Design structure for CePr mixed oxide catalysts in soot combustion

Abstract

Four CePr mixed oxides with different structures were designed and synthesized using a solid-phase grinding method: a uniform solid solution of Ce and Pr (CePr-NN), Pr₆O₁₁-coated CeO₂ (CePr-NO), CeO₂-coated Pr₆O₁₁ (CePr-ON), and particle packing of CeO₂ and Pr₆O₁₁ (CePr-OO) were obtained, and characterized by XRD, H₂-TPR, TEM and TG. The results show that CePr-NN exhibits the best low temperature catalytic activity among the CePr catalysts. CeO₂ is the major active phase on the surface of the CePr catalysts, and the use of Pr₆O₁₁ as the framework maintains the thermal stability of the CePr composite oxide. Moreover, both the oxygen storage capacity and mobility of the active oxygen of the catalyst were improved with the incorporation of Pr into CeO₂, resulting in a higher combustion rate. The “molten state” which appeared during the preparation when nitrate was used as the precursor, plays a significant role in the migration of Ce and Pr, and is the premise of forming different structures of solid solution or coating structure.