CeO2的添加对柴油车氧化催化剂Pt/SiO2-Al2O3的NO氧化性能提高的影响

Effects of CeO2 Addition on Improved NO Oxidation Activities of Pt/SiO2-Al2O3 Diesel Oxidation Catalysts

The catalytic activities for NO oxidation achieved by different amounts of CeO₂-modified Pt/SiO₂-Al₂O₃ catalysts Pt/SiO₂-Al₂O₃-wCeO₂ (the mass fraction w being 0%, 5%, 10%, 15%, 30%), prepared using step-wise impregnation, were investigated in the presence and absence of CO and C₃H₆. The results showed that the NO oxidation activity could be efficiently improved by modification of CeO₂, wherein the 15%-CeO₂-modified catalyst exhibited the maximum NO conversion of 61% even in the presence of CO and C₃H₆, which were proved to inhibit NO₂ formation in this study. A series of characterization methods were performed over the as-prepared samples to correlate their surface and structural characteristics with their enhanced NO oxidation activities. CO-chemisorption illustrated that appropriate CeO₂-loading was effective for enhancing Pt dispersion, thus enhancing Pt surface-to-volume ratio, confirmed by transmission electron microscope (TEM) images. X-Ray Diffraction (XRD) further suggested that ceria addition could suppress the growth of the Pt crystal, resulting in higher surface Pt atomic ratio. Further, H₂ temperature-programmed reduction (H₂-TPR), together with TEM results, implied that the presence of ceria could enhance the interaction between metal and supports, thus facilitating reducibility of both active platinum and ceria. Hence, this study displays that ceria could act as a dispersion promoter and a reducibility booster, both of which are beneficial to NO oxidation activity. The improved NO oxidation activity is significant for the efficient purification of diesel integrated catalytic system.