Core-shell structure driving bimetallic synergy promotes the high-efficiently synergistic catalytic removal of chlorobenzene and NO.
Zhao Liming L, Liu Jing J, Yang Yingju Y, Guan Zelin Z et al.
The development of bifunctional catalysts for the simultaneous removal of chlorobenzene and nitric oxide still remains an extremely challenging objective, owing to the intrinsic trade-off effect between selective catalytic reduction (SCR) and catalytic oxidation. Herein, a strategy to enhance the SCR activity and catalytic degradation ability of chlorobenzene was proposed through boosting the metal-metal interaction in the core-shell structure. The designed SiO2@CoMn2O4 core-shell catalyst with multi-active centers showed excellent synergistic elimination of NO and chlorobenzene at a temperature range of 300-320 °C. While NH3 was found to inhibit chlorobenzene oxidation, chlorobenzene had little effect on the SCR activity of SiO2@CoMn2O4 but had a positive effect on N2 selectivity. The combination of core-shell structure and bimetallic synergy well balances activity and selectivity. SiO2 core significantly enriches surface acid sites and increases the specific surface area, facilitating reactant adsorption and activation. The synergistic effect between Co and Mn ions balances the types of surface oxygen species and increased the amount of lattice oxygen, facilitating NO oxidation activity, adsorption of chlorobenzene and CCl bond cleavage. The simultaneous removal mechanism of NO and chlorobenzene was investigated through in situ diffuse reflectance Fourier transform infrared spectroscopy (DRIFTS) and theoretical calculations. Chlorobenzene undergoes dichlorination to form phenyl group with assistance of the electron-withdrawing property of Lewis acid, which then reacts with reactive oxygen species through electrophilic attack to yield intermediates such as benzoquinone, maleate, and acetate.