Kenzi Suzuki

Adsorptive and photocatalytic performance of TiO2 pillared montmorillonite in degradation of endocrine disruptors having different hydrophobicity

Abstract TiO 2 pillared clay was applied for the adsorption-photocatalytic degradation of the endocrine disruptors with various hydrophobicities (di- n -butyl phthalate, diethyl phthalate, dimethyl phthalate and bisphenol-A). The hydrothermal treatment developed the crystallinity of the TiO 2 pillar and the size of the TiO 2 crystallites, and enhanced the photocatalytic degradation rate. However, the hydrothermal treatment in hard condition made the specific photocatalytic activity decrease since the size of crystallites increased. The surface hydrophobicity of the pillared clay was not affected so much, but reduced slightly, by the hydrothermal treatment. Higher hydrophobic endocrine disruptor was more adsorbed and enriched on the TiO 2 pillared clay. Enrichment of the reactant enhanced the rate of photocatalytic degradation on the pillared clay.

XPS, XANES and EXAFS investigations of CuO/ZnO/Al2O3/ZrO2 mixed oxide catalysts

Systematic X-ray photoelectron spectroscopy (XPS), X-ray induced Auger electron spectroscopy (AES), X-ray absorption near edge structure (XANES) and extended X-ray absorption fine structure (EXAFS) studies were undertaken to investigate the electronic structure, chemical states and local geometry of the active species in the CuO/ZnO/Al2O3/ZrO2 multicomponent mixed oxide catalysts employed in the oxidative steam reforming of methanol (OSRM) reaction for H2 production. The core level XPS and AES indicated the existence of CuO and ZnO-like species. Two kinds of zirconium species, one similar to that of ZrO2 and another with relatively higher electron density were noticed from the Zr 3d core level XPS of Zr- containing catalysts. The valence band (VB) XPS studies revealed that for Zr-containing catalysts, the Cu 3d anti-bonding orbital splits from the main nVB and shifts toward lower binding energy (BE). The surface Cu/(Alu2006+u2006Zr) ratios were found to be close to those in the bulk while segregation of Zn at the surface was evidenced in all samples. The XANES and EXAFS results also indicated the existence of CuO and ZnO-like species, whose local environments are modified with respect to the chemical composition. The EXAFS study of the Zr-containing catalysts indicated the existence of a “Cu–O–Zr” bonding with a Cu–Zr distance in the range 3.5 to 3.9 A. The results indicated the existence of a Cu–Zr synergistic interaction in these catalysts which improved the catalytic performance in the OSRM reaction

Crystallization of hydrothermally treated TiO2 pillars in pillared montmorillonite for improvement of the photocatalytic activity

A novel pillared clay, i.e. pillared montmorillonite with crystallized TiO2, has been developed as a highly active photocatalyst. The TiO2 pillars in pillared montmorillonite were crystallized to anatase by hydrothermal treatment, while the porosity of the pillared clay was retained. The size of the crystallized TiO2 pillars and the average pore diameter showed good agreement, and both sizes could be controlled in the range ca. 40–90xa0A by changing the treatment conditions. The photocatalytic properties of the TiO2 pillars were investigated in the degradation of trichloroethylene in water. The hydrothermal crystallization enhanced the catalytic activity both per unit weight of TiO2 and per exposed unit surface area of TiO2. The catalytic activity of the TiO2 pillars was also enhanced by quantum-size effects: as the TiO2 pillar size decreased, the pillared montmorillonites exhibited higher catalytic activity and showed larger blue-shifts in their UV absorption spectra.

Maintenance of large surface area of alumina heated at elevated temperatures above 1300 °C by preparing silica-containing pseudoboehmite aerogel

Abstract Silica-containing pseudoboehmite aerogel was prepared so that the surface area of alumina was maintained large after heating at elevated temperatures. Below 1300 °C, depending on the amount of silica added, the prepared samples transformed to γ-, δ-, and θ-alumina with columnar shaped particles, but not to α-alumina. As a result of the suppression of the phase transformation, heated samples had large pore volume (0.6–1.8 cm 3 / g ) and large surface area (70–300 m 2 / g ) . After heating at 1400 °C, while complete transformation to α-alumina occurred for 2.5 and 10 wt% silica with the additional formation of mullite for the latter, θ-alumina still remained present up to 5 wt% silica. When there was no formation of mullite, the surface area was quite large (23–37 m 2 / g ) . The cause for the maintenance of large surface area of alumina was discussed from the structure of the starting alumina source and the effect of the added silica.

Preparation of High-Performance Co3O4 Catalyst for Hydrocarbon Combustion from Co-Containing Hydrogarnet

Supported Co3O4 catalysts were prepared via the calcination of Co-containing hydrogarnet, (Ca3-xCox)Al2(SiO4)3- y(OH)4y, at 400 °C. Such precursors with various extents of substitution were synthesized from the hydrothermal reaction of a stoichiometric mixture of calcium oxide, amorphous silica, alumina sol, and cobalt hydroxide at 200 °C. It was found that the catalyst consisted of Co3O4, CaO, and mayenite and exhibited a high activity for the combustion of propylene, benzene, and toluene at temperatures below 300 °C.

Selective catalytic reduction of NO by C3H6 over Co/Al2O3 catalyst with extremely low cobalt loading

In order to reveal the optimum Co loading, the selective catalytic reduction of NO with C3H6 over Co/Al2O3 catalyst was studied in a systematic fashion by varying the amount of cobalt oxide. It was found that upon loading a small amount of cobalt oxide (namely 0.5 wt% on a Co metal basis), the combination between Co(II) acetate salt and a high-purity alumina provided an active catalyst in the presence of excess oxygen and water. TPR measurement showed the presence of Co species other than CoAl2O4 spinel in the most excellent performance catalyst, from which the active sites should be produced.