Yoshie Souma

Photocatalytic decomposition of NO at 275 K on titanium oxide catalysts anchored within zeolite cavities and framework

Abstract Titanium oxide species prepared in the Y-zeolite cavities via an ion-exchange method and those of the Ti-silicalite catalyst prepared hydrothermally exhibit high photocatalytic reactivity for the direct decomposition of NO into N2, O2 and N2O at 275 K with a high selectivity for the formation of N2. The in situ photoluminescence and XAFS investigations indicate that these titanium oxide species are highly dispersed and exist in a tetrahedral coordination in the zeolite cavities and its framework. The charge transfer excited state of these titanium oxide species plays a significant role in the direct decomposition of NO with a high selectivity for the formation of N2, while the catalysts involving the aggregated octahedrally coordinated titanium oxide species and the bulk powdered TiO2 catalyst mainly produce N2O.

Hydrogenation of CO and CO2 toward methanol, alcohols and hydrocarbons on promoted copper-rare earth oxides catalysts

The recent development of a copper-rare earth oxid catalyst (CuLa2Zr2O7) with cubic pyrochlore structure allows to synthesize alcohols and hydrocarbons from CO + H2 and CO2 + H2 feeds. A good activity in methanol synthesis is obtained by promoting the given catalysts by addition of oxides, e.g., ZnO or ZrO2. C2+ alcohols and C2+ hydrocarbons are formed in the presence of a transition metal promotor like Co. Finally, a composite catalyst prepared by mixing the CuLa2Zr2O7 methanol catalyst with a HY zeolite yields mainly C2+ hydrocarbons.

Novel effective poly(2,2′-bipyridine-5,5′-diyl)-CuCl2 catalyst for synthesis of dimethyl carbonate (DMC) by oxidative carbonylation of methanol

Abstract A novel type of polymer-supported CuCl2 catalyst for dimethyl carbonate (DMC) synthesis has been obtained by choosing π-conjugated poly(2,2′-bipyridine-5,5′-diyl) (PBpy) as the supporting ligand; its catalytic activity for oxidative carbonylation of methanol in the liquid phase reaction has been investigated. The catalyst gives higher DMC yield and DMC selectivity than similar heterogeneous poly(vinylpyridine) (PVP)-CuCl2 catalyst. The high catalytic activity is associated with the π-conjugated conductive properties of the supporting ligand, PBpy. Both the PBpy-CuCl2 and PVP-CuCl2 catalysts can be easily recycled after filtration, and the catalytic activity is maintained after three times use. The PBpy-CuCl2 catalyst is much less corrosive toward stainless steels compared with the PVP-CuCl2 and ligand-free CuCl2 catalyst.

Change of catalytic properties of FeZnO/zeolite composite catalyst in the hydrogenation of carbon dioxide

Abstract The hydrogenation of carbon dioxide was examined using the composite catalysts which were obtained by the physical mixing of Fe ZnO and HY zeolite. Fe ZnO was a typical F-T (Fischer-Tropsch) catalyst and Fe ZnO/HY is a composite catalyst which is able to induce a combined methanol synthesis and MTG (Methanol-to-Gasoline) reaction. To study these unique catalytic behaviors of Fe ZnO/HY, the adsorption and the dissociation of carbon monoxide on Fe ZnO as well as TPR measurements were carried out. Fe ZnO is able to produce hydrocarbons by F-T reaction and methanol. In the absence of zeolite, Fe ZnO exerts its ability for F-T reaction. However, HY diminishes the activity for F-T reaction and hydrocarbons were obtained via methanol formed over the modified Fe ZnO

Poly(pyridine-2,5-diyl)–CuCl2 catalyst for synthesis of dimethyl carbonate by oxidative carbonylation of methanol: catalytic activity and corrosion influence

A π-conjugated polymer, poly(pyridine-2,5-diyl) (PPy) was investigated as a support for CuCl2 in the synthesis of dimethyl carbonate by oxidative carbonylation of methanol. The PPy–CuCl2 adduct had high catalytic activity which was comparable to that of the homogeneous CuCl2 catalyst. The adduct caused corrosion of stainless-steel vessels only to minor extent, compared with the homogeneous CuCl2 catalyst. This PPy–CuCl2 catalyst was easily recycled by filtration and showed a similar catalytic activity in the third time use. The presence of the π-conjugated system in PPy, through which electrons can move, may bring about the high catalytic activity for the oxidative carbonylation of methanol, which involves Cu(II)/Cu(I) redox processes.

Metal carbonyl cations in strong acids and their catalytic activities

Recent advances on metal carbonyl cations and their catalytic activities are reviewed and discussed in relation to the property of M–CO bonding. In strong acids, the carbonyl cations of monovalent copper, silver and gold catalyze the carbonylation of olefins, alcohols, dienes, diols, aldehydes and saturated hydrocarbons at room temperature and atmospheric pressure to produce tert-alkanoic acids in high yields.

Hydrogenation of carbon dioxide over CuZn-chromate/zeolite composite catalyst: The effects of reaction behavior of alkenes on hydrocarbon synthesis

Abstract The hydrogenation of carbon dioxide was studied using composite catalysts comprised of CuZn-chromate and HY zeolite. These composite catalysts enabled the reaction combining methanol synthesis and methanol-to-gasoline reaction, and achieved the formation of ethylene and propene as the first example of the composite catalysts. The addition of alkaline metals, especially cesium, to CuZn-chromate enhanced the selectivities of those alkenes. The influences of the reaction pressure and the space velocity on the production of alkenes show that alkanes are obtained by the hydrogenation of the corresponding alkenes. The composite catalysts producing alkenes in high selectivity afforded heavier hydrocarbons preferentially. These results indicate that the hydrogenation of alkenes inhibits the carbon homologation of alkenes to result in the predominant formation of the corresponding lighter alkanes. From these observations, it was found that methanol synthesis catalysts used for the composite catalysts are required to be effective for methanol synthesis at high temperature (over 300°C) and to bear the low activity of the hydrogenation of alkenes.

Hydrocarbon synthesis from carbon dioxide and hydrogen over Cu–Zn–Cr oxide/zeolite hybrid catalysts

The combination of Cu–Zn–Cr oxides and zeolites was effective for hydrocarbon synthesis via methanol by the hydrogenation of carbon dioxide, and the conversion of carbon dioxide into C2+ hydrocarbons was much higher than the thermodynamic equilibrium conversion of methanol.

A comparative study on hydrogenation of carbon dioxide and carbon monoxide over iron catalyst

Abstract Hydrogenation of CO 2 to hydrocarbons over iron catalysts reduced with hydrogen at 350°C and 500°C has been compared with that of CO. The space time yield of hydrocarbons from CO 2 at 250°C is significantly lower than from CO and the selectivity to olefin compounds is also lower from CO 2 . During the reaction with CO, χ-Fe 2.2 C is formed, and the surface, which is oxidized even after the reduction at 500°C, is further reduced. On the other hand, formation of the carbide species is slight in hydrogenation of CO 2 while the surface is rather oxidized. The formation of the carbide species, which is probably the active site of hydrocarbon formation, is suppressed in the presence of CO 2 .

Synthesis of tert.-Alkanoic acid catalyzed by Cu(CO)n+ and Ag(CO)2+ under atmospheric pressure

Abstract Copper(I) and silver carbonyl catalysts were prepared in strong acids such as sulfuric acid, hydrogen fluoride, boron trifluoride-hydrate and fluoro sulfuric acid. Carboxylation of olefins, alcohols, dienes, diols, aldehydes and saturated hydrocarbons were carried out under atmospheric pressure and at room temperature by using copper(I) and silver carbonyl catalysts and tert. -alkanoic acids were obtained in high yields. If these catalysts were not used, carboxylation required high pressure and temperature.