Kei Inumaru

Molecular selective adsorption of dilute alkylphenols and alkylanilines from water by alkyl-grafted MCM-41: tunability of the cooperative organic–inorganic function in the nanostructure

Molecular selective adsorption of alkylphenols and alkylanilines onto n-alkyl grafted MCM-41 with different alkyl chain lengths and Al contents was studied. Octyl groups gave better adsorbent performance than pentyl and dodecyl groups. Nitrogen and water adsorption isotherms revealed that the octyl-grafted sample has a large volume of strongly hydrophobic nanospaces between the grafted alkyl chains. Octyl-grafted MCM-41 adsorbed alkylphenols from aqueous solutions with high molecular selectivity: Nonylphenol, an endocrine disrupter, is efficiently removed by adsorption onto n-octyl grafted MCM-41, while adsorption of t-amylphenol is small and that of phenol is undetectable. Comparison of molecular selectivities for alkylphenols and alkylanilines reveals that hydrophilic and hydrophobic groups on molecules independently affect the selectivity. Infrared spectra of n-heptylaniline captured in the adsorbent show that the amino groups are strongly hydrogen-bonded to silanol groups on the inorganic pore walls: The molecules fit into the organic–inorganic nanostructure, interacting with the inorganic walls as well as the organic moiety. Since the amounts of Al that could be doped into MCM-41 were much lower than the adsorption amounts of the 4-nonylphenol and 4-n-heptylaniline, changes in the adsorption amounts due to the formation of acidic sites by Al doping could not be clearly observed. It was concluded that a large volume of highly hydrophobic nanospaces surrounded by ionic inorganic walls was important for efficient adsorption of these molecules.

Catalysis by heteropoly compounds Part 39 The structure and redox behaviour of vanadium species in molybdovanadophosphoric acid catalysts during partial oxidation of isobutane

The states and roles of vanadium of 11-molybdo-1-vanadophosphoric acid (H4PMo11VO40, PMo11V) catalyst in the partial oxidation of isobutane (2-methylpropane) were analysed by EPR, 51V and 31P NMR, IR spectroscopy, and redox titration, and compared with dodecamolybdophosphoric acid (H3PMo12O40, PMo12) catalyst. Thermal treatment of PMo11V at 623 K in O2 caused the elimination of V from the Keggin anion and formed undefined polymeric and a monomeric V species. It was shown based on the redox titration and EPR spectra that the average valency of V in used catalysts significantly changed with the oxygen partial pressure, while that of Mo remained almost unchanged for both PMo11V and PMo12. The selectivities to methacrylic acid (MAA) and methacrolein (MAL) extrapolated to zero conversion were similar for both catalysts, but PMo11V showed a significantly higher selectivity as the conversion increased. This is because the secondary reaction, that is, oxidative decomposition of MAL and MAA, was slower over PMo11V than over PMo12. This was consistent with the marked difference in the reaction order in oxygen pressure, and corresponded to the differences in the above redox properties.

Pulsed laser deposition of epitaxial titanium nitride on MgO(001) monitored by RHEED oscillation

Titanium nitride was grown epitaxially on MgO(001) by a pulsed laser deposition (PLD) method, and the oscillations of reflection high energy electron diffraction (RHEED) for this system were observed for the first time. The RHEED patterns and atomic force microscope (AFM) analysis revealed the two-dimensional growth of highly flat TiN films. The high-resolution reciprocal space mapping of X-ray diffraction of the TiN film showed that the lattice dimensions of the TiN shrunk along the plane parallel to the surface of the MgO(001) substrate by 0.6% with no structural relaxation and no mosaic disorder, demonstrating the deposition of the high-quality epitaxial film.

Direct nanocomposite of crystalline TiO2 particles and mesoporous silica as a molecular selective and highly active photocatalyst

Well-crystallised TiO2 particles (P-25, 20-30 nm in diameter) were directly incorporated into surfactant-templated mesoporous silica particles (pore diameter: 2.7 nm), and the composite material with a high TiO2 content (60 wt%) showed molecular selective and enhanced photocatalysis for decomposition of 4-nonylphenol.

EXAFS analysis of vanadium oxide thin overlayers on silica prepared by chemical vapour deposition

The structure of vanadium oxide overlayers of V2O5/SiO2 catalysts prepared by chemical vapour deposition (CVD) and impregnation methods has been determined by using vanadium K-edge EXAFS and XANES. The Fourier transform of EXAFS for the vanadium oxide overlayers obtained by CVD of VO(OC2H5)3 showed very weak peaks due to V—O—V bonds, even at the high loading level of V2O5(17 wt.%), while crystalline V2O5 gave strong peaks due to V—O and V—O—V bonds. On the basis of the EXAFS and XANES results, it has been concluded that the vanadium oxides obtained by the CVD method were present as thin overlayers on SiO2, and were stable to calcination at 773 K. On the other hand, with an impregnation method, XANES of V2O5/SiO2 at loading levels less than 5 wt.% gave peaks different from those of crystalline V2O5. It was presumed that an isolated V species was formed as reported in the literature. At loading levels >5 wt.%, XANES and EXAFS for V2O5/SiO2 catalysts prepared by the impregnation method were very similar to those of crystalline V2O5, indicating that crystallites of V2O5were formed on SiO2 in this case. This occurs because aggregates of vanadium compounds, e.g. oxalate, were formed as precursors of V2O5 during the drying process.

Molecular selective adsorption of nonylphenol in aqueous solution by organo-functionalized mesoporous silica

Octylsilane-grafted hexagonal mesoporous silica removed low-concentrated nonylphenol, an endocrine disrupter, in water with high efficiency comparable to that of activated carbon, while the adsorbent showed no detectable uptake of phenol.

Nanocomposites of crystalline TiO2 particles and mesoporous silica: molecular selective photocatalysis tuned by controlling pore size and structure

Preformed well-crystallized TiO2 particles (P-25, 20–30 nm in diameter) were directly embedded into surfactant-templated mesoporous silica having tuned pore sizes (1.4–5.3 nm). These nanocomposites (containing as much as 60 wt% TiO2) demonstrated molecular-selective photocatalysis toward the decomposition of mixed alkylphenols in water. Even in the presence of highly concentrated phenol, the nanocomposite decomposed dilute nonylphenols (NP) and heptylphenol (HP) completely, which is in contrast to pristine TiO2, highlighting the importance of the nanocomposite structure. The molecular selectivity could be tuned by systematically controlling the pore size: catalysts having large pores (2.7–5.3 nm) decomposed NP and HP at similar fast rates due to their preferential adsorption onto the catalysts. Catalysts having small pores (1.4–1.9 nm and smaller micropores) decomposed HP faster than NP because of their different diffusion rates. Furthermore, it was found that the nanocomposite structures were significantly improved by TiO2 particle surface alkyl-grafting: SEM and TEM images of the nanocomposite prepared from surface alkyl-grafted TiO2 particles revealed that the TiO2 particles were almost completely surrounded by mesoporous silica, whereas in the case of unmodified TiO2 particles, parts of them were left uncovered with the mesoporous silica. The nanocomposite prepared from alkyl-grafted TiO2 particles showed much higher molecular selectivity and activity than that prepared from unmodified TiO2.

High-pressure synthesis and superconductivity of a new binary barium germanide BaGe3.

A new binary barium germanide BaGe(3) was prepared by high-pressure and high-temperature reactions using a Kawai type multi-anvil press. It crystallizes in a hexagonal unit cell with a = 6.814(1) Å, c = 5.027(8) Å, and V = 202.2(5) Å(3) (the space group P6(3)/mmc, No. 194). The unit cell contains two layers along the c axis composed of Ba atoms and Ge(3) triangular units. The triangular units stack along the c axis to form 1D columns in which the adjacent Ge(3) units turn to opposite directions. The columns, therefore, can be described as the face-sharing stacking of elongated Ge(6) octahedra. Each Ba atom is surrounded by six columns. BaGe(3) is metallic and shows superconductivity at 4.0 K. The band structure calculations revealed that there are four conduction bands mainly composed of Ge 4p and Ba 5d orbitals. From Fermi surface analysis, we confirmed that three of them have a large contribution of Ge 4pz orbitals in the vicinity of the Fermi level and show a simple 1D appearance. The remaining one contains Ge 4px, 4py, and Ba 5d contributions and shows a 2D property.

Catalytic properties of metal loaded silica-pillared manganese titanate for CO oxidation

Abstract Semiconducting microporous solids were prepared by pillaring layer structured manganese titanate, Rb x Mn x Ti 2− x O 4 ( x =0.75) with silica. These solids were then chemically modified by loading various kinds of metals by cation exchange and impregnation methods. The samples with copper loaded by the impregnation method showed a high catalytic activity for the oxidation of carbon monoxide with oxygen. The highest activity was obtained for the sample with the copper content, [Cu]/[Cu+Mn]≈0.3; the CO conversion of more than 90% was achieved at 60°C. The high catalytic activity is attributed to the microporous pillared structure with a high porosity and the charge transfer between copper and the manganese titanate layers.

High-pressure synthesis and superconductivity of a new binary lanthanum germanide LaGe3 with triangular Ge3 cluster units

We prepared a new binary lanthanum germanide, LaGe(3), under high-pressure and high-temperature conditions (3-12 GPa, 500-1200 °C). It crystallizes in the BaPb(3) structure (the space group R ̅3m) with lattice constants of a = 6.376(1) Å, c = 22.272(3) Å, and V = 784.1(2) Å(3). We refined the structure using Rietveld analysis from X-ray powder data. The structure is composed of two types of close-packed atom layers. In one layer, every La atom is surrounded solely by Ge atoms with the same distance of 3.188 Å. The other layer contains Ge(3) regular, triangular cluster units with a Ge-Ge distance of 2.634 Å. The electron localization function and crystal orbital Hamilton population calculations suggest that the triangular cluster is composed of three Ge-Ge covalent bonds and that each Ge atom has a lone pair. The temperature dependence of the magnetic susceptibility and electrical conductivity measurements revealed that LaGe(3) is metallic and shows superconductivity at 7.4 K. This critical temperature is highest for the La-Ge system.