GB926291A - Improvements in or relating to processes for producing halogeno-diphenyl-sulphones - Google Patents

Abstract

In a process for producing a polychlorodiphenylsulphone by reacting a chloro-benzene sulphohalide with benzene or a chlorobenzene in the presence of aluminium chloride as condensation-agent, the reactants and the condensation-agent are mixed at the reaction-temperature, or a short time before the mixture is raised to the reaction-temperature, this temperature being so chosen that the reaction is substantially completed within 20 minutes, after which the polychloro-diphenylsulphone is separated from the product. In a batch process, the reactants may be separately brought to the reaction-temperature, and then mixed with efficient agitation; alternatively, the cold reactants may be mixed, and the mixture immediately and rapidly heated to reaction-temperature. But the reaction is preferably carried as a continuous process wherein the sulphohalide and aluminium chloride are mixed at a temperature at which a liquid complex of these components is formed, and this complex is subsequently mixed with the benzene or chlorobenzene. A small proportion of water, added to the liquid complex, improves the yield of sulphone. In Example 1, aluminium chloride (which contains about 1% by weight of ferric chloride) is dissolved in 2,4,5-trichlorobenzenesulphochloride at a temperature between 100 DEG and 110 DEG C. Moist air is then passed through the solution at about 75 DEG C. until about 1% by weight of water, based on the weight of aluminium chloride, has been absorbed. This solution is heated to 115 DEG C. and continuously supplied to a tubular reactor maintained at 115 DEG C., and monochlorobenzene (also at 115 DEG C.) is continuously and separately supplied to the reactor, the rate of addition of the reactants being such that the mixture is in the reactor for about 10 minutes. The mixture is continuously discharged from the reactor, and poured into cold water. The 2,4,5,41-tetrachlorodiphenylsulphone, obtained as a precipitate, is crystallized from ethanol. Examples 3, 4 and 5 relate to the preparation of 2,4,5-trichloro-, 4,41-dichloro-, and 2,5,41-trichlorodiphenylsulphone, respectively. Specification 761,837 is referred to.