Seong Youl Bae

CO2, N2 gas sorption and permeation behavior of chitosan membrane

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.

PYROLYSIS OF POLYSTYRENE IN A BATCH-TYPE STIRRED VESSEL

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.

Degradation of high density polyethylene, polypropylene and their mixtures in supercritical acetone

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.

Plasticization of chitosan membrane for pervaporation of aqueous ethanol solution

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.

Measurement and correlation of vapor sorption equilibria of polymer solutions

Abstract 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.

Growth mechanism of monodispersed TiO2 fine particles by the hydrolysis of Ti(OC2H5)4

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.

Preparation of Anthracene Fine Particles by Rapid Expansion of a Supercritical Solution Process Utilizing Supercritical CO 2

The rapid expansion of a supercritical solution (RESS) process is an attractive technology for the production 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 °C, and a pre-expansion temperature range of 70–300 °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 were produced with increasing extraction pressure and preexpansion temperature. In addition, the smaller the nozzle diameter, the smaller the particles and the narrower the PSD obtained.

Heat Transfer of a Smoldering Flammable Substrate. Part 2. A Theoretical Model and Its Application

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).

Characterization of Automobile Shredder Residues for Chlorine Content and Estimation of it’s Circulation in Cement Kiln

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.

H2/CO2 Gas Separation Characteristic of Zeolite Membrane at High Temperature

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).