Complex metal oxide catalysts active for gas-phase selective oxidations of olefins and alkanes are usually constructed with molybdenum oxide as a main and key component with various metal elements. Two catalytic systems, multicomponent Mo-Bi oxide catalysts for propylene selective oxidation and crystalline Mo-V oxide-based catalysts for alkane selective oxidation have been described in details in terms of catalytic component collaboration sustained by high dimensional catalyst structures.
Among base metal oxides, Co3O4, MnO2, and NiO, which have p-type semiconducting properties, hold potential catalytic capability for the oxidation of carbon monoxide (CO) at temperatures below 0oC. Either of the following requirements should be fulfilled; low moisture content in reaction feed, optimum temperature and atmosphere for catalyst pretreatments, and the control of metal oxide morphology. Surface oxygen vacancies are assumed to play a key role in low temperature CO oxidation.
This paper introduces specific dehydration of diols over rare earth oxides (REOs) to produce the corresponding unsaturated alcohols in the vapor phase. 3-Buten-2-ol and trans-2-buten-1-ol were produced selectively in the dehydration of 1,3-butanediol over CeO2, and 3-buten-1-ol was produced in the dehydration of 1, 4-butanediol over REOs such as Yb2O2. The reaction mechanism was discussed in connection with the surface structure of REOs using quantum-chemical analysis.
Synthesis and catalysis of three types of solid acid catalysts containing of W oxides were reviewed. The first one is the amorphous metal oxides consisting of Nb and W oxides, different in nature from those of Nb2O5 and WO3. The second one is the hydrothermally synthesized Nb2O5-WOx having nano-fiber structure which showed much higher activity in Friedel-Crafts reactions compared to that prepared by co-precipitation methods. Finally, solid acid catalysts generated through thermal decomposition of Keggin- and Dawson-type heteropoly acids will be reviewed.
Electron-hole recombination kinetics was observed in NaTaO3 photocatalysts doped with Ca, Sr, Ba, and La using time-resolved infrared absorption. The recombination rate was compared with the ultraviolet light-derived H2 production rate in the water splitting reaction to estimate the electron-to-H2 conversion efficiency. The conversion efficiency was sensitive to the nanometer-scale topography of the photocatalyst surface. The particularly high efficiency on the nondoped and 0.5 mol% Sr-doped photocatalysts was related to the flat (100) crystalline surfaces exposed on the photocatalyst particles. In the presence of NiO cocatalysts, the rate of electron trasfer across the La-doped photocatalyst surfaces was enhanced. These results demonstrate intense demand to do surface science on metal oxide particles.
New material design and microstructure control are key issues to advance current fuel cell systems. To satisfy high requirements of efficiency and power density, further accelerations of electrode reaction and ionic conductivity should be investigated. This report reviews oxide materials for electrode and electrolyte of solid electrolyte fuel cells, especially focusing on control over surface and interfacial microstructures. The formation of heterointerfaces is effective approach to accelerate electrode reaction and ionic conductivity. Ion transport phenomena at heterointerfaces provide new insights, which can suggest potential applications in fuel cell systems.
In this paper, we tried to evaluate the contact angle for a droplet on the solid surface based on elasticity theory for the elastic bulk and thermodynamics. At first, we provided the surface tension of the solid which was a direct rule factor of the wettability as the function of strain in the imaginary layer with thin finite thickness τ by using elasticity theory. And by applying this function to the thermodynamic system consisting of a droplet on the solid surface, we get the equations to be satisfied with the contact angle of the droplet. Solutions of these equations showed good agreement with the experimental contact angle surveyed for droplet on Alkyl Ketene Dimers (AKD) which had fractal structure.
This paper introduces our studies of the topology and dynamics in biological molecules (i.e. lipids and proteins) observed using atomic force microscopy (AFM). Samples for observation were adsorbed on hydrophilic mica and nanofabricated silicon substrates. Topological information about proteins enabled us to understand their physiological mechanisms and biophysical properties. Lipid bilayers were successfully formed on a solid substrate and could be used as an interface between proteins and substrates.