The highly chlorinated methanes, e.g., carbon tetrachloride, are improvedly dechlorinated by reacting same with hydrogen in the presence of oxygen or an oxygen-containing gas, e.g., air, and a catalytically effective amount of a metal of the copper or precious metal Groups of the Periodic Table, typically in the form of a fixed or fluidized bed thereof, and advantageously in the gaseous phase.
A process for the manufacture of chloroform by catalytic hydrogenolysis of carbon tetrachloride in liquid phase, wherein liquid phase carbon tetrachloride is reacted with hydrogen gas or a gas containing molecular hydrogen, at a pressure below 8,000 kPa and at a temperature below 250.degree. C., in the presence of a catalyst formed by a metal selected from the group consisting of palladium, rhodium, ruthenium and platinum, deposited on a substrate and held in suspension in the liquid.
The present invention relates to a method for producing a hydrogen-containing chloromethane such as chloroform at high selectivity in good yield by reducing a polychloromethane such as carbon tetrachloride in the presence of a reduction catalyst. In the present invention, it is important to conduct the reduction reaction in a liquid phase, whereby formation of impurities such as polymers which deactivate the catalyst, can effectively be suppressed, and the high selectivity and high activity of the reduction catalyst can adequately be obtained. As the reduction catalyst, at least one member selected from elements of Groups 8, 9 and 10, such as ruthenium, rhodium, palladium and platinum, may suitably be employed. Also a catalyst comprising, as the main component, such an element and having at least one member of Group 11 elements such as copper, silver and gold added thereto, may also suitably be employed. In a case where the liquid phase reduction reaction is conducted continuously, it is preferred to adopt a fixed bed system, particularly a trickle bed system. The method of the present invention is valuable also as a method for converting carbon tetrachloride which is regulated from the standpoint of global environmental protection, to chloroform which is useful as raw material for various fluorine-containing compounds.
Chloromethane compounds including carbon tetrachloride and the chlorofluoromethane compounds, such as dichlorodifluoromethane, can be catalytically hydrodechlorinated, e.g., in the case of dichlorodifluoromethane to monochlorodifluoromethane and/or difluoromethane, by treatment with hydrogen in the presence of a transition metal carbide catalyst, for example, a Group IVB metal carbide, such as tungsten carbide, supported on an oxidic support, such as alumina, optionally with a passivating layer of ceramic, such as silicon carbide, between the oxidic support and catalyst. The catalyst preferably has a surface area of no less than about 1 m.sup.2 /gm.
Halocarbons such as CCl.sub.2 F.sub.2, CF.sub.3 CFHCl or CF.sub.3 CFCl.sub.2 which contain chlorine and/or bromine are contacted with hydrogen in the presence of silicon carbide and/or a metal selected from aluminum, molybdenum, titanium, nickel, iron or cobalt (or their alloys) at temperatures of 350.degree. to 700.degree. C. and pressures of 0 to 1000 psig to obtain a product wherein at least one chlorine or bromine in the starting material has been replaced by hydrogen.
