Methane polychlorination

PCBs and PCTs are particularly troublesome liquids because of their toxicity and persistence in the environment. They are defined as polychlorinated biphenyls, polychlorinated terphenyls, monomethyl-dibromo-diphenyl metliane, monomethyl-dichloro-diphenyl metliane or monomethyl-tetrachlorodiphenyl methane. With low electrical conductivity and heat resistance they found wide use as dielectric fluids and were formerly used as hydraulic fluids. PCBs have not been made in the UK since 1977 and whilst most new uses for the substance are banned in most countries, around two-thirds of the 1.5 million tonnes manufactured in Europe and the US prior to 1985 still remain in equipment such as transformers. PCTs have been used in the past in a restricted range of specialist industrial applications. 

Bimetallic nanomaterials such as Pd/Fe, Ni/Fe, and Pd/Au are also active catalysts for the degradation of organic contaminants, including halogenated pesticides, nitroaromatics, polychlorinated biphenyls, and halogenated aliphatics (ethenes and methanes) [151]. 

Neostar A process for destroying waste organic chlorides (e.g., polychlorinated biphenyls) by heating with steam and hydrogen at over 1,000°C. The products are methane, ethane, other chlorine-free hydrocarbons, and hydrochloric acid. Developed by Cerchar, France. 

As a result, free-radical chlorination of alkanes is a nonselective process. Except when only one type of replaceable hydrogen is present (methane, ethane, neopentane, unsubstituted cycloalkanes), all possible monochlorinated isomers are usually formed. Although alkyl chlorides are somewhat less reactive than alkanes, di- and polychlorinations always occur. The presence of a chlorine atom on a carbon atom tends to hinder further substitution at that carbon. The one exception is ethane that yields more 1,1-dichloroethane than 1,2-dichloroethane. The reason for this is that chlorination of an alkyl chloride occurs extremely slowly on the carbon atom adjacent to the one bearing the chlorine atom (vicinal effect).115... 

Anaerobic bioreactors have been used since the 1880s to treat wastewaters with large amounts of suspended solids. However, anaerobic reactors are sensitive to toxic pollutants and vulnerable to process upsets, and have been used mainly for municipal sludge digestion. For methane production the sequential metabolism of the anaerobic consortia must be balanced, and the methanogens in particular are vulnerable to process upsets. Recently, anaerobic-aerobic processes (Figure 1.1) have been developed for the mineralization of xenobiotics. These processes take advantage of an anaerobic reactor for the initial reductive dechlorination of polychlorinated compounds or the reduction of nitro substituents to amino substituents. If the reduced compounds are more readily mineralized in an aerobic reactor, an anaerobic-aerobic process is feasible. 

Polychlorination of methane yields the di-, tri-, and tetrachloromethanes cheaply and efficiently ... 

Other than those listed elsewhere includes chlorophenylphenyl ethers, bromophenylphenyl ethers, bis(dichloroisopropyl) ether, bis(chloroethoxy)methane, and polychlorinated diphenyl ethers. 

As mentioned, the spectrum and amount of impurities formed during oxychlorination is much larger compared with direct chlorination. Some key impurities are listed below 1,1,2-trichloroethane (TCE), chloral (CCl3-CHO), trichloroethylene (TRI), 1,1- and 1,2-dichloroethylenes, ethyl chloride, chloro-methanes (methyl-chloride, methylen-chloride, chloroform), as well as polychlorinated high-boiling components. In particular, chloral needs to be removed immediately after reaction by washing because of its tendency to polymerization. 

Direct oxidation of the lesser chlorinated ethenes, ethanes, polychlorinated benzenes, and chlorobenzene has been reported. Wiedemeier et al. [25] summarize a number of studies that report direct aerobic oxidation of vinyl chloride (VC), 1,2-dichloroethane, the three dichlorobenzene isomers, 1,2,4-trichlorobenzene, and 1,2,4,5-tetrachlorobenzene. Bradley [33] reports that DCE has served as a primary substrate for energy production with oxygen as the electron acceptor, though use of DCE as a sole carbon source has not been demonstrated. Rittmann and McCarty [29] also report that the two least chlorinated methanes (dichloromethane and chloromethane) as well as chloroethane can be directly oxidized under aerobic conditions. Direct oxidation of the chlorinated compounds is typically modeled using either first-order or Monod kinetics [29,31]. 

Thousands of papers and patents have appeared on the direct synthesis of organochlorosilanes since 1940 when Rochow reported the direct reaction.4 These results are comprehensively accounted for in a number of earlier reviews and books.3 8 The purpose of this review is to describe the recent developing trend of the direct reaction of elemental silicon with activated or unactivated alkyl chlorides, in particular, emphasizing direct reactions with a mixture of hydrogen chloride and activated alkyl chlorides such as polychlorinated methanes, silylmethyl chlorides and dichlorides, allyl chloride, etc. 

As shown in Fig. 6, some of the reduction reactions, including intermediate steps, for the destruction of a variety of contaminants using the gas-phase chemical reduction process. The process primarily involves the gas-phase reduction of organic compounds by hydrogen at temperatures of 850°C or higher. Chlorinated hydrocarbons, such as PCBs and polychlorinated dibenzo-p-dioxins (dioxins), are chemically reduced to methane and... 

The conversion of methane to chloromethane has been observed under various reaction conditions. The data at constant temperature and pressure, summarized in Table I, display several trends. Note that methane conversion and polychlorination both decrease with space velocity. The production of... 

To determine the tolerance of ZSM-5 to the presence of polychlorinated methanes, mixtures of mono- and dichloromethane were reacted over ZSM-5. Feed streams containing a molar ratio of 2.75 1 mono- to dichloromethane reacted over ZSM-5, and coking of the catalyst was no greater than that experienced for either chloromethane alone or methanol. As expected, the product mixture contained a larger aromatic fraction than the product from chloromethane oligomerization. 

Because oxygen, carbon dioxide, methane, and other alkanes are completely miscible with dense supercritical water, combustion can occur in this fluid phase. Both flameless oxidation and flaming combustion can take place. This leads to an important application in the treatment of organic hazardous wastes. Nonpolar organic wastes such as polychlorinated biphenyls (PCBs) are miscible in all proportions in supercritical water and, in the presence of an oxidizer, react to produce primarily carbon dioxide, water, chloride salts, and other small molecules. The products can be selectively removed from solution by dropping the pressure or by cooling. Oxidation in supercritical water can transform more than 99.9 percent of hazardous organic materials into environmentally acceptable forms in just a few minutes. A supercritical water reactor is a closed system that has no emissions into the atmosphere, which is different from an incinerator. 

Haloethers [chlorophenylphenyl ether, bro-mophenylphenyl ether, bis(dichloroisopro-pyl)ether, bis(chloroethoxy)methane, and polychlorinated diphenyl ethers] Halomethanes (methylene chloride, methyl chloride, methyl bromide, bromoform, di-chlorobromomethane, trichlorofluorometh-ane, and dichlorodifluoromethane) Heptachlor and metabolites Hexachlorobutadiene Hexachlorocyclohexane (all isomers) Hexachlorocyclopentadiene Isophorone Naphthalene Nitrobenzene... 

Regioselective chlorocarbonylation with oxalyl chloride and AICI3 in dichloro-methane at 15 °C of polybenzyl cores 1269 resulting from the CpFe+-induced oc-tabenzylation of durene has been reported [953]. Reaction of the resulting polychlorinated cores with amines and alcohol nucleophiles has opened new rapid synthetic routes toward dendritic materials. 

Watanabe, M., Kannan, K., Takahashi, A., Loganathan, B.G., Odell, D. K., Tanabe, S., and Giesy, J.P. (2000) Polychlorinated biphenyls, organochlorine pesticides, tris(4-chlorophenyl)methane and tris(4-chlorophenyl)methanol in livers of small cetaceans stranded along Florida coastal waters, USA. Environ. Toxicol. Chem., 19, 1566-1574. 

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