Chlorinated volatile organic compound oxidation over SO42−/Fe2O3 catalysts

Abstract

SO42−/Fe2O3 catalysts were prepared by precipitation of FeSO4 and Fe2(SO4)3 and used in catalytic combustion of chlorinated volatile organic compounds (CVOCs). Characterization by XRD, TEM, Raman, FT-IR, XPS, H2 TPR, and NH3 TPD identifies SO42−/Fe2O3 catalysts as the form of hematite α-Fe2O3. Residual SO42− species as chelating or bridged bidentate complexes with Fe3+ ions provide a large amount of acid. SO42−/Fe2O3 catalysts present considerable activity for dichloromethane combustion, which is dependent on both super-strong acidity and surface oxygen. Turnover frequency (based on the mole number of transformed dichloromethane per second per mole super-strong acid) obtained on SO42−/Fe2O3-II reaches 0.0036 s−1 at 200 °C at GHSV of 30,000 h−1. High stability in dry or wet feed is maintained at 330 °C for at least 50 h. Moreover, other CVOCs such as 1,2-dichloroethane, trichloroethylene, chlorobenzene, and 1,2-dichlorobenzene can be oxidized effectively over SO42−/Fe2O3-II. In situ FTIR indicates that CVOCs adsorb onto SO42−/Fe2O3 catalysts mainly through the formation of organic sulfates. Dichloromethane and 1,2-dichloroethane have much higher reactivity toward the SO42− complex than chlorobenzene, and different reaction pathways were related to different types of acid sites.