOROISOBUTYLENE materials and which operates without isolation of toxic This application is a continuation of application Ser. 5 intermediates. No. 580,083 filed Feb. 14, 1984. Other objects and advantages of the invention will become apparent from the following description. BACKGROUND OF THE INVENTION SUMMARY OF THE INVENTION 1. Field of the Invention The present invention relates to a vapor phase syn 10 In accordance with one form of the invention there is thesis of hexafluoroisobutylene directly from hexafluor provided a process for which comprises opropylene oxide. The present invention also relates to (a) contacting, in a catalyst Zone B of a reactor, in the a vapor phase synthesis of hexafluoroisobutylene di vapor phase, a stream comprising hexafluoropropylene rectly from hexafluoropropene. oxide with a fluorinated catalyst at a temperature in the 2. Description of the Prior Art 15 range of about 400 to about 650 C. for a residence time Hexafluoroisobutylene is a known compound which sufficient to form a vapor stream comprising hexafluor is known to be useful for a variety of purposes such as, oacetone; for example, a comonomer which forms polymers of (b) directly contacting in a heating zone of the reac exceptional thermal, chemical and mechanical proper tor, in the vapor phase the vapor stream comprising ties with other comonomers such as vinylidene fluoride. 20 hexafluoroacetone with a compound selected from the The preparation of such copolymers is described in U.S. group consisting of acetic anhydride, acetone, acetic Pat. No. 3,706,723 to Chandrasekeran et al., issued Dec. acid, isopropenyl acetate, acetylacetone, diketene and 19, 1972. mixtures thereof, at a temperature in the range of about Hexafluoroisobutylene has been previously prepared 500 to about 700 for a residence time sufficient to form 25 a stream comprising hexafluoroisobutylene, substan by methods which include the reaction of hexafluoroac tially free of perfluoroisobutylene; and etone with ketene (U.S. Pat. No. 3,894,097 to N. Van (c) recovering hexafluoroisobutylene product. In derkooi), the reaction of hexafluorothioacetone with accordance with another form of the invention there is ketene or a ketene-generating compound (U.S. Pat. No. provided a process for converting hexafluoropropylene 4,244,891 to Van Der Puy et al.), the reaction of anti 30 directly into hexafluoroisobutylene which consists es mony trifluorodichloride with a chlorofluoroisobuty sentially of: lene R. N. Hazeldine, J. Chem. Soc., 3565 (1953)and (a) contacting, in catalyst zone A of the reactor, in the the dehydration of hexafluoro-2-methyl-2-propanol vapor phase, a stream comprising hexafluoropropene with phosphorus pentachlordie M. H. Kaufman et al., with less than a stoichiometric amount of oxygen gas J. Org. Chem. 31, 3090 (1966)or with sulfur tetrafluo 35 required to convert substantially all hexafluoropropene ride (E. E. Gilbert et al. in U.S. Pat. No. 3,656,786). See into hexafluoropropylene oxide in the presence of a also U.S. Pat. No. 4,367,394 (Anello) which discloses a fluorinated catalyst at a temperature in the range of liquid phase synthesis of hexafluoroisobutylene starting about 400 to about 600 C. for a residence time suffi from hexafluoropropene, elemental sulfur, and alkali cient to form a vapor stream comprising hexafluoropro metal fluoride in an aprotic solvent. pylene oxide substantial free of oxygen; U.S. Pat. No. 4,165,340 (Tohzuka et al.) discloses a (b) contacting in a catalyst Zone B of a reactor, in the process for preparing hexafluoropropanone-2 from hex vapor phase, the stream comprising hexafluoropropyl afluropropene by one step reaction which comprises ene oxide with a fluorinated catalyst at a temperature in contacting hexafluoropropene and oxygen with a fluori the range of about 400 to about 600° C. for a residence nated alumina or a fluorinated silica-alumina as a cata 45 time sufficient to form a vapor stream comprising hexa lyst in the presence or absence of water, provided that fluoroacetone; water is present when the catalyst is the fluorinated (c) directly contacting in a heating Zone of the reac alumina. See also U.S. Pat. Nos. 4,284,822 and 4,057,584 tor, in the vapor phase, the vapor stream comprising also to Tohzuka et al. hexafluoroacetone with a compound selected from the U.S. Pat. No. 3,600,409 (Milian et al.) discloses a 50 group consisting of acetic anhydride, acetone, acetic process for oxidation of hexafluoropropene to hexa acid, isopropenyl acetate, acetylacetone, diketene and fluoropropylene epoxide, which operates in the pres mixtures thereof, at a temperature in the range of about ence of an inert aromatic compound to eliminate the 500' to about 700' for a residence time sufficient to form formation of hexafluoroacetone. a stream comprising hexafluoroisobutylene, substan These preparations and others suffer trom one or 55 tially free of perfluoroisobutylene; and more disadvantages from a commercial standpoint. For (d) recovering hexafluoroisobutylene product. example, although the preparation involving hexafluor oacetone is a high-yield process, hexafluoroacetone DETAILED DESCRIPTION OF THE represents a starting material of high cost, high toxicity INVENTION and limited availability. The chlorofluoroisobutylene The present invention provides a single stage process route involves several steps including a slow dehydro for the preparation of hexafluoroisobutylene, substan chlorination step, while the dehydration of the fluori tially free of perfluoroisobutylene, starting from hexa nated tertiary butyl alcohol requires excessively long fluoropropylene oxide or hexafluoropropene without reaction times or expensive reagents The reaction of isolation and/or purification intermediate products such hexafluorothioacetone with ketene operates in the gas 65 as hexafluoroacetone, a highly toxic substance. Hexa phase at elevated temperature (300-800° C) and re fluoropropylene oxide may be prepared from hexafluor quires special precautions for handling and preparing opropene (which is commercially available) by the pro hexafluorothioacetone. cedure described in U.S. Pat. No. 3,600,409 (Milian et 4,705,904
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