New insight into the structure of CeO2–TiO2 mixed oxides and their excellent catalytic performances for 1,2-dichloroethane oxidation

Abstract

A series of CeO2–TiO2 mixed oxides with different Ce/Ti molar ratios were prepared by sol–gel method and evaluated in catalytic oxidation of 1,2-dichloroethane (DCE), as a typical model reactant of chlorinated volatile organic compounds (CVOCs). The CeO2 and TiOx nanoparticles in the mixed oxides are highly dispersed into each other, but there is strong interaction between CeO2 and TiOx, which obviously improves their redox ability, texture and acid properties. The crystallite size of CeO2 is greatly reduced with increasing TiO2 content, and the lattice distortion and lattice defects of CeO2 are increased. CeO2–TiO2 mixed oxides with Ce/Ti>1.0 are composed of c-CeO2 (S.G. Fm-3m, Z=4), titanium suboxides [Ti2O3 (S.G. R-3c) and TiO1.25 (S.G. Fm-3m)] and h-TiO2 (S.G. Pbcn) nanoparticles, while only c-CeO2 and h-TiO2 nanoparticles when Ce/Ti=0.5–0.25. CeO2–TiO2 mixed oxides with Ce/Ti molar ratios of 0.5–0.25 exhibit much higher catalytic activities than pure CeO2 or TiO2, and high selectivity of HCl and COx formations. Moreover, the CeO2–TiO2 mixed oxides also exhibit good durability for DCE oxidation at lower temperature, whether in dry air or in the presence of water and benzene.