Thermal Decomposition Of Trichloroethylene Under A Reducing Atmosphere Of Hydrogen

摘要

The thermal reaction of trichloroethylene (TCE: C_2HCl_3) has been conducted in an isothermal tubular flow reactor at 1 arm total pressure in order to investigate characteristics of chlorinated hydrocarbons decomposition and pyrolytic reaction pathways for formation of product under excess hydrogen reaction environment. The reactions were studied over the temperature range 650 to 900 ℃ with reaction times of 0.3-2.0 s. A constant feed molar ratio C_2HCl_3: H_2 of 4 : 96 was maintained through the whole experiments. Complete decay (99%) of the parent reagent, C_2HCl_3 was observed at temperature near 800 ℃ with 1 s reaction time. The maximum concentration (28%) of C_2H_2Cl_2 as the primary intermediate product was found at temperature 700 ℃ where up to 68% decay of C_2HCl_3 occurred. The C_2H_3Cl as highest concentration (19%) of secondary products was detected at 750 ℃. The one less chlorinated methane than parent increased with temperature rise subsequently. The number of qualitative and qualitative chlorinated products decreased with increasing temperature. HCl and dechlorinated hydrocarbons such as C_2H_4, C_2H_6, CH_4 and C_2H_2 were the final products at above 800 ℃. The almost 95% carbon material balance was given over a wide range of temperatures, and trace amounts of C_6H_6, C_4H_6 and C_2HCl were observed above 800 ℃. The decay of reactant, C_2HCl_3 and the hydrodechlorination of intermediate products, resulted from H atom cyclic chain reaction via abstraction and addition replacement reactions. The important pyrolytic reaction pathways to describe the important features of reagent decay, intermediate product distributions and carbon mass balances, based upon thermochemical and kinetic principles, were suggested. The main reaction pathways for formation of major products along with preliminary activation energies and rate constants were given.