Molecular simulations have been performed on adsorption equilibria and diffusivities of pure and mixed-gases of ethanol/water in micropores of an NaA zeolite crystal by using the μVT-ensemble orientational-bias Monte Carlo and the NVT-ensemble equilibrium molecular dynamics techniques. The temperature and the total pressure were set at 378 K and 0.1 MPa respectively for comparison with the data of vapor permeation of a corresponding system. Adsorption equilibrium selectivity of water to ethanol was found to increase with an increasing ethanol composition in the gas phase, which was qualitatively in agreement with the experimental permselectivity, though the latter was three orders of magnitude higher than the first. The diffusivity of water in the zeolite was found to be in the region of 3.9–7.9 × 10–10 m2/s while the ethanol molecules were confined in the α-cage and did not go through the window during a simulation period of 3 ns, which indicated that the diffusivity of ethanol might be much smaller than that of water. Therefore, it is concluded that the high permselectivity of water through an NaA zeolite membrane is ascribed to the cooperation of two factors: the high adsorption selectivity and the high diffusivity of water. It is also noted that the selective adsorption of water may be important for preventing the blockage by ethanol molecules at the entrance and inside of the membrane.
Latent heat transportation by ice/water slurry is an effective technology to establish the energy saving air conditioning system. Modak et al. (2002) reported a new surfactant system in which the good agglomeration control of ice particles was available, and effective turbulent drag reduction was simultaneously attained. However, this system needed the addition of a considerable amount of sodium chloride. In this paper, the combined use of zwitterionic surfactant with a suitable brine with no corrosive characteristic is proposed to prepare ice/water slurry. It is certified that newly prepared ice/water slurry shows a good dispersion condition of ice particles and the flowability of the slurry is much improved if it is compared with the previous ice/water slurries. The ice/water slurry thus obtained is promising for the use of the high efficiency heat transportation technology by utilizing surfactant drag reduction and latent heat transportation.
It is known that the particle characteristics and method of coating affect the performance of the electrode in PEMFC technology. The slurry to be used for the preparation of the PEMFC electrode is the suspension of carbon-supported Pt nano-particles (Pt/C) in a Nafion solution. The agglomeration nature of this slurry is obtained both experimentally and theoretically. Information on slurry dispersion is compared with the cross sectional SEM image of the membrane. It is certified that there exists a good correlation between agglomeration characteristic length and the void diameter observed in SEM images. The evaluation of PEMFC electrode performance is done by using several kinds of electrode membranes prepared under different coading speeds. Slight increases both in cell voltage and internal resistance are observed for the case of cathode performance experiments according to the increase of the coating speed. On the other hand, no effect of the coating speed is detected for the case of anode performance experiments due to the cell voltage results were affected mainly by the electrocatalytic activity of the cathode, which results in no effect of the agglomeration. It is concluded that higher coating speed is preferable to get good PEMFC electrode performance within the range of the present experimental conditions.
The densities of the aqueous solutions of poly(ethylene glycol) 2000 (PEG 2000), and its aqueous mixtures with electrolytes and nonelectrolytes, poly(ethylene glycol) 2000 + NaNO3, poly(ethylene glycol) 2000 + sucrose, and poly(ethylene glycol) 2000 + sucrose + NaCl of various compositions have been measured at 20, 25 and 30°C. The density data of the aqueous binary solutions of PEG 2000 up to 0.5 molal have been fitted to a density–molality polynomial. The isopycnotic mixing rule (same density) has been used to predict the densities of the aqueous multicomponent solutions. The predicted and observed densities are in good agreement (overall average error percentage of 0.036%).
A multi-pass laminar counterflow mass exchange device is an open conduit divided into four subchannels with uniform wall concentration, by inserting three permeable barriers. Only the composition of the flow stream varies along the channels. The Sherwood numbers as well as the improvement of mass transfer efficiency have been investigated analytically by using an Eigenfunction power series expansion. The device performance results in multi-pass operations are represented graphically and compared with those in a single-pass device (without permeable barriers inserted). Analytical results show that there exists a best permeable-barrier position when both the mass transfer improvement and the increment of power consumption are considered and thus can effectively enhance the mass transfer efficiency compared with that of single-pass operations.
The onset position of the hydraulic jump formed by a water-impinging jet on an inclined substrate was measured. It was found that the outlined shape at the onset of the hydraulic jump became elliptical with the major axis increasing as the inclination angle of the substrate increased. A set of equations were proposed for predicting the onset position of the hydraulic jump. The prediction can be made with a reasonable accuracy, within ±13% errors, so that these equations can be used to estimate the onset position of the hydraulic jump on an inclined substrate. Moreover, it is also possible to determine the appropriate inclination angle of the substrate and the flow rate of a water-impinging jet for detaching fine particles from an inclined substrate.
Various wall-type nickel catalysts were prepared on aluminum plates by electroless plating under changing conditions for displacement plating of zinc and chemical reduction plating of nickel, and their physicochemical properties were investigated. Correlation between these physicochemical properties and the decomposition properties of methanol over these plated catalysts was examined. The results show that the decomposition performance of the plated catalysts does not correlate with the surface areas of the plated layer but depends on the ratio of the crystallite size of nickel particles, as determined by XRD, to that of aluminum particles. This finding suggests the involvement in catalytic activity of aluminum that dissolves from the substrate in the plated layer as well as nickel, which is considered as the active site. Elemental component analysis and elemental state analysis in the plated layer indicate that the use of sodium hypophosphite monohydrate as a reducing agent results in the incorporation of phosphorus in the plated layer, and the plated catalyst with high selectivity of carbon monoxide and hydrogen for methanol decomposition contains large amounts of zinc and phosphorus, and a small amount of aluminum, with nickel in the bulk layer of this catalyst being in a metallic-state. The finding in which granular Ni3P and Ni/ZnO catalysts, with high selectivity for methanol decomposition, had metallic-state nickel suggests that some incorporation of phosphorus and zinc oxide, that increased the metallic-state of nickel, and the small amount of aluminum in the plated layer produce the high selectivity for methanol decomposition.
CO removal from a reformed gas by catalytic methanation on Ru/Al2O3 was studied for Polymer Electrolyte Fuel Cell (PEFC) systems. The effects of the gas composition and the reaction temperature on CO methanation activity were examined. The ratio of methanation of CO to that of CO + CO2 was also investigated. Consequently, it was found that CO could be removed from a reformed gas to below 10 ppm by controlling CO2 methanation by multi-stage CO methanation, while CO could not be reduced to below 10 ppm by single-stage CO methanation due to the presence of CO2.
A gel adsorbent which adsorbs and/or desorbs specific heavy metal ions selectively by temperature swing was prepared by copolymerizing the chelating monomer, N-(4-vinyl)benzyl ethylenediamine (Vb-EDA) with N-isopropylacrylamide (NIPA) as thermosensitive component by using the molecule imprinting technique. Copper ion, Cu(II) was selected as a target ion in imprinting. The adsorption amount of Cu(II) ions on imprinted gel depended on the temperature, and the maximum amount was obtained at a specific temperature where the size of gel network corresponds to that memorized in the preparation of gel. The adsorption amount depended on the gel composition, namely, the concentrations of NIPA and cross-linker. The adsorption amount increased linearly with the increasing Vb-EDA content in the gel, and the slope was almost 1/2. This implies that one Cu(II) ion coordinates with two molecules of Vb-EDA. The adsorption amount was well described by the Langmuir isotherm formula. The adsorption and desorption could be done repeatedly by temperature swing. Furthermore, the selective adsorption of Cu(II) ions was confirmed by comparing the adsorption amounts of other metal ions, Ni(II), Zn(II) and Mn(II).
Esters of volatile organic flavor compounds were recovered from dilute aqueous solutions by pervaporation; ethyl acetate (EA), propyl acetate (PA), and butyl acetate (BA). A surface-modified tube-type alumina membrane was used to evaluate the effects of the feed concentration (0.15–0.60 wt%) and feed temperature (30–50°C) on the separation of EA, PA, and BA from dilute aqueous solutions. The permeation flux increased with the increasing feed ester concentration and operating temperature. The separation factors for the 0.15–0.60 wt% feed solutions of EA, PA, and BA at 40°C were in the range of 66.9–78.9, 86.0–89.0, and 117.1–94.7, respectively. EA, PA, BA in the permeate were concentrated up to 9.13–32.26, 11.44–34.95, and 14.96–36.37 wt%, respectively. Due to the high selectivity, phase separation occurred in the permeate stream because the ester concentration in the permeate was above the saturation limit. The fluxes of EA, PA, and BA at 0.60 wt% feed concentration and 40°C were 254, 296, and 318 g/m2·h, which are much higher than those obtained with polymer membranes. In the case of PDMS at feed concentrations of 90–4800 pp, and at 45°C, it was reported that the permeate flux of EA was 1.1–58 g/m2·h. Compared to PDMS, the surface-modified membrane investigated in this study showed a much higher flux of esters.
A drug substance AE1-923 (4-[[2-[N-(5-Methylfuran-2-sulfonyl)-N-isopropylamino]-5-(trifluoromethyl)phenoxy]methyl]benzoic acid), which was developed for the indications of pollakiuria and pain, was crystallized from the solution prepared with a mixed solvent of ethanol and water. AE1-923 was found to have three kinds of crystal polymorphs in the mixed solvent; namely the unstable A-form, the meta-stable B-form, and the stable C-form. The method of reliable and exclusive production of the meta-stable crystals among the three kinds of crystals was investigated. Three kinds of crystallization operation were attempted. Operation-1 was designed for directly precipitating the B-form crystals by cooling crystallization without precipitating the unstable A-form crystals. However, it was failed by a rapid transformation of polymorph from the B-form to the C-form. Operation-2 was designed for actively utilizing the transformation of polymorph from the A-form crystals to the B-form crystals by cooling crystallization. However, this operation was also failed by the same reason, namely a rapid transformation to the stable C-form. Operation-3 was also designed for actively utilizing the transformation of polymorph by poor solvent crystallization. By Operation-3, each polymorph including the B-form could be exclusively and consecutively produced. From these results, it was concluded that the utilization of the solvent-mediated transformation from the unstable polymorph to the meta-stable polymorph is effective for the production of meta-stable crystals even when three kinds of polymorphs may be simultaneously precipitated.
The extraction of total alkaloids from Sophora alopecuroides L. was enhanced by using ion exchange resin at reduced pressure. At room temperature and 0.08 MPa vacuity for 12 h, 96% of the total alkaloids was extracted from the seed particles of 0.18–0.25 mm using deionized water of pH 3.0 in the presence of the cationic ion exchange resin 001×7 (cross-linked polystyrene, particle size 0.32–1.25 mm, exchange capacity 4.5 mmol g–1 resin, dry wt.). In contrast, it took the same time to get 72% of total alkaloids in the case without the resin. The yield of total alkaloids extracted at 0.06 MPa vacuity without the resin reached 60%, while that was only 47% in the case at normal pressure.
The effects of the reduced pressure on the minimum bubbling velocity and on the homogeneous fluidization region were investigated for three kinds of glass bead powders that belonged to group-A in Geldart’s classification. The minimum bubbling velocity as well as the minimum fluidization velocity increased with a decrease in the pressure. It was found that the Reynolds number at the minimum bubbling velocity was related to the Knudsen number. The effects of the particle diameter and reduced pressure on the homogeneous fluidization region were experimentally examined. The homogeneous fluidization region became larger as the particle diameter decreased, and it became smaller as the pressure decreased.
The extraction of lactic acid from an aqueous solution by microcapsules containing extractants was investigated in order to prevent the dissolution of the extractants in the aqueous solution. Microcapsules containing tri-n-octyl phosphine oxide (TOPO) and a mixture of tri-n-butyl phosphate (TBP) and tri-n-octylamine (TOA) showed high extractability at low pH, but low extractability at the optimum pH of the fermentation. Then, toxicity of these microcapsules to immobilized Lactobacillus rhamnosus was investigated. The microcapsules containing TOA-TBP showed high toxicity to the cells, on the other hand, the microcapsules containing TOPO slightly affected lactate production. The microcapsules containing TOPO were used in the extractive fermentation process by reasons of their lower toxicity to the microbes than those containing TOA-TBP. The extractive fermentation of lactic acid coupled with a column packed with the microcapsules was found to be very effective method from the point of view of cell growth.
In order to develop the admicellar system, lipase from Candida rugosa was immobilized into an admicellar system consisting of silica gel and nonionic surfactant, Triton X-100. Adsorption mechanism of lipase on the admicelles was different from bare silica gel. On bare silica, multilayer adsorption of lipase molecules was supposed due to a scarce affinity to the silica surfaces. On the other hand, in the case of admicelles, the adsorption isotherm of lipase was well correlated with the Langmuir model. Such transformation of isotherms was not observed in the case of lysozyme. These behaviors were explained by two aspects; electrostatic interaction due to the isoelectric point of both enzymes and surface charge of silica gel, and affinity originated in hydrophobicities of enzyme surface. From H.F.S. values, it was presumed that the surface of lipase from Candida rugosa was relatively hydrophobic and lysozyme had a rather hydrophilic surface. In addition, activity of lipase could be maintained in Triton X-100 layers on silica gel after washing by buffer solution.
This research involved field surveys in different geographical locations in Tanzania for collection of fungi species, identification of the isolates, and screening for lignin-degrading enzyme production. Out of 18 saprophytic fungi (both wood and non-wood inhabiting) isolates, 17 were positive in the rhemazol brilliant blue-R (RBBR) decolorization test; 15 of the isolates oxidized guaiacol while 7 and 12 oxidized α-naphthol and pyrogallol, respectively. The cultures with 1% glucose concentration showed the fastest growth of mycelia and highest MnP, LiP, and Lac activities. MnP was found to be dominant among the tested isolates and Laetiporus sulphurae had the highest LiP activity of 65.2 U/ml. Most of the fungi isolates produced more than two extracellular enzymes, suggesting that these isolates possess the ability to degrade lignin or related polyphenolic compounds, and thus they can be used in upgrading low quality animal feed. The selected fungi isolates reduced cellulose and hemicellulose contents in rice straw by an average of 10% and 35%, respectively, delignification ratio of 23% and increased its relative crude protein content by more than 50%.
Coalescence of aqueous droplet on macroscopic oil/water interface was investigated. The interface had intrinsic instability which induced the self-pulsing of the dynamic interfacial tension and the macroscopic interfacial flow due to the Marangoni effect. Di-2-ethylhexyl phosphoric acid was used as a surfactant, and calcium chloride or calcium hydroxide was used as an electrolyte. Coalescence time was compared with the equilibrium interfacial tension and the strength of the spontaneous interfacial flow. The coalescence time decreased with an increase in the aging time during which the oil/water interface kept intact and took a maximum near a certain concentration of the surfactant. An experiment with an artificial interfacial flow due to the Marangoni effect was also performed. Coalescence time was completely independent of the interfacial coverage or composition of the surfactants, and only affected by the strength of the interfacial flow at the interface. We concluded that the spontaneous interfacial flow retarded the coalescence since it interrupted the fusion process with molecular reorganization. One can easily think that the droplet surrounded by the intrinsically unstable surfactant film has a short life time. However, there are cases that the droplet with an unstable surfactant film has a longer life time than that covered by a stable surfactant film.