Facile preparation, catalytic performance and reaction mechanism of Mn x Co 1− x O δ /3DOM-m Ti 0.7 Si 0.2 W 0.1 O y catalysts for the simultaneous removal of soot and NO x

In this work, three-dimensionally ordered macroporous–mesoporous Ti 0.7 Si 0.2 W 0.1 O y (3DOM-m TiSiWO) supported Mn x Co 1− x O δ catalysts with different x values were prepared using the colloidal crystal templating method and incipient wetness impregnation method. The characterization results reveal that the as-prepared catalysts have highly ordered macroporous and mesoporous structures. Among the developed catalysts, the Mn 0.5 Co 0.5 O δ /3DOM-m TiSiWO catalyst exhibits the best catalytic performance for the simultaneous removal of diesel soot and NO x under simulated real conditions owing to its best redox performance, largest number of active oxygen species and acid sites of medium strength, and highest O latt /O ad and TOF values compared to the other Mn x Co 1− x O δ /3DOM-m TiSiWO catalysts. Furthermore, the reaction mechanism of the Mn 0.5 Co 0.5 O δ /3DOM-m TiSiWO catalyst was deduced using in situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS), and the adsorption behaviors of NO, NO 2 and NH 3 on the Mn 0.5 Co 0.5 O δ /3DOM-m TiSiWO catalyst surface were also analyzed using density functional theory (DFT) calculations. The proposed reaction mechanisms indicate that the catalyst follows both the Eley–Rideal (E–R) and Langmuir–Hinshelwood (L–H) schemes for selective catalytic reduction (SCR) at low temperatures. Meanwhile, the combustion of soot at high temperatures is mainly based on the NO 2 -assisted mechanism. More importantly, the role of H 2 O in simultaneous removal of soot and NO x was also studied.