Chlorinated methane

Most of the HCl produced is consumed captively, ie, at the site of production, either in integrated operations such as ethylenedichloride—vinyl chloride monomer (EDC/VCM) plants and chlorinated methane plants or in separate HCl consuming operations at the same location. Captive use of anhydrous HCl accounted for 80—85% of the total demand in 1989. The combined merchant market for anhydrous and aqueous HCl in that same year was about 9.1 X 10 metric tons on the basis of 100% HCl (see Table 12) (73). 

Methyl Chloride. Most of the HCl consumed in the manufacture of methyl chloride [74-87-3] from methanol (qv) is a recycled product. The further reaction of methyl chloride with chlorine to produce higher chlorinated methanes generates significant amounts of HCl which are fed back into methyl chloride production. Another source of recycled HCl is siUcone production based on methyl chloride. 

Methane, chlorine, and recycled chloromethanes are fed to a tubular reactor at a reactor temperature of 490—530°C to yield all four chlorinated methane derivatives (14). Similarly, chlorination of ethane produces ethyl chloride and higher chlorinated ethanes. The process is employed commercially to produce l,l,l-trichloroethane. l,l,l-Trichloroethane is also produced via chlorination of 1,1-dichloroethane with l,l,2-trichloroethane as a coproduct (15). Hexachlorocyclopentadiene is formed by a complex series of chlorination, cyclization, and dechlorination reactions. First, substitutive chlorination of pentanes is carried out by either photochemical or thermal methods to give a product with 6—7 atoms of chlorine per mole of pentane. The polychloropentane product mixed with excess chlorine is then passed through a porous bed of Fuller s earth or silica at 350—500°C to give hexachlorocyclopentadiene. Cyclopentadiene is another possible feedstock for the production of hexachlorocyclopentadiene. 

Thermal chlorination of methane was first put on an industrial scale by Hoechst in Germany in 1923. At that time, high pressure methanol synthesis from hydrogen and carbon monoxide provided a new source of methanol for production of methyl chloride by reaction with hydrogen chloride. Prior to 1914 attempts were made to estabHsh an industrial process for methanol by hydrolysis of methyl chloride obtained by chlorinating methane. 

The most widely used method of analysis for methyl chloride is gas chromatography. A capillary column medium that does a very good job in separating most chlorinated hydrocarbons is methyl siUcone or methyl (5% phenyl) siUcone. The detector of choice is a flame ionisation detector. Typical molar response factors for the chlorinated methanes are methyl chloride, 2.05 methylene chloride, 2.2 chloroform, 2.8 carbon tetrachloride, 3.1, where methane is defined as having a molar response factor of 2.00. Most two-carbon chlorinated hydrocarbons have a molar response factor of about 1.0 on the same basis. 

Chloroform can be manufactured from a number of starting materials. Methane, methyl chloride, or methylene chloride can be further chlorinated to chloroform, or carbon tetrachloride can be reduced, ie, hydrodechlorinated, to chloroform. Methane can be oxychlorinated with HCl and oxygen to form a mixture of chlorinated methanes. Many compounds containing either the acetyl (CH CO) or CH2CH(OH) group yield chloroform on reaction with chlorine and alkali or hypochlorite. Methyl chloride chlorination is now the most common commercial method of producing chloroform. Many years ago chloroform was almost exclusively produced from acetone or ethyl alcohol by reaction with chlorine and alkali. 

Oxychlorination of Hydrocarbons. Methane was oxychlorinated with HCl and oxygen over a 4 3 3 CuCl—CUCI2—KCl molten mixture to give a mixture of chlorinated methanes, 60 mol % of which was carbon tetrachloride (28). Aqueous 20% HCl was used in the multistep process as the source of the acid. Anhydrous HCl is more typically used. Other oxychlorination processes can be made to yield high percentages of carbon tetrachloride starting from any of several hydrocarbon feeds (29—31). The typical reaction temperature is 400—600°C (see Chlorocarbons and chlorohydrocarbons. Methyl cm oRiDE Methylene cphoride and Cphoroform). 

Caibon tetiachloiide, as aie the other chlorinated methanes, is heavily regulated at the national, state, and local level. The manufacturing, storage, and... 

C With chlorinated methanes and ethanes as solvents, the yields vary between 45 and 80% [< /] (equation 51)... 

Jeffers PM, Ward LM, Woytowitch LM, et al. 1989. Homogenous hydrolysis rate constants for selected chlorinated methanes, ethanes, ethenes and propanes. Environmental Science and Technology 23 965-969. 

Klaunig JE, Ruch RJ, Pereira MA. 1986. Carcinogenicity of chlorinated methane and ethane compounds administered in drinking water to mice. Environ Health Perspect 69 89-95. 

The liquid alloy gives mixtures with halocarbons even more shock-sensitive than those with potassium. Highly chlorinated methane derivatives are more reactive than those of ethane, often exploding spontaneously after a delay [1]. Contact of... 

Chlorinated fluorocarbons (CFCs), 21 591 Chlorinated glycolurils, 73 109-110 Chlorinated hydantoins, 13 110 Chlorinated hydrocarbons (CHC) contamination by, 23 111—112 for PVC polymers, 25 674 Chlorinated isocyanurates end use of chlorine, 6 135t as pool sanitizers, 26 175-176 Chlorinated methanes... 

Hatch GG, Mamay PD, Ayer ML, et al. 1983. Chemical enhancement of viral transformation in Syrian hamster embryo cells by gaseous and volatile chlorinated methanes and ethanes. Cancer Res 43 1945-1950. 

Kitchin KT, Brown JE. 1989. Biochemical effects of three carcinogenic chlorinated methanes in rat liver. Teratogen Carcinogen Mutagen 9 61-69. 

Matheson, L.J. and Tratnyek, P.G. Reductive dehalogenation of chlorinated methanes by iron metal. Environ. Sci. TechnoL, 28(12) 2045-2053, 1994. 

TABLE II. Effect of Residual Chlorine on Concentrations of Chlorinated Methanes in Drinking Water at 4°C. 

Most CFCs are manufactured by combining hydrogen fluoride and either carbon tetrachloride or chloroform. The hydrogen fluoride comes from fluorspar, CaF2, reacting with sulfuric acid. The chlorinated methanes are manufactured from methane. Important reactions in the manufacture of CFC-11 and -12 and HCFC-22 are given in Fig. 12.2. 

Bogen KT. 1990. Risk extrapolation for chlorinated methanes as promoters vs initiators of multistage carcinogenesis. Fund AppI Toxicol 15 536-557. 

CEH. 1985. CEH product review. Chlorinated methanes. Chemical Economic Handbook-SRI International, pp 635.2020A to 635.2022B. 

Hughes CS. 1985. Chlorinated methanes. In Chemical economics handbook. Menlo Park, CA SRI International. 

Plaa GL, Larson RE. 1964. Relative nephrotoxic properties of chlorinated methane, ethane and ethylene derivatives in mice. Toxicol AppI Pharmacol 7 37- 44. 

Chlorine or bromine reacts with alkanes in the presence of light (hv) or high temperatures to give alkyl halides. Usually, this method gives mixtures of halogenated compounds containing mono-, di-, tri- and tetra-halides. However, this reaction is an important reaction of alkanes as it is the only way to convert inert alkanes to reactive alkyl halides. The simplest example is the reaction of methane with CI2 to yield a mixture of chlorinated methane derivatives. 

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