Nickel, copper and cobalt ions were intercalated into fluorotetrasilisic mica (TSM) and hectorite (Hect) by an exchanging method. X-Ray photoelectron spectroscopy (XPS) studies indicated that the exchanged cations were intercalated into the interlayer space. After hydrogen treatment at 723 K (for Cu catalysts: 523 K), the layered structure of TSM was maintained while that of Hect collapsed.
In order to investigate catalytic activities using these intercalated catalysts after hydrogen treatment, water-gas shift (WGS) reaction was carried out. The WGS reaction was selectively conducted over Ni/TSM and Co/TSM, while methanation occurred concomitantly over conventional metal-supported catalysts such as Ni/Al₂O₃ or Ni/SiO₂ and Co/Al₂O₃. In the case of supported copper catalysts, hydrogen was the only product observed on the WGS reaction regardless of supports investigated in this work (TSM, Hect, Al₂O₃, Cu/SiO₂).

抄録全体を表示

The particle-size distribution of illite and iron oxide-precipitated illite was examined as a function of pH by means of the sedimentation balance. Due to the precipitation of 5% iron oxides on the illite surfaces, aggregation occurred over a pH range of 3 to 10, and the degree of aggregation was greater for higher pH values. The aggregation was explained by the decrease of repulsion between face surfaces of illite due to the partial neutralization of the negative charge of illite surfaces, based on the electron micrographs and zeta potential measurement.

抄録全体を表示

Heptylviologen-montmorillonite-polymer intercalation compounds were synthesized by the reaction of heptylviologen with an Na-montmorillonite-poly (vinyl alcohol) or an Na-montmorillonite-poly (ethylene glycol) intercalation compound, and their electrochemical behavior was investigated. Heptylviologen dications were co-intercalated with poly (vinyl alcohol) in the interlayer of montmorillonite whereas poly (ethylene glycol) was almost deintercalated by the intercalation of heptylviologen. Heptylviologen ions, which were incorporated into the clay mineral by ion-exchange of Na⁺ ions, electrochemically underwent a redox reaction in two steps. The co-intercalated polymer species did not affect the electrochemical property. The electrochemical reaction had irreversible nature, and this was presumed to be due to dimerization of heptylviologen radical cations, which formed by oneelectron reduction of the dications, in the interlayer spaces. Similarity and difference in electrochemical behavior between the present system and previously reported MV²⁺-montmorillonite systems were discussed.

抄録全体を表示

Pyrophyllite and talc were shown to have acid sites on their surface, and the strength and amount of the acidity were much higher for pyrophyllite than talc. The strength and amount of the acidity of both minerals were not affected by the exchangeable cation species. Water molecules previously adsorbed on the surface of the minerals lowered both the strength and amount of the acid sites, although the degrees of the decrease were smaller than the case of montmorillonite. When the water was introduced after the adsorption of indicators, the water molecules did not affect both the strength and amount of the acidity.
From above observations, it is suggested that the acidity of pyrophyllite and talc are not attributed to any known origin of the acidity for layer silicates. We concluded that the acidity of pyrophyllite and talc are the Lewis type, and derived from their nature as electron acceptor due to their ‘neutral’ layer compositions. The difference in the acidity between pyrophyllite and talc may come from the difference in their octahedral cation species.

抄録全体を表示

The adsorption of tris (1, 10-phenanthroline) copper (II)([Cu (phen) ₃] ²⁺) by a clay mineral has been studied with electron spin resonance (ESR) measurements. The chelate, tris (1, 10-phenanthroline) copper (II)([Cu (phen) ₃] ²⁺), is co-adsorbed with a large excess of racemic or enantiomeric [Ru (phen) ₃] ²⁺. The spectra of a freezedried sample of a clay-chelate adduct at 77k show that there are two kinds of adsorption states: the one (denoted by state A) is characterized by the parameters of g_II=2.263-2.275 and A_II=151-160G and the other (denoted by state B) by g_II=2.213-2.229 and A_II=150-186G. States A and B are postulated to be the adsorptions on an external surface and in the interlayer space of a clay mineral, respectively. The effects of chelate loading and swelling with organic solvents on the relative abundances of these two states are interpreted on the basis of the above assumption.

抄録全体を表示

Some clay raw materials in Nepal were characterized and their aptitude for porcelain raw material was studied. The main constituent minerals in the samples were identified to be halloysite (7A), mica, quartz, feldspar, and gibbiste by X-ray powder diffraction (XRD), differential thermal analysis (DTA) and transmission electron microscopy (TEM). The chemical composition of the bulk sample showed very low Fe₂O₃ and TiO₂ contents, and therefore, the whiteness of sintered body is on a very good level. The vitrification temperature was around 1200°C and high bulk density still maintained in the temperature range from 1200 to 1350°C, which increased further by grinding the raw materials. Microstructure of the sintered bodies fired at an appropriate temperature showed only small pores homogeneously in the sintered bodies. The samples examined in this study were found to be suitable for raw materials of porcelain.

抄録全体を表示