Carbon oxidation with Ag/ceria prepared by self-dispersion of Ag powder into nano-particles
2011
Shimizu, Ken-ichi | Kawachi, Hiroshi | Komai, Shin-ichi | Yoshida, Kaname | Sasaki, Yukichi | Satsuma, Atsushi
This study reports a unique and novel method of preparation of Ag/CeO₂ catalyst for carbon oxidation. A calcination of physical mixture of Ag metal powder and CeO₂ at 500°C results in self-dispersion of Ag into nano-particles on CeO₂. From TEM images, the average diameter of Ag particles in Ag power before calcination was around 66nm, while the particle size of Ag became smaller around 8nm with very narrow distribution. Oxygen vacancy on CeO₂ surface is suggested to play an important role in the self-dispersion of Ag. The obtained catalyst showed high activity for soot oxidation comparable to Ag/CeO₂ prepared by impregnation method. The promotion effect of CeO₂ was not observed in physical mixtures with Cu, Au and Pt. Mechanical mixtures of Ag and various metal oxide supports were also examined. The addition of Ag to CeO₂, SnO₂, ZrO₂, ZnO, TiO₂, and Nb₂O₅ significantly lowered the temperature of carbon oxidation than those of supports, while that to Co₃O₄, CaO, La₂O₃, NiO, SiO₂, Al₂O₃ and MgO did not.
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