Methyl ethyl carbonate, pyrolysis

Rayon-based ACFs are used in the adsorption of many volatile organic compounds including formaldehyde (80), methyl ethyl ketones (81), and benzene (81). ACFs are also finding uses in natural gas storage (82), electrodes for batteries (83), catalyst supports (84), and NO removal (85). Stabilized rayon fibers are carbonized and then activated with air (80), steam (86), or carbon dioxide (87), much as in granular carbon activation. The extent of pyrolysis governs the pore structure, carbon yield, and surface area of the fiber, while activation impacts the presence of functional groups on the pore surface (12). Properties of some commercial ACFs are summarized in Table 6. 

Chlorinated by-products of ethylene oxychlorination typically include 1,1,2-trichloroethane chloral [75-87-6] (trichloroacetaldehyde) trichloroethylene [7901-6]-, 1,1-dichloroethane cis- and /n j -l,2-dichloroethylenes [156-59-2 and 156-60-5]-, 1,1-dichloroethylene [75-35-4] (vinyhdene chloride) 2-chloroethanol [107-07-3]-, ethyl chloride vinyl chloride mono-, di-, tri-, and tetrachloromethanes (methyl chloride [74-87-3], methylene chloride [75-09-2], chloroform, and carbon tetrachloride [56-23-5])-, and higher boiling compounds. The production of these compounds should be minimized to lower raw material costs, lessen the task of EDC purification, prevent fouling in the pyrolysis reactor, and minimize by-product handling and disposal. Of particular concern is chloral, because it polymerizes in the presence of strong acids. Chloral must be removed to prevent the formation of soflds which can foul and clog operating lines and controls (78). 

By-products from EDC pyrolysis typically include acetjiene, ethylene, methyl chloride, ethyl chloride, 1,3-butadiene, vinylacetylene, benzene, chloroprene, vinyUdene chloride, 1,1-dichloroethane, chloroform, carbon tetrachloride, 1,1,1-trichloroethane [71-55-6] and other chlorinated hydrocarbons (78). Most of these impurities remain with the unconverted EDC, and are subsequendy removed in EDC purification as light and heavy ends. The lightest compounds, ethylene and acetylene, are taken off with the HCl and end up in the oxychlorination reactor feed. The acetylene can be selectively hydrogenated to ethylene. The compounds that have boiling points near that of vinyl chloride, ie, methyl chloride and 1,3-butadiene, will codistiU with the vinyl chloride product. Chlorine or carbon tetrachloride addition to the pyrolysis reactor feed has been used to suppress methyl chloride formation, whereas 1,3-butadiene, which interferes with PVC polymerization, can be removed by treatment with chlorine or HCl, or by selective hydrogenation. 

Taylor in 1925 demonstrated that hydrogen atoms generated by the mercury sensitized photodecomposition of hydrogen gas add to ethylene to form ethyl radicals, which were proposed to react with H2 to give the observed ethane and another hydrogen atom. Evidence that polymerization could occur by free radical reactions was found by Taylor and Jones in 1930, by the observation that ethyl radicals formed by the gas phase pyrolysis of diethylmercury or tetraethyllead initiated the polymerization of ethylene, and this process was extended to the solution phase by Cramer. The mechanism of equation (37) (with participation by a third body) was presented for the reaction, - which is in accord with current views, and the mechanism of equation (38) was shown for disproportionation. Staudinger in 1932 wrote a mechanism for free radical polymerization of styrene,but just as did Rice and Rice (equation 32), showed the radical attack on the most substituted carbon (anti-Markovnikov attack). The correct orientation was shown by Flory in 1937. In 1935, O.K. Rice and Sickman reported that ethylene polymerization was also induced by methyl radicals generated from thermolysis of azomethane. 

This study on the kinetic chlorine isotope effect in ethyl chloride50 was extended to secondary and tertiary alkyl halides pyrolyses51. The isotope effects on isopropyl chloride and terf-butyl chloride pyrolysis were found to be primary and exhibited a definite dependence on temperature. They increased with increasing methyl substitution on the central carbon atom. The pyrolysis results and model calculations implied that all alkyl chlorides involve the same type of activated complex. The C—Cl bond is not completely broken in the activated complex, yet the chlorine participation involves a combination of bending and stretching modes. 

Products obtained by pyrolysis of other polymers is reviewed in Table 4.5. Some specific applications of the chromatography-MS technique to various types of polymers include the following PE [34,35], poly(l-octene) [29], poly(l-decene) [29], poly(l-dodecene) [29], CPE [36], polyolefins [37, 38], acrylic acid-methacrylic acid copolymers [39, 40], polyacrylate [41], nitrile rubber [42], natural rubbers [43, 44], chlorinated natural rubber [45, 46], polychloroprene [47], PVC [48-50], polysilicones [51, 52, 53], polycarbonates [54], styrene-isoprene copolymers [55], substituted olystyrene [56], PP carbonate [57], ethylene-vinyl acetate [58], Nylon 66 [59], polyisopropenyl cyclohexane-a-methyl styrene copolymers [60], cresol-novolac epoxy resins [61], polymeric flame retardants [62], poly(4-N-alkyl styrenes) [63], polyvinyl pyrrolidone [64], polybutyl-cyanoacrylate [65], polysulfides [66], poly(diethyl-2-methacryl-oxy) ethyl phosphate [67, 68], polyetherimide [69], bisphenol-A [70], polybutadiene [71], polyacenaphthalene [72], poly(l-lactide) [73], polyesterimide [74], polyphenylene triazine [75], poly-4-N-vinyl pyridine [76], diglycidylether-bisphenol-A epoxy resins [77], polyvinylidene chloride [78] and poly-p-chloromethyl styrene [79]. 

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