A comparative study of the catalytic oxidation of chlorobenzene and toluene over Ce-Mn oxides

The morphology effects on the activity and stability of Ce-Mn oxide catalysts for chlorobenzene (CB) and toluene oxidation were compared and investigated in this work. Ce-Mn nano-sheets (CMS), nano-particles (CMP) and nano-rods (CMR) were firstly prepared. The obvious morphology effects on the reactions were observed: the activity for toluene oxidation followed the order of CMS > CMP > CMR. In contrast, the activity for CB oxidation followed the order of CMR > CMP > CMS. For toluene oxidation, toluene adsorption and the CH bond dissociation occurred at lower temperatures on the CMS catalyst. The experimental results demonstrated that the higher content of surface adsorbed oxygen species and oxygen vacancies, as well as the enhanced Olatt species mobility of the CMS catalyst were responsible for its highest catalytic activity. For CB oxidation, inactive planar CB adsorption on the 2D surface of CMS catalyst and the strongly adsorbed Cl species from the CB decomposition resulted in serious deactivation of the catalyst. On the other hand, CB adsorption and the C-Cl bond dissociation occurred at lower temperatures on the CMR catalyst, Cl-contained species can be easily removed during the Deacon Reaction and gas phase oxygen can be adsorbed on the CMR surface to replenish the consumed oxygen, resulting in the improved activity and stability. These results showed that the catalytic performance of Ce-Mn oxides for CB and toluene oxidation was greatly affected by their morphologies.