https://www.sciencedirect.com/science/article/pii/S0021951720303183

Highlights

• •There exists Cr-O-Ti, Cr2O72- and (-(O=)2Cr-O-)n in CrxTi1-x prepared by sol-gel way.

• •The incorporation of Cr into TiO2 promotes strong acidity and reducibility.

• •CrxTi1-x is highly active in the oxidation of chlorinated alkane, alkene and benzene.

• •There is a synergism between Cr6+=O and Ti-OH during the oxidation.

• •Chlorination is inhibited over CrxTi1-x at the conversion of 90% or higher.

Abstract

CrxTi1-x oxide catalysts prepared by sol-gel way 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 hydrogen bond between Ti-OH and Cl atom and then interacted with surface Cr6+=O in Cr2O72- species to form reactive enolic species, which was further oxidized with surface oxygen. The activity was greatly depending on Cr6+ as both strong Lewis acid and reducible sites. TOFCr6+ at 200 oC was 0.59–1.12×10-3 s-1. Any chlorination products were not observed with the conversion approaching complete below 300 oC. The activity on stream feed containing 1000 ppm reactants at 245 and 285 oC 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 high activity and stability of CrxTi1-x catalysts.