A study on the preparation of supported metal oxide catalysts using JRC-reference catalysts. I. Preparation of a molybdena–alumina catalyst. Part 4. Preparation parameters and impact index

The effects of the volume and pH of the impregnation solution and of the calcination conditions were examined on the physicochemical and catalytic properties of a 13 wt% MoO₃/Al₂O₃ extrudate catalyst. The Al₂O₃ support and drying procedures (static conditions without flowing air) were fixed in the preparations. In the present series of catalysts, the amount of crystalline MoO₃ was marginally small. It was found that the dispersion of Mo oxide species increased as the volume of the impregnation solution increased, gradually approaching a maximum value. The increase in pH (2–8) of the impregnation solution was found to reduce the dispersion of Mo oxide species. The Mo dispersion increased slightly for the impregnation catalysts as the calcination temperature increased (673–873 K), whereas it decreased for the equilibrium adsorption catalysts. The effects of the calcination atmosphere (with or without flowing air, or with flowing humid air) were very small on the dispersion of Mo oxide species under the present preparation conditions. On the other hand, the methanol oxidation activity of MoO₃/Al₂O₃ was sensitive to the preparation parameters examined here. It was demonstrated by means of EPMA and XPS that a considerable migration of Mo took place during the calcination.

In the present study on the preparation of a 13 wt% MoO₃/Al₂O₃ catalyst, an impact index is proposed to measure the magnitude of the effects of the respective parameter(s) on the physicochemical and catalytic properties. With the Mo dispersion, the effects of the preparation parameter decreased in the order, surface area of the support >> drying process > volume of the impregnation solution > pH, calcination temperature and atmosphere. The size of the impact index for the dispersion of Mo sulfide species is 70–75% of that for the Mo oxide species. The HDS activity of the catalyst was less affected by the preparation parameters than the Mo sulfide dispersion. The preparation parameters affected the segregation of Mo on the outer surface of extrudates in a decreasing order: drying process > volume of the impregnation solution > pH, calcination conditions. It was found that the oxidation of methanol was affected most intensely by the drying procedures. The volume of the impregnation solution, calcination conditions and pH of the impregnation solution also strongly affected the oxidation activity. The impact index suggests that the sensitivity to the preparation variables of the physicochemical and catalytic properties of MoO₃/Al₂O₃ decreases in the order, methanol oxidation activity > surface Mo segregation > Mo oxide dispersion > Mo sulfide dispersion > HDS activity.     

Photocatalytic microreactor study using TiO2-coated porous ceramics

Two kinds of porous ceramic disks, having through-holes with diameters of 0.1 and 0.05 mm, were coated with TiO₂ using two different starting solutions: titanyl(IV)acetylacetonate and a commercial titania sol (STS-01). The morphology of these porous ceramics before and after TiO₂ coating was observed by SEM. The TiO₂-coated porous ceramics were examined as honeycomb photocatalytic microreactors. The photocatalytic activity was evaluated using the decomposition of methylene blue solution for radiation angles of 0° and 10° with respect to the pore axis. The highest photocatalytic activity was obtained for the porous ceramic having the pore diameter of 0.1 mm, coated with titanyl(IV)acetylacetonate and irradiated with a light angle of 0° with respect to the pore axis.     

Effect of steric hindrance on hydrogen‐bonding interaction between polyesters and natural polyphenol catechin

The phase behaviors for the blends of poly(3‐hydroxypropionate) (PHP), poly(L ‐lactide) (PLLA), poly(D ‐lactide) (PDLA), and poly(D,L ‐lactide) (PDLLA) with catechin were investigated by differential scanning calorimetry. In PLLA/catechin, PDLA/catechin, and PDLLA/catechin blends, two glass transitions were detected when the catechin content was ≥40 wt %, whereas in PHP/catechin blends only one glass transition was observed over the whole range of blend compositions. The former and the latter results should reflect the inhomogeneous and the homogeneous nature of the blends, respectively, in the amorphous phase. These different phase behaviors should arise from the differences in the chemical structures between PHP and PLLA/PDLA/PDLLA, which dominates the strength and the number of intermolecular hydrogen‐bonding interactions between the ester carbonyl groups of polyesters and the phenol groups of catechin. As detected by FTIR spectroscopy, in comparison with PHP, the steric hindrance of side‐chain methyl groups of PLLA, PDLA, and PDLLA might restrain the formation of hydrogen bonds between their ester carbonyl groups and the phenol hydroxyl groups of catechin, even weakening the strength of such hydrogen bonds. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 91: 3565–3573, 2004     

Effect of sintering additive on crystallographic orientation in AlN prepared by slip casting in a strong magnetic field

The preparation of oriented AlN bulk ceramics with and without additives was achieved by slip casting in a high magnetic field. The a and b axes of the AlN were aligned parallel to the direction of the magnetic field. The degree of crystallographic orientation was controlled by the viscosity of the slurry and the grain growth during sintering attributed to the sintering additives. The mechanical properties of the textured AlN depended on the direction of the crystallographic orientation.     

An experimental study on moisture transport through a porous plate with micro pores

An experiment was carried out to examine heat and mass transfer between constant-temperature water and dry air through a porous plate having extremely small pores. The effects of the thermal conductivity in the porous plate on moisture transport were investigated. The controlling factor for moisture transport was found to be the thermal resistance inside the porous plate having a low-thermal-conductivity and the heat transfer at the surface of the porous plate having a high-thermal-conductivity.     

Synthesis of optical quality ZnO nanowires utilizing ultrasonic spray pyrolysis

ZnO nanowires were grown by an ultrasonic spray pyrolysis technique. The aspect ratio and size of the wire were dependent mainly on the pH value of a precursor solution and the growth temperature. By high-resolution transmission electron microscopic analysis and photoluminescence measurements, it was confirmed that the nanowires are monocrystalline with good optical quality.     

Liquid lithium divertor system for fusion reactor

One of the most critical issues for the steady state fusion reactor is the heat flux in the divertor target. This paper proposes a liquid lithium divertor system to solve this problem. The proposed divertor system consists of a liquid lithium target, an evaporation chamber and a differential evacuation chamber. The heat coming from the fusion plasma along the divertor leg is removed by evaporation of lithium. The lithium vapor is condensed on the wall and is circulated with a pump. The coolant temperature for the wall is high enough to drive a power generator. Narrow slits along the divertor leg and the differential evacuation chamber reduce leakage of lithium vapor to the plasma chamber. A preliminary estimation predicts that the lithium ion density in the core plasma is lower than the plasma density.     

Implementation of Fault-Tolerant GridRPC Applications

A task parallel application is implemented with Ninf-G, a GridRPC system. A series of experiments are conducted on the Grid testbed in Asia Pacific for three months. Through tens of long executions, typical fault patterns were collected, and instability of the network throughput was determined to be a major reason of the faults. Several important points are stressed to avoid task throughput decline due to the fault-recovery operations: Timeout minimization for fault detection, background recovery, redundant task assignments, and so on. This study also issues a steer for design of the automated fault-tolerant mechanism in an upper layer of the GridRPC framework.