The spatial liquid-phase concentrations were measured by means of an electrical conductivity probe in a 0.289-m ID bubble column operated at superficial gas velocities (u_g) of 0.018, 0.031 and 0.038 m/s, respectively. The column was equipped with a perforated plate gas distributor (0.002 mø × 31 holes). Carbon dioxide was used as a tracer gas, whereas deionized water was used as a liquid phase. The local liquid-phase axial dispersion coefficient E_L was derived from the local liquid-phase concentrations by means of the graphical method developed by Khang and Kothari (1980). It was found that the spatial distribution of the local E_L coefficients becomes radially non-uniform as a function of u_g. At the regime transition velocity (U_trans = 0.031 m/s) between bubbly and transition flow regimes the mean, E_L coefficient for the upper zone (UZ) becomes identical to the one for the lower zone (LZ). At both lower and higher u_g values E_L(UZ) is systematically higher than E_L(LZ). The same result also holds if the overall bubble bed (BB) is divided into core and annulus regions. It was proven that, in the bubbly flow regime (u_g < U_trans), E_L (core region) ≈ E_L (annulus region), whereas in the transition flow regime (u_g > U_trans), E_L (annulus region) > E_L (core region). The effect of the aerated liquid height L on the spatial distribution of the local E_L coefficients was studied, as well. Three different BBs, viz. L = 0.64 m (shallow BB), 1.28 m (medium BB) and 2.1 m (deep BB) were examined at u_g = 0.038 m/s. The spatial distribution of the local E_L coefficients was most scattered in the shallow BB (L = 0.64 m). In a medium BB with an aerated liquid height L = 1.28 m the existence of a well-developed helical flow structure was detected.
It was shown that the graphically determined mean E_L coefficient (for the overall BB) increases as a function of both the superficial gas velocity u_g and aerated liquid height L, and a useful empirical correlation was derived. It covers the following range of bed aspect ratios: 2.1 ≤ L/D_c ≤ 7.3.

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A double-pass mass exchanger with external recycle by inserting a permeable barrier to divide a circular tube into two subchannels of uniform wall concentration, resulting in substantially improving the mass transfer rate, has been investigated theoretically. The mathematical formulation to such a double-pass concentric circular mass exchanger with external recycle, as referred to conjugated Graetz problems, and theoretical analysis on mass transfer efficiency improvement have been developed using an orthogonal expansion technique in power series.
The analytical results show that considerable improvement in mass transfer is obtained with a suitable adjustment of the permeable-barrier position and recycle ratio. The numerical example in mass transfer efficiency by arranging the recycle ratio were illustrated with the mass-transfer Graetz number as a parameter. The effects of permeable-barrier position and recycle ratio on the mass-transfer efficiency improvement as well as on power consumption increment have been also discussed.

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The bubbling characteristics, the bubble rising velocity, the bubble diameter and the bed expansion ratio, were examined under vertical vibration with a two-dimensional fluidized bed. A high-speed camera was used to measure the bubble rising velocity and the bubble diameter. The bubble diameter and the bubble rising velocity had a minimum when a certain vibration strength was added to the bed. At such vibration strength, the bed expansion ratio was the largest. When the convective particle flow enhanced by vibration appeared, the particle flow was significant to clarify the bubbling characteristics under a vibration condition.

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The behavior of carbon particles was numerically studied for various sizes (0.01–5 μm) in the air on which a gradient magnetic field was imposed. One thousand particles were released randomly in one of the vertical cylindrical cross sections whose height is equal to its radius. An electric coil was placed coaxially at the bottom level of the enclosure to produce a magnetic field. The Brownian motion was taken into consideration and the Langevin equation was solved for the particle motion. The effect of the magnetic field on the particle movement increased with the particle size, but the Brownian motion decreased. For those particles with diameter d ≤ 1 μm, the Brownian motion was so strong that the magnetic and gravitational fields had almost no effects on the particle behavior. For the particles of d ≥ 1 μm, the Brownian motion could be ignored mostly, and the particles accumulated at the bottom or upper walls of the enclosure depending on the magnetic strength.

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An LDMA-FCE (long differential mobility analyzer–faraday cup electrometer) system capable of measuring particle sizes up to larger than 1 μm was developed, and a data reduction process for converting an electrical mobility distribution measured by the LDMA-FCE system into a particle size distribution was derived by the modification of a process previously used for a DMA-CNC (differential mobility analyzer–condensation nucleus counter) system. The performance of the LDMA was evaluated by a tandem DMA system, electrical classification of the PSL standard particles, and field emission-scanning electron microscopy observations. The accuracy of the modified data reduction process was confirmed by comparing particle size distributions measured by the LDMA-FCE system with those determined using an LDMA-CNC system. Particle electrical mobility distributions, as measured by the tandem DMA system, were in good agreement with the theoretical distribution. Good agreement was also found between particle size distributions measured with the LDMA-FCE and the LDMA-CNC systems. Thus, the LDMA-FCE system performed well and represents a useful device for measuring the size of submicron aerosol particles over a wide range.

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Microcapsules containing limonene oil as a core material were prepared by interfacial polycondensation polymerization between isocyanate and amine. In the experiment, emulsions were made by dispersing limonene oil in the aqueous solution of poly(vinyl alcohol) and then, microencapsulation was started. It was investigated how the adsorption layer of poly(vinyl alcohol) affected the growth rate of microcapsule shell. The growth rate of the microcapsule shell was estimated by measuring the transient shell thickness of microcapsules which were sampled out at anytime of microencapsulation process. It was found that the growth rate of microcapsule shell decreases with the adsorption amount of poly(vinyl alcohol) on the interface.

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In this study, Ce_0.75Zr_0.25O₂ mixed oxide catalysts and with 1, 5 and 10 wt% Nb-doped were prepared via urea hydrolysis and tested for methane oxidation. The XRD patterns of Ce_0.75Zr_0.25O₂ mixed oxide catalysts and Nb-doped indicate a cubic fluorite structure. The evidence for extra peaks due to non-incorporated Nb was not observed in any XRD patterns of Nb-doped Ce_0.75Zr_0.25O₂. The Raman spectra of niobium oxide surface species were found in 1 wt% Nb loading. The incorporation of 1 wt% Nb was found to promote the reduction of Ce_0.75Zr_0.25O₂ mixed oxide whereas increasing the amount of Nb (5 and 10 wt%) retarded surface reduction. The methane oxidation activity of the mixed oxides was apparently dependent on Nb loading, which relates to the degree of reducibility. In general the catalytic activity decreased with increasing Nb content (above 1 wt%). Nevertheless, it was found that 1 wt% Nb loading promotes the catalytic activity of Ce_0.75Zr_0.25O₂ mixed oxides.

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PEG microspheres immobilizing lipase complexes were prepared using an oil-in-water-in-oil (O/W/O) multiple emulsion. The performance of the PEG microspheres with respect to esterification in isooctane was examined by changing the preparation conditions. We found that the molecular weight of PEG, the PEG concentration, the pH and the type of salts in the aqueous buffer solution are predominant factors influencing the enzyme activity in organic media. These preparation conditions significantly affect enzymatic functions of PEG microspheres containing lipase complexes. The lipase-containing PEG microspheres provide a similar enzymatic activity to that of the lipase complex itself dissolved in organic solvents. The PEG microspheres containing lipase complexes show a heat-resistant property. The PEG microspheres, therefore, exhibit a higher enzyme activity than the lipase complex without a microsphere at all the reaction temperatures tested. In enantioselective esterification, the PEG microspheres show high enantioselectivity in isooctane.

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The formation processes of nanostructures in spherical mesoporous silica were investigated for a two-phase system consisting of hydrophobic tetrabutoxysilane (TBOS) and an alkali solution containing a surfactant as a template. The formation process was deduced as follows: During the initial 2 hours of the reaction, the surfactant in the aqueous phase was extracted with water molecules into the TBOS phase and W/O type microemulsion were formed. Then, the hydrolysis and condensation of TBOS subsequently proceeded at the interface and/or in the water pools in microemulsion, and the viscosity in the TBOS phase increased. After 8 hours, spherical mesoporous silica dispersed in the aqueous phase was obtained under the agitation. The water pools in the TBOS phase were connected to each other, and a regularly arranged nanostructure was formed by the self-assembly of surfactant. Thus, the nanostructure of spherical mesoporous silica was determined to be the reverse of MCM41, in which the continuous mesopores were developed. The solubilizing quantity of phenol for the reversed MCM41, was greater than those for MCM41 and MCM48, due to the continuous mesopore structure.

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An ultrasonic atomizing method is installed into many chemical process systems. In ultrasonic atomization of ethanol water solution, it was confirmed that the enrichment of the ethanol in the droplets. However, it is imperative that atomizing characteristics of liquid fuels are comprehended, taking into account the use of ultrasonic atomization for combustors. In this work, a performance of selective atomization on hydrocarbons–alcohol mixtures is investigated experimentally from a viewpoint of polarity of the solute and solvent. Preparing several sample mixtures, we compared the compositions of the mist produced by ultrasound with bulk composition. As experimental results, the selective atomization of the polar–nonpolar solution has a different tendency compared with the nonpolar–nonpolar solution. In the case of the polar solute, especially, the solute was enriched in the mist under CMC (critical micelle concentration) in the bulk because of the influence of a surface excess. On the other hand, larger than CMC, the enrichment was not confirmed because the surface excess was saturated and inverted micelle was formed.

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A mechanochemical method was used to treat a used evaporation tape, aiming at recovering the contained cobalt (Co) metal and achieving dechlorination non-thermally by dry grinding the tape only or cogrinding with calcium oxide (CaO), respectively. The induced mechanochemical reaction between Co and chlorine in the tape leads to the formation of cobalt chloride, which is water-soluble, offering a novel process to recover the metal from the tape. On the other hand, cogrinding with CaO allows the complete transformation of chlorine in the tape into water-soluble inorganic chloride. The mechanochemical dechlorination process was characterized by an XRD analysis, TG-DTA analysis, SEM photography, Raman analysis and quantitative measurement of the soluble compositions.

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