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When the product was treated with 14 moles of AgF2 a t 200" C. i n a steel pot, the result was a colorless oil with a boiling range of 145-190" C. (10 mm.) that contained 15.5y0 chlorine. The over-all yield was 60% of theory from chloroterphenyl assuming the final product \vas C1,F2&lr. The chlorofluorocarbons prepared from chlorinated 0- and mterphenyl with AgFl were colorless oils boiling from 140" to 230" C. (10 mm.). A mixture of the two terphenyls gave a chlorofluoro oil with a viscosity about 5 centipoises lower than either component alone a t 210' F. A n analysis of such a mixed product indicated ClsHo.lCl6F2a.3 as a n average formula. The chlorofluoro oil had a viscosity of 20-25 centipoises a t 210" F.; a t room temperature it mas a clear, sticky mass. The density a t 210" F. was 1.8 compared t o 1.85 for fluorocarbon oil prepared by the AgF2 liquid-phase process. T h e viscosity index 1100; the viscosity change with temperaturr, thereforc, was was greater than t h a t of fluorocarbon material which had a viscosity index of -700. Chlorofluoro oil was thermally unstable in glass above 250 ' C. a n d slowly gave off acid fumes; thermally it was not so stable a s fluorocarbons which withstand heating a t 300" C. in glass. Furthermore, the chemical stability to AgF2 was not so high as t h a t of the fluorinated material, in that, upon retreatment, with .AgFp a t 220-240' C., i t gradually broke down into lower boiling products. Exposure to 2070 fluorine (diluted with nitrogen) caused explosive decomposition a t 240" C. Vapor-phase per-
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fluoro oil did not react with dilute fluorine a t 300" C. The chloro compounds shown in Table I were fluorinated with A4gF2. K i t h the exception of chlorinated p-terphenyl, the yields of chlorofluorocarbons in the desired boiling range mere poorer than with o- or nz-terphenyl. It appears noteworthy that the oxygen linkage in Chlorinated 4phenoxydiphenyl survived, inasmuch as the oil boiled above 140' C. (10 mni.), as do terphcnyl oili. The chlorinated aromatic compounds listed in Table I1 mere reacted with SbF, and then treated with AgF,. They were less interesting than the terphenyls in fulfilling the objective of preparing a chlorofluoro oil, both in respect to yield and properties. The reaction with SbFs (15-20 moles) was effected in an aluminum bomb a t 200-225' C . The aftertreatment with AgF2 (515 mcles) was carried out in a small steel pot a t 150-200 ' C. The nitrogen bond was apparently intact in both triphenylamine and S-phenylcarbazole reaction products, as indicated by the boiling range of the chlorofluoro oils. However, the oxygen bond in chlorinated 4-phenoxydiphenyl, which survived the AgFg reaction, n x s split by SbFj as indicated by low boiling reaction products. P R E S E S ~ Lbefore D the Symposium o n Fluorine Chemistry as paper 88, Division of Industrial and Engineering Chemistry, 110th Meeting of the AMERICANCHEXICAL SOCIETY,Chicago, Ill. T h e work described in thin paper is covered also in a comprehensive report of work with Buorine and fluorinated compounds undertaken in connection with the hianhattan Project. This report is soon t o be published as Volume I of Division V I 1 of the M a n h a t t a n Project Technical Series.
(PREPARATION OF CHLOROFLUOROCARBOY S)
Fluorination o fpetroleum oils in vapor phase with cobalt trifluoride C. F. Irwin, R. G. Benner, A. F. Benning, F. B. Downing, H. XI. Parrnelee, and W. V. W-irth E. I. DUPONT D E N E M O U R S
& COMPANY, IUC., WILMINGTON, DEL.
A METHOD is described for the preparation of perfluorocarbons having a boiling range of 180" to 350" C. at 760 mm. niercury by the fluorination of hydrocarbon oils in the vapor phase over cobalt trifluoride. The equipment used, variables affecting the yields, methods of finishing the fluorination, and some physical properties of the perfluorocarbons are discussed.
provisions were made t o ensure vaporization of the feed stock and reaction products in the reactor and auxiliary equipment. This was accomplished by employing an electrically heated preheater (n) for heating the inert gas used to assist in vaporizing the feed stock, an electrically heated vaporizer and manifold ( b ) , and an elcctrically heated screen stack and take-off line (c), in place of the 0.5-hch coil condenser used in diperfluoromethylbenzene work were two condensers ( d ~i n series, one cooled with water a t H E vapor-phase fluorination of hydrocarbons with cobalt 30-40" C. t o condense high boiling perfluorocarbons, and the trifluoride (1) was extended t o the higher boiling oils, such as second cooled with carbon-ice-trichloroethylene t o condense kerosene and light lubricating oils, in order to obtain pcrfluorohydrogen fluoride and low boiling perfluorocnrbons resulting from cracking. These conclcnsers had a wide bore to prevent carbons with a boiling range of 180" t o 350" C. a t 760 mm. plugging by the very viscous products. *L calcium chlorideAmong the uses for such perfluorocarbons is that of a reaction medium for some fluorination reactions. manometer attachment was u w l t o check the prcwure in the The react,ions involved in the preparation of perfluorocarbons reactor. by this method may be written as follows: The reactor was loadcd with 83 pounds of CoF2 irhich, after conversion to CoFp, was theoretically sufficient to produce 11 200-300 a C.+ 2CoFI (l) pounds of perfluorocarbon from 3 pounds of hydrocarbon i n a 2CoF2 Fn single cycle. This amount of C o F 2 left ahout 1.3 cubic feet of free space in the reactor or about half of the total 4nCoFa -(CHn)n275-350" "+ -(CFn).4nCoFn 2nHF (2) volume. The procedure used in fluorinstion follows: The tcamperature At the temperatures used, the replacement of hydrogen by fluoof the oil vaporizer wvne adjusted to 350" C., the reactor t o 300°, rine was fairly complete, but the yields were seldom above 80% and the icrwn-stack and takc-off line to 380". The floLv of inert because of cracking or thermal decomposition. gas (hydrogen fluoride or nitrogen) wvns adjusted to 8 reactor EQUIPMENT AND PROCEDURE volumcs (free space) per hour, and the flow of feed stock waa started into the vaporizer. The rate of feed varied, as will be T h e equipment (Figure 1) was essentially the mme a8 that discussed later, from about 22 to 51 reactor volumes per hour, ueed i n the fluorination of hexafluoroxylene (8) except that
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#FEED PUMP
Figure 1.
Equipment Used i n Fluorinating H>-tlrocarbons
% DISTILLED
Figure 2. Boiling Range of Fluorocarbone
based on tlie products of Equation 2, where n was assumed to be 21. The oil vaporized, passed into the reactor, was fluorinated, passed out of the reactor, and was condensed. During the oil feed, the temperature in the reactor \\-as not allon-ed to rise above 350" C. After the oil feed was completed, the reactor was s m p t R-ith 14 reactor volumes of hydrogen fluoride or nitrogen over a period of 1.5 hours. This displaced all orgqnic matter from the reactor and eliminated all danger of explosion or fire ivhen elemental fluorine was introduced into the reactor in the regeneration of CoF2. The best yields were obtained when sufficient' oil \vas fed to consume 50% of the CoFa. The effect of the variation in amounts of oil fed will be discussed later in more detail. The crude perfluorocarbon (specific gravity OIL F E E D (ccs./min.) 1.9)was separated from Figure 3. Effect of Feed Rate on the hydrogen fluoride Yield of Fluorocarbon (specific gravity 1,I bv. layer separation. . heated to reniove most of the dissolved hydrogen fluoride, treated with caustic to remove the remaining hydrogen fluoride, and filtered. Figure 2 shows distillation ranges of typical crudes prepared in this way; the solid lines indicate the yields of desired material and the dotted lines indicate unsuitable high and low boiling perfluorocarbons. KO actual comparison was made of distillation ranges of the perfluorocarbon and the parent hydrocarbons since cracking occurred. Cracking in the lower hydrocarbons was much less than in those with higher molecular weight. From kerosene only 187, of low boiling material !vas obtained, and the total crude has a distillation range of 100" C. as did the original kerosi.ne. Hov-ever, from a lubricating oil with a boiling range of 80" C. a crude product wa3 obtained with more than 30% low-boiler eonti-nt and with a boiling range of 200" C!. The rariaLles affecting the yields and quality of perfluorocarbons from any given oil were: temperature of reaction, oil
feed rate, and exhaustion of tlie CoF3. The first, variable wa6 not investigated since earlier nork had shoim that, excessive cracking of hexafluoroxylene and n-heptane occurred Trhen they were fliiiirinatetl aliove 373" C., and the lower temperature limit waa that n-hich would not allow material t o condense in the reactor. I n separate n-ork this limit was found to be 275' C. Figure 3 s h o w the effect on yield due to varving the oil feed rate; only the variation of yicltl of desir
