Search

Chiral mesoporous silica (CMS) has been successfully synthesized in the presence of basic amino acids; the use of basic amino acids in combination with the chiral anionic surfactant is advantageous for the formation of CMS in terms of uniformity in the twisted morphology. We first demonstrate that thus obtained chiral mesoporous silicas can be used for the enantioselective separation of racemic compounds; the helical rod-shaped CMS is found to be capable of asymmetric separation of racemic N-trifluoroacetylalanine ethyl ester (CF3CO-Ala-OEt). The left handedness-rich CMS shows asymmetric preferential adsorption of the L isomer and vice versa.

Complete oxidation of 2,000 ppm CO in H2 is attained over 10 wt.% Pt/CNT (carbon nano-tube) catalyst (0.019 g) at room temperature by adding 2,000 ppm O2 to hydrogen flowing at 100 mL/min. By insetting 5 wt.% Pt/CNT catalyst (0.8 g) in front of a PEFC (polymer electrolyte hydrogen fuel cell), the PEFC generated maximum wattage of 0.45 V × 0.75 A/cm2 with no suppression for more than 7 h in a flow of H2 (400 mL/min) containing 1,000 ppm CO. This result suggests a possibility of the hydrogen fuel cell operating in the shift gas.

Pt catalyst supported on carbon nano-tube (CNT) was extremely active for the selective oxidation of CO in H2 at room temperature, which was remarked contrast to the Pt supported on an active carbon (Vulcan carbon) and a graphite powder. Complete oxidation of CO was attained on a 5 wt.% Pt/CNT catalyst (0.8 g) at ca. 40 °C when the O2/CO ratio in a flow of H2 (20 mL/min) + CO (3.0 mL/min) + O2 + N2 was adjusted to be larger than 0.75 at the total flow rate of 100 mL/min. Specific activity of the Pt/CNT catalyst was explained by efficient provision of reactant molecules diffusing on CNT surface to Pt particles.

Catalytic activity of a 1 wt% Au/TiO2 catalyst is markedly improved by loading a large amount of FeO x , on which the oxidation of CO in excess H2 is selectively promoted at temperature lower than 60 °C. Oxidation of CO with O2 on the FeO x /Au/TiO2 catalyst is markedly enhanced by H2, and H2O moisture also enhances the oxidation of CO but its effect is not so large as the promotion by H2. We deduced that activation of Au/TiO2 catalyst by loading FeO x is not caused by the size effect of Au particles but a new reaction path via hydroxyl carbonyl intermediate is responsible for the superior activity of the FeO x /Au/TiO2 catalyst.

Supermicroporous (1.5–2.5 nm pore diameter) niobium oxide is synthesized using a nonionic block copolymer as a structural directing reagent, which is removed by water washing after aging. The oxide contains water in the bulk material in the form of a water-rich niobium oxide. The supermicroporous niobium oxide is applicable for various acid-catalyzed reactions.

Some mesoporous Ta2O5 were synthesized and characterized by N2 adsorption isotherms, TEM and XRD. Although the one prepared by the ligand-assisted templating (LAT) method was neither thermally nor mechanically stable, its hydrophobicity was found to be utilized for efficient intercalation of large dye molecules from aqueous solution. On the other hand, the thick wall of the mesoporous Ta2O5 synthesized by neutral surfactant templating (NST) method partly maintained mesopores even after calcination at crystallization temperature (1023 K). By the mixing of Ta and Nb sources (1:1), homogeneous (Nb, Ta)2O5 was prepared. The amorphous thick wall of as-prepared mesoporous (Nb, Ta)2O5 was crystallized by calcination at 923 K, while maintaining the mesopores in single crystal particles.

Direct splitting of water using a particulate photocatalyst would be a good way to produce clean and recyclable hydrogen on a large scale, and in the past 30 years various photocatalysts have been found that function under visible light. Here we describe an advance in the catalysis of the overall splitting of water under visible light: the new catalyst is a solid solution of gallium and zinc nitrogen oxide, (Ga(1-x)Zn(x))(N(1-x)O(x)), modified with nanoparticles of a mixed oxide of rhodium and chromium. The mixture functions as a promising and efficient photocatalyst in promoting the evolution of hydrogen gas.