Patent GB-600296-A (GB)
Title: Improvements in or relating to the preparation of fluorohydrocarbons
IPC: C07C17/08
Filed: 1945-10-22
Abstract: Catalysts for the preparation of vinyl fluorides from hydrogen fluoride and acetylenic compounds having a molecular weight of not more than 85 and of the type R.C­CH, where R is hydrogen or a hydrocarbon radical (see Group IV (b)) comprise carrier supported mercuric acetate, mercuric chloroamide, beta-chloroethenyl mercuric chloride, mercuric phosphate and mercuric sulphide.  Specified carriers include charcoal, magnesium fluoride and alkaline earth metal salts such as are described in Specification 590,381.  Examples describe catalysts prepared (1) by impregnating charcoal with a solution of mercuric acetate in aqueous acetic acid followed by drying on a steam bath under vacuo; (2) by adding excess ammonia to an aqueous suspension of charcoal previously impregnated with mercuric chloride and then filtering off and drying the resulting mercuric chloroamide impregnated charcoal and (3) by impregnating charcoal with a benzene solution of chlorovinyl mercuric chloride.ALSO:Vinyl fluorides are prepared by passing a mixture of hydrogen fluoride and an acetylenic hydrocarbon having a molecular weight of not less than 85 and of the general formula RC­ CH where R is hydrogen or a monovalent hydrocarbon radical, over a catalyst comprising at least one of the salts mercuric acetate, mercuric chloroamide, beta-chloroethenyl mercuric chloride, mercuric phosphate and mercuric sulphide, supported on a carrier, said mixture being passed over the catalyst in the vapour phase under substantially anhydrous conditions and at a temperature within the range 25 DEG  to 250 DEG  C.  Acetylenic hydrocarbons mentioned are acetylene, mono-vinyl acetylene, methyl acetylene. pentene-3-yne-1, hexene-3-yne-1 and 3-methylbutene-3-yne-1; a suitable class of starting materials have the general formula R1CH= CR11C­CH where R1 and R11 may each be hydrogen or a monovalent saturated hydrocarbon radical.  The preferred catalyst carrier is active charcoal but magnesium fluoride and alkaline earth metal salts such as those described in Specification 590,381 may also be used.  Suitable apparatus for the process consists of an iron tube containing the catalyst and immersed in a liquid for controlling the temperature; the issuing gaseous reaction mixture is treated with an absorbent, such as soda-lime to remove hydrogen fluoride, and then is passed through a drier and condensed.  In synthesizing 2-fluorobutadiene-1 : 3 from vinylacetylene and hydrogen fluoride, the reacting gases must not be allowed to mix before entering the reaction vessel; they may be introduced separately via a T-piece at the entry to the reactor or may be mixed over a granular material such as charcoal, and this may be contained in the T-piece.  An inert gas such as nitrogen may be mixed with either reactant.  Examples describe the reaction of hydrogen fluoride and acetylene to yield vinyl fluoride and some 1,1-difluoroethane using as catalysts: (a) mercuric acetate on charcoal prepared by impregnating charcoal with mercuric acetate in aqueous acetic acid solution and drying on a steam-bath in vacuo, (b) mercuric chloramide on charcoal prepared by adding excess ammonia to a suspension of charcoal in aqueous mercuric chloride solution, filtering, washing and then drying and (c) betachloroetheneyl mercuric chloride on charcoal prepared by impregnating charcoal with a benzene solution of chlorovinyl mercuric chloride made by treating a saturated solution of mercuric chloride in aqueous hydrochloric acid with acetylene.  Specifications 469,421 and 580,910 also are referred to.