• Applied Chemistry for Engineering
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• v.2 no.2
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• pp.108-118
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• 1991

Interactions between pyridine hydrodenitrogenation (HDN) and m-cresol hydrodeoxygenation(HDO), and the kinetic analysis were studied over sulfided $CoMo/{\gamma}-Al_2O_3$ catalyst at the range of temperatures between 473 K and 723 K, the total pressures between $10{\times}10^5Pa$ and $50{\times}10^5Pa$, and the contact times between 0.0125 g-cat. hr/ml-feed and 0.03g-cat. hr/ml-feed. HDN of pyridine and HDO of m-cresol were inhibited by each other and the inhibition effect of HDO by pyridine is higher than that of HDN by m-cresol. But reactivity of m-cresol is higher than that of pyridine. The rate equations of pyridine and m-cresol were given to be ${\gamma}_{HDN}=k_{HDN}{\cdot}K_pC_p/(1+K_cC_c+K_pC_p)$ and ${\gamma}_{HDO}=k_{HDO}{\cdot}K_cC_c/(1+K_cC_c+K_pC_p)$ in terms of Langmuir-Hinshellwood-Hougen-Watson model. At each temperature, reaction rate constants and adsorption equilibrium constants were determined and activation energies of pyridine HDN and m-cresol HDO are 13.83kcal/mol, respectively and the heat of adsorption are -6.458 and -5.045kcal/mol, respectively.

• Resources Recycling
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• v.17 no.6
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• pp.34-42
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• 2008

The properties of sodium silicate solution were surveyed by using the yellow silicomolybdic method, and the formation of silica sol from sodium silicate solution and the growth of silica sol were investigated in this study. The $SiO_2$ content of 2 wt% in sodium silicate solution was proper to oxidize sodium silicate with sulfuric acid. After the removal of sodium ions in sodium silicate solution, the pH of silicate solution had to be controlled above 9 for the stabilization of silicate solution. The condensation between silicic acid species and silica nuclei surfaces has been studied at $20{\sim}80^{\circ}C$ and pH 10 in silicate solutions with silica nuclei. The reaction falls into two kinetics regimes, limited at high silicic acid species concentration by polymerization, but at lower concentration by a process whereby deposited silicic acid species condenses further to silica. The overall condensation is first-order in silicic acid species concentration, proceeded toward to pseudo equilibrium concentration, $C_x$, rather than the solubility of amorphous silica. The heat of solution of amorphous silica was 3.34 kcal/mol and exhibits an Arrhenius temperature dependence with an apparent activation energy of 3.16 kcal/mol in the range of $20{\sim}80^{\circ}C$.

• Applied Chemistry for Engineering
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• v.5 no.5
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• pp.825-835
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• 1994

Synthesis of ETBE as an octane number enhancer from ethanol and isobutene in a flow reactor under atmospheric pressure was studied. Amberlyst-15 and Amberlyst XN-1010 were used as catalysts within the temperature range of $70-140^{\circ}C$. The activity of Amberlyst 15 was higher than that of Amberlyst XN-1010. The reaction rate data obtained under differential reactor condition were tested by a linear regression method to determine the reaction mechanism and kinetic parameters. The ETBE synthesis reaction seems to be proceeded via the LHHW(Langmuir-Hinshelwood-Hougen-Watson) machanism. The activation energy of the surface reaction was estimated by the reaction rate constants as well as the adsorption equilibrium constants. Apparent activation energies are 18.64 and 24.19kcal/mol for Amberlyst-15 and Amberlyst XN-1010, respectively.

• KSBB Journal
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• v.11 no.6
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• pp.712-717
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• 1996

Cellulase was modified with synthetic copolymers of polyoxyethylene derivative and maleic acid anhydride. The saccharification characteristics and enzymatic reaction kinetic mechanism of modified and native cellulases were observed. In modification reaction of cellulase, degree of modification(DM) increased, as mass ratio of copolymers to enzyme increased. Maximum DM was 55% at mass ratio of 4 and remained activity was 75%. In saccharification experiment modified enzyme had maintained higher stability than native enzyme over all the reaction and the final conversion yield of modified enzyme was greater than that of native enzyme. Numerical simulation based on the reaction mechanism considering enzymatic deactivation was performed. Modified enzyme had kept higher free enzyme concentration over all the reaction than that of native enzyme. Comparing calculation values with experimental data, calculation values were in accordance with experimental data.

• Journal of the Korean Electrochemical Society
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• v.10 no.2
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• pp.132-140
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• 2007

The phase-shift method and correlation constants for studying a linear relationship between the behavior ($-{\varphi}\;vs.\;E$) of the phase shift ($0^{\circ}{\leq}-{\varphi}{\leq}90^{\circ}$) for the optimum intermediate frequency and that (${\theta}\;vs.\;E$) of the fractional surface coverage ($1{\geq}\theta{\geq}0$) have been proposed and verified to determine the Langmuir, Frumkin, and Temkin adsorption isotherms (${\theta}\;vs.\;E$) at noble metal/aqueous electrolyte interfaces. At an Ir/0.1 M KOH aqueous electrolyte interface, the Langmuir and Temkin adsorption isotherms (${\theta}\;vs.\;E$), equilibrium constants ($K=3.3{\times}10^{-4}\;mol^{-1}$ for the Langmuir and $K=3.3{\times}10^{-3}{\exp}(-4.6{\theta})\;mol^{-1}$ for the Temkin adsorption isotherm), interaction parameter (g = 4.6 for the Temkin adsorption isotherm), and standard free energies (${\Delta}G_{ads}^0=19.9kJ\;mol^{-1}\;for\;K=3.3{\times}10^{-4}\;mol^{-1}$ and $16.5<{\Delta}G_{\theta}^0<23.3\;kJ\;mol^{-1}\;for\;K=3.3{\times}10^{-3}{\exp}(-4.6{\theta})\;mol^{-1}\;and\;0.2<\theta<0.8$) of H for the cathodic $H_2$ evolution reaction are determined using the phase-shift method and correlation constants. The inhomogeneous and lateral interaction effects on the adsorption of H are negligible. At the intermediate values of ${\theta},\;i.e,\;0.2<{\theta}<0.8$, the Temkin adsorption isotherm (${\theta}\;vs.\;E$) correlating with the Langmuir or the Frumkin adsorption isotherm (${\theta}\;vs.\;E$), and vice versa, is readily determined using the correlation constants. The phase-shift method and correlation constants are accurate and reliable techniques to determine the adsorption isotherms (${\theta}\;vs.\;E$) and related electrode kinetic and thermodynamic parameters(K, g, ${\Delta}G_{ads}^0, {\Delta}G_{\theta}^0$).

• Journal of the Korean Electrochemical Society
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• v.7 no.1
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• pp.21-25
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• 2004

The electrochemical behaviors of dissolved hydrogen and hydrogen peroxide at a platinum disk electrode were investigated in boric acid solution by potentiostatic polarization method at the temperature of 25 and $200^{\circ}C$. The oxidation of dissolved hydrogen at $25^{\circ}C$ was kinetically controlled reaction, the rate of which depends upon the electron transfer on the electrode surface. As temperature was raised, however, the electrochemical characteristics of dissolved hydrogen were changed from a kinetically controlled reaction to a diffusion controlled one. One notable feature, with dissolved hydrogen at high temperature, is that an abnormal potential range was observed, where the oxidation rate of dissolved hydrogen rapidly decreased just before starting potential of water oxidation. We think it is caused by the deactivation of the electrode that results from the adsorption of hydroxyl ion on the surface of the platinum disk. On the contrary, a definite change with temperature was not identified in the case of the hydrogen peroxide except for the increase in current density that was due to the increasing diffusion coefcient with an increase of temperature.

• Applied Chemistry for Engineering
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• v.9 no.2
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• pp.255-260
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• 1998

Metal hydrides, $LaNi_5$ and $LaNi_{4.5}Al_{0.5}$, were prepared using chemical synthetic method, and their physical properties were examined using various analytic techniques such as TGA, XRD, SEM and EDX. The activation of the chemically prepared $LaNi_5$ and $LaNi_{4.5}Al_{0.5}$ was achieved by two hydriding/dehydriding cycles only. The miasurements of P-C-T curves revealed that 6 and 5.5 hydrogen atoms were stored in LaNi5and $LaNi_{4.5}Al_{0.5}$, respectively. The hydriding reaction rated for $LaNi_{4.5}Al_{0.5}$ were measured by the method of initial rates. It was found that the shrinking unreacted core model could be applied for the analysis of hydriding kinetics of $LaNi_5$. The rate controlling step of this reaction was the dissociative chemisorption of hydrogen molecules on the surface of $LaNi_5$. The activation energy was $9.506kcal/mol-H_2$. The rates measured in the temperature range from 273 to 343K and in pressure difference ($P_o-P_{eq}$) range form 0.25 to 0.66atm could be expressed as the following equation ; $\frac{dX}{dt}=4.636(P_o-P_{eq})$ exp($\frac{-9506}{RT}$).

• 한국신재생에너지학회:학술대회논문집
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• 2010.06a
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• pp.215.2-215.2
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• 2010

지구온난화의 주범으로 알려진 $CO_2$의 대기 중 농도는 산업혁명 이전 280ppm에서 산업 혁명 이후 375ppm으로 증가하였다. 정부 간 기후변화패널(IPCC)의 기후변화 시나리오에 의하면, 지금부터 다양한 감축노력을 한다 할지라도 $CO_2$ 증가추세는 계속되어 2100년경에는 대기 중 $CO_2$농도가 600~950ppm에 이를 것으로 예측하고 있다. 현재까지 화력발전부분은 온실가스($CO_2$)의 최대 배출 원으로 알려져 있으며 이 분야의 $CO_2$ 회수기술은 연소 후 포집(Post-combustion), 순산소 연소(Oxy-fuel combustion), 연소 전 탈탄소화(Pre-combustion) 3가지로 크게 구분된다. 이중 석탄가스화복합발전(IGCC)기술과 연계하여 $CO_2$를 회수할 수 있는 방법이 연소 전 탈탄소화 기술이다. 핵심기술은 $CO_2$ 분리공정으로 적용 될 수 있는 기술로서는 흡착 흡수법, 막분리법 그리고 가스 하이드레이트가 있으나 아직까지 우리나라의 가스 하이드레이트 기술은 전무한 형편이다. 본 연구에서는 가스 하이드레이트 형성원리를 이용하여 정온 정압 조건에서 $CO_2/H_2$ 하이드레이트를 제조하였으며 특히, 하이드레이트 형성 촉진제인 TBAB(Tetra-n-butyl ammonium bromide)를 첨가하여 TBAB 농도에 따른 상평형 및 속도론 실험을 수행 하였다. 또한 라만 분석을 통하여 $CO_2$ 회수 분리에 대한 연구도 병행하였다.

• 한국신재생에너지학회:학술대회논문집
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• 2010.11a
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• pp.153.2-153.2
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• 2010

화력발전 분야에서 $CO_2$ 분리는 크게 연소전 탈탄소화(pre-combustion capture)와 연소후 포획(post-combustion capture)으로 나누어진다, 연소후 포획은 연료를 연소한 후 발생하는 $CO_2$와 $N_2$가스에서 $CO_2$를 분리하는 기술로 흡수나, 흡착, 막분리 등을 주로 이용한다, 연소전 탈탄소화는 연소 전에 $CO_2$가 발생되지 않도록 하는 기술로써, 부분 산화나 개질 및 수성가스 변위반응 등이 포함되며 생성된 $H_2$와 $CO_2$를 분리하여 수소를 생산하는 기술($CO_2/H_2$분리가 핵심)이다. 우리나라는 대부분 연소후 포획 위주로 많은 연구가 진행되어 왔다, 하지만 최근 고유가 시장이 형성되면서 석탄화력 발전 및 복합가스발전(IGCC)에 필요한 연소전 탈탄소화($H_2/CO_2$ 가스로부터 $CO_2$ 회수) 연구에 산업적 관심이 급상승되고 있다. 특히, 연소전 탈탄소화 과정에서는 높은 자체압력(약 2.5 - 5.0MPa)과 비교적 높은 농도의 $CO_2$(약 40%의)가 발생되기 때문에, 연소전 탈탄소화는 가스하이드레이트 형성/분해 원리가 가장 잘 적용될 수 있는 기술이라 할 수 있다. 본 연구에서는 가스 하이드레이트 형성원리를 이용하여 정온 정압 조건에서 $CO_2/H_2$ 하이드레이트를 제조하였으며 특히, 하이드레이트 형성 촉진제인 THF(Tetrahydrofuran)와 TBAB(Tetra-n-butyl ammonium bromide)를 첨가하여 각각 0.5, 1, 3mol% 농도에 따른 상평형 및 속도론 실험을 수행 하였다. 또한 라만 분석을 통하여 $CO_2$ 회수 분리에 대한 연구도 병행하였다. 이러한 연구는 연소전 탈탄소화 기술에서의 $CO_2$ 회수 분리에 대한 핵심 연구임과 동시에 탄소배출권 규제에 실질적인 기여를 할 수 있을 것으로 사료된다.

• Microbiology and Biotechnology Letters
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• v.30 no.1
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• pp.73-78
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• 2002

Four inorganic packing materials (zeocarbon, porous celite, porous glass, zeolite) and a earthworm cast were compared with regard to the removal of ammonia in a biofilter inoculated with earthworm cast. Physical adsorption of ammonia on packing materials were negligible except zeocarbon (23.5 g-$NH_3$/kg), and cell immobilization capacity have similar values irrespective of packing materials. Pressure drops of the packed bed were in order of earthworm cast zeocarbon zeolite porous glass porous. The maximum elimination capacity ($g-Nkg^{-1}$ $d^{-1}$ ) of ammonia, which were based on a unit volume of packing material, were in order of zeocarbon (526) earthworm cast (220) porous celite (93) > zeolite (68) > porous glass (53). By using kinetic analysis, the maximum removal rates ($V_{m}$ ) and the saturation constant ($K_{s}$ ) for ammonia were determined, and zeocarbon showed superior performance among the five materials.