Kinetic studies on pyrolytic and oxidative decomposition of chlorocarbons in a tubular flow reactor

Section I: Thermal decomposition of chloroform in absence and presence of added O{dollar}sb2{dollar} and/or CH{dollar}sb4{dollar}. Chloroform was used as a model chlorocarbon system with high Cl/H ratio to investigate the thermal decomposition processes of chlorocarbons in both oxidative and pyrolytic reaction environments. The reactions were studied in tubular flow reactors at a total pressure of 1 atm with residence times of 0.3-2.0 sec in the temperature range 535-800{dollar}spcirc{dollar}C.; Chloroform decay and product distributions were distinctly different in the absence and presence of added O{dollar}sb2{dollar} and/or CH{dollar}sb4{dollar}. Increases in O{dollar}sb2{dollar} concentration were observed to speed reagent loss, with a slower decay of chloroform observed for the CHCl{dollar}sb3{dollar}/CH{dollar}sb4{dollar}/Ar pyrolysis system.; A detailed kinetic reaction mechanism to describe the important features effecting product formation and reagent loss was developed.; The mechanism includes bimolecular QRRK analysis of the chemically activated adduct formed in recombination reactions of chlorinated hydrocarbon radicals with OH, O, HO{dollar}sb2{dollar}, ClO and from addition reactions with O{dollar}sb2{dollar} to correctly describe the temperature and pressure dependence of plausible reaction pathways. Unimolecular reactions are analyzed with unimolecular QRRK analysis for the proper treatment of fall-off dependencies. Model predictions for loss of reagents and product distributions show good agreement with the experimental observations.; We conclude that the primary decomposition reaction pathway for chloroform is: CHCl{dollar}sb3{dollar} {dollar}to{dollar} HCl +:CCl{dollar}sb2{dollar}.; We also postulate the major pathways for O{dollar}sb2{dollar} interaction with CCl{dollar}sb2{dollar} and CCl{dollar}sb3{dollar} radicals, and present estimates of kinetics and mechanistic pathways for these reactions.; Section II: Thermal decomposition of dichloromethane/1,1,1-trichloroethane mixture diluted in H{dollar}sb2{dollar}. Dichloromethane/1,1,1-trichloroethane mixture was used to investigate pyrolysis reactions and the conversion of chlorocarbons in the presence of excess hydrogen. Profiles for the formation and subsequent loss of intermediates and the formation of final products are presented as functions of both time of reaction at fixed temperature and of temperature at uniform reaction time in tubular flow reactors of three different surface to volume ratios and 1 atm pressure.; A detail kinetic reaction mechanism was developed and used to model results obtained from the experimental reaction system. Model predictions for the loss of the reagents and the formation product distributions show good agreement with the experimental observations. (Abstract shortened with permission of author.)2...