Facile synthesis of catalytically active CeO2 for soot combustion

Abstract

Pure ceria catalysts were prepared by a facile modified homogeneous co-precipitation method, and their catalytic performance was evaluated in the soot oxidation reaction. The structure and textural properties of the synthesized catalysts were characterized via XRD, N₂ adsorption/desorption, TG-DSC-MS, H₂-TPR, FE-SEM, HR-TEM and XPS techniques. It is shown that CeO₂ samples prepared by the improved co-precipitation method exhibit obviously better catalytic activity than those prepared by the conventional co-precipitation method. The CeO₂-CP4-F sample shows the best activity, for which the peak temperature, T_p, values of soot combustion are about 465 °C in O₂ stream gas and 430 °C in a NO/O₂ stream under soot/catalyst “loose contact” conditions. Moreover, after high temperature aging, the activity of CeO₂-CP4-A becomes even better, for which the T_p value of soot combustion is lowered to 445 °C in O₂ air gas. The catalytic activity is not well associated with the physicochemical properties of BET surface area, particle size and reducibility at low temperatures. The number of lattice oxygen and its mobility in the series of CeO₂ may be the crucial factor to decide the overall catalytic performance. According to the HRTEM result, the excellent migration of lattice oxygen may result from the preferential exposure of more-reactive planes, which may be the essential reason to explain the good performance of CeO₂ catalysts in soot oxidation.