GB1046244A - Production of halogenated hydrocarbons - Google Patents

Abstract

Aromatic hydrocarbons are halogenated by passing them with a halogen over an halogenated catalyst prepared by treating an halogenatable inorganic oxide with a compound containing a group <FORM:1046244/C2/1> in which Ha and Ha1 are the same or different halogen atoms. The reaction of the aromatic hydrocarbon with the halogen may be effected in the vapour or liquid phase at - 30-300 DEG C. at atmospheric, reduced or raised pressure and in the presence or absence of an inert gas. Specified hydrocarbons which may be halogenated are benzene, toluene, ethylbenzene, the xylenes, diphenyl, naphthalene, anthracene, phenanthrene and pyrene. The inorganic oxide from which the catalyst is derived may be alumina, boria, silica, titania, zirconia, or ferric oxide. Activated alumina is preferred, but reference is made also to the use of platinum-on-alumina and palladium-on-alumina composites. Before treatment with a halogenated compound of the formula given above, the catalyst is preferably treated with an alkali-metal or an alkaline-earth metal compound under such conditions that some alkali or alkaline-earth metal is retained in the catalyst. Thus, the catalyst may be impregnated with a formate, acetate or oxalate of an alkali or alkaline-earth metal and then calcined. The halogenated compound of the formula above, used for pretreating the catalyst, may have the formula <FORM:1046244/C2/2> in which X and Y may be the same or different and may be hydrogen, chlorine, bromine or fluorine atoms or a group -SCl or may together be an oxygen or sulphur atom. Specified pretreating agents are carbon tetrachloride, chloroform, methylene chloride, dichlorodifluoromethane, trichlorobromomethane, phosgene and thiophosgene. Reference is made also to the use of methylene fluoride, fluoroform and carbon tetrafluoride. The treatment of the catalyst with the halogenated pretreating agent is preferably effected at 300-1100 DEG F. under non-reducing conditions. An example is given of the chlorination of benzene.ALSO:Halogenation catalysts prepared by treating an halogenatable inorganic oxide with a compound containing a group <FORM:1046244/B1-B2/1> in which Ha and Ha1 are the same or different halogen atoms. The inorganic oxide from which the catalyst is derived may be alumina, boria, silica, titania, zirconia or ferric oxide. Activated alumina is preferred, but reference is made also to the use of platinum-on-alumina and palladium-on-alumina composites. Before treatment with a halogenated compound of the formula given above, the catalyst is preferably treated with an alkali-metal or alkaline-earth metal compound under such conditions that some alkali or alkaline-earth metal is retained in the catalyst. Thus, the catalyst may be impregnated with a formate, acetate or oxalate of an alkali of alkaline alkaline-earth metal and then calcined. The halogenated compound of the formula above, used for pretreating the catalyst, may have the formula <FORM:1046244/B1-B2/2> in which X and Y may be the same or different and may be hydrogen, chlorine, bromine or fluorine atoms or a group -SCe or may together be an oxygen or sulphur atom. Specified pretreating agents are carbon tetrachloride, chloroform, methylene chloride, dichlorodifluoromethane, trichlorobromomethane, phosgene and thiophosgene. Reference is made also to the use of methylene fluoride, fluoroform and carbon tetrafluoride. The treatment of the catalyst with the halogenated pretreating agent is preferably effected at 300-1100 DEG F. under non-reducing conditions. An example is given of the chlorination of benzene.