GB589167A - Improvements in or relating to the production of fluorinated derivatives of aliphatic hydrocarbons - Google Patents

Abstract

Antimony halo-fluorides, used as fluorinating agents in reaction with halogenated aliphatic hydrocarbons to yield hydrocarbon having three fluorine atoms attached to one carbon atom (see Group IV), are prepared by reacting anhydrous hydrogen fluoride with an antimony pentahalide not containing fluorine, the amount of hydrogen fluoride present being at least equivalent to that required to convert the whole of the pentahalide to the pentafluoride. The compounds have a composition represented by the general formula SbFn x5-n + (5-n) HF where X is a halogen other than fluorine and n, which is an integer not less than 3, represents the number of halogen atoms replaced by fluorine. Preferably, the process is carried out in a closed vessel at temperatures rising to 125 DEG C. or higher under the corresponding antogenic pressures. In example (1), 600 parts by weight of antimony pentachloride and 200 parts of anhydrous hydrogen fluoride are heated in an autoclave for four hours, the temperature and pressure being 130 DEG C. and 900-1,000 lbs. yielding a compound of the composition SbF3Cl2.2HF.ALSO:Fluorinated aliphatic hydrocarbons or halohydrocarbons, in which three fluorine atoms are attached to one carbon atom and which may or may not contain further fluorine atoms attached to other carbon atoms and other halogens, are prepared by reacting in a closed vessel, a halogenated aliphatic hydrocarbon containing at least three halogen atoms in the molecule and having three halogen atoms, at least one of which is a halogen other than fluorine attached to one carbon atom, at a temperature of at least 30 DEG C. and at the corresponding autogenic pressure, with a fluorinating agent obtained by reacting anhydrous hydrogen fluoride with an antimony pentahalide not containing fluorine, the amount of hydrogen fluoride present being at least equivalent to that required to convert the whole of the antimony pentahalide to the pentafluoride; the fluorinating agent has the composition SbFnX5-n+(5 - n)HF, where X is halogen other than fluorine and n, an integer not less than 3, is the number of atoms of halogen in the original pentahalide replaced by fluorine. Preferably, an antimony pentahalide containing halogen other than fluorine is reacted in an autoclave with anhydrous hydrogen fluoride in an amount equivalent to at least 5 moles per mole. of pentahalide at a temperature of at least 125 DEG C., suitably 150 DEG C., then the autoclave is vented to remove hydrogen chloride liberated in the reaction and the material to be fluorinated, say dichloro difluoromethane, is charged into the autoclave which is again heated to about 160 DEG C. The autoclave is cooled, excess pressure released and the gaseous reaction products scrubbed to remove traces of acid. The spent fluorinating agent may be regenerated by adding thereto an amount of anhydrous hydrogen fluoride equivalent to that consumed in the previous fluorination and then heating as described above. In this manner alternate regenerations and fluorinations may be carried out or the two operations may be combined. Accordingly, a continuous process may be effected by adding hydrogen fluoride and halohydrocarbon continuously while withdrawing the fluorinated product. In examples: (1) monochlorotrifluoromethane was prepared by reaction of dichloro-difluoromethane and a fluorinating agent of the composition SbF3Cl2.2HF prepared from 600 parts antimony pentachloride and 200 parts anhydrous hydrogen fluoride (see Group III); further batches were prepared by reacting the spent fluorinating agent with a mixture of additional halomethane and an amount of hydrogen fluoride equal to that used in the previous operation or by first regenerating the fluorinating agent and then reacting it with more halomethane; (3) fluoroform was prepared by reacting chloroform with the fluorinating agent described in (1), further batches being prepared by adding chloroform and hydrogen fluoride to the spent agent; (4) fluoroform was prepared as in (2) from monochlorodifluoromethane and hydrogen fluoride, using a spent fluorinating agent prepared as in (1); (5) 1,1,1-trifluoro-2-chloroethane was prepared as in (2) from 1,1-difluoro-1,2-dichloroethane, using as fluorinating agent the product obtained from 600 parts antimony pentachloride and 240 parts hydrogen fluoride. By the process described, methyl chloroform may be converted to methyl fluoroform and carbon tetrachloride to monochlorotrifluoromethane. The trifluoromethanes are useful as refrigerants. Specification 391,168 and U.S.A. Specifications 2,005,705, 2,005,710, 2,024,095, 2,062,743 and 2,230,925 are referred to.