• Title/Summary/Keyword: kinetics

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Rigorous Modeling and Simulation of Multi-tubular Reactor for Water Gas Shift Reaction (Water Gas Shift Reaction을 위한 Multi-tubular Reactor 모델링 및 모사)

  • Park, Junyong;Choi, Youngjae;Kim, Kihyun;Oh, Min
    • Korean Chemical Engineering Research
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    • v.46 no.5
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    • pp.931-937
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    • 2008
  • Rigorous multiscale modelling and simulation of the MTR for WGSR was carried out to accurately predict the behavior of process variables and the reactor performance. The MTR consists of 4 fixed bed tube reactors packed with heterogeneous catalysts, as well as surrounding shell part for the cooling purpose. Considering that fluid flow field and reaction kinetics give a great influence on the reactor performance, employing multiscale methodology encompassing Computational Fluid Dynamics (CFD) and process modeling was natural and, in a sense, inevitable conclusion. Inlet and outlet temperature of the reactant fluid at the tube side was $345^{\circ}C$ and $390^{\circ}C$, respectively and the CO conversion at the exit of the tube side with these conditions approached to about 0.89. At the shell side, the inlet and outlet temperature of the cooling fluid, which flows counter-currently to tube flow, was $190^{\circ}C$ and $240^{\circ}C$. From this heat exchange, the energy saving was achieved for the flow at shell side and temperature of the tube side was properly controlled to obtain high CO conversion. The simulation results from this research were accurately comparable to the experimental data from various papers.

Synthesis of Diketo Copper(II) Complex and Its Binding toward Calf Thymus DNA (CTDNA) (이케토 구리(II) 착물의 합성 및 송아지 Thymus DNA(CTDNA)와의 상호작용)

  • Tak, Aijaz Ahmad;Arjmand, Farukh
    • Journal of the Korean Chemical Society
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    • v.55 no.2
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    • pp.177-182
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    • 2011
  • A diketo-type ligand was synthesized by the Knoevenagel condensation reaction of thiophene-2-aldehyde with acetylacetone, subsequently its transition metal complexes with Cu(II), Ni(II), and Co(II) chlorides were also prepared. All the complexes were characterized by various physico-chemical methods. The molar conductivity data reveals ionic nature for the complexes. The electronic spectrum and the EPR values suggest square planar geometry for the Cu(II) ion. Interaction of the Cu(II) complex with CTDNA (calf thymus DNA) was studied by absorption spectral method and cyclic voltammetry. The $k_{obs}$ values versus [DNA] gave a linear plot suggesting psuedo-first order reaction kinetics. The cyclic voltammogram of the Cu(II) complex reveals a quasi-reversible wave attributed to Cu(II)/Cu(I) redox couple for one electron transfer with $E_{1/2}$ values -0.240 V and -0.194 V. respectively. On addition of CTDNA, there is a shift in the $E_{1/2}$ values 168 mV and 18 mV respectively and decrease in Ep values. The shift in $E_{1/2}$ values in the presence of CTDNA suggests strong binding of Cu(II) complex to the CTDNA.

Feasibility Study of Employing a Catalytic Membrane Reactor for a Pressurized CO2 and Purified H2 Production in a Water Gas Shift Reaction

  • Lim, Hankwon
    • Clean Technology
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    • v.20 no.4
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    • pp.425-432
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    • 2014
  • The effect of two important parameters of a catalytic membrane reactor (CMR), hydrogen selectivity and hydrogen permeance, coupled with an Ar sweep flow and an operating pressure on the performance of a water gas shift reaction in a CMR has been extensively studied using a one-dimensional reactor model and reaction kinetics. As an alternative pre-combustion $CO_2$ capture method, the feasibility of capturing a pressurized and concentrated $CO_2$ in a retentate (a shell side of a CMR) and separating a purified $H_2$ in a permeate (a tube side of a CMR) simultaneously in a CMR was examined and a guideline for a hydrogen permeance, a hydrogen selectivity, an Ar sweep flow rate, and an operating pressure to achieve a simultaneous capture of a concentrate $CO_2$ in a retentate and production of a purified $H_2$ in a permeate is presented. For example, with an operating pressure of 8 atm and Ar sweep gas for rate of $6.7{\times}10^{-4}mols^{-1}$, a concentrated $CO_2$ in a retentate (~90%) and a purified $H_2$ in a permeate (~100%) was simultaneously obtained in a CMR fitted with a membrane with hydrogen permeance of $1{\times}10^{-8}molm^{-2}s^{-1}Pa^{-1}$ and a hydrogen selectivity of 10000.

Experimental Study of Char Oxidation and Kinetic Rate in O2/CO2 and O2/N2 Environments (O2/CO2조건과 O2/N2조건에서의 촤 연소특성 및 산화 반응성에 관한 실험적 연구)

  • Kim, Song-Gon;Lee, Cheon-Seong;Lee, Byoung-Hwa;Song, Ju-Hun;Chang, Young-June;Jeon, Chung-Hwan
    • Transactions of the Korean Society of Mechanical Engineers B
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    • v.34 no.12
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    • pp.1101-1109
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    • 2010
  • We investigated the combustion rate and kinetic rate of char when burning in oxygen-enriched atmospheres with either an $N_2$ or $CO_2$ bath gas in a drop tube furnace. The experiments were performed with sub-bituminous coal (Adaro) and bituminous coal (Coal valley) under atmospheric pressure conditions. Two different coals were investigated over 12 to 30 vol% oxygen and furnace temperatures of 900, 1100, and $1300^{\circ}C$. For both coals, the particle temperature and overall reaction rate are lower in the $CO_2$ bath gas. However, analysis of single-particle data shows that the surface-specific burning rate of char oxidation is similar in both gases. In addition, the kinetic rate and activation energy for each coal were similar for both gases. Generally, the particle temperature and overall reaction rate of sub-bituminous coal are higher than those of bituminous coal.

Miscibility and Properties of Ethyl-Branched Polyethylene/Ethylene-Propylene Rubber Blends (II) (에틸 가지화된 폴리에틸렌과 에틸렌-프로필렌 고무 블렌드의 혼화성과 물성(II))

  • Cho, Ur-Ryong
    • Elastomers and Composites
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    • v.37 no.2
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    • pp.79-85
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    • 2002
  • Ethyl-branched polyethylene [PE(2)] containing 2mole% ethyl branch and three ethylene-propylene rubbers (EPR's) having the same ethylene(E)-propylene(P) molar ratio(E/P=50/50) with different stereoregularity, that is, random EPR (r-EPR), alternating-EPR (alt-EPR) and isotactic-alternating-EPR (iso-alt-EPR) were mixed for the investigation or their properties depending on the stereoregularity. Crystallinity of the prepared blends decreased with increasing content of amorphous EPR because of a decrease in both the degree of annealing and kinetics of diffusion of the crystallizable polymer content. With blend composition, crystallinity was reduced with the stereoregularity in EPR. The thermodynamic interaction parameter(x) for the three blend systems approximately equals to zero near the melting point. These systems were determined to be miscible on a molecular scale near or above the crystalline melting point or the crystalline PE(2). From the measurement of $T_m$ vs. $T_c$, the behavior of PE(2) is mainly due to a diluent effect of EPR component. The spherulite size measured by small angle light scattering (SALS) technique depended upon blend composition, and stereoregularity of EPR. The size of spherulite was enlarged with the content of rubbery EPR and the decrease of stereoregularity in EPR.

The Potential Energy Recovery and Thermal Degradation of Used Tire Using TGA (열분석법을 이용한 사용후 타이어의 열적 특성과 포텐셜 에너지의 회수)

  • Kim, Won-Il;Kim, Hyung-Jin;Hong, In-Kwon
    • Elastomers and Composites
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    • v.34 no.2
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    • pp.135-146
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    • 1999
  • The thermal degradation kinetics of SBR and tire were studied using a conventional thermogravimetric analysis in the stream nitrogen at a heating rate of 5, 10, 15, $20^{\circ}C/min$, respectively. Thermogravimetric curves and their derivatives were analyzed using various analytical methods to determine the kinetic parameters. The degradation of the SBR and tire was found to be a complex process which has multi-stages. The Friedman method gave average activation energies for the SBR and tire of 247.53kJ/mol and 230.00kJ/mol, respectively. Mean-while, the Ozawa method Eave 254.80kJ/mol and 215.76kJ/mol. It would appear that either. Friedman's differential method or Ozawa's integral method provided satisfactory mathematical approaches to determine the kinetic parameters for the degradation of the SBR and tire. Approximately 86% and 55% of oil products were obtained at a final temperature of $700^{\circ}C$ and a heating rate of $20^{\circ}C/min$ for the SBR and tire respectively.

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Inhibitory Action of YJA20379, a New Proton Pump Inhibitor on Helicobacter Pylori Growth and Urease

  • Woo, Tae-Wook;Chang, Man-Sik;Chung, Young-Kuk;Kim, Kyu-Bong;Sohn, Sang-Kwon;Kim, Sung-Gyu;Choi, Wahn-Soo
    • Archives of Pharmacal Research
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    • v.21 no.1
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    • pp.6-11
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    • 1998
  • The activities of two types of antiulcer agents against 9 strains of Helicobacter pylori (H. pylori) were determined by the agar dilution method. The antiulcer agents were YJA20379, a newly synthesized proton pump inhibitor developed by Yung-jin Pharmaceutical company, and omeprazole. Both compounds were found to have significant activities against this organism. The MIC values of YJA20379 and omeprazole were 11.7 and $31.25{\mu.g/ml}$ respectively. In addition, the inhibitory potency of both compounds was investigated on H. pylori urease which is believed to be an important colonization and virulence factor in the pathogenesis of gastritis and peptic ulcers. These compounds dose-dependently inhibited urease extracted with distilled water and their $IC_50$ values were $16.4{\times}10^{-5} M and 14.3{\times}10^{-5}M,$ respectively. In addition, a pH-dependent study to determine whether inhibitory potency would be activated by acid condition was performed. It was found that unlike omeprazole, YJA20379 was not affected by acid condition. To determine the inhibition pattern and optimal concentration of substrate, kinetics were evaluated at various pH levels (pH 5.0, 7.0, and 8.5). The data show that YJA20379 noncompetitively inhibited H. pylori urease and $K_M/K_i$values were 0.96 $mM/60{\mu}M (pH 5.0), 0.56 mM/141.5 {\mu}M (pH 7.0)$, and $1.94mM/34{\mu}M (pH 8.5)$, respectively. Based on data obtained, it is concluded that YJA20379 is a significant inhibitor of H. pylori growth and urease and therefore, taking these results into consideration, YJA20379 might be a beneficial therapy for gastritis and peptic ulcers induced by H. pylori.

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Improved Performance of Direct Carbon Fuel Cell by Catalytic Gasification of Ash-free Coal (무회분탄 연료의 촉매 가스화에 의한 직접탄소연료전지의 성능 향상)

  • Jin, Sunmi;Yoo, Jiho;Rhee, Young Woo;Choi, Hokyung;Lim, Jeonghwan;Lee, Sihyun
    • Clean Technology
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    • v.18 no.4
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    • pp.426-431
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    • 2012
  • Carbon-rich coal can be utilized as a fuel for direct carbon fuel cell (DCFC). However, left-behind ash after the electrochemical oxidation may hinder the electrochemical reactions. In this study, we produced ash-free coal (AFC) by thermal extraction and then tested it as a fuel for DCFC. DCFC was built based on solid oxide electrolyte and the electrochemical performance of AFC mixed with $K_2CO_3$ was compared with AFC only. Significantly enhanced power density was found by catalytic steam gasification of AFC. However, an increase of the power density by catalytic pyrolysis was negligible. This result indicated that a catalyst activated the steam gasification reactions, producing much more $H_2$ and thus increasing the power density, compared to AFC only. Results of a quantitative analysis showed much improved kinetics in AFC with $K_2CO_3$ in agreement with DCFC results. A secondary phase of potassium on yttria-stabilized zirconia (YSZ) surface was observed after the cell operation. This probably caused poor long-term behavior of AFC with $K_2CO_3$. A thin YSZ (30 ${\mu}m$ thick) was found to be higher in the power density than 0.9 mm of YSZ.

Electron Beam Radiation Syntheses of Carboxymethylcellulose-based Composite Superabsorbent Hydrogels: Dependence of Gel Properties on Polymer Composition and Additives (전자빔 조사에 의한 카르복시메틸셀룰로스 기반 복합 초흡수제 제조시 폴리머 조성 및 첨가물질의 종류에 따른 겔 특성 변화)

  • Sung, Yoonki;Kim, Tak-Hyun;Lee, Byunghwan
    • Clean Technology
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    • v.22 no.4
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    • pp.258-268
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    • 2016
  • In this work, carboxymethylcellulose-based composite superabsorbent hydrogels were prepared by electron beam radiation. The composition of carboxymethylcellulose (CMC) varied from 4 wt%, 5 wt%, and 6 wt% to 7 wt% based on the amount of distilled water in the syntheses of hydrogels. Graphite oxide, reduced graphene oxide, activated carbon, and bentonite were used as additives for the synthesis of composite superabsorbent. The effect of CMC composition and the type of additives on the gel properties of the prepared hydrogels was investigated. In order to verify the functional groups in the prepared materials, Fourier transform infrared spectroscopy was used. In addition, mechanical strength, gel fraction, swelling kinetics, and equilibrium swelling ratios were measured for the prepared hydrogels. Swelling experiments were carried out in distilled water, urea solution, and physiological saline water. Prepared hydrogels were reused for 5 times, and gel fraction and swelling ratio were measured at every 24 hours. Among the prepared hydrogels, $C_{5%}GO$ and $C_{5%}rGO$ exhibited excellent mechanical property and relatively high swelling ratios for urea solution and physiological saline water with promising applicability as slow-release fertilizers.

Kinetics and Mechanism for Aquation of $[Co(en)_2Cl_2]^+$ in the $Hg^{2+}$ Aqueous Solution ($Hg^{2+}$수용액에서 $[Co(en)_2Cl_2]^+$의 아쿠아 반응속도론과 메카니즘)

  • Byung-Kak Park;Joo-Sang Lim;Sung Nak-Jung;Il-Bong Lee;Kwang-Jin Kim;Sung-Gu Kang
    • Journal of the Korean Chemical Society
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    • v.32 no.4
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    • pp.342-350
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    • 1988
  • An experimental investigation is made to determine the mechanism of the aquation of $[Co(en)_2Cl_2]^+$ in $Hg^{2+}$ aqueous solution. The progress of reaction is followed UV/vis-spectrophotometrically by a measurment of the absorbance at a specific wavelength of Co(III) complex as a function of time. The aquation of cis-$[Co(en)_2Cl_2]^+$ and trans-$[Co(en)_2Cl_2]^+$ has been found to be first order and second order with respect to the concentration of $Hg^{2+}$ catalyst, respectively. It has been found that the reaction rate for aquation of the trans-form is faster than that of cis-form, and that the product of either cis-form or trans-form is always in the mixture ratio of 97 % to 3 %. Plausible reaction mechanism is proposed for the reaction system on the basis of kinetic data and activation parameters. Theoretical rate equation derived from the proposed mechanism is consistent with the observed one.

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