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Lipid extraction from Scenedesmus sp. microalgae using hot compressed hexane (HCH) was investigated. Extraction performance was evaluated near the critical point of hexane and was compared with that of hexane extraction performed at room temperature and pressure, and the Bligh and Dyer extraction method. Experimental data showed that HCH significantly improves the lipid yield and rate of lipid extraction compared to the use of hexane at ambient conditions. High yields of biodiesel-convertible lipid fractions were rapidly achieved at the critical point of hexane, at a level comparable to that of the Bligh and Dyer method.

In this study, a supercritical one-pot process combining transesterification and partial hydrogenation was proposed to test its technical feasibility. Simultaneous transesterification of soybean oil and partial hydrogenation of polyunsaturated compounds over Cu catalyst in supercritical methanol was performed at 320 °C and 20 MPa. Hydrogenation proceeded simultaneously during the transesterification of soybean oil in supercritical methanol, and hydrogenation occurred during the reaction despite the absence of hydrogen gas. The polyunsaturated methyl esters obtained in the biodiesel were mainly converted to monounsaturated methyl esters by partial hydrogenation. Key properties of the partially hydrogenated methyl esters were improved and complied with standard specifications for biodiesel.

In this work, hydrolytic reaction conditions of various temperatures (300–370 °C) and times (0–30 min) at a constant pressure of 20 MPa were applied to the thermal decomposition of three kinds of fatty acids (FAs), stearic acid, oleic acid, and linoleic acid, in subcritical water. The degradation characteristics were investigated from the derived data, and the thermal stability of FAs in subcritical water was estimated. The primary reactions we observed were isomerization and pyrolysis of FAs. The main pathway of degradation was deduced by analyzing the contents of pyrolyzed products. We found that more saturated FAs have greater thermal stability in subcritical water. All FAs remained stable at 300 °C or below. Based on these results, we recommend that hydrolysis of vegetable oils and fats using subcritical water should be carried out below 300 °C (at 20 MPa) and for less than 30 min to obtain high-yield FA production.

In this study, used vegetable oils (VO) were transesterified in supercritical methanol with a Cs-doped heteropolyacid (HPA) catalyst so as to produce biodiesel. The stability of the prepared catalysts was determined by measuring the amount of dissolved heteropoly anions. Cs 2.5 PW 12 O 40 exhibited the highest stability in supercritical methanol. Kinetic parameters were determined at the initial stage of the reaction to examine the reaction rate of the process. The effects of the reaction parameters, including the molar ratio of methanol to oil, reaction pressure, temperature, and time, on the content of fatty acid methyl esters (FAMEs) were also investigated in order to obtain optimum reaction conditions. The content of FAME reached 92% under the optimum reaction conditions of 260 °C, 20 MPa, a molar ratio of methanol to oil of 40, and a reaction time of 40 min in the presence of 3% catalyst. The results showed that supercritical methanol compensated for the low reaction rate of solid acid catalytic transesterification, while the Cs-doped HPA catalyst mitigated the harsh operation conditions of the supercritical methanol process.

Biodiesel production via transesterification of rapeseed oil in supercritical methanol was performed without catalysts. Response surface methodology (RSM) was used to evaluate the relationships between the content of fatty acid methyl esters (FAMEs) and reaction parameters, such as reaction temperature, reaction pressure, reaction time, and the molar ratio of methanol to oil. A central composite design was employed to fit the available response data to a second order polynomial RS model. The optimal conditions maximizing the content of FAMEs in the biodiesel were investigated. Results showed that the optimum processing conditions were 330 °C, 210 bar, a reaction time of 16 min, and a molar ratio of methanol to oil of 50 mol/mol. The predicted response value for these conditions was 93.6% methyl esters and it was in agreement with the experimental value.

In recent years, non-catalytic supercritical processes for biodiesel production have been proposed as alternative environmentally friendly technologies. However, conditions of high temperature and pressure that occur while biodiesel is in supercritical fluid can cause fuel degradation, resulting in low yield. In this study, we performed the thermal decomposition of fatty acid methyl esters (FAMEs) in supercritical methanol at temperatures ranging from 325 °C to 420 °C and pressure of 23 MPa to investigate the degradation characteristics and thermal stability of biodiesel. The primary reactions we observed were isomerization, hydrogenation, and pyrolysis of FAMEs. The main pathway of degradation was deduced by analyzing the contents of degradation products. We found that if FAME has shorter chain length or is more saturated, it has higher thermal stability in supercritical methanol. All FAMEs remained stable at 325 °C or below. Based on these results, we recommend that transesterification reactions in supercritical methanol should be carried out below 325 °C (at 23 MPa) and 20 min, the temperature at which thermal decomposition of FAMEs begins to occur, to optimize high-yield biodiesel production.

EPDM/organoclay nanocomposites were prepared by a melt mixing of a semicrystalline EPDM grafted with maleic anhydride and an organoclay (Cloisite 20A) in an internal mixer. XRD and TEM analysis revealed that the EPDM/clay forms a partially exfoliated nanocomposite and the silicate layers of the clay are uniformly dispersed at a nanometer scale in the rubber matrix. DSC studies indicated that the clay nanoparticles caused an increase in the nonisothermal crystallization temperature of the EPDM. Tensile and dynamic mechanical analysis showed that a small amount of the clay nanoparticles effectively enhanced the stiffness of the EPDM without adversely affecting its flexibility. The EPDM/clay nanocomposites were used to produce foams by using a batch process in an autoclave, with supercritical carbon dioxide as a foaming agent. The exfoliated nanocomposite produced a microcellular foam with average cell size as small as 6.23 μm and cell density as high as 2.4×1010 cell/cm3.

The degradation of polystyrene (PS) in supercritical methanol was carried out under reaction temperatures ranging from 340 to 420°C and pressures of 10–30 MPa. The selectivity of liquid products was investigated at various reaction conditions. As the reaction proceeded, the selectivity of styrene monomer, dimer, 1,3-diphenyl propane, and 1,3-diphenyl butane had a declining tendency, whereas that of the rest (i.e., toluene, ethyl benzene, isopropyl benzene, and 3-phenyl propanol, etc.) had an inclining tendency. The sequences of decomposition reaction could be reasoned by analyzing the variation of selectivity of liquid products. The kinetic behavior of PS in supercritical methanol had been investigated. The degradation processes of PS in such supercritical fluids could be formulated by the first-order kinetic law at the initial stage of reaction. The activation energy for the degradation in supercritical methanol was evaluated to be 117.2 kJ/mol and it was also compared with the activation energies for depolymerization in other supercritical fluids and that for thermal pyrolysis. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008

Due to the need for CO2 sequestration associated with H2 production from fossil fuels, zeolite membrane are very promising due to their low cost, high stability and high permeance. Recently, the faujasite(FAU), the silica/aluminophophate(SAPO-4) framework family of zeolite have been studied for CO2 gas separation. In our study, ZSM-5 membrane was prepared on the porous alumina support using a hydrothermal technique. The thickness of zeolite membrane was controlled by the hydrothermal reaction time and temperature. The prepared zeolite membranes were characterized with SEM and thin film XRD. The hydrogen permeability and selectivity toward carbon dioxide gas were 0.6x 10-6 mole/m2.s.pa and 3.16, respectively. The hydrogen selective zeolite membranes show promising application in hydrogen separation from coal gasification such as Integrated Gasification Combined Cycle (IGCC).

The possible utilization of automobile shredder residue as a fuel in the cement kiln process was investigated. The detailed characteristics of the automobile shredder residues were investigated in terms of it’s chlorine content as a fuel feed and its circulation in cement kiln. For estimation of the chlorine content in the cement kiln system, the Weber model which is one of the circulation material’s forecast model was used. From the results, we estimated the chlorine by-pass rate should be 1 ~ 2 percent, for maintaining the present level of chlorine content’s on the hot-meal of the cement kiln system.

This paper investigates the effect of the pair-minerializer (CaSO4,-CaF2) on the reaction of alite, belite and calcium langbeinite formation with different alkali and sulfate contents. A set of clinker samples was prepared by adding laboratory grade reagents of (NH4)2SO4, CaF2 and K2CO3 to the cement raw mixes. The mineralogical composition of clinker was analyzed by X-ray powder diffraction, and the quantity of minerals was evaluated by using TOPAS software. As the experimental results, the total amount of calcium silicate minerals was rapidly increased with the addition of F and SO3 components simultaneously as pair-mineralizer with K2O more than the value which mineralizer was added separately. Also, in the case of adding K2O only to the raw mixes, the amount of alite is decreased after clinkering. However, if alkali (K2O) and pair-minerializer (CaSO4,-CaF2) were added simultaneously, the quantity of alite and calcium langbeinite mineral increased because of the formation of stable clinker minerals by the reaction of alkali (K2O) and sulfate.

Nanoporous SiC membrane was developed on the porous alumina plate for the hydrogen separation using preceramic polymers such as polyphenylcarbosilane. The prepared preceramic polymers were characterized with FT-IR, TGA, GPC and XRD. Nanoporous SiC membrane was derived from the preceramic polymer using a spin coating method. The SiC membrane spin coated using 20 wt.% of polyphenylcarbosilane solution in cyclohexane does not show any cracks on the surface after heat treatment at 800oC. The average thickness of the SiC membrane is about 1µm. SiC coated porous alumina possesses asymmetric pore size distribution. There are micropores that originated from porous alumina substrate, and nanopores that derived from amorphous state of SiC membranes. The pore size distribution measurement showed that the sample contains 1-3 nm sized nano pores.

In our preceding work, the simultaneous deviation from the conventional dual-mode sorption and mobility model was observed in a case of CO2 in polystyrene (PS) membrane (glass transition temperature of pure polymer = 95°C) at 60 and 70°C. The plasticization effect of sorbed CO2 on both the sorption and diffusion processes tends to be brought about in glassy polymer membranes near the glass transition temperature. The behavior was simulated based on the concept that only one population of sorbed gas molecules of plasticizing ability to the polymer should exist. In the present work, the sorption and permeation behavior for CO2 in NH3-plasma-treated and untreated PS membranes at 40°C was investigated, where NH3-plasma treatment was executed at plasma discharge powers of 40, 80, 120, and 160 W for an exposure time of 2 min. The sorption isotherm could be described by the sorption theory of Mi et al. (Macromolecules 1991, 24, 2361), where the glass transition temperature is depressed by a concentration of sorbed CO2 of plasticizing ability. NH3-plasma treatment on PS membrane had little influence on the sorption behavior of CO2 at plasma discharge powers up to 160 W. The mean permeability coefficients were somewhat increased only at a discharge power of 160 W. At CO2 pressures below 0.9 MPa, the pressure dependencies of mean permeability coefficients for CO2 in both NH3-plasma-treated and untreated PS membranes at 40°C could also be simulated on the basis of the concept that only one population of sorbed gas molecules of plasticizing ability should exist. At CO2 pressures above 0.9 MPa, however, a plasticization action of sorbed CO2 had much more influence on the diffusion process rather than on the sorption one, and such a combined concept underestimated the mean permeability coefficient. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 1798–1805, 2007

The degradation of polystyrene (PS) in sub- or supercritical water was carried out at reaction temperatures ranging from 370°C to 420°C and pressures of 240 to 320 bar. At 370°C, where water is in a subcritical state, the degradation was in equilibrium in about 5 min, whereas at 380°C and 390°C, where water is in a supercritical state, it was completed in 15 and 3 min, respectively. The equilibrium conversion in the supercritical state (100 wt %) was higher than that in the subcritical water (ca. 80 wt %). The dependence on time of selectivity for the degradation products—styrene monomer, styrene dimer, styrene trimer, toluene, ethyl benzene, isopropyl benzene, and triphenyl benzene—were investigated at 400°C and 280 bar. As the reaction proceeded, selectivity for styrene monomers, dimers, and trimers decreased, whereas that for toluene, ethyl benzene, and isopropyl benzene increased because of the difficulty of decomposing the benzene rings and phenyl radicals. Triphenyl benzene increased with reaction time for the same reason. With increasing temperature, selectivity for the styrene monomers and dimers decreased slightly, whereas selectivity for toluene and ethyl benzene increased a little. The kinetic behavior of PS in supercritical water along with supercritical acetone and n-hexane were investigated. The degradation processes of PS in such supercritical fluids could be formulated by the first-order kinetic law at the initial stage of the reaction. The activation energy for the degradation in supercritical water was evaluated to be 157 kJ/mol compared to an activation energy of 132 kJ/mol in the supercritical n-hexane. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 695–700, 2006

A kinetic analysis method for the degradation of polymer in supercritical fluid was proposed in this work. The method was applied to predict the degradation of polystyrene (PS) in supercritical acetone by nonisothermal weight loss technique with heating rates of 3, 5, and 7°C/min. To verify the effectiveness of the kinetic analysis method proposed in this work, the experimental values were compared with those of the numerical integration results using kinetic parameters obtained in this work. It was found that the kinetic analysis method proposed in this work gave a reliable value of kinetic parameter for PS degradation in supercritical acetone. The kinetic parameters were also compared with the values of thermal degradation of PS in the nitrogen atmosphere reported in the literature.

Polyethylene-octene elastomer (POE)/organoclay nanocomposite was prepared by melt mixing of the POE with an organoclay (Cloisite 20A) in an internal mixer, using poly[ethylene-co-(methyl acrylate)-co-(glycidyl methacrylate)] copolymer (E-MG-GMA) as a compatibilizer. X-ray diffraction and transmission electron microscopy analysis revealed that an intercalated nanocomposite was formed and the silicate layers of the clay were uniformly dispersed at a nanometre scale in the POE matrix. The nanocomposite exhibited greatly enhanced tensile and dynamic mechanical properties compared with the POE/clay composite without the compatibilizer. The POE/E-MA-GMA/clay nanocomposite was used to produce foams by a batch process in an autoclave, with supercritical carbon dioxide as a foaming agent. The nanocomposite produced a microcellular foam with average cell size as small as 3.4 µm and cell density as high as 2 × 1011 cells cm−3. Copyright © 2005 Society of Chemical Industry

The reutilization of waste plastics as a fuel in the cement kiln precalciner process was investigated. For uniform feeding into the fluidized bed calciner, waste plastics were prepared to form of pellet type by shredding, melting, pressing, cutting and screening. We examine the property of combustion for different pellet size using the Computational Fluid Dynamic analysis program to minimize a risk and to optimize condition of an actual proof plant. Based on the results from the computational fluid dynamic analysis, the waste plastic for the industrial scale experiment were used as 20mm, 50mm and 100mm in size. The experimental result of an actual proof plant showed comparatively good correlation with the computational fluid dynamic analysis.

The rapid expansion of a supercriti cal solution (RESS) process is an attractive technology for the produc- tion of small, uniform and solvent-free particles of low vapor pressure solutes. The RESS containing a nonvolatile solute leads to loss of solvent power by the fast expansion of the supercritical solution through an adequate nozzle, which can cause solute precipitation. A dynamic flow apparatus was used to perform RESS studies for the preparation of fine anthracene particles in pure carbon dioxide over a pressure range of 150-250 bar, an extraction temperature range of 50-70 o C, and a pre-expansion temperature range of 70-300 o C. To obtain fine particles, 100, 200 and 300 µm nozzles were used to disperse the solution inside of the crystallizer. Both average particle size and particle size distribution (PSD) were dependent on the extraction pressure and the pre-expansion temperature, whereas extractor temperature did not exert any significant effect. Smaller particles we re produced with increasing extraction pressure and pre- expansion temperature. In addition, the smaller the nozzle diameter, the smaller the particles and the narrower the PSD obtained.

The effect of NH3-plasma treatment on glassy polyethersulfone (PES) membranes upon the diffusion process for CO2, O2, and N2. was investigated from the permeability measurements. The permeation behavior for O2 and CO2 in untreated and NH3-plasma-treated PES membranes was simulated well in terms of the dual-mode mobility model. For O2 transport, NH3-plasma treatment on PES membrane had a little influence on the diffusion process of Langmuir species and very little influence on the diffusion process of Henry's law species. For CO2 transport, it promoted the transport of Henry's law mode but had very little influence on the transport process of Langmuir species. Both the mean permeability coefficient to CO2 and the ideal separation factor for CO2 relative to N2 took maximum values at a treatment power of 40 W. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 94: 758–762, 2004

Degradation of polystyrene was carried out in supercritical n-hexane under reaction temperature ranging from 330 °C to 390 °C, pressure ranging from 30 bar to 70 bar and reaction duration of 90 min. The conversion of polystyrene increased with rising temperature and pressure. The degradation performance was influenced by the temperature rather than applied pressure. Polystyrene rapidly degraded in 30 min after reaching a prescribed temperature ranging from 350 °C to 390 °C. At a prescribed temperature of 390 °C, the degree of degradation was higher than 90%. The degradation reaction was examined experimentally at a relatively low temperature of 330 °C. The degradation of polystyrene by using supercritical n-hexane has been found to be more effective compared to general pyrolysis (thermal degradation). Among the selectivity of liquid products, that of a single aromatic ring group like styrene at 390 °C increased up to 65% in 90 min. It was found from the analysis by a gel permeation Chromatograph (GPC), that high molecular-weight compounds decreased but oligomers increased with rising temperature.

The degradation of high density polyethylene (HDPE), polypropylene (PP) and their mixtures was carried out in supercritical acetone under the reaction temperature ranging from 450 ‡C to 470 ‡C, pressure ranging from 60 atm to 100 atm and reaction duration time as 60 min. The yields of gas, oil and wax components and the compositions and distributions of liquid-like products were measured by means of gas chromatography and gas chromatography/mass spectrometer. In every run, the reaction was completed in 30 min after reaching the prescribed temperature. The yields of oil and gas degraded from PP were not greatly influenced by the temperature, whereas in HDPE, the yields of oil decreased and that of gas increased, respectively, with rising temperature. The yields of oil from HDPE and PP increased with increasing pressure up to 7 atm and the values under higher pressure remained almost constant, i.e., 88% for HDPE and 96% for PP. Correspondingly, the yields of wax from HDPE and PP decreased with increasing pressure below 75 atm and above the value they remained almost constant, especially zero with PP. Generally, the degradation performance was influenced by the temperature rather than applied pressure. For the degradation of mixtures of HDPE and PP, with increasing PP composition, the yield of oil increased, whereas that of wax decreased, and above 80% of PP composition, it decreased to zero. For example, the yields of oil, wax and gas from a 52 wt% HDPE-48 wt% PP mixture, amounted to 90 wt%, 1 wt% and 9 wt%, respectively. The yield of wax decreased with increasing PP percentage.

The sorption equilibria and permeation rates for carbon dioxide in such glassy polymer memrbanes with high glass-transition temperature as polyimide, polyetherimide, polysulfone and polyethersulfone membranes, were measured. The sorption isotherms for these systems can be described well in terms of the dual-mode sorption model, whereas the pressure dependences of the mean permeability coefficients are simulated better by a modified dual-mode mobility model than the conventional dual-mode mobility model in which the Henry's law and Langmuir populations execute four kinds of diffusive movements.

A mathematical model developed by Muramatsu, Umemura, and Okada (1979) was modified and improved by changing the relative amounts of radiative and conductive heat transfer to study the effects of moisture content in the cigarette, cigarette packing density, and cigarette circumference on the smoldering rates, heat flux, and total heat released during natural smolder of a cigarette. A mathematically predicted temperature profile was fitted to the corresponding experimental values with a nonlinear least-square fitting routine to obtain a smoldering rate and the relative amounts of radiative and conductive heat transfer. Then, based on the relative contribution of heat transfer modes, the heat flux and the total heat released were calculated with the fitted smoldering rate as a function of cigarette design parameters. Results show that the circumference of the cigarette is the major physical factor affecting mass burn rate (MBR), while the packing density of the cigarette strongly affects the linear burn rate (LBR), heat flux, and total heat released.

The depolymerization of polyethyleneterephthalate (PET) in supercritical methanol was carried out using a batch-type autoclave reactor. The total conversion and the yield of dimethylterephthalate (DMT) increased with rising temperature. The final yield of DMT at 300°C and 310°C reached 97.0% and 97.7%, respectively. The yield of DMT was markedly increased when the methanol density was 0.08 g/cm3, and leveled off at higher densities. A kinetic model to describe the depolymerization of PET in supercritical methanol was proposed, where the scission of one ester linkage in PET by a methanol molecule produces one carboxymethyl group and one hydroxyl group. The values of the forward reaction rate constant at different temperatures were determined by comparing the observed time dependence of carboxymethyl group concentration with that calculated by the proposed model. The activation energy was evaluated to be 49.9 kJ/mol, a value close to a literature value (55.7 kJ/mol). © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 81: 2102–2108, 2001

Hydrocarbon oils with molecular weight below 300 were obtained from automotive tire by supercritical decomposition with toluene and cyclohexane. Experiments were carried out at various temperatures (523.15, 573.15, and 623.15 K) and pressures (5, 10, and 15 MPa) for 25 g sample tires. For each solvent, the sample tire was completely decomposed within an hour at 623.15 K and 10 MPa. By measurement of the weight of residual solids and TGA analysis after each decomposition reaction, the percent decomposition and the decomposition characteristics were evaluated with respect to temperature and pressure. Also, by GC-MS analysis of decomposed oil, the major components of oil and their molecular weight were confirmed. Based on the results, the advantage and shortcomings of using each solvent are discussed.

Spherulites, spherical multilamellar vesicles (300−10 000 nm in diameter), were formed by applying shear force to the mixture of two lamellar phases, containing inorganic salts (indium nitrate and tin chloride) in one lamellar phase (I) and a precipitating agent (ammonium hydroxide) in another lamellar phase (II). These spherulites were employed as a reaction medium to prepare the indium−tin hydroxide nanoparticles. The chemical reaction for the formation of indium−tin hydroxide particles took place in the hydrophilic layers of lamellar phase I in spherulites composed of AOT (dioctyl sulfosuccinate sodium salt), because the vesicle wall is selectively permeable to the anions but practically impermeable to cations. Inorganic salts were encapsulated within the hydrophilic layers of spherulites. Indium−tin hydroxide particles were collected by breaking the spherulite structures by adding acetone after reaction, and spherical indium−tin oxide (ITO) particles of about 10−30 nm in size were obtained after calci...

With toluene in the supercritical state, scrap tire was decomposed into low molecular weight hydrocarbon liquid and solid residual. The experiment was carried out at 523.15, 573.15 and 623.15 K and pressures of 5, 10, and 15 MPa. The liquid and solid residual products were further separated by a simple filtering method. The reaction time, tire weight and the amount of the solvent were determined for the optimal thermolysis. The decomposition percent and TGA were used to evaluate the decomposition characteristics in terms of temperature and pressure. The GC-MS was applied to the decomposed liquid products from the various conditions. The average molecular weight of the decomposed liquid products tended to become lower with the increasing temperature.

Lecithin is a natural amphiphilic molecule, the microemulsions of which are often employed as a transdermal delivery medium of drugs and cosmetics. However, it constructs a microemulsion and lamellar phase in a phase diagram without co-surfactant only at a narrow range of composition. In this study, the effect of several short-chain alcohols on pseudo-ternary phase diagrams composed of lecithin, water and dodecane containing 1.0 wt% lidocaine (local anesthetic) was investigated in relation to the application of lecithin-based microemulsion for transdermal drug delivery. The phase diagram for an aqueous solution containing 80.0 wt% ethanol showed a lamellar structure (LC) and bicontinuous isotropic regions. When the mixing ratio of lecithin to alcohols (1-propanol, 1-butanol and n-pentanol) was 2: 1, water-in-oil (L2) and oil-in-water (L1) microemulsions and LC were obtained in a certain range of compositions. The maximum solubilization of water into L2 phase was 38 wt% when the total surfactant was 43 wt% with butanol as cosurfactant.

Isothermal pyrolysis of PS was investigated in the relatively low temperature range of 370 to 400 °C, using a stirred tank of batch-type with respect to the liquid phase; the gas phase was operated in an open system. To maintain an isothermal condition, the stirring speed was 80 rpm. At the initial stage of pyrolysis at each temperature, the first-order kinetic law was found to be operative. The activation energy was evaluated to be 224 kJ/mol a value close to the previously reported one. The main liquid products were single and double aromatic ring species: styrene, α-methylstyrene, toluene and 1,3-diphenylpropane, 1,3-diphenylbutene. The yield of styrene was much larger than any other product and amounted to ca. 70 % by weight. The present reactor, operated in an open system with respect to the gas phase, tends to suppress the scission of volatile diphenyl radicals because of short residence times of these radicals.

Solvent sorption equilibrium data of binary solvent/polymer systems were measured using a vacuum electromicrobalance. Solvents tested were benzene, cyclohexane, n -hexane, water and methanol. Rubbery polymers tested were poly(dimethylsiloxane, PDMS), poly( iso -butylene, PIB), poly(propylene oxide, PPO) and poly(vinyl alcohol, PVA). Data obtained in the present study, together with existing literature data, were correlated by both the UNIQUAC, Gibbs function ( g E )-model and a recent volumetric EOS (equation of state) proposed by the present authors based on a non-random lattice-hole theory.

The sorption equilibria for CO2 and N2 in dry chitosan membrane at 20 and 30 ‡C were measured by a pressure decay method. The steady-state permeation rates for CO2 and N2 in dry and wet (swollen with water vapor) chitosan membranes at 20 and 30 ‡C were measured by a variable volume method. The sorption equilibrium for N2 obeyed Henry’s law, whereas that for CO2 was described apparently by a dual-mode sorption model. This non-linear sorption equilibrium for CO2 could be interpreted by the interaction of sorbed CO2 with the chitosan matrix expressed as a reversible reaction. The logarithm of the mean permeability coefficient for CO2 in dry chitosan membrane increased linearly with upstream gas pressure. A linear increase of the logarithmic mean permeability coefficient for CO2 with the pressure could be interpreted in terms of a modified free-volume model. The mean per-meability coefficient for N2 in dry chitosan membrane only slightly increased with upstream gas pressure. The per-meabilities for CO2 and N2 in wet chitosan membrane increased by 15 to 17 times and 11 to 15 times, respectively, as compared to those in the dry membrane.

This paper is the second part of two describing the development of a theoretical model for the heat transfer of a flammable substrate. The mathe matical model presented in Part 1 of this series of papers is the first known suc cessful attempt to describe the interaction between a cigarette and a substrate analytically. The calculated distribution profile of temperature approximates the experi mental results measured using thermocouples. Then, the predicted temperature distribution in the substrate was fit to the corresponding measured values with a nonlinear, least-squares fitting routine to obtain a net heat flux from the moving heat source to the substrate. The average of heat flux from the burning cigarette to the substrate through the window is approximately 1.56 ± 0.01 cal/(s cm2).

The process of pervaporation in which two components diffuse through a nonporous polymer membrane was modelled when one of the penetrants can exert a plasticization action to the membrane material. Thereat a phenomenological model was employed for describing the plasticization effect on the diffusivities for penetrants in the membrane. The sorption equilibria and permeation fluxes for aqueous ethanol solutions in a chitosan membrane were measured, and the permeation fluxes for water were compared with those predicted by the proposed model. The concentration of sorbed water was linear with its weight fraction (x4) in the feed solution, whereas the permeation flux of water was. affected by the plasticization action of sorbed water to the polymer. This plasticization effect on the diffusion process can be simulated in terms of the proposed phenomenological model.

The deviation from the conventional dual-mode sorption and mobility model for a gas in glassy polymer membranes has separately been studied thus far, and to simulate sorption and diffusion behavior, an extended dual-mode sorption model and a modified dual-mode mobility model, respectively, have been proposed independently. However, simultaneous deviation from the conventional dual-mode sorption and mobility model was observed in cases of CO2in poly-4-methyl-1-pentene membrane at 20°C and in polystyrene membrane at 60 and 70°C. The plasticization effect of sorbed CO2 on both the sorption and diffusion processes tends to be brought about in glassy polymer membranes near the glass transition temperature. The behavior was simulated based on the concept that only one population of sorbed gas molecules exists. © 1996 John Wiley & Sons, Inc.

The promotional effectof tungsten in theCoMo/γ-Al2O3catalystwas studied for series of W-incorporatedCoMo/γ-Al2O3catalysts with different content of tungsten. Twoseries of the catalysts were prepared by changingthe impregnation order of cobalt and tungsten onto a baseMo/γ-Al2O3catalyst. Impregnationof tungsten was achieved under thecondition that the pH of an aqueous impregnatingsolution of W anion was controlled to 9.5. Thehydrodesulfurization (HDS) and hydrogenation(HYD) activities of the sulfided catalysts wereevaluated by thiophene HDS and ethylene HYDreactions at atmospheric pressure, respectively.Low-temperature O2chemisorption at195 K was conducted for the sulfided catalysts inorder to determine the W-incorporation effects onthe surface concentration of coordinativelyunsaturated sites related to the catalyticactivities. The dependence of catalyticactivities on tungsten content showed initiallyan increase and subsequent decrease withincreasing tungsten content. The maximumpromotion of HDS and HYD activities occurred at alow content of tungsten corresponding to 0.025 inW/(W + Mo) atomic ratio regardless of theimpregnation order of tungsten and cobalt. Oxygenuptake correlated well with catalytic activities.In general, the catalysts prepared byimpregnating tungsten onto theCoMo/γ-Al2O3showedhigher activities than the catalysts prepared byimpregnating tungsten onto Mo/γ-Al2O3prior toimpregnation of cobalt.

Series of W-incorporatedCoMo/γ-Al2O3catalysts werecharacterized with TPR, DRS, ESR, and XPS. Two series ofcatalysts with varying content of tungsten were prepared forcharacterization by changing the impregnation order of cobaltand tungsten to a baseMo/γ-Al2O3catalyst. The activitypromotion by relatively low content of tungsten arose from theroles of tungsten in changing the Mo-oxide coordination from tetrahedral tooctahedral, facilitating the reduction of Mo-oxide species, andincreasing the dispersion of MoS2. By incorporation of tungstenat a content as much as 0.025 in W/(W + Mo)atomic ratio, the MoS2dispersion of CoMo/γ-Al2O3catalyst was considered to bemaximized without noticible detriment to the active Co–Mo–Ophase, resulting in the maximum activity promotion. Theformation of the Co–Mo–O phases was more favored in thecatalysts prepared by impregnating W ontoCoMo/γ-Al2O3than inthose by impregnating W ontoMo/γ-Al2O3before impregnation ofCo. The effect of tungsten on the dispersion of active phase wasnot discriminated between the two series of catalysts. Theactivity decrease observed in the catalysts containing highercontent of tungsten originated from the increase in theW-oxide coverage on the surface of Mo-oxides or Co–Mo–Ophases, resulting in not only impeding the reduction orsulfidation of the oxidic precursor but facilitating theformation of less active Co–W–O at the sacrifice of moreactive Co–Mo–O phase.

In order to investigate the growth mechanism of TiO2, the monodispersed TiO2 fine particles were prepared by hydrolysis of Ti(OC2H5)4 using the seed preparation method. Although it was impossible to grow TiO2 particles to more than 1 μm with conventional liquid phase reaction method, we obtained monodispersed T1O2 fine particles of up to 2.5 urn. Nielsen’s chronomal analysis and Overbeek’s theory were applied to clarify the particle growth mechanism. The particle growth mechanism was found out as a first-order polynuclear layer growth mechanism and the growth rate constant, kP was about 6.45X10-6 cm/s.

The modified dual-mode mobility model for permeation of a gas in glassy polymer membranes was combined with the extended dual-mode sorption model to take account of the plasticization effect of sorbed gas molecules on both sorption and diffusion processes. The combined model was further simplified by the introduction of a concentration of the mobile gas species. However, the observed pressure dependence of mean permeability coefficients of carbon dioxide in methylmethacrylate-n-butyl acrylate copolymer and polymethylmethacrylate films at 30°c and also that of oxygen in a polycarbonate film at 50°C and 60°C showed that a plasticization action of sorbed gas species has an influence on the diffusion process rather than on the sorption process, that is, were simulated by the modified dual-mode mobility model combined with the conventional dual-mode sorption model.

Sorption equilibria and permeation rates for oxygen and carbon dioxide in polycarbonate membrane were measured at different temperature between 30 and 60°C and at pressures up to 2.5 MPa. The pressure dependence of mean permeability coefficient to oxygen obeyed the conventional dual-mode mobility model, whereas that to carbon dioxide followed a modified dual-mode mobility model with concentration-dependent diffusivities, as that of polystyrene to the same gas did.

In this study, transesterification of refined lard in supercritical methanol with no pre-treatment was performed in a temperature range of 320–350 °C, molar ratios of methanol to oil from 30 to 60, pressures from 15 to 25 MPa, reaction times from 5 to 20 min, and agitation speeds of 0–1000 rpm. The effects of reaction parameters were investigated to determine the optimum reaction conditions. The highest content of fatty acid methyl esters (FAMEs) from refined lard was 89.91%, which was obtained at a temperature of 335 °C, a molar ratio of methanol to oil of 45, a pressure of 20 MPa, a reaction time of 15 min, and an agitation speed of 500 rpm. Biodiesel production from waste lard under the optimal reaction conditions was also carried out to validate the use of waste lard as a feedstock. Even though waste lard samples contain various free fatty acids and water contents, FAME contents from waste lard with no pre-treatment were found to be comparable with those from refined lard. From this result, it is concluded that waste lard can be utilized as an alternative feedstock for biodiesel production using a supercritical process, thus replacing the high-cost refined vegetable oil feedstock.

A new correlation predicting the activity coefficients of aqueous electrolyte solutions between Pitzer ion interaction parameters and ionc properties (ionic charge, radius and entropy) is developed. The substances include uni-uni and uni-bi type of single salts for which data are available. The results of correlation show linear relations for uni-uni type, and quadratic equations for uni-bi type. Many of the trends in the calculated activity coefficients for electrolyte solutions can be correlated with respect to the effect of the ions on the structure of the water and explained by structure-making and -breaking concept. These kinds of correlation may be useful in predicting values for salts that have no measurement of the activity coefficients.

Retinol, a cosmetic ingredient, was entrapped within inorganic microspheres obtained from sol-gel reaction of TEOS in o/w/o multiple emulsions as microreactors. In o/w/o multiple emulsions, the retinol was emulsified as an internal oil phase in a aqueous solution of 3.0 wt% Tween 20 prior to emulsification into an external oil phase. The multiple emulsions appeared to be stable enough in the presence of HPC polymer in the external oil phase. In sol-gel reaction, the hydrolysis and condensation rate of TEOS were greatly dependent upon the catalyst and the molar ratio of H(2)O to TEOS (R(W)). In this study, sphere-like microspheres entrapping retinol were best formed with the addition of NH(4)OH as a catalyst when the concentration of TEOS was at the R(W) value of 4. Microspheres obtained under these conditions were 15-40mgr;m with very dense surfaces containing a few globules 1.17-2.35mgr;m. Also, they showed the slower release of retinol into the external ethanol phase and higher loading and encapsulation efficiency. Copyright 2001 Academic Press.