• 한국유변학회:학술대회논문집
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• 한국유변학회 2002년도 춘계 학술발표회 논문집
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• pp.105-108
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• 2002

• Bulletin of the Korean Chemical Society
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• 제33권7호
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• pp.2269-2273
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• 2012

Pseudo-first-order rate constants $k_{amine}$ have been measured spectrophotometrically for the reactions of benzyl 4-pyridyl carbonate 6 with a series of alicyclic secondary amines in $H_2O$ at $25.0^{\circ}C$. The plots of $k_{amine}$ vs. [amine] curve upward, indicating that the reactions proceed through a stepwise mechanism with two intermediates, a zwitterionic tetrahedral intermediate $T^{\pm}$ and its deprotonated form $T^-$. This contrasts to the report that the corresponding reactions of benzyl 2-pyridyl carbonate 5 proceed through a forced concerted pathway. The $k_{amine}$ values for the reactions of 6 have been dissected into the second-order rate constant $Kk_2$ and the thirdorder rate constant $Kk_3$. The Br${\o}$nsted-type plots are linear with ${\beta}_{nuc}=0.94$ and 1.18 for $Kk_2$ and $Kk_3$, respectively. The $Kk_2$ for the reaction of 6 is smaller than the second-order rate constant $k_N$ for the corresponding reaction of 5, although 4-pyridyloxide in 6 is less basic and a better nucleofuge than 2-pyridyloxide in 5.

• 한국생물공학회:학술대회논문집
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• 한국생물공학회 2000년도 추계학술발표대회 및 bio-venture fair
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• pp.47-47
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• 2000

• Bulletin of the Korean Chemical Society
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• 제15권6호
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• pp.424-427
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• 1994

Effects of iron compounds in known biomimetic oxidation systems (Gif IV and GoAgg II) have been studied on activity and ketone/alcohol selectivity of cyclohexane oxidation. Both ketone/alcohol ratio and cyclohexane conversion were affected by counter-ion Z of iron compounds Z-Fe. When Z has a more electron withdrawing property, the reactivity is increased and the formation of ketone is favored. From these experimental results, a new mechanism is proposed for the biomimetic oxidation system.

• Korean Chemical Engineering Research
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• 제53권5호
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• pp.540-544
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• 2015

나노입자를 기판 위에 직접 부착시키는 방법인 전착(electrodeposition)을 이용하여 저가의 그라파이트(graphite) 기판 위에 백금 나노입자를 직접 부착시킬 수 있는 전착 욕(bath)을 개발하였고, 백금 나노입자 전착반응의 전기화학적인 특성을 분석하였다. 백금 나노입자 전착의 분극 거동 분석을 통하여 반응메카니즘을 파악하였고, 순환전위측정(cyclic voltammetry)을 통하여 백금 나노입자 전착에서는 물질전달이 속도결정단계임을 확인하였다. 또한 시간대전류법(chronoamperometry)으로 분석한 백금 나노입자 전착의 전류밀도 변화 양상은 백금 나노입자의 결정핵 생성 메카니즘이 instantaneous로 판명되었다. 그라파이트는 다른 탄소계열 기판에 비하여 매우 저가이기 때문에 그라파이트 기판 위에 백금 나노입자를 직접 부착시키는 기술은 산업적으로 유용할 것으로 기대한다.

• 한국연소학회지
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• 제9권4호
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• pp.28-34
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• 2004

Numerical simulations of freely propagating flames burning $H_2/HCl/Air$ Air mixtures were performed at atmospheric pressure in order to understand the effect of hydrogen chloride on flame structures. The chemical and physical effects of hydrogen chloride on flame structures were observed. A chemical kinetic mechanism was developed, which involved 26 gas-phase species and 198 forward elementary reactions. Under several equivalence ratios the flame speeds were calculated and compared with those obtained from the experiments, the results of which were in good agreement. As hydrogen chloride as additive was added into $H_2/Air$ flame, the flame speed, radical concentration and NO production rate were decreased. The chemical effect of hydrogen chloride caused the reduction of radical concentration, and then the decrease of the net rate of NO production. It was found that the influence in the reduction of $EI_{NO}$ with the addition of hydrogen chloride was attributed more due to the chemical effect than the physical effect.

• 한국연소학회지
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• 제7권1호
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• pp.23-30
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• 2002

Instability of oblique detonation waves (ODW) at off-attaching condition was investigated through a series of numerical simulations. Two-dimensional wedge of finite length was considered in $H_2/O_2/N_2$ mixtures at superdetonative condition. Numerical simulation was carried out with a compressible fluid dynamics code and a detailed hydrogen-oxygen combustion mechanism. Present result reveals that there is a chemical kinetic limit of the ODW detachment, in addition to the theoretical limit predicted by Rankine-Hugoniot theory with equilibrium chemistry. Result also presents that ODW still attaches at a wedge as an oblique shock-induced flame showing periodically unstable motion, if the Rankine-Hugoniot limit of detachment is satisfied but the chemical kinetic limit is not. Mechanism of the periodic instability is considered as interactions of shock and reaction waves coupled with chemical kinetic effects. From the investigation of characteristic chemical time, condition of the periodic instability is identified as follows; at the detaching condition of the Rankine-Hugoniot theory, (1) flow residence time is smaller than the chemical characteristic time, behind the detached shock wave with heat addition, (2) flow residence time should be greater than the chemical characteristic time, behind an oblique shock wave without heat addition.

• Bulletin of the Korean Chemical Society
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• 제31권10호
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• pp.2830-2834
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• 2010

The degradation efficiencies of phenol in aqueous solution were studied by semi-continuous experiments in the processes of ozone alone, ozone/bulky $Co_3O_4$ and ozone/$Co_3O_4$ nanoparticles. Catalyst samples (bulky $Co_3O_4$ and $Co_3O_4$ nanoparticles) were characterized by X-ray diffraction and transmission electron microscopy. The Brunauer-Emmett-Teller surface area, $pH_{pzc}$ and the density of surface hydroxyl groups of the two catalyst samples were also measured. The catalytic activity of $Co_3O_4$ nanoparticles was investigated for the removal of phenol in aqueous solutions under different reaction temperatures. Tert-butyl alcohol had little effect on the catalytic ozonation processes. Based on these results, the possible catalytic ozonation mechanism of phenol by $Co_3O_4$ nanoparticles was proposed as a reaction process between ozone molecules and pollutants.

• 대한화학회지
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• 제63권4호
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• pp.260-265
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• 2019

Alcohol dehydrogenase (ADH) (EC 1.1.1.1) was selected as the enzyme which will be immobilized on ultrafiltration membrane by fouling with different transmembrane pressure of 1, 2 and 3 bars. ADH will catalyze formaldehyde (CHOH) to methanol ($CH_3OH$) and simultaneously oxidized nicotinamide adenine dinucleotide (NADH) to $NAD^+$. The concentration of enzyme and pH are fixed at 0.1 mg/ml and pH 7.0 respectively. The objective of the study focuses on the effect of different transmembrane pressure (TMP) on enzyme immobilization in term of permeate flux, observed rejection, enzyme loading and fouling mechanism. The results showed that at 1 bar holds the lowest enzyme loading which is 1.085 mg while 2 bar holds the highest enzyme loading which is 1.357 mg out of 3.0 mg as the initial enzyme feed. The permeate flux for each TMP decreased with increasing cumulative permeate volume. The observed rejection is linearly correlated with the TMP where increase in TMP will cause a higher observed rejection. Hermia model predicted that at irreversible fouling with standard blocking dominates at TMP of 3 bar, while cake layer and intermediate blocking dominates at 1 and 2 bar respectively.

• 문화기술의 융합
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• 제4권2호
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• pp.211-216
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• 2018

흡착과 막을 융합시킨 분리기술은 수처리와 같은 환경 분야에서 많은 응용이 기대된다. 이 융합기술에 막분리 공정에서 문제가 되는 막 fouling을 억제시키기 위해 막표면에 카본휘스커를 성장시킨 기능성 카본막을 개발하였다. 본 연구에서는 기능성 카본막의 제조 Mechanism을 밝히기 위해, 각각의 혼합비율인 폴리머라텍스로 전처리를 하고 CVD(Chemical Vapor Deposing)법에 따라 막을 제조하였다. 이 막을 주사전자현미경(Scanning Electron Microscope(SEM)), CHN분석기(Elemental Analyzer), X-선회절법(X-Ray Diffraction(XRD))으로 분석하였다. 그 결과 3번막(PVdC(PolyVinyl di-Chloride):PVC(Polyvinly Chloride)=4.5:55)의 경우가 카본휘스커의 직경과 밀도가 높았다. 이것은 폴리머라텍스의 수소함유량에 따라 카본휘스커의 직경과 밀도를 조절하는 것이 가능할 것으로 보인다.