Simultaneous catalytic removal of NO and chlorobenzene over MnCeSmSnO_x: Catalytic performance and removal mechanism

Mn-based catalysts have great potential in the synergistic removal of NO and chlorobenzene but exhibit serious chlorine poisoning and low catalytic activity at low temperatures. In this study, the performance of MnCeO_x for simultaneous catalytic removal of NO and chlorobenzene at low temperatures was optimized by the modification of Sm and Sn. Results showed that the modification of Sm and Sn afforded a loose overall structure of the catalyst with a large specific surface area. The addition of Sm and Sn effectively increased the concentration of Mn⁴⁺, Ce³⁺, chemisorbed oxygen, and the amount of acid on the catalyst surface. This considerably improved the activity of the catalyst for simultaneous removal of NO and chlorobenzene at low temperatures. The intermediates formed by the MCSS-0.086 catalyst during the low-temperature simultaneous catalytic removal of NO and chlorobenzene were CHCl₃, CCl₄, C₂HCl₃, and C₂Cl₄. The presence of SnO₂ promoted the deep oxidation of chlorobenzene and inhibited the chlorine poisoning of the catalyst. Thus, the low-temperature stability of the catalyst was improved. The chlorobenzene-oxidation efficiency and the NO-removal efficiency of MCSS-0.086 were more than 90% and 95%, respectively, within the range of 178 °C-300 °C. The NH₃-selective catalytic reduction curve of NO removal over the MnCeSmSnO_x catalyst followed the Langmuir–Hinshelwood mechanism at low temperatures. The catalytic degradation of chlorobenzene finally yielded small molecules: CO₂, H₂O, and HCl.