GB713179A - Improvements in or relating to the production of polychloromethanes - Google Patents

Abstract

Polychloromethanes are obtained by passing chlorine in admixture with either vaporized methyl chloride alone or in admixture with vaporized methyl chloride and vaporized methylene chloride and/or vaporized chloroform, the molar ratios of total chloromethanes to chlorine being in the range from 0.9 to 1 to 4.0 to 1 into a reaction zone maintained at from 250 DEG to 390 DEG C., and containing a bed of finely divided inert material, with a linear velocity sufficient to maintain the finely divided inert material in turbulent suspension within the reaction zone, recovering one or more polychloromethanes from the exit gas and returning unrecovered chloromethanes to the reaction. The chloromethanes are recovered by passing the exit gases through a series of fractionation columns, from the first of which methyl chloride and hydrogen chloride are recovered, the methylene chloride, chloroform, carbon tetrachloride and high boilers being recovered from subsequent fractionation columns. After recovering the polychloromethanes it is preferred to react the hydrogen chloride with methanol, without any prior separation of the methyl chloride, to produce quantities of methyl chloride, a portion or the whole of which is then recycled back to the process. A suitable inert solid material is sand of fine particle size, e.g. of size 50 to 150 mesh (British Standard Specification). The reaction vessel may be constructed of nickel, the upper portion of the vessel being much wider than the bottom portion, and the reactor should preferably communicate with a separator from which any small quantity of sand may be returned to the reactor. When a mixture of chlorine, methyl chloride and methylene chloride or of chlorine, methyl chloride, methylene chloride and chloroform are reacted the whole of the recovered methylene chloride, and if desired, additional methylene chloride may be recycled to the process, also when a mixture of methyl chloride, methylene chloride, chloroform, and chlorine or a mixture of methyl chloride, chloroform, and chlorine are reacted, a portion or the whole of the chloroform may be recycled to the process. In examples: (1) a mixture of vaporized methyl chloride and chlorine (molar ratio 1:1) is passed into a reaction vessel containing sand of particle size 50 to 100 mesh maintained at about 350 DEG C. with a velocity sufficient to maintain the sand in turbulent suspension, the reaction products comprise methyl chloride, methylene chloride, chloroform, carbon tetrachloride and a small amount of high boiling material; (2) as in (1) except that the molar ratio is 1.25:1 and the temperature 360 DEG C.; (3) a mixture of methyl chloride, methylene chloride and chlorine is used, the mole ratio of total organics feed/chlorine being 3.2:1 and the reaction temperature being about 380 DEG C.; (4) a mixture of methyl chloride, methylene chloride, chloroform, and chlorine is used, the molar ratio of total organics feed/chlorine being 0.95:1 and the temperature being 370 DEG C.; (5) as in (4) except that the molar ratio is 1.55:1 and the temperature is 378 DEG C.