GB445288A - Improvements in or relating to the dehalogenation of organic halogen derivatives - Google Patents

Abstract

Halogenated hydrocarbons are dehalogenated (i.e. halogen is replaced by hydrogen) by treating them in the vapour phase with hydrogen in the presence of a sulphide of a metal of the sixth periodic group or a mixture of such sulphides. The reaction is effected at a raised temperature, preferably 200--600 DEG C., and at atmospheric or raised pressure. Mono- or poly-halogenated aliphatic or aromatic hydrocarbons may be treated. A large excess of hydrogen is preferably used. Sulphides of chromium, molybdenum, tungsten and uranium or mixtures thereof are the preferred catalysts; they may be prepared by treating the corresponding oxides with hydrogen sulphide at a raised temperature, or by treating solutions of the hydrated oxides with hydrogen sulphide, or by passing hydrogen sulphide into solutions of chromates, tungstates, molybdates or uranates and acidifying the products. The process may be applied in the purification of hydrocarbons containing halogenated hydrocarbons as impurities. In the examples: (1) chlorobenzene and hydrogen are passed over a catalyst prepared by treating an aqueous or aqueous ammoniacal solution of ammonium molybdate with hydrogen sulphide and treating the product with sulphuric acid; benzene is obtained; (2) chlorobenzene and hydrogen are passed over a catalyst prepared by treating a solution of ammonium molybdate and ammonium bichromate with hydrogen sulphide, and treating the product with nitric acid; benzene is again obtained; (3) chlorotoluene and hydrogen are passed over a catalyst prepared as in example 1, toluene being obtained; (4) benzene recovered from a chlorination process is purified by passing it with hydrogen over the catalyst of example 2; (5) propyl chloride and hydrogen are passed over the catalyst of example 2, propane being obtained; (6) mixed propyl and butyl bromides are passed with hydrogen over the catalyst of example 2, a mixture of propane and butane being obtained. Reference is made to the deiodination of iodinated hydrocarbons, and to the dehalogenation of aromatic hydrocarbons halogenated in a side chain.ALSO:Sulphides of chromium, molybdenum, tungsten and uranium or mixtures thereof are prepared by treating the corresponding oxides with hydrogen sulphide at a raised temperature, or by treating solutions of the hydrated oxides with hydrogen sulphide, or by passing hydrogen sulphide into solutions of chromates, tungstates, molybdates or uranates and acidifying the products. In the examples: (1) an aqueous or aqueous ammoniacal solution of ammonium molybdate is treated with hydrogen sulphide and the product is treated with sulphuric acid; (2) a solution of ammonium molybdate and ammonium bichromate is treated with hydrogen sulphide, and the product is treated with nitric acid.