Catalytic oxidation of hexachlorobenzene in simulated gas on V2O5-WO3/TiO2 catalyst

Hexachlorobenzene (HCB) is one of priority unintentionally produced persistent organic pollutants (UPOPs) listed in Stockholm Convention. In this study. V2O5-WO3/TiO2 catalyst was used to oxidize vapor phase hexachlorobenzene (HCB). It is found that the HCB oxidation efficiency is positively correlated with temperature and oxygen concentration while negatively correlated with gas hourly space velocity (GHSV) and water vapor content. The catalytic oxidation kinetics of HCB could be well fitted by the power rate law model, and the partial reaction orders and activation energy were obtained. The role of lattice oxygen was investigated with the aid of oxygen on-off experiment and XPS analysis. The intermediates from oxidation of HCB were detected by the stationary experiment conducted in glass ampule and conformed by off gas analysis. Desorption of chlorinated intermediates from catalyst surface to gas phase was observed at high GHSV (60,000 h(-1)) but could be minimized at high temperature and low GHSV. The electrophilic attack of oxygen on benzene structure followed by ring-cracking and oxygen insertion is the possible oxidation mechanism. (C) 2012 Elsevier B.V. All rights reserved.