Preparation Of Nano-CeO₂ Powder And Catalysis On Oxidation Of Methanol

Nano-powder CeO₂ by ultrasonic automization method and adsorption method with exfoliated graphite(EG) as adsorbent, respectively. XRD, BET, FT-IR, DSC-TGA, SEM and TEM techniques were used to characterize the microstructures of CeO₂ particles. CuO-CeO₂ powder was prepared by the optimized parameters, which catalysis properties were investigated by catalyze methanol.The experimental results showed that crystal nucleus generated by decomposition of cerous nitrate were adsorpted by EG, during the process of preparation of CeO₂ nano-powder. The morphologies and dispersed states of CeO₂ powder were affected obviously by concentration and expanding volume. With the increase of concentration and expanding volume of EG, the size of CeO₂ increased and the dispersed state decreased. The effects of temperature on property of CeO₂ prepared by EG adsorbed method were also investigated. Flake CeO₂ was obtained at high calcine temperature and EG was uncompleted oxidated at low temperature. Pure granular CeO₂ were obtained at 600℃.The different precursors were obtained at various automizated temperatures during preparing nano CeO₂ powder. At low solution temperature, main product was CeOCO3·xH2O, while main product was CeO₂ at high temperature. The particles prepared at higher temperature were more homogeneous and smaller. The size of CeO₂ powder grew up and specific area decreased when calcining at high temperature. Increase of size of single particle was obscure with the variety of concentration but obvious aggregation of particles would formatted when excessive dense. Because surfactants (ethanol or PEG-400) could decrease the surface tension of solution, the little drips were formed during automization process. The size of CeO₂ powder prepared with surfactants was smaller and more homogeneous than pure water, and has no obvious aggregation of particles. The size and morphologies of CeO₂ powder were also affected by precipitant. Smaller and more homogeneous nano-CeO₂ could obtain using NaOH as precipitant than that using NH4HCO3.Nano-powder CuO-CeO₂ were prepared by optimized ultrasonic automization method and adsorption method with exfoliated graphite as adsorbent, respectively. The result of XRD showed that CuO-CeO₂ powder was fluorite structures, and copper ions have embedded into the crystal lattice of CeO₂. The crystal size was miniarurized owning to adding copper ion. Smaller and more homogeneous nano-CeO₂ powder could obtain by ultrasonic automization method than by adsorption method with exfoliated graphite as adsorbent. The result of catalysis performance measurement showed that catalytic activity of CeO₂ was increase in high temperature.When the temperature was above 280℃, catalytic activity of methanol was increased. Those catalyst prepared by ultrasonic automization method, owing to bigger specific surface and lower calcining temperature, have higher catalytic activity than that of adsorption method. At 300℃, the catalytic activity of CuO-CeO₂ was so high that it could potentially replace silver loading catalyst in the future.