Inhibition mechanism of chlorobenzene on NH3-SCR side reactions over MnOx-CeO2 confined titania nanotubes

Abstract

The influence mechanism of CB on SCR side reactions including nonselective catalytic reduction (NSCR) and NH3 peroxidation is still a major challenge of current research. The inhibition mechanism was identified qualitatively and quantitatively on MnOx-CeO2 confined titania nanotubes catalyst with good co-remove efficiency. We decoupled NSCR into L-H and E-R mechanism routes and each mechanism were further decomposed into adsorption and reaction steps for the first time. It revealed that CB preferred to inhibit L-H mechanism (99%) and adsorption step (53.5% in E-R and 98% in L-H) in NSCR.CB dominated the inhibition of L-H mechanism and adsorption steps. As for NH3 peroxidation, N2O, NO and NO2 are produced with the increase of oxygen activity. After 240 °C, the inhibition of CB on N2O weakens and starts to inhibit NO and NO2 instead. It can be attributed that CB competitively reacts with higher active oxygen, weakening the oxidization of NH3 to NO/NO2. The inhibition mechanism is that the active oxygen is continuously consumed in CB oxidation process, and the dissociated Cl produced by nucleophilic substitution limits the supplement of the lattice oxygen, finally resulting in the reduction of high valence active centers and the loss of active oxygen.