CdSe nanocrystals were prepared in a microreactor in which of reaction conditions can be precisely controled, and the controlability of particle size and photoluminescence properties, and the effect of reaction conditions on the properties of the product were examined. Particle size and photoluminescence properties were found to be highly reproducible, and the effect of the reaction conditions on particle growth and photoluminescence properties showed basically the same trend with that of a batch reactor, regardless of the shorter reaction time in the microreactor.

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Polymerizations were carried out in a stainless steel capillary of 500 μm inner diameter as a microreactor. Polystyrene of number average molecular weight of 10000 was synthesized during radical polymerization with 2, 2′-azoisobutyronitrile (AIBN) as initiator without plugging the capillary. Copolymerization of styrene (St) and methyl methacrylate (MMA) was carried out in capillary-type microreactor with T-type joint. St and MMA monomers were fed into branched capillaries separately and AIBN initiator was well mixed with St or MMA before polymerization. Two-phase flow was formed at the entrance region of the microreactor, and the difference in viscosity between the each phases increased with the degree of polymerization. Flow behaviors of two phases with different viscosities were also investigated. When AIBN initiator was mixed with MMA, polymerization of MMA caused an increase in viscosity and a prolongation of residence time. As a result, polymer composition could be significantly altered in two-phase microsystem compared to that synthesized in homogeneous reaction system.

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A new method is presented for the preparation of carbon membranes having both catalytic and gas separation properties that could utilize the advantages of laminar flow and high conduction in a microchannel. The carbon membranes with highly dispersed metal were prepared by the carbonization at 500-900°C of polyamide acid membrane loaded with bivalent cations of Cu, Ni or Zn by ion exchange. The metal-loaded carbon membranes carbonized at 700°C have macropores of about 100 nm in diameter. The micropore volume of the membranes carbonized at 700°C was much larger than that of the carbon membranes without exchanged cations.
The cations can form ionic crosslinks between two carboxyl groups and were converted to highly dispersed metal oxide or elemental metal particles during the carbonization. The particle diameter in the carbon membranes loaded with Cu, Ni and Zn had particle diameters of about 20, 25 and 100 nm, respectively, and were expected to possess high activity. Using the prepared catalytic membranes, the high hydrogen yields were obtained in methanol decomposition.

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Microchannel (MC) emulsification is a novel technique for producing monodispersed emulsions. In this study, we investigated the effect of interfacial tension and viscosities of the dispersed and continuous phases on the droplet formation behavior with various surfactant concentrations and various dispersed and continuous phases. Experimental results showed that interfacial tension did not greatly affect the resultant droplet diameter, while the viscosities of both phases had significant effects. Droplet diameter increased with increasing viscosity ratio between the dispersed and continuous phases but did not change in the case of constant viscosity ratio. These results indicated that the droplet diameter is controlled by the viscosity ratio when the MC structure is identical. On the other hand, detachment times increased with increasing viscosities of dispersed and continuous phases. This indicated that the emulsion productivity would decrease with increasing viscosities of the two phases.

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The influence of channel depth on the performance of a micro-separator/classifier (Ookawara et al., 2003), whose main section is a curved microchannel with a rectangular cross section, was studied experimentally and numerically. The width of the examined microchannel was 400 μm and the depths of three models (400a, 400b and 400c) were 250 μm, 170 μm and 100 μm, respectively. Suspensions with weight concentration of 0.06 wt% were prepared as test fluids using ion-exchanged water and acrylic polydisperse particles with average diameters of 7 μm, 10 μm and 20 μm, respectively. For the 7 μm particles, none of the models provided sufficiently high classification, although 400c showed a high concentration effect. The high concentration was possibly caused by the balance of extremely high centrifugal acceleration and a weak Dean vortex that enhances mixing and redispersion of concentrated particles near the outer wall. For the 10 μm and 20 μm particles, 400b always showed better performance than 400a because of the higher centrifugal acceleration in 400b and similar Dean vortex intensities. It is concluded, based on these results, that the channel depth is one of main factors that influence the performance of the micro-separator/classifier.

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A microreactor for high temperature catalytic reaction was designed and fabricated using thin aluminium plates. A microreactor module consists of a parallel array of ten microreactor units, each made of two aluminium plates (Plate-A, Plate-B) connected in series and having ten microchannels. Leakage, pressure drop, and gas velocity of the reactor were measured. In order to perform forced composition cycling of partial oxidation of hydrocarbons, the pulse response method was employed to estimate the flow condition in the microreactor. At 773 K, where the catalytic reaction occurs, the reactor became highly airtight by thermal expansion and diffusion welding of the aluminium plates. The leakage was only 0.006-0.008% of the total flow rate, and the pressure drop of the reactor increased in proportion to the increase of the total flow rate in accordance with Fanning’s equation. Additionally, the RTD curve of the microreactor module was calculated from the pulse response results. It was concluded from the results of the mean residence time, variance and standard deviation obtained from the curve that forced composition cycling could be performed within the period of 2-5 s. Moreover, the gas seems to flow equally to all the channels and units through by-passing flow or stagnation by deformation of the micro-channel during pressurization and heating were not observed.

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The stability of the interface between two liquids in T-shape confluence of microchannels was studied experimentally and numerically. The width and depth of the channels examined in this study were 400 μm and 150 μm, respectively. Visualization showed that fluctuation of the interface occurred in the Re range of above 25. Further, it was observed that one liquid penetrated the other through a symmetrical plane at Re of around 70. On the other hand, numerical simulation showed that the length of the adverse pressure gradient region near the corners increased with Re monotonously. It was confirmed that the slope apparently become smaller at Re=25. Further, it was observed that a twisted flow was formed near this region, and this intensity increased with Reynolds number. Based on these results, it was supposed that the interaction of two twisted flows near the corners caused the fluctuation of the interface. Further, it was shown numerically that a three-dimensional vortex appeared near the interface formed near the wall at Re of 69. Since the shape of the vortex is very similar with that of the observed penetration, it was concluded in this study that the vortex is the main factor that causes the penetration.

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A simple surface modification method using sol-gel method was developed to immobilize an enzyme on the inner surface of a microreactor. In this study, a fused silica capillary used as a microreactor, and lipase was immobilized on it as a hydrolytic enzyme. After the sol-gel modification, a nanoporous structure was obtained on the inner surface of the microchannel. Compared with a batchwise reaction under similar conditions, the efficiency of enzymatic hydrolysis was greatly improved, and the reaction was complete within 30 sec. A decreased reaction yield with a microchannel of larger internal diameter revealed the strong influence of the diameter on the reaction efficiency.

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Microchannel reactors were designed and made from stainless steel through high-precision processing technology. The flow condition of oil and aqueous liquids in the microreactor was observed. The microchannel reactor with a settler could completely separate oil and aqueous layers at the outlet of the reactor. Extraction of Cu²⁺ was examined by using the reactor with the settler. Extraction properties were compared with those of conventional batchwise liquid-liquid extraction with stirring. The following results were obtained. 1) The microchannel reactor with a settler could completely separate heavy-phase and light-phase layers over a wide flow range of 0.03-0.5 cm³/min when a syringe pump was used to feed the solutions. 2) The extraction rate of 0.01 mol Cu²⁺/dm³ of the microchannel reactor with a settler was fast enough to attain extraction equilibrium within 20 second. 3) Back extraction rate of Cu²⁺ in the microchannel reactor was slower than by batchwise extraction operation with stirrer.

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This study was undertaken with the intent of examining the aqueous polymer two-phase system for microscale extraction of protein. Polyethylene glycol (PEG) solution including protein and dextran solution without protein were separately poured into two inlets of a microprocessing device with a microchannel (500 μm width, 300 μm depth). The concentrations of the two polymers were 90 g/L and that of BSA was 200 mg/mL. Protein concentrations in the PEG and dextran layers were measured, and the partition coefficient was calculated as the ratio of the protein concentrations in the two layers. The partition coefficient of the microprocess found to be about 0.2, equal to that obtained by conventional centrifugal separator. As control experiments, (i) two-phase extraction without mixing, and (ii) aqueous polymer two-phase extraction using Teflon tubes (φ=2 mm or 1 mm) were carried out. As a consequence of increase in the specific surface area, the extraction rate in the microprocess was improved, and the extraction period was reduced below that of macro scale processes. In addition, a kinetic model of protein extraction in microsize aqueous polymer two-phase systems was constructed, and the overall mass transfer coefficient K of the microdevice was calculated. It was observed that an increase in the specific surface area resulted in an increase in K. We also confirmed that volumetric mass transfer coefficient could be evaluated from the equivalent hydraulic diameter and linear velocity.

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A novel DNA analysis method suitable for terminal medical facilities has been developed using a microchannel device, which allows high accuracy DNA detection simple operation. Our method does not require immobilization of probe or sample DNA; solutions are simply injected into the microchannel, and all the reactions are performed in the liquid phase. The coefficient of variation of sequence-selective DNA detection was ca. 5%. The method will also make it be applicable to various sequences. These features make it suitable for use in medical examination sites and terminal medical facilities.

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A microchannel for the formation of droplets was fabricated on an acrylic resin plate by mechanical machining. The flow behavior in a droplet formed through a microchannel was investigated. A computational fluid dynamics (CFD) simulation was conducted to investigate the fluid flow during the formation of a hexane droplet in water from a micronozzle with diameter of 100 μm. As a result, the fluid in the droplet was found to recirculate at a high rate due to the effect of contraction flow formed by an expanding droplet in microspace. An experimental study was conducted to validate the simulation results. A continuous n-hexane phase was introduced into the microchannel. Water containing a small number of fluorescent particles was fed from a branch channel. The rotating trajectories of fluorescent particles in the water droplet were then observed.

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The applicability of a microcapillary system to solution crystallization and polymorphism control of glycine was examined. The precipitated crystals were observed under an optical microscope in the case of 1) spontaneous cooling of a solution droplet on a glass plate, 2) external cooling in a small agitated vessel, 3) rapid cooling using the capillary. With natural cooling and cooling in the small agitated vessel (cases 1 and 2), hexagonal crystals were obtained, while rapid cooling using capillary (case 3)yielded orthorhombic crystals which seemed to be a metastable phase. By cooling the solution using the capillary, extremely rapid cooling was achieved, which is impossible in the conventional agitated vessel, and such cooling resulted in a higher degree of supersaturation, from which metastable orthorhombic crystals were stably obtained.

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The solid-phase synthesis of oligopeptide was achieved for the first time in a microfluidic device. We fabricated a microchannel (width 300 μm, depth 160 μm)with a bead trap on a glass plate. Resin beads were loaded in the bead trap for the solid-phase peptide synthesis, and the synthesis of pentapeptide (Met-enkephalin) was conducted in the microchannel. The yield of the synthesized pentapeptide was confirmed to be 20% by MALDI-TOF MS and HPLC analyses.

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Direct hydroxylation of benzene to phenol was attempted using a micro plasma reactor, in which the plasma was generated by dielectric barrier discharge under atmospheric pressure. The experimental results showed that the reactor did not explode even with the concentrations of benzene and oxygen involving a danger of explosion, and the formation of phenol was observed. Effects of gas residence time and benzene-to-oxygen ratio in feed were investigated. An optimum residence time was found for the yield of phenol and the yield gradually decreased with increase in the benzene-to-oxygen ratio. Maximum yield of about 2% was achieved, suggesting that the proposed method was effective for the production of phenol.

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Emulsions composed of droplets of sub-micrometer size have widely been used as industrial products due to their peculiar characteristics. However, little research has been reported on the use of high pressure homogenizers to form emulsions composed of sub-micrometer droplets. In the present work, oil in water (o/w) emulsions composed of sub-micrometer droplets were produced by means of a high pressure wet-type jet mill, using liquid paraffin of different viscosities as a dispersed phase, and the effects of dispersed phase viscosity and operating conditions on the mean droplet size were investigated, together with the effects on emulsion viscosity to the dispersed phase viscosity, operating conditions and droplet diameter.
When the number of passages (N) was unity, the volumetric drop size distribution showed a clear bimodal pattern with an increase in dispersed phase viscosity (η_d). For N≥3, the drop size distribution showed a log-normal pattern at any η_d within the present experimental range. Sauter mean diameter (d₃₂) decreased with increasing number of passages and reached a constant value at η_d and processing pressure (P) covered here. d₃₂ reached a constant value quickly with decreasing η_d, and the effect of P on d₃₂ became extremely small. At high dispersed phase viscosities, d₃₂ reached a nearly constant value. For all the present experimental conditions at N=1, the maximum droplet diameter (d_max) based on droplet number was expressed in the form of d_max=1.96d₃₂ However, the proportionality constant increased with increasing η_d, and decreased with increasing φ. For N=1, the relationship between d₃₂ and P at the various combinations of η_d and φ could be expressed by a straight line on lognrithmic coordinates. The slope became steeper with increasing φ and η_d. Emulsion viscosity (η_e) increased with increases in N, P and φ. However, as η_d increased, the effect of N and P on η_e became very small. Also. η_e increased sharply when d₃₂ became smaller than 0.1 μm.

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Flow properties of steam and their effect on separation efficiency of droplets in mist separators are discussed based on computer simulation. The scales of the separators reflect units installed in a geothermal power plant. The diameters of the inner and outer cylinders are 1 and 3 m, respectively, and the diameter of the inlet pipe is 0.8 m. The distance between the inlet pipe and the outlet mouth, H, is varied between 3.4 and 13.4 m. The average velocity of steam in the inlet pipe is 22 m/s. The steam including droplets is tangentially introduced via the inlet pipe. The steam then forms rotating vortices in the annular section of the separator, moves upwards and finally enters the downward outlet pipe. The droplets are transported toward the inner wall of the outer cylinder by centrifugal force due to the rotating vortices. In the separator of H=3.4 m, the minimum droplet size which is trapped is 20-30 μm. In the separator of H=13.4 m, the steam forms stable rotating vortices, the diameter of which decreases with increasing vertical position. This flow towards the inside of the annular space partially cancels the centrifugal force. Thus the critical droplet size does not significantly change. From the practical point of view, the optimum separation height, H, is estimated to be 7-8 m.

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Adsorptive removal of fluoride ions from water by hydroxyapatite (HAp) prepared from spent mold gypsum for producing ceramics was investigated. The HAp exhibited high adsorption of fluoride ions at neutral pH. Various HAps with different molar ratios of calcium to phosphorus prepared from spent mold gypsum were compared with commercially available HAp for column chromatography. It was found that the HAp prepared from spent mold gypsum effectively adsorbs fluoride ion over a wider pH range, up to the weakly alkaline region, than commercially available HAp, and that the adsorption is not affected by the molar ratio of calcium to phosphorus. A column packed with the HAp prepared from spent mold gypsum was tested for removal of excess fluoride ions from hot-spring water. Fluoride ions were selectively adsorbed from among other anionic and cationic species present and their concentration was successfully lowered below the environmental standard value.

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Batch distillation is an important operation in the small-scale of fine-chemicals. Since such processes often involve expensive materials, it is desirable to separate a product of high purity and in good yield. However, there are few reports on methods to determine theoretically the number of stages of batch distillation appropriate to achieve a specified separation, and the number is determined empirically. This study presents a method to determine the appropriate number of stages to achieve high purity separation and compare optimal reflux policy and constant reflux policy. Recently, small holdup regular packed columns are used in batch distillation, and adequate simulation is considered possible by assumption of no holdup. Here, a technical examination of batch distillation was performed using the McCabe-Thiele calculation method for a no-holdup model.

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The “flux comparative method” was applied to the adsorption process, and an “adsorption characteristic function” was proposed. This method was originally proposed to predict the dependency on moisture content of the moisture transfer coefficient by using a drying rate curve with a constant material temperature. The relation between adsorption rate and mean adsorption amount was obtained from simulations for adsorption on a slab with negligibly small mass-transfer resistance in the surface film. The simulation was done with a diffusion coefficient that was exponentially dependent on adsorption amount. An analytical form (adsorption characteristic function) was proposed by which one can predict the relation between adsorption flux and the mean adsorption amount from the diffusion coefficient. The function was derived through the ”flux comparative method”, in which the steady-state flux for a mean adsorption amount is assumed to be proportional to the flux in a non-steady state with the same mean amount. Calculated results with the function showed a good agreement with the simulated ones.

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To develop a dry process of decomposition, fixation and resource-reconversion of SF₆ gas, which has a global warming potential (GWP) of 23, 900 times that of CO₂, the high-temperature decomposition of SF₆ gas without steam (the basic requirement for dry process fixation technology development) was examined. The gaseous decomposition products were further reacted with calcium carbonate and sodium bicarbonate, and the purity of the fluorides obtained was examined.
It was found that 99% or more of the SF₆ gas could be decomposed at or below temperatures of 1000°C by adding hydrogen gas. Furthermore, the decomposition reaction rate of SF₆ gas could be evaluated with a first-order rate equation of SF₆ gas concentration, and the apparent rate constant could be determined. In addition, the frequency factor (2.08×10³s^-1) and the activation energy (8.314×10⁴J/mol) for decomposition of SF₆ gas were calculated from an Arrhenius plot of the rate constants. It was also confirmed that the decomposition products HF and H₂S could be separated and fixed by a gas solid reaction with calcium carbonate or sodium bicarbonate, and the products formed were of sufficient purity for easy re-use (CaF₂: 98% or more and NaF: 99% or more).

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Many kinds of chemical decomposition processes for polychlorinated biphenyls (PCBs) have been attempted. In this work, a solvothermal process using methanol and sodium hydroxide (alkaline methanol solvent) has been developed as a mild and safety process for the dechlorination of PCBs in transformer oil.
Dispersed PCBs in transformer oil, especially at low concentration, can not be dechlorinated by conventional alkaline hydrothermal treatment. However, we found that PCB concentration can be decreased below 0.5 g/kg-oil (regulated value of PCBs in waste oil) by using thermal alkaline methanol solvent. The dechlorination of PCBs mainly depends on reaction temperature and initial concentration of PCBs, and the new method is particularly effective at temperatures near the critical point of alkaline methanol. Initial PCB concentration from low (200 ppm) to high (10000 ppm) range can be treated effectively.
The spent solvent after reaction is easily separated from oil, and this solvent can be reused as fresh solvent. Furthermore, after dechlorination, transformer oil can be reused without decomposition and polymerization. Therefore the process proposed in this paper offers a suitable closed system for treatment of dispersed PCBs in transformer oil with high dechlorination efficiency.

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A judgment model for adhesion of a particle was developed in order to predict the adhesion phenomenon between solid particles and the furnace wall in a coal gasifier, and it was used to predict the phenomena due to impaction of particles. The Voigt Kelvin model, which is able to express realistically the contact between spherical particles, was adapted for use as the judgment model. If the particle velocity after the impaction was smaller than a threshold value, the particle adhered; otherwise, it did not. The coal combustion in the coal combustor in the runup to the coal gasification reaction in the coal gasifier was numerically analyzed, and calculated velocity gave the trajectory of the particles. The adhesion judgment model was applied to predict the deposition occurring through the impaction of particles with the wall of the furnace. When the van der Waals force was adopted as the only adhesive force acting between the particle and the wall, the adhesive mass of particles calculated by the model developed in this study differed from the one calculated by the traditional model based on ash viscosity.

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An attempt was made to separate copper, zinc and nickel contained in plating wastewater by sulfuration treatment. Simulated plating solutions and plating wastewater from a plating industry that contained these metals at concentrations of 100 to 300 mg/dm³ were treated with sodium sulfide (Na₂S).
It was found that individual precipitation of metal sulfides was achieved by selective sulfuration of mixed metal solutions of copper, zinc and nickel by controlling the pH of the solutions. In the pH range of 1.4-1.5, copper was first separated from the solution as copper sulfide. Next, zinc sulfide was formed in the pH range of 2.4-2.5. Subsequently, nickel sulfide was formed in the residual solution at pH 5.5-5.6. It was also found that copper, zinc and nickel in plating wastewater could be recovered separately as metal sulfides, in a similar way to the selective sulfuration of simulated mixed metal solutions.

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Lead-free glasses with a low melting point and good chemical durability are desirable for the sealing process in the ceramic and electronic fields. In this study, V₂O₅, ZnO, BaO and TeO₂ were used to prepare lead-free sealing glasses with a low melting temperature. The glass forming region, glass transition temperature, softening temperature, thermal stability, thermal expansion property, and X-ray properties were investigated in detail in the ternary (V₂O₅-ZnO-BaO) and quaternary (V₂O₅-ZnO-BaO-TeO₂) systems. The dependencies of these properties on composition were quantitatively characterized. The ternary system glass (50.9 mol% V₂O₅-18.9 mol% ZnO-30.2 mol% BaO)had a low melting property, a high chemical stability (ΔT=101°C), and an amorphous structure. Furthermore, the quaternary lead-free glass (35.9 mol% V₂O₅-13.4 mol% ZnO-21.3 mol% BaO-29.4 mol% TeO₂) showed even higher thermal stability (ΔT=135°C) and good bonding and sealing properties. The quaternary glass also had a high water resistance compared to commercial lead glass. In a sealing test with a plane fluorescence lamp incorporated in a digital camera, perfect sealing was achieved. The prepared lead-free glass showed an excellent performance as a substitute for the commercial lead glass.

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