GB708194A - Improvements in process and apparatus for the production of chloromethanes, particularly methylene chloride and chlorethanes - Google Patents

Abstract

Methylene chloride is continuously produced by maintaining a stirred boiling mixture of methanol, hydrochloric acid and water in an esterifying zone, passing the product of chlorination of methyl chloride in vapour phase through the mixture in the esterifying zone to cause further production of methyl chloride from methanol and the hydrogen chloride present in the chlorination product, supplying fresh methanol to the mixture in the esterifying zone in proportion to the amount of methyl p chloride produced therein, and treating the vapours which are continuously distilled from the esterifying zone for separation of methylene chloride and of methyl chloride, the separated methyl chloride being subjected to vapour phase chlorination to yield a product which is recirculated to the esterifying zone. Fresh methanol supplied to the esterifying zone is preferably passed countercurrent to the vapours issuing from the esterifying zone so as to act as a scrubbing agent. For starting the reaction it is necessary to use hydrogen chloride from an extraneous source, after which hydrogen chloride required for esterifying methanol is supplied continuously from conversion of methyl chloride to methylene chloride. Hydrogen chloride from any source may be used initially but it is preferred to feed hydrogen and chlorine into the zone where the methyl chloride is chlorinated so as to produce hydrogen chloride, cutting off the hydrogen supply as soon as a sufficient amount of methyl chloride has been produced. The chlorination of the methyl chloride is preferably carried out in the presence of a catalyst such as activated carbon. In order to operate the process continuously the water formed during the formation of methyl chloride is removed as soon as it is produced. The process may be adapted for the manufacture of chloroform or carbon tetrachloride. The methyl chloride and methylene chloride are recycled to the chlorinating zone. The process may also be adapted to the production of chloro derivative of ethane from ethanol and chlorine. Other suitable chlorination catalysts which may be used are bone carbon and metal chlorides capable of acting as chlorine exchangers, such as ferric chloride, aluminium chloride, antimony chloride and molybdenum chloride. Esterification catalysts, e.g. sulphuric acid, zinc chloride and magnesium chloride may be used for the esterification reaction.