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Volume 28 (2003)
- Issue 6 Pages 248-
- Issue 5 Pages 206-
- Issue 4 Pages 162-
- Issue 3 Pages 102-
- Issue 2 Pages 46-
- Issue 1 Pages 2-
Volume 28, Issue 4
Displaying 1-6 of 6 articles from this issue
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Masayoshi Kobayashi, Junya Togawa2003 Volume 28 Issue 4 Pages 162-169
Published: July 01, 2003
Released on J-STAGE: March 04, 2011
JOURNAL FREE ACCESSThe partial oxidation of propene (PP) to propylene oxide (PO) in a heterogeneous system was challengingly studied by using a ceramic membrane reactor immobilized with a Cs-Ag catalyst or a Re-Ag catalyst. Three different reactors, convection flow reactor (CFR), diffusion flow reactor (DFR) and plug flow reactor (PFR), were compared in the view point of PO productivity. The Re-Ag-CFR chosen as the best reactor gave 20-75% of PO selectivity at 453-493K. The steady state rate clearly exhibited a characteristic hysteresis kinetics depending on the PP-concentration increase (Ppp-up) or decrease (Ppp-down) and the hysteresis was interpreted by a dynamic change in stable intermediate (In) amount. The (In) formed from the Ppp-up or the Ppp-down was characterized as its amount forming CO2 by the reaction with 02 or forming propane by the reaction with H2. The amount of (In) was considered as a key role to control both an oxidation activity and the amount of surface oxygen which could accelerate a successive oxidation of PO to CO2.View full abstractDownload PDF (1010K) -
Toshinori Tsuru2003 Volume 28 Issue 4 Pages 170-176
Published: July 01, 2003
Released on J-STAGE: March 04, 2011
JOURNAL FREE ACCESSA TiO2 photocatalytic membrane reactor, in which permeation of organic molecules through a membrane and a photocatalytic reaction occur simultaneously, is reviewed for liquid phase as well as gas-phase reactions. The advantages of the system are (1) the forced transport of reactants by convection to the TiO2 membranes, (2) the oxidation reaction on the outer and inner surface of the porous TiO2 membranes where high concentrations of OH radicals would be expected, (3) the potential for obtaining a permeate stream oxidized with OH radicals after a one-pass permeation through the TiO2 membranes, and (4) improved selectivity combined with the molecular sieving mechanism. For the liquid phase reactions of trichloroethylene (TCE), a decomposition ratio in excess of 95% in the permeate stream to that in feed stream was achieved by a TiO2 photocatalytic membrane reactor, when approximately 1 ppm TCE solutions was fed under blacklight irradiation. For the case of gas-phase reactions, photocatalysis with membrane permeation resulted in a large decomposition rate and the formation of a large amount of intermediate products, compared to photocatalysis without membrane permeation.View full abstractDownload PDF (989K) -
Norikazu Nishiyama, Shunsuke Tanaka, Yasuyuki Egashira, Yoshiaki Oku, ...2003 Volume 28 Issue 4 Pages 177-184
Published: July 01, 2003
Released on J-STAGE: March 04, 2011
JOURNAL FREE ACCESSLow-k dielectric materials have been in demand in order to solve the physical limits of interconnects for a new LSI technology system. Ordered mesoporous silica films are promising materials as low-k dielectrics because of their high porosity and high mechanical strength. Here, we show two preparation methods for thermally stable mesoporous silica films.
First, a mesoporous silica film was prepared on a silicon substrate using a spin-coating process followed by a vapor treatment using tetraethyl orthosilicate (TEOS). The TEOS-treated mesostructured silica film did not contract during calcination, showing high structural stability. A flat mesoporous silica film about 250 nm thick was grown from the silicon substrate. No silica particle was deposited on the surface of film. FTIR studies suggested that the Si-OH groups in the film significantly decreased after the TEOS treatment. TEOS molecules penetrate into an originally deposited silicate film and react with the silanol groups. The densified silica wall has high structural stability and hardly contracts under a calcination process.
Vapor-phase synthesis is another promising method for the preparation of thermally stable mesoporous silica film. We found nano-phase transition of an organic-inorganic nanocomposite under vapor infiltration of TEOS. The rearrangement into a hexagonal periodic structure implies high mobility of the surfactant-silicate composites in solid phase. The vapor infiltration method is a simpler process than conventional sol-gel techniques and attractive for mass production of a variety of organic-inorganic composite materials and inorganic porous films.View full abstractDownload PDF (1382K) -
Katsuki Kusakabe2003 Volume 28 Issue 4 Pages 185-190
Published: July 01, 2003
Released on J-STAGE: March 04, 2011
JOURNAL FREE ACCESSAdvanced membrane reactor systems with FAU-type zeolite membranes were described. An FAU-type zeolite membrane was formed on a porous α-Al2O3 support tube, for use in the selective separation of benzene and hydrogen from cyclohexane. The membrane was used for the catalytic dehydrogenation of cyclohexane in a membrane reactor packed with a Pt/Al2O3 catalyst. The conversion of cyclohexane in the membrane reactor increased beyond the thermodynamic equilibrium value due to the simultaneous removal of hydrogen and benzene from the reaction site without the coke formation. In order to prepare Pt-loaded catalytic zeolite membranes (PtY membrane) for the selective oxidation of CO in an H2-rich mixture, FAU-type zeolite membrane was ion-exchanged and calcined in air. A mixture of CO (10000 ppm), O2 and H2 was fed to the outer surface of the membrane, and CO was selectively oxidized during its permeation through the thin layer. The PtY membrane rejected CO at a H2/CO separation factor of 10. When the O2-feed rate exceeded the CO feed rate, the CO concentration on the permeate side was decreased to less than 8 ppm. Permeation fluxes were calculated by means of a mathematical model using effective diffusion coefficients and reaction kinetics. The oxidation rates of CO were determined over a particulate catalyst that had the same composition as the PtY membrane. The predicted permeation fluxes of H2 and CO using the mathematical model were in good agreement with the experimental data.View full abstractDownload PDF (779K) -
Junji Michizoe, Takahiro Kotani, Jo Tominaga, Tatsuo Maruyama, Hirofum ...2003 Volume 28 Issue 4 Pages 191-197
Published: July 01, 2003
Released on J-STAGE: March 04, 2011
JOURNAL FREE ACCESSWe have investigated the oxidation of phenolic compounds by manganese peroxidase (MnP) hosted in aerosol OT/isooctane reverse micelles. The MnP hosted in reverse micelles exhibited high peroxidase activity in isooctane, while the dry powder of lyophilized MnP suspended in isooctane did not exhibit peroxidase activity at all. Factors affecting the MnP activity in the reverse micellar solution were studied and it appeared that MnP in reverse micelles showed the highest activity under the following conditions : pH 3.0, Wo=20, 0.5 mM peroxidase and reaction temperature of 40°C. Under the optimized conditions, the oxidation of hydrophobic phenolic compounds, 2, 4-dichlorophenol, 2, 4, 6-trichlorophenol and bisphenol A was carried out in organic solvents. After the 6 h reaction, these compounds were oxidized with the conversion ratio of 22, 24 and 52%, respectively. Furthermore, the addition of 1-hydroxybenzotriazole (HBT) to the reaction medium improved the oxidation rates of all the substrates, indicating that HBT served as a mediator in the MnP-catalyzed oxidation in reverse micelles.View full abstractDownload PDF (736K) -
T. Koyama, K. Ozawa2003 Volume 28 Issue 4 Pages 198-202
Published: July 01, 2003
Released on J-STAGE: March 04, 2011
JOURNAL FREE ACCESSWe have developed a new fuel cell evaluation system. A concept to develop this system is to easily and precisely measure the ohmic over-potential and Tafel-slope through current interrupt. This system consists of a load unit with a wide range of capacity and a fuel supply system with versatile options. The load unit is able to make a very fast and stable control of voltage or current and has two current ranges selectable for a wide range of measurements. The fuel supply unit provides a humidification function and a temperature controller for fuel cells, and hydrogen and air are controlled by two mass flow controllers. A combination of this fuel supply unit and a methanol supply unit can be applied easily for evaluation of direct methanol fuel cells with a reference electrode. This new evaluation system can be greatly contributed to the fundamental research into fuel cells.View full abstractDownload PDF (1034K)
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