YoonKook Park

Pseudo-binary molecular diffusion of vapors into air

Abstract A novel open-tube evaporation method was developed to determine the experimental diffusion coefficients of the vapors of various liquids diffused into air. The mass losses of the volatile liquids chosen for this study were measured with a balance rather than changes in the level of the liquid in a diffusion tube for various evaporation durations and no fresh air was passed over the top end of the diffusion path by forced convection, as opposed to the conventional open-tube evaporation method. A diffusion equation was developed which is suitable for the novel open-tube evaporation method. The experimental diffusion coefficient values obtained from the novel experimental diffusion methods were in reasonable agreement with the diffusion coefficient values predicted with both the Wilke-and-Lee method and the Fuller et al. method. The experimental diffusion coefficients of n-heptane diffused into air are independent of the lengths and the evaporation areas of the diffusion paths chosen for this study. The experimental diffusion coefficients of normal alcohols and hydrocarbons in air decrease with increased number of carbon atoms in their molecular formulas. The overall root mean squares of deviation of the diffusion values of this experimental study from those predicted with the Wilke-and-Lee method and the Fuller et al. method are 5.8 and 6.0%, respectively.

Synthesis of higher carbon ethers from olefins and alcohols: I. Reactions with methanol

Abstract Higher carbon ether compounds (HME; hexyl methyl ether and OME; octyl methyl ether) are produced from olefins (C 6 olefins: 23DM1B; 2,3-dimethyl-1-butene and 23DM2B; 2,3-dimethyl-2-butene and C 8 olefins: 244TM1P; 2,4,4-trimethyl-1-pentene and 244TM2P; 2,4,4-trimethyl-2-pentene) and methanol in the presence of commercially available Amberlyst 15 ion exchange catalyst. Stainless steel batch reactors are used and the experiments are conducted from 333 to 373 K. It appeared that α-olefins are much more reactive to produce the corresponding ether compounds than β-olefins are. Probably due to steric hindrance, the reactivity of C 8 olefins seems to be less than that of C 6 olefins. Analysis of variance (ANOVA) shows that the amount of catalyst and reaction medium is significant at 2.5% and 1% levels for the production of octyl methyl ether and at 25% and 10% levels for the production of hexyl methyl ether, respectively. The implications of the current results to the design of a continuous process for the preparation of higher carbon ethers from olefins and synthesis gas in a single-step etherification reactor are discussed.

Molecular diffusion of volatile-liquid vapors into air

Diffusion coefficients of vapors diffused into stagnant air were determined at room temperature and atmospheric pressure. Experimental data on diffusion coefficients were obtained from the steady-state open-tube evaporation method modified for this study. No fresh air is passed over the top end of a diffusion tube, and amounts of volatile liquids evaporated in the diffusion tube are measured with a balance rather than a change of the liquid level in a diffusion tube. Experimental molecular diffusion coefficients are obtained by applying experimental data of mass losses of volatile liquidsversusevaporation durations to a diffusion equation developed suitable for the novel open-tube evaporation method. Three main experimental errors of the novel open-tube evaporation method are described in detail. Predicted diffusion coefficients are calculated with the Wilke-Lee method and compared with experimental values obtained from this diffusion study.

Reactivity of sorbents with hot hydrogen sulfide in the presence of moisture and hydrogen

Hot-gas desulfurization for the integrated gasification combined cycle (IGCC) process has been investigated by many researchers to remove effectively hydrogen sulfide (H2S) with various metal oxide sorbents at elevated temperatures. Various metal oxide sorbents are formulated with metal oxides such as Fe, Co, Zn, and Ti. In this article, reactivity of AHI-1 sorbent, obtained from the Research Triangle Institute (RTI), was investigated. Initial reactivity of AHI-1 sorbent with hydrogen sulfide was studied in the presence of various amounts of moisture and hydrogen at various reaction temperatures. AHI-1 sorbent consists of 20-w% Fe2O3, 10-w% ZnO, and 70-w% spent fluid cracking catalyst (FCC). The objectives of this research were to study initial reaction kinetics for the AHI-1 sorbent–hydrogen sulfide heterogeneous reaction system, to investigate effects of concentrations of hydrogen sulfide, hydrogen, and moisture on dynamic absorption of H2S into the sorbent, to understand effects of space time of reaction gas mixtures on initial reaction kinetics of the sorbent–hydrogen sulfide system, and to evaluate effects of temperature and sorbent amounts on dynamic absorption of H2S into the sorbent. Experimental data on initial reaction kinetics of hydrogen sulfide with the metal oxide sorbent were obtained with a 0.83-cm3 differential reactor. The sorbent in the form of 130-μm particles was reacted with 1000 to 4000 ppm hydrogen sulfide at 450 to 600°C. The range of space time of reaction gas mixtures is 0.03 to 0.09 s. The range of reaction duration is 4 to 14,400 s.

Usage of a deep eutectic solvent based on three compounds for toluene separation

The separation of toluene from a mixture composed of toluene and heptane was carried out in the presence of a deep eutectic solvent (DES). The DES used in this study was synthesized using choline chloride, urea and glycerol with mole ratio of 1 : 2 : 1. The liquid-liquid equilibria (LLE) of the ternary system of toluene, heptane, and DES were determined at atmospheric pressure and three temperatures of 298.2-313.2 K with an interval of 10 K. The distribution coefficients and selectivities of toluene were reported. Only a small amount of heptane was detected in the extract phase, resulting in high value of selectivity. The experimental LLE data were reasonably well correlated using non-random two-liquid (NRTL) model. The ab initio results revealed that the interactions between the DES and toluene are stronger than those between DES and heptane, which may be a reasonable explanation for the high value of selectivity in this ternary system.

Experimental determination and prediction of phase behavior for 1-butyl-3-methylimidazolium nonafluorobutyl sulfonate and carbon dioxide

The vapor-liquid equilibrium of the binary system CO2+1-butyl-3-methylimidazolium nonafluorobutyl sulfonate ([BMIM][NfO]) was measured over a temperature range of 298.2–323.2 K at intervals of 5.0 K for CO2 mole fraction ranging from 0.137 to 0.900 using a high-pressure variable-volume view cell. The Peng-Robinson equation of state was then applied with two-parameter mixing rules over the same range and the results compared with the experimentally obtained data. Increasing the alkyl chain length in perfluorinated sulfonate from methyl to butyl markedly increased the CO2 solubility. To investigate the effect of the number of fluorine atoms in the anion on the phase behavior of imidazolium based ionic liquid, these experimental results were then compared with those reported in previous experimental studies of 1-alkyl-3-methylimidazolium cations and with modeling data. It looks likely that both the number of fluorine atoms in the anion and the presence of S=O groups play an important role in designing CO2-philic molecules.

Measurement and correlation of vapor-liquid equilibria for a binary system containing 1-butyl-3-methylimidazolium tridecafluorohexylsulfonate and carbon dioxide

Using a high-pressure variable-volume view cell, the vapor-liquid equilibria of the binary system CO2 and 1-butyl-3-methylimidazolium tridecafluorohexylsulfonate ([BMIM][TDfO]) were determined. The CO2 mole fraction ranged from 0.104 to 0.952 over a temperature range of 298.2-323.2 K. Both the Peng-Robinson and Soave-Redlich- Kwong equations of state were applied with two different mixing rules to correlate with the experimentally obtained results. Increasing the alkyl chain length in perfluorinated sulfonate anion mother structure from methyl to hexyl markedly increased the CO2 solubility. To investigate the effect of the number of fluorine atoms in the anion on the phase behavior of imidazolium-based ionic liquid, these experimental results were then compared with those reported in previous experimental studies of 1-alkyl-3-methylimidazolium cations-including ionic liquid+CO2 binary system.

Effects of additives on the mechanical and thermal properties of epoxy-based nanocomposites produced using sonication

Epoxy nanocomposites were synthesized in the presence of hydroxyapatite with the aid of an ultrasonicator. In general, as the amount of hydroxyapatite increased from 0wt% to 10wt%, the mechanical properties of the hydroxyapatite-containing nanocomposite were enhanced. The mechanical properties of the nanocomposite were significantly enhanced by the simple addition of 10 wt% of hydroxyapatite. Specifically, the storage modulus of the 10 wt% hydroxyapatite-containing nanocompsote was 3.2GPa, which is 46% higher compared to that of the pristine epoxy nanocomposite. The glass transition temperature of hydroxyapatite-containing nanocomposites generally decreased by few degrees in Celsius. To investigate the effect of additives on the mechanical properties of the epoxy-based nanocomposite, nanocomposites were synthesized using both montmorillonite and tellurium dioxide instead of hydroxyapatite. Intrestingly, both additive-based nanocomposite materials resulted in an increase in the storage modulus while the glass transition temperature decreased. These results demonstrate that the addition of few wt% of all three additives (hydroxyapatite, montmorillonite, and tellurium dioxide) can enhance the mechanical properties of epoxy-based nanocomposites.

RHEOLOGICAL CHARACTERIZATION OF NON-NEWTONIAN FLUIDS WITH A NOVEL VISCOMETER

A hydrostatic head viscometer and its novel viscosity equation were developed to determine flow characteristics of Newtonian and non-Newtonian fluids. The objective of this research is to test capabilities of the hydrostatic head viscometer and its novel non-Newtonian viscosity equation by characterizing rheological behaviors of well-known polyethylene oxide aqueous solutions as non-Newtonian fluids with 60 wt.% sucrose aqueous solution as a reference/calibration fluid. Non-Newtonian characteristics of 0.3–0.7 wt.% polyethylene oxide aqueous solutions were extensively investigated with the hydrostatic head viscometer and its non-Newtonian viscosity equation over a 294–306 K temperature range, a 0.14–40 Reynolds number range, and a 55–784 s−1 shear rate range at atmospheric pressure. Dynamic viscosity values of 60 wt.% sucrose aqueous solution were determined with the calibrated hydrostatic head viscometer and its Newtonian viscosity equation over a 3–5 Reynolds number range at 299.15 K and atmospheric pressure and compared with the literature dynamic viscosity value.

Liquid-liquid equilibria of toluene+n-heptane+{1-benzyl-3-methyl-imidazolium bis(trifluoromethylsulfonyl)imide or 1-benzyl-pyridinium bis(trifluoromethylsulfonyl)imide}

Both 1-benzyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide, [BzMeIM][NTf2], and 1-benzylpyridinium bis(trifluoromethylsulfonyl)imide, [BzPY][NTf2], were used to separate toluene from heptane through liquidliquid equilibria (LLE). The LLE of two ternary systems of toluene, n-heptane, and [BzMeIM][NTf2] and [BzPY][NTf2], were experimentally determined at temperature of 293.2 K and 0.1MPa. The LLE experiments were also performed at 303.2 and 313.2 K to investigate the effect of temperature on toluene recovery. The distribution ratio of toluene and the selectivity in these two ternary systems were calculated and compared with different ternary mixtures. The LLE measured data were well correlated with nonrandom two-liquid (NRTL).