Investigation of chlorine-poisoning mechanism of MnOx/TiO2 and MnOx-CeO2/TiO2 catalysts during o-DCBz catalytic decomposition: Experiment and first-principles calculation

Abstract

The catalytic activity and stability of MnOx/TiO2 and MnOx-CeO2/TiO2 catalysts for the oxidative degradation of 1,2-dichorobenzene (o-DCBz) at low temperatures (≤275 °C) were experimentally examined. The chlorine (Cl) poisoning mechanism of the catalysts was also clarified based on the catalyst characterization combined with theoretical calculations. Experimental results show that the MnOx/TiO2 catalyst is considerably deactivated during o-DCBz catalytic decomposition, mainly due to the chlorination of the catalytic active component. Ce addition and high temperature can effectively promote the resistance of MnOx/TiO2 catalyst to Cl poisoning. Density functional theory (DFT) calculations in the framework of first-principles reveal that Cl atom prefers to anchor on surface oxygen vacancy (OV) rather than on top site of Mn atom. The adsorption of Cl atom on surface OV hinders the dissociated adsorption of O2 on surface OV and interrupts the regeneration of the surface reactive oxygen species. The adsorption of Cl atom on top site of Mn atom increases the formation energy of surface OV and damages the surface Lewis acid sites which act as the important adsorption sites for o-DCBz molecules. Ce addition causes Cl atom to adsorb preferentially onto the OV around Ce atom, which weakens the interaction between Cl atom and Mn atom. Consequently, the chlorination of the MnOx species is prevented and the oxygen mobility of the catalyst is guaranteed to some extent.