Sulfur deactivation mechanism of Pt/MnOx-CeO2 for soot oxidation: Surface property study.

In this work, an advanced diffuse reflectance infrared fourier transform spectra (DRIFTS) technology is used to describe the formation of surface sulfates on Pt/MnO x -CeO 2 and study the possible deactivation mechanism for soot oxidation reactions in NO + O 2 . IR spectra of CO adsorption and H 2 -TPR results reveal the surface coverage of Pt by sulfates and the loss of partial active oxygen species after the sulfation, respectively. More importantly, in situ DRIRT spectra show sulfur poisoning apparently inhibits the formation of surface intermediates such as monodentate/bidentate nitrates and nitro species, which directly limits the production of NO 2 . Furthermore, the O 2 -TPD results indicate that the sulfation weakens the desorption of surface active oxygen resulting from the decomposition of surface nitrates. The sulfate formation would affect the production of oxygen vacant sites and thereby the mobility of surface oxygen species in both NO + O 2 and O 2. These factors above would play an important role on the deactivation mechanism for soot oxidation. [ABSTRACT FROM AUTHOR]