島津 省吾

Mesoporous molecular sieves are promising as adsorbents for purification of biological molecules, such as arm no acids, due to their tuneable mesopore sizes and high surface area. In this study, the adsorption of the basic amino acid, lysine, onto MCM-41, a siliceous mesoporous molecular sieve, has been investigated Under a range of solution conditions. It was found to adsorb according to a Langmuir-type isotherm with a maximum capacity at pH 6 of 0.21 mmol/g. The extent of adsorption depends strongly on the pH and ionic strength of the adsorbate solution, due to a combination of ion exchange and electrostatic interactions governing the adsorption process. (c) 2005 Elsevier B.V. All rights reserved.

Two series of zirconium beta-diketonates: tris(benzoylacetonato)zirconium (IV) perchlorate (3b) and tris(dibenzoylmethanato)zirconium (IV) perchlorate (3c) were synthesized. The complexes were synthesized by a reaction of zirconium tetrachloride with corresponding ligands in a 1:3 molar ratio, followed by a reaction with silver perchlorate. Characterization was by elemental analyses, UV-Vis, FTIR and H-1 NMR spectroscopies. The complexes were prospective to serve as Lewis acid catalysts for ring opening reactions of oxiranes with alcohols for synthesizing primary alkoxyalcohols. Previously reported tris(acetylacetonato)zirconium (IV) chloride (2a) was used as comparison. The effect of phenyl ring on ligand frame towards enhancement of Lewis acidity of zirconium is focused. Other factors, such as nucleophile strength of alcohols and alkyl substituent of oxiranes are also discussed. (c) 2005 Elsevier B.V. All rights reserved.

Alumina supported gold catalyst prepared by spray reaction method (spr) provides gold particles with about 20nm diameter. The gold particle size is larger than for conventional gold catalysts. However, the spr catalyst shows catalytic activity for NO-CO reaction. In the present paper, we discuss the local structures of spr-Au/Al2O3 catalyst by using Au L3-edge XANES spectra. In order to investigate the local structures of Au-sites, multiple scattering approach to XANES analysis was applied. Calculated Au L3-edge XANES spectrum for fcc-Au and Au 2O3 were in good agreement with the observed spectra. XANES spectra for spr-Au/Al2O3 were characterized by 4 types of Au sites (bulk, interface, surface and peripheral). In this case, almost all gold sites (&gt 90%) are bulk sites. Less than 10% of the gold particles are in interface sites. However, the experimental result for spr-Au/Al2O3 requires about 30% of gold oxide or hydroxide. Bulk of Al2O3 contains a certain number of gold nano-particles, which was incorporated in the Al2O3 support. In the interface area, gold oxide forms a few layers. This result was also supported by DV-Xα electronic structure calculations. © Physica Scripta 2005.

Mesoporous silica supported Nb catalyst (imp Nb/SBA-3) was prepared by impregnation of NbCl5 to the SBA-3 support. The mesoporous silicate-wall incorporated Nb catalyst (inc Nb-SBA-3) was synthesized by introducing NbCl5 into an SBA-3 precursor solution. Both catalysts were carburized by a temperature programmed reaction (TPR) method under CH 4/H2 gas stream. Nb K-edge in-situ XAFS analysis revealed that Nb2O5 was reduced to NbO2 in the first stage of TPR and converted into NbC in the second stage. The silica-wall incorporated Nb species were highly dispersed and hardly reduced nor fully carburized. The difference in the carburization process between imp Nb/SBA-3 and inc Nb-SBA-3 was clarified. © Physica Scripta 2005.

Silica supported molybdenum oxide catalysts were prepared from Mo dimer complex (Mo2(CH3CO2)4) by using photochemical anchoring (PCA) method. The local environments of Mo atoms on both attached and oxidized catalysts were investigated by Mo K-edge EXAFS, XANES, Raman spectroscopy and thermal gravimetric analysis. The bond distance between dimeric Mo atoms could be changed depending on the energy of UV irradiation. By using the lower irradiation energy (λ &gt 350 nm), the attached structure was close to the original Mo dimer complex. After oxidation of the catalyst, dimeric structure was formed with bridging oxygen and the Mo-(O)-Mo bond distance was 0.316 nm. On the other hand, in the case of higher irradiation energy (λ &gt 250 nm), the Raman spectrum of the attached catalyst had bands due to acetate ligands except a band at 405 cm-1 due to Mo-Mo skeleton bond. It means that Mo2(CH3CO2) 4 is decomposed by UV irradiation. The oxidized form of the higher energy irradiated catalyst showed monomer-pair structure. © Physica Scripta 2005.