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Oxidation Characteristics of Phthalic and Adipic Acids by Supercritical Water
Yoo, Ki Pung,Ahn, Sang Hoon,Joung, Seung Nam,Noh, Min Jeong,Han, Joo Hee,Han, Seung Ho 한국화학공학회 1998 Korean Journal of Chemical Engineering Vol.15 No.4
Supercritical water oxidation (SCWO) was carried out in a flow-type reactor for modeling of wastewater containing phthaiic or adipic acid. For each acid, the reaction order and rate constant, k, were determined over a wide range of experimental conditions : temperatures from 633.15 to 713.15 K, pressures from 18 to 29 MPa, excess amounts of hydrogen peroxide from zero to 800 percent, and the mean residence time in the reactor from 101 to 49.1 seconds. The concentration of both acids in model wastewater was set by 500 ppm. For phthalic acid, we found that the orders of decomposition reaction with respect to the reactant concentrations were 0.56 for phthalic acid, 0.31 for hydrogen peroxide, and 0.53 for water. For adipic acid, the orders of oxidation were 0.78 for adipic acid, 0.53 for hydrogen peroxide, and 0.74 for water. Then measured activation energy for phthalic acid was 33.08 ㎉/㏖ and that for adipic acid was 19.51 ㎉/㏖, respectively.
Effects of Basic Modifiers on SFE Efficiencies of Ephedrine Derivatives from Plant Matrix
Yoo, Ki Pung,Kim, Jin Yeol 한국화학공학회 2000 Korean Journal of Chemical Engineering Vol.17 No.6
The effect of basified modifiers in supercritical CO₂( SCF-CO₂) such as diethylamine has been investigated on the SFE efficiencies of ephedrine derivatives (e.g. methylephedrine, norephedrine, ephedrine, and pseudoephedrine) from aerial parts of Ephedra sinica. The addition of basified modifiers in SCF-CO₂showed a greater enhancement of SFE efficiency of ephedrine derivatives than pure modifiers. These results might be due to the fact that the salts of Ephedra alkaloids (insoluble in CO₂) in plant tissues would be changed to their free bases (freely soluble in CO₂) by basified modifiers such as diethylamine in methanol. In addition to enhancing the solubilities, it could increase the degree of desorption of the compounds from plant matrix. Also, the SCF-CO₂modified with methanol basified with diethylamine showed a difference of extractability of ephedrine and its diastereomer, pseudoephedrine.
Rediscovering the Lattice - Fluid Thoery for Phase Equilibria of Complex Mixtures
Yoo,Ki Pung,Lee,Chul Soo 한국화학공학회 2000 Korean Chemical Engineering Research(HWAHAK KONGHA Vol.38 No.3
Various lattice statistical-thermodynamic theories after E. A. Guggenheim [Guggenheim, 1952] have been proposed with different assumptions on nonrandomness, the explicitness of the solution, and the model parameters. During the last decade, the present authors proposed a general approximation tool to the quasichemical solution of the nonrandom lattice-fluid combinatory and formulated a new rigorous EOS and the improved versions including the unified group contribution extensions and systems with strong association. In this study, developments of those EOSs are discussed with emphasis on the practical utility of each model.
Yoo, Ki Pung,Shin, Hun Yong,You, Seong Sik,Choi, Eun Sun 한국화학공학회 1997 Korean Journal of Chemical Engineering Vol.14 No.4
The solubility of isomeric o-, m- and p-coumaric acids in supercritical carbon dioxide were measured by a flow-type experimental apparatus at 308.15-323.15 K and 8.5-25 MPa. The data were modeled by an empirical density-based correlation and a recent EOS formulated by the authors based on approximated lattice-hole theory. We found that m-coumaric acid showed the highest solubility and o-coumaric acid showed the lowest solubility at the experimental pressures and temperatures.
Yoo, Ki Pung,Lee, Chul Soo,Kim, Hwa Yong 한국화학공학회 1995 NICE Vol.13 No.5
In part I of the present article [Yoo et al., 1995], new rigorous and simplified lattice-fluid equations of state(EOS) were derived and their characteristic features of the molecular thermodynamic foundation were discussed by applying to pure fluids. In this part II, both EOSs were extended to various phase equilibrium properties of mixtures. Comparison of the models with experimental mixture data ranges from density, to equilibria of vapor-liquid, vapor-solid and liduid-liquid phases for nonpolar/nonpolar, nonpolar/polar, olar/polar mixtures. Both models were also applied to supercritical fluid phase equilibria and activities of solvents in polymer solutions. With two temperature dependent parameters for pure compounds and one temperature-independent binary interaction energy parameter for a binary mixtures, results obtained to date illustrated that both EOSs are quantitatively applicable to versatile phase equilibria of mixtures over a wide range of temperatures, pressures and compositions.
Yoo, Ki Pung,Noh, Min Jeong,Choi, Young Hae,Kim, Jin Woong,Park, Eun Mee 한국화학공학회 1996 NICE Vol.14 No.3
Experimental results concerning the processing feasibility of using supercritical CO₂ were reported for the extraction of epicuticular wax from Ephedra herb. Subsequently the isolability of nonacosan-l0-ol from the total extract of epicuticular wax was evaluated by TLC and gas chromatography. Also, Soxhlet extractions of Ephedra herb by n-hexane and chloroform were petformed and these results were compared with those obtanied by supercritical CO₂ extraction. As a result, we could demonstrate that supercritical CO₂ can be an economical alternative to the organic solvents in processing the medicinal plant.