Catalytic combustion of CVOCs over CrxTi1-x oxide catalysts

Abstract

CrxTi1-x oxide catalysts prepared by a sol–gel process were investigated in catalytic combustion of 1,2-dichloroethane, vinyl chloride, chlorobenzene, 1,2-dichlorobenzene, and trichloroethylene. FT-IR spectra on Cr0.1Ti0.9 showed that 1,2-dichloroethane, vinyl chloride, and chlorobenzene adsorbed through the hydrogen bond between TiOH and Cl atoms and then interacted with surface Cr6+=O in Cr2O72− species to form a reactive enolic species, which was further oxidized with surface oxygen. The activity was greatly dependent on Cr6+ as both a strong Lewis acid and reducible sites. TOFCr6+ at 200 °C was 0.59–1.12 × 10−3 s−1. Chlorination products were not observed with the conversion approaching completion below 300 °C. The activity on a stream feed containing 1000 ppm reactants at 245 and 285 °C was maintained for at least 100 h. The formation of Cr-O-Ti effectively inhibited the escape of Cr as Cl2CrO2. It was confirmed by physically closed contact of Cr2O3 and TiO2 that a synergism between Cr6+ and Ti-OH was responsible for the high activity and stability of CrxTi1-x catalysts.