UNITED STATES PATENT Office

Patented Feb. 12, 1952 2,585,644 UNITED STATES PATENT office PROCESS FOR PRODUCING FLUOROCARBONS Robert D. Fowler, William B. Burford, III, and Harry C. Anderson, Baltimore, Md., assignors to the United States of America as represented by the United States Atomic Energy Commis sion . No Drawing. Application November 25, 1946, Serial No. 712,038 6 Claims. (C. 260-653) 1. 2 The present invention relates to a process for also be fluorinated by the method of the present producing fluorocarbons and, more particularly, invention. The term “hydrocarbon' may be to a process for preparing fluorocarbons from understood to include hydrocarbons of the paraf hydrocarbons of relatively high molecular weight. finic, olefinic, aromatic and naphthenic series. Highly fluorinated hydrocarbons, especially 5 The bismuth pentafluoride is preferably in completely fluorinated hydrocarbons and hydro comminuted form and may be prepared by carbons having not more than one to three un fluorination of bismuth trifluoride with ele Substituted hydrogens, are particularly valuable mental fluorine. for use as lubricating oils in processes where it . The range of temperatures employed varies is desirable to provide inert lubricants. It has O Somewhat With the particular hydrocarbon to be recently been found that hydrocarbons may be fluorinated but, in general, the reaction tempera highly fluorinated by passing vapors of said hy ture in the present process is lower than that drocarbons into contact with fluorides of certain employed in fluorination with certain other metal metals, Such as cobalt, manganese and silver, in fluorides, such as cobalt trifluoride and manga a higher Valence state at temperatures between 5 nese trifluoride. Bismuth pentafluoride is so 150° C. and 400° C. Although such processes in drastic a fluorinating agent that, once the re general produce high yields in the case of the action has started, it is desirable to control the OW molecular weight hydrocarbons (say, up to temperature to prevent degradation of the prod heptane), disappointing results have been ob uct. Such control may be effected by provision tained by the application of these processes to 20 of cooling means. In Vapor phase reaction the hydrocarbons of high molecular weight, say, of temperature must be somewhat above the boil the order of about 17 to about 23 carbon atoms ing point of the feed stock at the start of the re per molecule. Moreover, the high temperatures action, and may have to be increased as much employed tend to produce a higher proportion of as 100-200° C. to complete the reaction, although, Scission and fluorinolysis products than is desir 25 because of the greater reactivity of BiF5, Such able. increases Will be much Smaller than the cor It is an obect of the present invention to pro responding values for the other fluorinating vide a simple and inexpensive process for produc agentS. ing fluorocarbons of relatively high molecular One of the great advantages in the use of weight in high yield. bismuth pentafluoride is its effectiveness as a It is another object of this invention to provide fluorinating agent in liquid phase reaction. Due a relatively low temperature fluorinating process to the powerful filorinating character of bismuth * for hydrocarbons which produces a fluorocarbon pentafluoride when used to fluorinate hydrocar product with relatively low production of scission bons, various types of fluorocarbons, formerly and fluorinolysis products. either difficult or impossible to produce with the According to the present invention, hydrocar fluorinating agents of the prior art, may be pro bons are contacted with bismuth pentafluoride at duced when employing bismuth pentafluoride at relativelv low temperatures to produce fluorocar relatively low temperatures. Thus, the use of bons. The hydrocarbons in vapor phase may be bismuth pentafluoride in the liquid phase results paSSe? over and/or through comminuted bismuth 40 in the fluorination of long chain or high molecu pentafluoride, or the hydrocarbons may be con lar weight compounds to a high degree of com tacted in the liquid phase with the bismuth pletion, whereas more drastic methods, especially pentafluoride with or without a suitable diluent temperaturewise, with other fluorinating agents or solvent for said hydrocarbons. are incapable of producing the desired products ... While the present invention is more particular 45 without relatively high loss through Scission and ly concerned with the fluorination of hydrocar fluorinolysis. Better yields of fluorocarbons are bons of relatively high molecular weight, such as thus produced by the process of this invention those having about 17 to about 23 carbon atoms than have formerly been found possible when per molecule, preferably those boiling between fluorinating these materials. about 250° C. and about 400° C., it is also ap 50 In carrying out the reaction in the vapor phase, plicable to the fluorination of hydrocarbons of it is preferred to have the bismuth pentafuoride lower or of higher carbon content, including in a rotary reaction cylinder equipped with agi those having about 6 to about 30 carbons. tator blades and to paSS the hydrocarbon to be Certain other substances, such as halogenated fluorinated in vapor phase in intimate contact hydrocarbons, vaseline, and phenol resin, may 55 with the bismuth pentafluoride therein. ... The 2,585,644 3 bismuth pentafluoride may only partially occupy nitrogen may be present in the molecule with the volume of the cylinder or may fill the same out materially affecting the predominantly fluo Substantially entirely. If desired, an inert gas, rocarbon character of the Solvent. such as nitrogen or a vaporized fluorinated hy A proportion of the desired fluorination prod drocarbon (usually of low molecular Weight), s ucts themselves may also be employed as fluoro may be enployed as a diluent gas and may be carbon solvents, their use having the advantage passed into the reaction cylinder in admixture that the introduction of foreign materials is with the vaporized hydrocarbon. A slow rotation thereby avoided. The process may be carried out of the cylinder is preferably provided for obviat in cyclic manner, with a part of the product of ing channelling of the bismuth pentafluoride i) each fluorination being returned to the next suc upon the introduction of the gaseous hydro cessive fluorination for use as a fluorocarbon sol carbon. vent therein. The fluorination of bismuth trifluoride to form As in the vapor phase operation, the liquid bismuth pentafluoride is carried out at high tem phase procedure may also be carried out in batch, peratures, of the order of approximately 450° C., intermittent, or continuous operation. Good agi by contacting the bismuth trifluoride with ele tation promotes uniform reaction and prevents mental fluorine. The reaction may be brought local over-heating thus facilitating temperature about in a high pressure autoclave, or, if car control. In batch operation, the gradual addition ried out in a reactor similar to that employed for of the hydrocarbon to a mixture of the solvent the vapor phase fluorination described in the 2 and the bismuth pentafluoride permits a lower preceding paragraph, condensing means are pro ratio of Solvent to total hydrocarbon. This ratio vided for rapid reduction of the temperature of may, in general, vary between about four parts the effluent gases, as bismuth pentafluoride has a of weight of fluorocarbon solvent to one part high sublimation pressure at the temperature of of hydrocarbon and about thirty parts to one. its formation. Cooling means may be provided for maintaining Upon completion of the vapor phase fluorina the temperature below the point where disad tion reaction described, the vaporized fluorocar vantageous formation of scission and fluorinolysis bon and the hydrogen fluoride formed in the re products results. - action are removed from the reaction chamber The following examples are illustrative of the together and are condensed in a cooling chain 30 present invention, but it will be understood that ber. Two liquid phases are formed, and these the invention is not limited thereto: may be separated by settling, decantation and/or centrifugation. Thereafter, each layer may be Eacample. 1 separately purified by fractional distillation or A parafinic oil having an average molecular fractional condensation, or, if desired, the origi- 3: weight of approximately 240 is vaporized, and nal vapors as removed from the reaction cham the vapors passed at a rate of 10 parts/min. into, ber may be fractionally condensed. and through a rotating cylinder containing 4000 The process may be carried out in batch or in parts of bismuth pentafluoride. The contents continuous operation, as well as in an intermit of the cylinder are maintained at a temperature tent operation. Thus, vaporized hydrocarbons of about 225 C., and the effluent gases are passed may be passed into contact with bismuth penta through a water-cooled container where the fluoride in a reaction vessel, which is thereafter product and hydrogen fluoride are condensed. closed and heated to the reaction temperature, The liquid thus formed separates into two lay the products of the reaction being withdrawn ers, the lower of which comprises the large por after a suitable time period. Again, while not 45 tion of the fluorinated oil, containing some hy preferred, the hydrocarbons may be continuously drogen fluoride. The fluorinated product is ob passed through a reaction cylinder of suitable tained in

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