• Bulletin of the Korean Chemical Society
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• 제6권4호
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• pp.191-196
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• 1985

The MNDO was found to be the most reliable semi-empirical SCF-MO method for the studies of $S_N2$ reactions involving anion and neutral molecule. The results of our MNDO calculations on the $S_N2$ reactions of $CH_3X$ + $Y^-$ → $CH_3Y$ + X- where X = H, F, Cl, CN, $CH_3$, and Y = F, $CH_3$ showed that the order of the leaving group ability is the reverse of the order of proton affinities. It was also found that there is no symbiosis involved in the SN2 transition state and the departure of the leaving group is relatively late in contrast to the early bond formation of the nucleophile. The Marcus equation was found to apply to the MNDO barriers and energy changes.

• 멤브레인
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• 제10권4호
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• pp.192-197
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• 2000

상용 고분자막으로 많이 사용되는 Polysulfone(PSF)을 오존으로 처리하여 기체의 투과 및 분리특성을 조사하였다. 고분자막의 오존처리는 chamber 내부에 막을 설치하고 약 5vol.%의 오존을 포함한 산소를 chamber에 연속적으로 공급하면서 일정시간 동안 오전처리를 수행하였다. PSF막의 선택도는 오존처리시간에 따라 증가하였으며 적정 오존처리 시간은 1.5시간이면 충분한 것으로 조사되었다. 그리고, 오존처리에 의한 He/$N_2$, $H_2$/$N_2$, $O_2$/$N_2$, $CO_2$/$CH_4$등의 선택도의 증가는 분자크기가 큰 $N_2$나 $CH_4$의 투과도의 감소에 기인하며 분자크기가 작은 기체의 투과도의 감소는 매우 작은 것으로 나타났다. 오존처리에 의한 선택도의 증가는 오존이 PSF 고분자를 부분적으로 산화시키고 이때 생성된 산소복합체들이 PSF의 자유부피를 감소시키기 때문으로 생각된다.

• 한국대기환경학회지
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• 제25권6호
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• pp.562-570
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• 2009

Although anthracite power plant acts as the important source of greenhouse gas emissions, relatively little is known about its emission potentials. Especially, because the emissions of Non-$CO_2$ greenhouse gas $CH_4$ and $N_2O$ are strongly dependent on fuel type and technology available, it is desirable to obtain the information concerning their emission pattens. In this study, the anthracite power plants in Korea were investigated and the emission gases were analyzed using GC/FID and GC/ECD to develop Non-$CO_2$ emission factors. The anthracite samples were also analyzed to quantity the amount of carbon and hydrogen using an element analyzer, while calorie was measured by an automatic calorie analyzer. The emission factor of $CH_4$ and $N_2O$ computed through the gas analysis corresponded to 0.73 and 1.98 kg/TJ, respectively. Compared with IPCC values, the $CH_4$ emission factor in this study was about 25% lower, while that of $N_2O$ was higher by about 40%. More research is needed to extend our database for emission factors of various energy-consuming facilities in order to stand on a higher position.

• 한국기후변화학회지
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• 제7권2호
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• pp.103-110
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• 2016

In this study, we researched the characteristics of $CH_4$ and $N_2O$ emission of the wastewater treatment (WWT) process in the dairy industry. For flux measurements at the air-water interface, a floating dynamic flow-through chamber was used above the water surface. $CH_4$ and $N_2O$ concentration from the WWT process was measured by NDIR (Non-Dispersive Infrared) Analyser. In the study, $CH_4$ and $N_2O$ fluxes results showed a distinct difference for each WWT process. 60% of the GHG emissions which was the highest percentage were from the equalization tank. Reactor tank was second with 27% of the total emissions from the WWT. Aeration tank was third with 12% of the total emissions. The tendency was that the more the wastewater was treated, the less GHGs were emitted. $CH_4$ and $N_2O$ showed the same tendency. This indicates that the concentrations and properties of wastewater could affect the tendency.

• 한국연소학회:학술대회논문집
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• 한국연소학회 제26회 KOSCO SYMPOSIUM 논문집
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• pp.129-136
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• 2003

Numerical study with momentum-balanced boundary conditions has been conducted to grasp chemical effects of added $CO_{2}$ and $H_{2}O$ to fuel- and oxidizer-sides on flame structure and NO emission behavior in $CH_{4}$/Air counterflow diffusion flames. The dilution with $H_{2}O$ results in significantly higher flame temperatures and NO emission, but dilution with $CO_{2}$ has much more chemical effects than that with $H_{2}O$. Maximum reaction rate of principal chain branching reaction due to chemical effects decreases with added $CO_{2}$. but increases with added $H_{2}O$. The NO emission behavior is closely related to the production rate of OH, CH and N. The OH radical production rate increases with added $H_{2}O$ but those of CH, N decrease. On the other hand the production rates of OR CH and N decrease with added $CO_{2}$. It is found that NO emission behavior is considerably affected by chemical effects of added $CO_{2}$ and $H_{2}O$.

• 한국분무공학회지
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• 제7권4호
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• pp.42-49
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• 2002

In this study, quantitative measurement of nitric oxide concentration distributions were investigated in the laminar CH4/O2/N2 premixed flame by laser-induced fluorescence (LIF). The NO A-X (0,0) vibrational band around 226nm was excited using a XeCl excimer-pumped dye laser. Selecting an appropriate NO transition minimizes interference from Rayleigh scattering and O2 fluorescence. The measurements were taken in CH4/O2/N2 premixed flame with equivalence ratios varying from $1.0{\sim}1.6$, and a fixed flowrate of 5slpm. NO was found to produce primarily between an inner premixed and an outer nonpremixed flame front, and total NO concentration is raised when equivalence ratios increase. These results suggest that prompt NO is likely to contribute to NO formation in CH4/O2/N2 premixed flame. Furthermore, this trend was well matched with previous works.

• 한국세라믹학회지
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• 제29권9호
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• pp.681-688
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• 1992

Ultrafine Si3N4 and Si3N4+SiC mixed powders were synthesized through thermal plasma chemical vapor deposition(CVD) using a hybrid plasma, which was characterized by the supersposition of a radio-frequency plasma and arc jet. The reactant SiCl4 was injected into an arc jet and completely decomposed in a hybrid plasma, and the second reactant CH4 and/or NH3 mixed with H2 were injected into the tail flame through double stage ring slits. In the case of ultrafine Si3N4 powder synthesis, reaction efficiency increased significantly by double stage injection compared to single stage one, although crystallizing behaviors depended upon injection speed of reactive quenching gas (NH3+N2) and injection method. For the preparation of Si2N4+SiC mixed powders, N/C composition ratio could be controlled by regulating the injection speed of NH3 and/or CH4 reactant and H2 quenching gas mixtures as well as by adjusting the reaction space.

• 한국환경과학회지
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• 제20권6호
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• pp.687-700
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• 2011

A new $N_3-O_2$ pentadentate ligand, H-BHPT, was synthesized. Hydrochloric acid salts of Br-BHPT, Cl-BHPT, $CH_3O$-BHPT and $CH_3$-BHPT, having Br-, Cl-, $CH_{3-}$ and $CH_3O-$ substituents at the para position of the phenol hydroxyl group of H-BHPT were synthesized. Hydrochloric acid salts of 3OH-BHPT and 4OH-BHPT, having different position of the phenol hydroxyl group of H-BHPT were also synthesized. The synthesis of each ligand was confirmed by C. H. N. atomic analysis and $^1H$ NMR, $^{13}C$ NMR, UV-visible, and mass spectra. The calculated proton dissociation constants ($log{K_n}^H$) of the phenol hydroxyl group and secondary amine group of the synthesized $N_3-O_2$ ligands showed five steps of the proton dissociations. The order of the overall proton dissociation constants ($log{\beta}_p$) of the ligands was Br-BHPT < Cl-BHPT < H-BHPT < $CH_3O$-BHPT < $CH_3$-BHPT. The order agreed with that of Hammett substituent constants (${\delta}_p$). However, dissociation steps of 3OH-BHPT were four and that of 4OH-BHPT was three. The calculated stability constants ($logK_{ML}$) between the ligands and transition metal ions agreed with the order of $log{\beta}_p$ values of the ligands. The order of the stability constants between the transition metal ions with the synthesized ligands was Co(II) < Ni(II) < Cu(II) > Zn(II) > Cd(II) > Pb(II). The order agreed well with that of the Iriving-Williams.

• 한국연소학회:학술대회논문집
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• 한국연소학회 2001년도 제22회 KOSCI SYMPOSIUM 논문집
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• pp.53-59
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• 2001

Experimental measurements are conducted to investigate the structure of flat $CH_4/O_2/N_2$ premixed flames. The flames are simulated using a detailed chemical kinetic mechanism. Four flames established at equivalence ratio = 0.55 are studied with the different $O_2$ enrichment level, ${\Omega}$ = 0.21, 0.25, 0.30, and 0.35. The measured flame speed and species composition profiles are compared with the calculations. Whereas there is overall good agreement between the measurements and predictions, it appears that as the $O_2$ enrichment level is increased the position of the flame is moved toward the exit of the burner and the rapid temperature rise happens near the exit of the burner, and some areas of further refinement in the kinetic mechanism are identified.

• Bulletin of the Korean Chemical Society
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• 제14권4호
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• pp.439-444
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• 1993

The aerobic oxidation of the Fe(II) complex of 1,4,8,11-tetraazacyclotetradecane, [Fe(cyclam)$(CH_3CN)_2](ClO_4)_2$, in MeCN in the presence of a few drops of $HClO_4$ leads to low spin Fe(III) species [Fe(cyclam)$(CH_3CN)_2](ClO_4)_3$. The Fe(III) cyclam complex is further oxidized in the air in the presence of a trace of water to produce the deep green binuclear bismacrocyclic Fe(II) complex $[Fe_2(C_{20}H_{36}N_8)(CH_3CN)_4](ClO_4)_4{\cdot}2CH_3CN$. The Fe(II) ions of the complex are six-coordinated and the bismacrocyclic ligand is extensively unsaturated. $[Fe_2(C_{20}H_{36}N_8)(CH_3CN)_4](ClO_4)_4{\cdot}2CH_3CN$ crystallizes in the monoclinic space group $P2_1/n$ with a= 13.099 (1) ${\AA}$, b= 10.930 (1) ${\AA}$, c= 17.859 (1) ${\AA}$, ${\beta}$= 95.315 $(7)^{\circ}$, and Z= 2. The structure was solved by heavy atom methods and refined anisotropically to R values of R= 0.0633 and $R_w$= 0.0702 for 1819 observed reflections with F > $4{\sigma}$ (F) measured with Mo K${\alpha}$ radiation on a CAD-4 diffractometer. The two macrocyclic units are coupled through the bridgehead carbons of ${\beta}$-diimitie moieties by a double bond. The double bonds in each macrocycle unit are localized. The average bond distances of $Fe(II)-N_{imine}$, $Fe(II)-N_{amine}$, and $Fe(II)-N_{MeCN}$ are 1.890 (5), 2.001 (5), and 1.925 (6) ${\AA}$, respectively. The complex is diamagnetic, containing two low spin Fe(II) ions in the molecule. The complex shows extremely intense charge transfer band in the near infrared at 868 nm with ${\varepsilon}$= 25,000 $M^{-1}cm^{-1}$. The complex shows a one-electron oxidation wave at +0.83 volts and two one-electron reduction waves at -0.43 and-0.72 volts vs. Ag/AgCl reference electrode. The complex reacts with carbon monoxide in $MeNO_2$ to form carbonyl adducts, whose $v_{CO}$ value (2010 $cm^{-1}$) indicates the ${\pi}$-accepting property of the present bismacrocyclic ligand.