Low temperature decomposition of PCB by TiO2-based V2O5/WO3 catalyst: evaluation of the relevance of PCDF formation and insights into the first step of oxidative destruction of chlorinated aromatics

The reduction of polychlorinated biphenyls (PCB) emissions to the environment are contemporary issues of global efforts. Within this goal, the destruction of PCB is a challenge also for applied catalysis, in particular with respect to the destruction of PCB waste and the off-gas cleaning of incineration facilities. s study, PCB were destroyed on a V2O5/WO3 supported titanium catalyst at low temperature in the range of 150–300°C. At a space velocity of 5000 h−1 more than 98% could be removed. Below 250°C, the higher chlorinated PCB remained partly unchanged on the catalyst for several minutes. In contrast, the oxidation process lasted up to hours at a temperature of 150°C. und 200°C and below a significant part of the PCB were oxidised to the more toxic polychlorinated dibenzofurans (PCDF). The PCDF remained mainly adsorbed on the catalyst. At 250°C, no significant amount of PCDF were detected and at 300°C no byproducts were found. idation of selected individual PCB isomers and the isomer specific analysis of PCDF formed give an insight into the initial step of degradation of chlorinated aromatics on V2O5/WO3-TiO2 catalysts. The results indicated that hydrogen abstraction is the preferred step and an initial abstraction of chlorine is only a minor pathway. This suggests an electrophilic oxygen transfer during the destruction of PCB. the destruction experiments, a slight chlorination of the non-degraded PCB occurred. On the other hand, no measurable dechlorination/hydrogenation was observed.