Factors determining gasoline soot abatement over CeO2–ZrO2-MnOx catalysts under low oxygen concentration condition

Abstract

Soot oxidation under a low concentration O2 (0.5% O2/N2) was investigated using CeO2–ZrO2-MnOx mixed oxides with varied amounts of MnOx, in order to gain low temperature catalytic activity and find out the main factors affecting the soot oxidation. The catalytic activity was remarkably improved over these catalysts compared to that of non-catalyst in such a low concentration of O2. In particular, CeO2–ZrO2-MnOx with 10% MnOx doping (M10-CZ) showed the highest catalytic activity with its T50 values of 340 °C under tight contact condition. The results of N2 adsorption-desorption and X-ray diffraction (XRD) indicated that the textural and structural properties were not positive correlation with soot oxidation, are not the main factors affecting the catalytic activity of CeO2–ZrO2 and CeO2–ZrO2-MnOx catalysts. The results of oxygen storage capacity (OSC), hydrogen-temperature programmed reduction (H2-TPR), O2 temperature program desorption (O2-TPD), UV Raman spectroscopy (UV Raman) and X-ray photoelectron spectroscopy (XPS) testified that redox ability, oxygen storage capacity, oxygen desorption capacity at low temperature and surface active oxygen species are more important for soot oxidation. The enhancements of the catalytic behavior after MnOx addition can be due to the improving of the adsorbed, activation and mobility of reactive oxygen species. In this work, these factors about generation and movement of reactive oxygen species are crucial for soot oxidation in a low oxygen concentration condition.