Outstanding Paper Award Subcommittee of Kagaku Kogaku Ronbunshu has assessed the 93 papers published in volume 37 into 2011, and the editorial board finally selected the two papers for Kagaku Kogaku Ronbunshu Paper Awards of 2011; those are the papers on “A Numerical Investigation of the Factor Decreasing Transfer Efficiency in a High-Speed Rotary Bell-Cup Atomizer,” and “A Novel Visualization Technique for Distinct Streaklines.”

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In a laminar flow in a mixing vessel, the velocity distribution is decided deterministically. When a blade rotates at a constant speed in a vessel, the velocity has perfect time-periodicity. In this convective mixing, there are definite rules controlling the fluid motion, and they are repeatedly applied. This mixing process is considered to be a deterministic process for which templates exist, and by the repeated use of them the mixing pattern is gradually develops. These templates are the time-invariant streaklines and the streak surface made by their assembly. The various forms of mixing blades and the use of baffles determine the curvature of the streaklines and the undulation of the streak surface as their assembly. Their deformations enhance fluid mixing in various manners. This study focuses on the geometry and the deformation of streaklines and the streak surface are focused. Through this, the mechanism of laminar fluid mixing in a mixing vessel and its enhancement effects on fluid mixing are clarified.

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Power consumption and mass transfer volumetric coefficient were measured with several sizes of mixing vessels and ring spargers. When the ratio of sparger radius to impeller radius was more than 1.3, the decrease of aerated mixing power consumption was suppressed, and the optimal position of the sparger was found. The action of aerated mixing power was correlated with the ratio of sparger clearance to impeller clearance. In addition, the power consumption and mass transfer volumetric coefficient in large-scale vessels (3 m³ and 4 m³) were measured, and it was shown that the mass transfer volumetric coefficient can be correlated with the equation of Sato et al. (1989).

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The power consumption and mass transfer volumetric coefficient were measured in mixing vessels equipped with a concave turbine and a large ring sparger. When the ratio of sparger diameter to impeller diameter was ≧1.3, no decrease was observed in aerated mixing power consumption. In addition, the mass transfer volumetric coefficient could be correlated with the equation of Sato et al. (1989).

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The deformation and breakup processes of particle-cluster aggregates of unequal-sized particles under shear flows were investigated numerically using the two-phase lattice Boltzmann method. The diameter of the larger particles was taken as double that of the smaller particles, and the van der Waals attraction force was taken into account for the interaction between the particles. Also, the Brownian force was applied to each particle in order to treat Brownian motion. Simulations were performed for various fluid forces acting on the particles and various inter-particle forces. Key parameters for estimating the dispersion of the aggregated particles were found to be the ratios of fluid force to the maximum inter-particle force, Y¹¹ (between small particles), Y¹² (between small and large particles), and Y²² (between large particles), and also the Péclet number, which is the ratio of the rate of diffusion by shear flow to the rate of diffusion by Brownian motion, Pe¹ (small particle) and Pe² (large particle). Thus, the aggregate of non-Brownian particles is dispersed when Y^max (the largest among Y¹¹, Y¹², and Y²²) is also over 0.002. In addition, the aggregated disperses to individual particles when Y^min (the smallest among Y¹¹, Y¹², and Y²²) is also over 0.002. Comparison of the calculated results of the dispersion of Brownian and non-Brownian particles indicated that Brownian motion retards the dispersion of small particles but promotes the dispersion of large particles. The effect of Brownian motion is remarkable when the Péclet number is under 10⁴. The results obtained were compared with the results for the dispersion of aggregates of the same-sized particles (Nishiyama et al., submitted). The threshold value of Y for the dispersion in the present paper (polydispersion) was approximately the same as that for monodispersion, but the effect of Brownian motion is not the same as that for monodispersion. The effect represents not only the retardation of the dispersion (small particles) but also the promotion of the dispersion (large particles).

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The capacity of FSM-16 to adsorb trimethylamine and the adsorption mechanism were investigated by experiment and simulation. Highly mesoporous FSM-16 was found to have much higher adsorptivity of trimethylamine than silica gel and activated carbon. The adsorption equilibrium of trimethylamine to these adsorbents was described by a Langmuir-type isotherm. At saturation, the amount of trimethylamine adsorbed by FSM-16 and silica gel increased in proportion to their specific surface area, and all the experimental data for these adsorbents were on the same line. The results indicate that the specific surface area of FSM-16 and silica gel is the most important factor regulating their capacity to adsorb trimethylamine. Further, the adsorption equilibrium constant of the Langmuir parameters suggested that silica-based adsorbents with ca. 2.5–2.7 nm pore size are the most suitable for trimethylamine removal. The results obtained by computer simulation were consistent with experimental ones, and suggested that the adsorption mechanism was dominated by hydrogen bonding.

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Bioethanol for fuel is a renewable energy alternative to petroleum. However, because of the azeotropic point between ethanol and water, the separation and concentration of ethanol to yield a product with low water content by the usual method of distillation requires considerable energy. To develop an environmentally friendly method for purification of bioethanol, we examined the adsorption of ethanol on activated carbon prepared from lignin. The adsorption properties of ethanol on activated carbons at 303 K were compared with those of commercially available high-silica zeolites in batchwise fashion. The specific surface areas of activated carbons were found to be about 2000 m² g⁻¹ by the nitrogen gas adsorption method. The adsorption rate of ethanol on activated carbons in powder form reached equilibrium within 0.5 min, and the adsorption isotherm of ethanol on activated carbons from aqueous solution was of the Freundlich type. The adsorption results revealed that the adsorption capacities of activated carbons for ethanol were influenced by their hydrophobicity, micropore size and percentage of micropore volume. The highest adsorption capacity for 5 vol% ethanol was 280 mg g⁻¹ of the activated carbons prepared from lignin (at 900°C and IR=2). Thermogravimetric analysis (TGA) of activated carbons and high-silica zeolites with adsorbed ethanol was carried out to examine the adsorption mechanisms of ethanol. In both cases, ethanol was found to be selectively adsorbed in preference to water. Finally, activated carbons prepared from lignin maintained their activity even over 20 cycles of adsorption and desorption.

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Ca–Mg–Al type layered double hydroxide (LDH) was synthesized using mixed solutions containing Ca²⁺ and Mg²⁺ as divalent cations by a co-precipitation method. The removal of anionic species in aqueous solution such as As(III), B, Cr(VI) and Se(IV) was examined with the reaction products obtained. The effects of Mg²⁺–Ca²⁺ mixing ratio on the physical properties of the products and their ability to remove anionic species were investigated.
Aluminum hydroxide (AH) and hydrotalcite-like compounds (HT) were formed at pH 10 by a precipitation reaction. In the co-precipitation operation, Mg²⁺ and Al³⁺ were completely precipitated at pH 10, while the percentage of Ca²⁺ precipitated was extremely low. The ability of the complex of AH and HT to remove B and As(III) was higher than those of AH and HT alone. For all anionic species, 90% or higher removal was achieved with the products synthesized from the solution at the mixing ratio of Ca²⁺ : Mg²⁺=1 : 1. Hydrocalumite-like compounds (HC) and HT were also produced at pH 12. All amounts of Mg²⁺ and Al³⁺, and 70–80% of Ca²⁺ were precipitated at pH 12 to form LDH products. Products containing both HC and HT showed no increase in the removal ability in comparison with HC and HT alone. The order of solubility of the product in an anion removal operation was as follows: HC>>HT>AH. The products obtained from the Ca²⁺–Mg²⁺ mixed solution, namely the complexes of AH and HT or HC and HT, had higher solubility than those of HC, HT and AH. The product containing HT as a main component was consider to be superior in the removal of anionic species and the stability of LDH structure among those obtained in Ca²⁺–Mg²⁺–Al³⁺ mixed solution.

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The preparation of nitrogen-rich activated carbon can be achieved by the use of nitrogen-rich precursor or by the nitrogenous modification for carbon surface. In this study, the activated carbon fiber (ACF) was prepared from polyacrylonitrile (PAN) containing ca. 25 wt% nitrogen as a precursor. The prepared PAN-ACF was further treated by urea as a nitrogen medium to introduce the nitrogen functional groups after air oxidation treatment. The surface analysis of urea-treated PAN-ACF by X-ray photoelectron spectroscopy (XPS) revealed that the amount of negatively charged nitrogen species was relatively high compared to PAN-ACF. The result of Cd(II) adsorption experiment indicated that the amount of Cd(II) adsorption was increased in the order of commercial ACFs, PAN-ACF and urea-treated PAN-ACF. The examination of the effect of coexistence between Cd(II) and aromatic compound indicated that Cd(II) adsorbed on π electron clouds of the nitrogen-poor ACF, while not only π electron clouds but also newly introduced specific basic nitrogen/oxygen functional groups contributed to Cd(II) adsorption. These specific sites would not be affected by aromatic compounds.

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Dead-end filtration experiments with semi-permeable ultrafiltration membranes were conducted by using bovine serum albumin (BSA) and dextran solutions, and the variations with time of the filtration rate and the apparent rejection of solutes by the membrane were measured during the course of filtration. It was shown that the increase in the solute rejection accelerated with the progress of filtration brought about the increase in the growth rate of the filter cake comprised of solutes rejected by the membrane. By introducing the concept of the equivalent filtrate volume per unit membrane area, the variations of filtration rate and apparent rejection were interrelated through the properties of the filter cake formed on the membrane surface, i.e., the average specific cake resistance and the average porosity of the filter cake, which were independent of the rejection properties of the membrane. Moreover, the average porosity of BSA filter cake was also evaluated by using a dead-end filter with a sudden reduction in its filtration area in filtration with semi-permeable ultrafiltration membranes.

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The Japanese government is promoting various means aimed at cutting the country's CO₂ emissions by 80% from 1990 levels by 2050. In order to facilitate the reduction of CO₂ emissions, it is important to formulate and introduce economically efficient systems combining sustainable natural energy and high efficiency of energy consumption. As a concrete example, this study examines the case of Okayama Prefectural University. We found that it is possible to formulate a highly economical system and achieve cuts of 35% or more in CO₂ emissions with the combination of 1) replacing absorption-type air conditioning equipment with the heat-pump type, 2) introducing photovoltaic power generation and 3) changing from internal-combustion-engine vehicles to electric vehicles (EV) for commutation.

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The thermo-physical properties of the phase-change latent heat storage material erythritol were elucidated in order to examine its temperature dependency and supercooling phenomenon. Heat transfer by natural convection was also investigated in a horizontal enclosed rectangular container filled with erythritol which was heated at the lower surface and cooled at the upper surface. The supercooling of erythritol was clearly influenced by the cooling rate, and two kinds of supercooling phenomena were found. It was also found that the heat transfer coefficient of the liquid phase coincides well with the conventional heat-transfer correlation of natural convection heat transfer in a horizontal enclosed rectangular container by applying the values of thermo-physical properties obtained in the present work.

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Severe defluidization occurs when reactions accompanied by a decrease in mole number are performed in a gas–solid fluidized bed. This phenomenon is due to a decrease in gas velocity to below the minimum fluidization velocity in the emulsion phase. For the stable operation of a fluidized bed reactor, it is important to control the gas volume reduction rate by reducing the reaction rate. However, this method leads to a low conversion at the reactor outlet. In order to increase the overall conversion, therefore, unreacted components should be separated from the product gas and recycled to the reactor inlet. We studied the gas recycle method on the basis of experimental data reported in previous studies and a fluidized-bed reactor model by considering the decrease in mole number. Because defluidization tends to occur when the gas volume reduction rate increases with the reaction rate, defluidization is minimized when the reaction rate constant reaches its maximum value. In this study, we established the influence of reaction conditions on the maximum reaction rate constant and the minimum recycle ratio.

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The feasibility was investigated of producing alcoholic beverages from astringent persimmon, a common fruit in Japan, by ethanol fermentation with yeast. With the untreated juice of astringent persimmons, the yield of ethanol obtained was 80.9%, which was higher than that of 61.9% for persimmon juice treated to remove astringency, and the highest value of alcohol concentration was about 8 vol%. In a similar experiment, the effect of the presence of persimmon flesh on the fermentation was examined, and it was found to have no effect on the yield of alcohol. Therefore, to make alcoholic beverages from astringent persimmons, it was concluded that there is no need to remove the flesh of the fruit or to carry out treatment to remove astringency, which should contribute to a lower cost of production.

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Continuous gas phase reduction of 4-methyl-2-pentanone catalyzed by immobilized commercial ketoreductase was investigated. Non-porous glass beads were employed as immobilization carriers. An optimal water activity was found to be 0.9 in terms of high enantioselective productivity, while the reaction temperature was optimized at 303–313 K. The stability and enantioselectivity of the immobilized enzyme were almost the same as a function of the substrate activities. The kinetic parameters (V_max=190 [μmol/min/g-protein], K_{m,4-methyl-2-pentanone}=0.405 [−], K_m,2-propanol=0.140 [−]) were estimated.

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