Synthesis of large surface area MnO_x-CeO₂ using CTA and its catalytic activity for soot combustion

抄録

Large surface area (n)MnO_x-(1-n)CeO₂ (0≤n≤1) catalysts were synthesized using a hybrid organic/inorganic route and characterized by XRD, N₂ adsorption and catalytic test. The addition of aqueous ammonia to mixed solutions of cerium and manganese nitrates in the presence of CTAB (cetyltrimethyl ammonium bromide) yielded gelatinous hydrous Ce-Mn oxide/CTA composites (MnCe_CTA). As calcined MnO_x-CeO₂ (n=0.25, 450°C) exhibited a largest surface area of 223 m²/g, which is quite larger than 80 m²/g for the corresponding oxide prepared from conventional co-precipitation route (MnCe_CP). As synthesized MnO_x-CeO₂ catalysts were tested for soot oxidation by O₂. The catalytic activity of MnCe_CP was highest at n=0.25-0.5, whereas the catalytic activity of MnCe_CTA was lower and increased monotonically with an increase of the Mn content (n). The different catalytic behavior seems to be associated with the activity of surface oxygens and lower oxidation state of MnCe_CTA.