SUPERCRITICAL WATER OXIDATION REACTION PATHWAY AND KINETICS OF POLYCHLORINATED BIPHENYLS

摘要

Supercritical water oxidation (SCWO) reaction is effective in destruction of polychlorinated biphenyls(PCBs) to mineral products of CO_2, HC1, and H_2O such that 99.95% conversion of Aroclor 1248 is possible in 54.5 seconds residence time at 823 K and 25.3 MPa. Yet to design and operate SCWO reactors to avoid harmful products formation such as polychlorinated dibenzofurans and dioxins, it is necessary to understand the PCB reaction pathway leading to final products. This study shows the dechlorination reaction pathway of 33'44'-Tetrachlorobiphenyl (a surrogate for Aroclor 1248) in methanol solutions. It is suggested that hydrogen species from methanol act as reaction rate enhancers and lead to a series reaction pathway of dechlorination to biphenyl followed by ring-opening oxidation to mineral products. Also, reaction kinetics for this system are presented. These results are of value for reactor design to ensure oxidation of these recalcitrant pollutants in an environmentally safe manner.