Junko N. Kondo

Green chemistry: Biodiesel made with sugar catalyst

The production of diesel from vegetable oil calls for an efficient solid catalyst to make the process fully ecologically friendly. Here we describe the preparation of such a catalyst from common, inexpensive sugars. This high-performance catalyst, which consists of stable sulphonated amorphous carbon, is recyclable and its activity markedly exceeds that of other solid acid catalysts tested for ‘biodiesel’ production.

An oxynitride, TaON, as an efficient water oxidation photocatalyst under visible light irradiation (λ≤ 500 nm)

Under visible light irradiation (λ = 420–500 nm), a tantalum oxynitride, TaON, functions as a stable and very efficient photocatalyst for oxidation of water into O2 with a sacrificial electron acceptor (Ag+).

Nb2O5·nH2O as a Heterogeneous Catalyst with Water-Tolerant Lewis Acid Sites

Niobic acid, Nb(2)O(5)·nH(2)O, has been studied as a heterogeneous Lewis acid catalyst. NbO(4) tetrahedra, Lewis acid sites, on Nb(2)O(5)·nH(2)O surface immediately form NbO(4)-H(2)O adducts in the presence of water. However, a part of the adducts can still function as effective Lewis acid sites, catalyzing the allylation of benzaldehyde with tetraallyl tin and the conversion of glucose into 5-(hydroxymethyl)furfural in water.

Cu2O as a photocatalyst for overall water splitting under visible light irradiation

Photocatalytic decomposition of water into H2 and O2 on Cu2O under visible light irradiation is investigated; the photocatalytic water splitting on Cu2O powder proceeds without any noticeable decrease in the activity for more than 1900 h.

Recent progress of photocatalysts for overall water splitting

Abstract Recent progress of photocatalysts for H2O decomposition into H2 and O2 was briefly reviewed with the emphasis on the results concerning the use of several ion-exchangeable layered materials. Very recent results concerned with the first successful example of overall water splitting induced by visible light irradiation was also presented.

A highly active photocatalyst for overall water splitting with a hydrated layered perovskite structure

Photocatalytic decomposition of H2O into H2 and O2 over a novel photocatalyst, K2La2Ti3O10, was accomplished. K2La2Ti3O10, a layered perovskite-type compound with a hydrated interlayer space, exhibited a high activity for overall water splitting with Ni-loading. The highest activity was obtained over Ni(3.0 wt%)–K2La2Ti3O10 when the reaction was carried out in aqueous KOH solution (0.1 M, pH=12.8). By comparison with other Ni-loaded photocatalysts reported previously, the reaction mechanism of Ni–K2La2Ti3O10 was discussed.

Protonated Titanate Nanotubes as Solid Acid Catalyst

Protonated titanate nanotubes are demonstrated to function as a highly active solid Lewis acid catalyst even near room temperature. The high catalytic activity for the reaction can be attributed to the unique nanotube structure, which contains both Brønsted and Lewis acid sites.

Highly Active Mesoporous Nb–W Oxide Solid-Acid Catalyst†

The synthesis of mesoporous transition-metal oxides has been extensively studied because of their wide range of potential applications. Examples of such compounds include mesoporous TiO2, [2, 3] ZrO2, [2, 4] Nb2O5, [2,3b, 5] Ta2O5, [2, 6] (Nb,Ta)2O5, [2, 7] SnO2, [2, 8] and WO3, [2] which are used as a variety of heterogeneous catalysts, such as solid-acid catalysts, 5d, 6f,g] photocatalysts, 6b,h] oxidation catalysts, and catalyst supports. Solid-acid catalysts, which are reusable and readily separable from reaction products, have been widely investigated as direct replacements for liquid acids to reduce the impact on the environment and to decrease costs. The use of mesoporous transition-metal oxides is an interesting approach to developing a solid-acid catalyst with enhanced activity. The mesopores in the oxide allows the reactants access additional active acid sites in the pores, resulting in improved rates of acid catalysis. Sulfated mesoporous niobium and tantalum oxides have been reported to exhibit remarkable activity in acid-catalyzed Friedel–Crafts alkylation and isomerization. 6f,g] However, the use of the recycled catalyst remains difficult, a result of the leaching of sulfate species, as reported for mesoporous silica and organosilicas bearing sulfonic acid groups. Herein, mesoporous Nb– W mixed oxides are examined as solid-acid catalysts, these give very high catalytic performance in Friedel–Crafts alkylation, hydrolysis, and esterification, which originates from the mesoporous structure and different acid properties formed by specific Nb and W concentrations. Mesoporous Nb–W mixed oxides were prepared from NbCl5 and WCl6 in the presence of a poly block copolymer surfactant Pluronic P-123 as a structure-directing agent. (Additional details are provided in the Supporting Information) Peaks attributable to mesopores were observed from NbxW(10 x) oxides with x values from 2 to 10 in the small-angle powder X-ray diffraction (XRD) pattern (see Figure S1 in the Supporting Information). Peaks attributed to (110) and (200) of the two-dimensional hexagonal structure were observed from an x = 10 sample (mesoporous Nb oxide), which was consistent with previous studies. Wide-angle powder XRD patterns revealed the presence of crystallized tungsten oxide (WO3) in W-rich samples (x = 0 to 2). The presence of mesopores was also indicated by the N2 sorption isotherms (Figure 1) for the same samples (x = 2 to 10). The surface areas were estimated using the Brunauer–Emmett–Teller (BET) method, and pore volumes were obtained by the Barrett–Joyner–Halenda (BJH) method. Although the surface area decreased gradually from 200 (mesoporous Nb oxide) to 52 m g 1 (non-mesoporous W oxide) with increasing addition of W, up to x = 0, the pore volume decreased up to x = 3. Then, the pore volumes increased in the non-mesoporous W-rich oxides (x = 0 to 2) due to the formation of void spaces between particles (Supporting Information, Figure S2). The pore diameter obtained by the BJH method decreased from 7 (mesoporous Nb oxide) to 4.2 nm (mesoporous Nb3W7 oxide) with increasing W content, and mesopores were not observed in the Nb1W9 oxide (Supporting Information, Figure S3). SEM and TEM images of the porous

Biodiesel made with sugar catalyst.

The production of diesel from vegetable oil calls for an efficient solid catalyst to make the process fully ecologically friendly. Here we describe the preparation of such a catalyst from common, inexpensive sugars. This high-performance catalyst, which consists of stable sulphonated amorphous carbon, is recyclable and its activity markedly exceeds that of other solid acid catalysts tested for ‘biodiesel’ production.

Metal ion and N co-doped TiO 2 as a visible-light photocatalyst

Powders of TiO2 doped with a metal ion and N species were prepared by a polymerized complex method and the visible-light photocatalytic activities of the products are investigated. Of the metal ions studied (K+, Ca2+, Sr2+, Ba2+, Nb5+, Fe3+, Zn2+, and Al3+), the photocatalyst prepared with Sr2+ exhibits the highest activity for acetaldehyde decomposition under visible-light irradiation. Results obtained from x-ray photoelectron spectroscopy (XPS) and electron spin resonance (ESR) analyses suggest that the doped N species reside at interstitial lattice positions in the catalyst. It was also found by XPS and ESR measurements that the doped N species combine with lattice oxygen to give rise to a paramagnetic property. The visible-light response of the catalyst is driven by the formation of paramagnetic N species at interstitial positions in the TiO2 lattice.