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Chlorine removal kinetics

Susa et al. [66] have investigated the kinetics of chlorine removal and the effects of sample size and structure on the extent of removal. They conclude that the residual chlorine content decreases exponentially with time, indicating first-order kinetics. There are apparently two oxidation reactions involved with activation energies of 113 and 138kJ/mol, compared to 473 kJ/mol for gas-phase oxidation of SiCl4 at 1000 to 1230°C. In regions of incomplete chlorination, Cl may also be removed according to the condensation reaction ... [Pg.328]

The stoichiometric relationship between chlorine dioxide added and color removed during bleaching is nonlinear, but it is independent of temperature, pH, and pulp concentration under conditions normally used. Models used to explain the kinetics and stoichiometry show a strong dependence on chromophore concentration that probably results from differences in the reaction rates of the various chromophores present in the pulps (80). [Pg.484]

Our 13C NMR analysis (2) of the E-V copolymers obtained via the (n-Bu)3SnH reduction of PVC led to k /kr=1.31 0.1 in excellent agreement with the kinetics observed for the removal of chlorines from m- and r-DCP. We also found no W diads in those E-V copolymers made by removing more than 80% of the chlorines from PVC. This observation is confirmed in the (n-Bu)3SnH reduction of DCP where the chlorines in this PVC diad model compound were found to be 4 times easier to remove than the isolated chlorines in 2-chloropentane, 2-, and 4-chlorooctane. [Pg.366]

Chloroff A process for removing chlorine from organic chlorides such as polychlorinated biphenyls by reaction with hydrogen under pressure, over a proprietary catalyst. Developed by Kinetics Technology International. See also Hi-ChlorofiF. [Pg.64]

Relube A process for removing sulfur and chlorine compounds from waste oils, particularly those contaminated by polychlorinated biphenyls. Developed by Kinetics Technology International, The Netherlands, and operated first in Greece. [Pg.226]

The effect of the ratio of H202 to Fe2+ on oxidation kinetics, the oxidation kinetics of THM mixtures, and the effect of the number of chlorine atoms in a THM on its oxidation were all investigated. Bromoform is the easiest to oxidize of the four THMs. Bromoform concentrations used in the study of Fenton s reagent ratio and oxidation kinetics were 49.2, 98.3, and 295 pg/L. As the ratio of H202 to Fe2+ increases, the removal efficiency increases with... [Pg.204]

Kinetic studies of the substitution reaction of 2-chloro-l-methylpyridinium iodide with phenoxides are consistent with the SnAt mechanism, with rate-determining nucleophilic attack.38 The effects of a variety of ring substituents on the reactivities of 2-fluoro- and 2-chloro-pyridines in reactions with sodium ethoxide in ethanol have been examined. The results were discussed in terms of the combination of steric, inductive, and repulsive interactions.39 Substitution in 2,4,6-trihalopyridines normally occurs preferentially at the 4-position. However, the presence of a trialkylsilyl group at the 3-position has been shown to suppress reaction at adjacent positions, allowing substitution at the 6-position.40 Methods have been reported for the introduction and removal of fluorine atoms for polyfluoropyridines. Additional fluorine atoms were introduced by metallation, chlorination, and then fluorodechlorination, while selective removal of fluorine was achieved by reduction with either metals or complex hydrides or alternatively by substitution by hydrazine followed by dehydrogena-tion-dediazotization.41... [Pg.159]

Beurskens et al. (1995) reported that an anaerobic microbial consortium enriched from Rhine River sediments was able to remove chlorine substituents from CDDs. A model CDD, 1,2,3,4-TCDD, was reductively dechlorinated to both 1,2,3- and 1,2,4-TrCDD. These TrCDD compounds were further dechlorinated to 1,3- and 2,3- DCDD and trace amounts of 2-MCDD. The TrCDD compounds were detected at low concentrations, but the 1,3- and 2,3- DCDD were detected at higher concentrations. The anaerobic culture dechlorinates 1,2,3,4-TCDD at a relatively rapid rate with a half-life value estimated at 15.5 days (first-order kinetics). The formation of metabolites with a conserved 2,3-substitution pattern from 1,2,3,4-TCDD indicates that dechlorination of highly chlorinated CDDs may result in metabolites that are potentially more toxic than the parent compounds. [Pg.455]

The synthesis of noncovalent hydrogen-bonded aggregates can often be accomplished simply by mixing the components in the correct molar ratio in an appropriate solvent (usually chlorinated hydrocarbons such as chloroform). In some cases, one of the components (usually the cyanuric acids) may be poorly soluble in chloroform in these cases it may be useful to dissolve the components in a more polar solvent or solvent mixture (e.g. chloroform-methanol), then remove this solvent and redissolve the residue in chloroform. This procedure can overcome kinetic limitations to formation of aggregates associated with solubilities. [Pg.8]

Vurzel and Polak (55) carried out extensive kinetic studies of the reduction of silicon tetrachloride to silicon in plasma devices. They first decomposed SiCl4 to SiCls in an adiabatic compression-expansion device and then completed the reduction in an RF plasma. They claimed that the decomposition of SiCl4 to silicon proceeded by a two-stage mechanism of chlorine atom removal ... [Pg.94]

Figure 12, Kinetics of hydrogen removal at different methods of degassing of an AL9 grade alloy melt. (1) Chlorine salts (2) Vacuum treatment (3) UST (4) UST in vacuum. Figure 12, Kinetics of hydrogen removal at different methods of degassing of an AL9 grade alloy melt. (1) Chlorine salts (2) Vacuum treatment (3) UST (4) UST in vacuum.
Removal of dissolved inorganic impurities from methanol Is of Interest from the point of view of utilization of methanol as an alternative to conventional fuels. Reports show that the corrosion rate of metal alloys used for turbines and fuel transportation is greater in methanol than in water in the presence of traces of chlorine and sodium ions ( , 10). Further, ion complexes in trace quantities have been observed in methanol and there is concern that they could alter the reaction kinetics for processes which use methanol as a feedstock or reaction medium (11). Methanol that Is used as a feedstock In the production of single cell protein could be sterilized as well as purified of heavy metals by reverse osmosis which can be integrated in the design of these processes. [Pg.339]

Figure 16.2 A 180 ° magnetic deflection spectrograph with a velocity filter. The filter eliminates the problem due to the quasi impossibility of having homogeneous and mono-kinetic beams. The diagram represents a sort of photographic recording of the spectrum of neon. The two series of broken lines represent the removal of one or two of the electrons from the different isotopes of elemental neon. The symbol - - signifies that the ion is both a radical (i.e. has an unpaired number of electrons) and a cation. J.J. Thomson, who around 1913 proved the existence of the isotopes of neon, is considered as the father of this kind of assembly. Later, work performed by F.W. Aston showed the existence of the isotopes of sulphur and chlorine. Figure 16.2 A 180 ° magnetic deflection spectrograph with a velocity filter. The filter eliminates the problem due to the quasi impossibility of having homogeneous and mono-kinetic beams. The diagram represents a sort of photographic recording of the spectrum of neon. The two series of broken lines represent the removal of one or two of the electrons from the different isotopes of elemental neon. The symbol - - signifies that the ion is both a radical (i.e. has an unpaired number of electrons) and a cation. J.J. Thomson, who around 1913 proved the existence of the isotopes of neon, is considered as the father of this kind of assembly. Later, work performed by F.W. Aston showed the existence of the isotopes of sulphur and chlorine.
The kinetics of the reactions of many xenobiotics with hydroxyl and nitrate radicals have been examined under simulated atmospheric conditions and include (1) aliphatic and aromatic hydrocarbons (Tuazon et al. 1986) and substituted monocyclic aromatic compounds (Atkinson et al. 1987c) (2) terpenes (Atkinson et al. 1985a) (3) amines (Atkinson et al. 1987a) (4) heterocyclic compounds (Atkinson et al. 1985b) and (5) chlorinated aromatic hydrocarbons (Kwok et al. 1995). For PCBs (Anderson and Hites 1996), rate constants were highly dependent on the number of chlorine atoms, and calculated atmospheric lifetimes varied from 2 days for 3-chlorobiphenyl to 34 days for 2,2, 3,5, 6-pentachlorbiphenyl. It was estimated that loss by hydroxylation in the atmosphere was a primary process for removal of PCBs from the environment. It was later shown that the products were chlorinated benzoic acids produced by initial reaction with a... [Pg.236]


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See also in sourсe #XX -- [ Pg.640 ]




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