Shizuka Tashiro

Catalytic oxidative decomposition of chlorofluorocarbons (CFCs) in the presence of hydrocarbons

Abstract The catalytic oxidative decomposition of CFCs containing two carbon atoms was investigated in the presence of hydrocarbons (C 1 –C 4 alkanes) over silica and various acidic metal oxides. It was found that CFC-115 was the most difficult to be decomposed among CFC-113, CFC-114, and CFC-115, and that γ-alumina was the most active catalyst. The CFC-115 conversion over γ-alumina was lower in the presence of methane than in the presence of the other hydrocarbons. In addition, the activities of γ-alumina-supported metal and metal oxide catalysts were investigated for the oxidative decomposition of CFC-115 in the presence of n-butane. Tungsten (VI) oxide and vanadium (V) oxide catalysts exhibited the highest activity.

Synthesis of silica-coated rhodium nanoparticles in reversed micellar solution

Silica (SiO2)-coated rhodium (Rh) nanoparticles were prepared using a water-in-oil microemulsion of polyoxyethylene (15) cetyl ether, cyclohexane and water. SiO2-coated Rh nanoparticles were obtained by hydrolyzing metal alkoxide (tetraethylorthosilicate, TEOS) in the solution containing Rh complex nanoparticles followed by thermal and reduction treatments. In the SiO2-coated Rh nanoparticle, a Rh particle with an average diameter of 4.1 nm was located nearly at the center of each spherical SiO2 particle. The SiO2 layer was approximately 15 nm thick. Since the Rh particle was wholly surrounded by SiO2, the Rh particle of the SiO2-coated Rh nanoparticle exhibited an extremely high thermal stability. Furthermore, the porous structure of the SiO2 layer could be controlled by the hydrolysis conditions of TEOS.

Oxidative decomposition of chloropentafluoroethane (CFC-115) in the presence of butane over metal oxides supported on alumina-zirconia

The catalytic oxidative decomposition of chloropentafluoroethane (CFC-115) was carried out in the presence of butane with various metal oxides supported on alumina-zirconia. Tungsten(VI) oxide alone had a positive effect on the activity among all the metal oxides. It was concluded that the active sites of the tungsten(VI) oxide catalyst supported on alumina-zirconia might be the acid sites formed by the interaction between tungsten(VI) oxide and tetragonal zirconia. This catalyst was found to be the most active of all the catalysts which have so far been examined, and kept a high activity during the oxidative decomposition of CFC-115 for 25 h.

Hydrogenation of carbon dioxide over rhodium catalyst supported on silica

In this work, it was found that the surface area of silica-supported rhodium catalysts could be controlled in the range between 60 and 600m2/g by using the preparation method which we have developed using water-in-oil microemulsion. The catalysts with a controlled surface area had the same average size of rhodium particles. By using these catalysts, it was also found that turnover frequencies for CO2 hydrogenation increased linearly with the catalyst surface area.