Cu-モンモリロナイトおよびそのε-カプロラクタム層間化合物のEXAFS

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Local structures around Cu^<2+> ions in Cu-montmorillonite and in intercalated compound of Cu-montmorillonite and ε-caprolactam were studied by X-ray absorption spectroscopy ; EXAFS and XANES, using laboratory-scale equipment. Cu^<2+> ions in Cu-montmorillonite coordinate about 6 water molecules and the Cu-O (in water) distance was 0.19 nm. The water molecules were removed by vacuum drying at 150℃, and the Cu^<2+> ions contacted with oxygen atoms in tetrahedral sheet of montmorillonite and the Cu-O or Cu-Si distances were 0.19 and 0.25 nm. The model for adsorption site of Cu^<2+> ions were proposed. The local structure around the Cu^<2+> ions was changed by heating the samples at 260℃ for 5 hours. After the 260℃-treatment. Cu^<2+> ions existed in tetrahedrons of oxygen atoms where Cu-O distance was 0.2 nm, which was similar to the local structure in CuO. The interlayer distance of Cu-montmorillonite was 1.22 nm. Although the interlayer distance was increased to 1.53 nm by forming the intercalated compound with ε-caprolactam, local structure around Cu^<2+> ions was not changed. The model that two layers of water molecules and one layer of ε-caprolactam molecules existed between the silicate layers was proposed. The ε-caprolactam was polymerized by heating at 260℃ for 10 hours, accompanied by the great increase in the interlayer distance from 1.53 to 12.1 nm. Following this, Cu^<2+> ions were reduced to metallic copper whose particle size was estimated to be about 10 nm by X-ray diffraction peak broadness. The metallic copper was oxidized by aging at 25℃ for 3 weeks in atmospheric environment, accompanied by decrease in interlayer distance to 5.7 nm. Local structure around the Cu^<2+> ions in this oxidized state was not similar to that in CuO but to that in Cu-montmorillonite .
日本粘土学会の論文
1986-08-08

Cu-モンモリロナイトおよびそのε-カプロラクタム層間化合物のEXAFS

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