Mechanistic insight into the selective catalytic reduction of NOx with propene on the Ce0.875Zr0.125O2 (110) surface

摘要

Selective catalytic reduction of NOx with hydrocarbons (HC-SCR) is a promising technology for the abatement of NOx from vehicles. The reaction mechanism is mainly investigated by in situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) experiments, but the detailed reaction scheme is not yet clear, especially the complex interactions between catalyst interfaces and gas molecules. In this study, by using the periodic density functional theory (DFT) method, we propose a SCR-C3H6 scheme on the Ce0.875Zr0.125O2 (110) surface. Firstly, C3H6 is partially oxidized by lattice or adsorbed oxygen to the acyl group following the Mars-van Krevelen (MVK) mechanism; then, the acyl group combines with nitrate to generate an RCOO-NO2 intermediate, followed by decarboxylation and O-shift reactions to produce R-NO2, R'CH-ONO, -NCO, and -CN species, which are finally converted into CO2 and N-2. The simulation results are in good agreement with experimental values. In addition, some catalytic characteristics are found: (1) NO3 can adsorb steadily on bride, bride, biden, and monoden sites of the Ce0.875Zr0.125O2 (110) surface; (2) the activity sequence of C3H6 by lattice O is C-sp3-H bond > C-sp2-H bond > C=C bond; (3) -NCO is formed more easily than -CN on the Ce0.875Zr0.125O2 (110) surface due to the admirable activity of surface lattice oxygen.