Organic compounds -- part of the class 532-570 series – Organic compounds – Halogen containing
Patent
1999-09-10
2000-10-03
Siegel, Alan
Organic compounds -- part of the class 532-570 series
Organic compounds
Halogen containing
570134, 570167, 570169, C07C 1708, C07C 1908
Patent
active
061275875
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to a chlorofluorohydrocarbon and to a novel process for its preparation. More particularly it relates to 1,1-difluoro-1,4-dichlorobutane and a process for preparing it from the known compounds 1,1,1,4-tetrachlorobutane or 1,1,4-trichlorobut-1-ene.
Accordingly the present invention provides a process for preparing 1,1-difluoro-1,4-dichlorobutane comprising reacting 1,1,1,4-tetrachlorobutane or 1,1,4-trichlorobut-1-ene with hydrogen fluoride in the vapour phase.
The process of the present invention when 1,1,1,4-tetrachlorobutane is used is illustrated by the following reaction scheme: ##STR1##
The reaction is conveniently conducted by passing a stream comprising a mixture of the reactants through a heated reaction zone, preferably defined by a tubular vessel whose lining is resistant to corrosion by chemical reaction with hydrogen fluoride, such as for example, one made from "Hastalloy" (Registered Trade Mark) or Monel metal.
The reaction can conveniently be carried out in the presence of a catalyst such as a polyvalent metal halide. Examples of polyvalent metal halides include halides of aluminium, iron, chromium, vanadium, tungsten, tantalum, antimony, titanium, tin, zirconium, nickel, niobium, molybdenum and mercury. Examples of specific catalysts include ferric chloride, particularly in the presence of activated charcoal, aluminium fluoride, aluminium oxide (.gamma.-alumina), chromium halides such as chromium chloride and chromium fluoride, manganese difluoride, ferric fluoride, cobalt dichloride, nickel difluoride, zirconium fluoride, thorium fluoride, oxyfluorides and antimony pentachloride, particularly in the presence of activated charcoal.
Chromium halides are preferred catalysts and a particularly useful catalyst is chromium (III) chloride. The catalyst may be supported on alumina, preferably one which has been pretreated by treatment with a fluorinating agent such as sulfur tetrafluoride, so as to convert it, at least in part, to aluminium trifluoride.
The reaction temperature is preferably within the range 100 to 400.degree. C., and more preferably within the range 135 to 250.degree. C. The reaction may be conducted under atmospheric pressure or at a pressure above atmospheric pressure, provided that the combination of pressure and temperature is chosen so as to ensure that the reactants and products remain in the vapour phase. The conversion rate is also dependent on various factors such as the residence time in the reaction zone, the ratios of the reactants and the concentration of the reactants as well as the presence of other components of the vapour stream. Preferably the stream contains an inert gaseous diluent to moderate the reaction. Nitrogen is a suitable diluent for this purpose. The reactants and other components of the vapour stream should be free of any water.
The reaction is preferably carried out by passing a gaseous mixture of hydrogen fluoride (which is a volatile material having a boiling point under normal atmospheric pressure of 19.5.degree. C.) together with 1,1,1,4-tetrachlorobutane (or 1,1,4-trichlorobut-1-ene) at an elevated temperature diluted with nitrogen through a reaction zone defined by a metal tube heated to a temperature within the range 130 to 250.degree. C., and thereafter cooling the reactant stream so as to condense out the mixture of reactants and products, which can then be separated by fractional distillation. In a preferred variant of this process a receiving vessel can be used which is equipped with means to permit the hydrogen chloride produced during the reaction to be vented, preferably continuously. This may be achieved by the use of a condenser which liquifies the hydrogen fluoride and the other less volatile components whilst permitting the escape of the more volatile hydrogen chloride gas.
The product mixture consists of the desired 1,1-difluoro-1,4-dichlorobutane, together with unreacted starting material and intermediate species formed during the process. Isolation of the desired product can be achieved readily by fr
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LeCroy David P.
Siegel Alan
Zeneca Limited
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