• Journal of the Korean Chemical Society
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• v.37 no.7
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• pp.648-654
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• 1993

$[M(cyclam)X_2]Y(M=Co^{3+},\;Fe^{3+},\;Mn^{3+}\;:\;X=Cl-^,\;Br^-,\;NCS^-\;:\;Y=Cl^-,\;Br^-,\;NCS^-),\;[Co(trans-14-diene)X_2]Y(X=Cl^-,\;Br^-\;:\;Y=ClO_4^-)\;and\;[Co(trans-14-diene)](ClO_4)_2$ were able to activate an molecular oxygen under sodium borohydride. 2,4-di-tert-butylphenol and 2,6-di-tert-butylphenol reacted with activated molecular oxygen to give 2,4-tert-butyl-1,6-benzoquinone(BQ) and 3,5,3',5'-tetra-tert-butyldiphenoquinone(DPQ). The saturated tetraazamacrocyclic complexes, $[Co(cyclam)X_2]Y$, were more an effective catalyst than $[Co(trans-14-diene)X_2]Y$ the unsaturated complexes in the formation of BQ and DPQ. The mole ratio of $O_2$ vs. catalyst $(O_2/M)$ for $[Co(cyclam)X_2]Y$ and [Co(trans-14-diene)X_2]Y$ was 1/1, while it was 1/2 for $[M(cyclam)Cl_2]Cl(M=Fe(III),\;Mn(III))$. The results suggested that Co(III)-macrocyclic complexes activated molecular oxygen as superoxolike ${O_2}^-$ and $[M(cyclam)Cl_2]Cl(M=Fe(III),\;Mn(III))$ activated that as peroxolike $O_2^{2-}$.

• Proceedings of the Materials Research Society of Korea Conference
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• 2003.03a
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• pp.216-216
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• 2003

현재 상용화되어 있는 리튬 이차전지용 양극재료로는 비교적 작동전압이 높은 층상 암염구조(LiCoO$_2$, LiNiO$_2$) 및 Spinet계(LiMn$_2$O$_4$) 전이금속 산화물이 대부분 이용되고 있다 하지만 LiCoO$_2$나 LiNiO$_2$ 같은 상용화 물질은 비교적 높은 비용과, 강한 독성 때문에 많은 문제점을 가지고 있다. 또 Spinel(LiMn$_2$O$_4$)는 낮은 비용과 환경친화적인 장점에도 불구하고 Jahn-Teller 변형과 관련된 구조적 변형이 심각하기 때문에 사이클시 비가역적인 용량의 감소가 심각하다. 이러한 관점에서 전이금속보다 그 양이 풍부하고 저렴할 뿐만 아니라 독성이 없는 Olivine 구조 (LiFePO$_4$)를 갖는 phosphate계 화합물에 관심을 가지게 되었다. LiFePO$_4$는 리튬 음극과 3.4V의 방전전압을 나타내며, 170mAh/g의 이론용량을 가지고 있어, Fe-base의 장점은 물론 안정적인 결정구조 및 현재 상용화된 재료들과 비슷한 에너지 밀도를 가진다. 따라서 본 연구에서는 양극물질의 기존 두 제조법인 고상반응법과 sol-gel법으로 대표되는 제조법의 단점을 상호 보완될 수 있다고 판단되는 기계적 합금화법(Mechanical Alloying, MA)공정을 도입하여 초미세립 분말 제조에 초점을 맞추어 Olivine phosphate계 양극물질의 제조 및 전기화학적 특성을 연구하였다.

• Clean Technology
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• v.24 no.1
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• pp.35-40
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• 2018

$Co_3O_4$ catalysts for $N_2O$ decomposition were prepared by co-precipitation method. Ce and Zr were added during the preparation of the catalyst as promoter with the molar ratio (Ce or Zr) / Co = 0.05. Also, 1 wt% $K_2CO_3$ was doped to the prepared catalyst with impregnation method to investigate the effect of K on the catalyst performance. The prepared catalysts were characterized with SEM, BET, XRD, XPS and $H_2-TPR$. The $Co_3O_4$ catalyst exhibited a spinel crystal phase, and the addition of the promoter increased the specific surface area and reduced the particle and crystal size. It was confirmed that the doping of K improves the catalytic activity by increasing the concentration of $Co^{2+}$ in the catalyst which is an active site for catalytic reaction. The catalytic activity tests were carried out at a GHSV of $45,000h^{-1}$ and a temperature range of $250{\sim}375^{\circ}C$. The K-impregnated $Co_3O_4$ catalyst showed much higher activity than $Co_3O_4$ catalysts with promoter only. It is found that the K-impregnation increased the concentration of $Co^{2+}$ more than the added of promoter did, and lowered the reduction temperature to a great extent.

• Applied Chemistry for Engineering
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• v.23 no.2
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• pp.176-182
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• 2012

The methane dry reforming has received the considerable attention in recent years, mainly as an attractive route to produce synthesis gas (CO, $H_2$) from green-house gases ($CH_4$, $CO_2$) for resources. However, this process has not been commercialized due to the high temperature and catalyst deactivation. In this study, Co-Ru-Zr catalysts supported on $SiO_2$ were studied for the characterization of methane dry reforming reaction and the preliminary data for process development were achieved. The crystal structure of catalysts was measured by XRD, the surface area and pore size were analyzed by BET, and the element composition of catalyst were analyzed by EDS. Conversions of methane and carbon dioxide were analyzed by GC. In addition, reaction rate constants were obtained from the reaction kinetic study and the optimum catalyst size that does not affect mass transfer from reactants was also determined. The selected pellet-type catalyst maintained activation for 720 h at $850^{\circ}C$.

• Journal of Energy Engineering
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• v.14 no.4 s.44
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• pp.219-225
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• 2005

for the removal of carbon dioxide in flue gas, which is the main cause of the global warming, chemical absorption methods were widely used for years. Alkanolamines such as MEA, AMP, MDEA are mainly used as an absorbent. In this study, cyclic amines - Piperazine, Piperidine and Cyclohelylamine are investigated to compare the chemical solubilities, absorption capacities and rate ot reaction. In conclusion, Piperazine is the most effective absorbent of $CO_2$ and ran be the excellent alternative to the former absorbents. Experiments were performed at 5, 10, 15 weight percent, 30, 40, $50^{\circ}C$, and the gas solubilities are determined by back-titration method, and using Gas Chromatography the absorption rate was compared.

• Journal of Korean Society of Environmental Engineers
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• v.39 no.8
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• pp.462-469
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• 2017

Eutrophication and shortage of phosphate ore raise the necessity of phosphate removal and recovery from wastewater treatment plants. Especially, a sludge treatment system containing highly concentrated phosphate should be targeted for phosphate removal and recovery. This study thus aimed to evaluate the capability of the struvite crystallization process for phosphate removal and recovery from a sludge treatment system of a wastewater treatment plant. Analysis on phosphate concentrations and masses in the sludge treatment system revealed that digested sludge and centrate have phosphate concentrations and masses, high enough to adopt the struvite crystallization process. Chemical equilibrium modeling indicated that the struvite crystallization reaction substantially occurred with pH higher than 8 and $Mg^{2+}$ concentration 1.2 times higher than its theoretical requirement. A series of batch tests with digested sludge and centrate indicated that the phosphate removal reaction by struvite crystallization followed a first-order kinetics and reached over 80% removal efficiency at equilibrium. Aeration in the batch tests was found to purge $CO_2$ in sludge or centrate and increase pH up to 8.7, without adding NaOH. Thus, we concluded that the struvite crystallization process could be an efficient and economical process for phosphate removal and recovery from a wastewater treatment plant.

• Clean Technology
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• v.19 no.2
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• pp.165-172
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• 2013

In this study, the hydrogen chloride removal using K-based dry sorbents ($K_2CO_3/Al_2O_3$, KEPRI, Korea) was studied with varying the pressure in a fixed bed reactor (15 cm tall bed with 0.5 cm I.d.). Working temperature was $400^{\circ}C$ and feed gas concentration was 750 ppm (HCl vol%, $N_2$ balance). The chloride sorption capacity of sorbent increases with increasing pressure (1, 5, 10, 15 and 20 bar). Also, after forming KCl crystal by reaction with $K_2CO_3$ and HCl, owing to the strong bonding energy, sorbent regeneration was practically impossible. Its optical, physical and chemical characterizations were evaluated by SEM, EDAX, BET, TGA and XRD. At $400^{\circ}C$ and 20 bar condition, working condition for the dehalogenation process after gasification, K-based dry sorbent showed high HCl sorption capacity and HCl/$N_2$ separation performances comparing with Ca-based and Mg-based dry sorbents.

• Clean Technology
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• v.10 no.3
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• pp.149-158
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• 2004

Supercritical carbon dioxide is often promoted as an environmentally friendly solvent having useful properties for a wide range of technical and chemical processes. But the limited ability of $CO_2$ to dissolve polar or non-volatile compounds represents a major drawback in many processes, because the key components will often fail to form homogeneous solution under practical conditions. The design of $CO_2$ soluble ($CO_2$-philic) surfactant to aid this process is therefore paramount in these areas, which has advanced the "greening" of demanding yet important applications in dyeing, cleaning of fibers and texiles, polymerization and polymer processing, photoresist removal, electroplating, and chemical synthesis.

• Proceedings of the Korea Society for Energy Engineering kosee Conference
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• 2004.05a
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• pp.119-124
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• 2004

최근 소형 다기능, 고기능 전자장비의 개발로 인하여 고밀도 전원이 필요성이 대두되고 있다. 연료전지는 높은 전력 밀도를 가짐으로 인하여 소형 전원 장비에 가능성을 가지는 것으로 여겨지고 있다. 연료전지 중 특히 고분자 전해질 연료전지는 높은 전력밀도와 낮은 작동온도 등으로 인하여 이차전지의 자리를 대체할 수 있을 것으로 보여지지만 현재까지 연료 공급장치의 문제로 인하여 실용화되지 못하고 있다. 본 연구에서는 여러 가지 수소저장 물질 중에서 알칼리 붕소 수소화물을 이용하여 연료전지에 수소를 공급하고자 하며, 수소발생에 사용되는 촉매에 대한 연구를 진행하였다. 알칼리 붕소 수소화물의 수소발생 반응에 사용되는 촉매로는 Pt, Ru, Co, Ni 등이 사용되어질 수 있다. 이중에서 가장 수소발생 능력이 높은 촉매는 Ru이며, 비귀금속 촉매 중에는 Co가 높은 활성을 나타내었다. 본 연구에서는 Ru 촉매와 Co 촉매의 특성을 비교하였으며 연료전지에 수소를 공급할 수 있는 가능성을 확인하였다. Ru와 Co 촉매의 공통적인 특징은 알칼리 붕소화물인 NaBH$_4$의 농도가 높아질수록, 온도가 높아질수록 수소의 발생속도를 높이는 현상을 보였다. 또한 안정화제인 NaOH에 대하여, Ru의 경우는 농도가 높아질수록 수소발생 속도가 낮아졌으며, Co는 그 반대의 결과를 보였다. NaBH$_4$의 분해 반응으로 발생된 수소를 연료전지에 공급하여 2W급의 휴대폰용 연료전지를 구동할 수 있었다. 이로써 알칼리 붕소수소화물로부터 발생된 수소를 이용하여 안정적으로 연료전지를 구동할 수 있는 가능성을 확인하였다. 유류 분해정도를 파악하는 지시자로써 특정 무기 오염물질을 이용할 수 있을 가능성이 있으므로 좀더 이들 관계성에 대한 연구가 진행될 필요성이 있다고 판단된다.고 과학적으로 분석할 수 있는 방법이 될 수 있을 것으로 기대된다. 의미를 되새기는 것으로 짧은 연구를 시작하겠다. 등은 활성 값이 70% 이상으로 퇴적물 독성이 상대적으로 낮았다. 이중나선 DNA 함량은 28.4 % - 49%로 대조군에 비해서 감소가 크다. 대부분의 정점이 대조군의 30% 내외로 정점 간의 차이는 크지는 않다. 그러나 다른 측정자료와 같이 정점 22에서 18%로 최소치를 나타내고, 정점 2, 12에서 20% 내외의 값을 보인다. 종합적으로 볼 때 오염물질의 유입이 크고, 광양제철 인근 정점 들이 모두 다른 정점에 비해서 낮아서, 퇴적물 독성이 높은 정점으로 조사되었다.hiwo의 광합성 능력은 낮은 농도들에서는 대조구와 유사하였으나, 5 $\mu\textrm{g}$/l의 높은 농도에서는 초기에 매우 낮은 광합성 능력을 보이다가 시간이 경과하면서 대조군보다 더 높은 경향을 나타냈다. 이러한 결과는 식물플랑크톤이 benso[a]pyrene의 낮은 농도에서 노출될 때는 이 물질을 탄소원으로 사용할 가능성이 있음을 시사한다. 본 연구의 결과들은 연안해역에 benso[a]pyrene과 같은 지속성 유기오염물질이 유입되었을 때 내정여부에 따라 식물플랑크톤 군집내 종 천이와 일차생산력에 크게 영향을 미칠 수 있음을 시사한다.TEX>5.2개)였으며, 등급별 회수율은 각각 GI(8.5%), GII(13.4%), GIII(43.9%), GIV(34.2%)로 나타

• Applied Chemistry for Engineering
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• v.4 no.2
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• pp.365-372
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• 1993

$CO_2$ methanation was performed over Ni supported on cation-exchanged Y zeolites under atmospheric pressure at $250{\sim}550^{\circ}C$ and $H_2/CO_2$ mole ratio of 4. Adsorption strength between carbon dioxide and nickel was found to be Influenced by the cation exchanged in the zeolite. TPD(Temperature-programmed desorption) results show that the adsorption strength decreases in the order of Ni/NaY>Ni/MaY>Ni/HY. TPSR(Temperature-programmed surface reaction) results indicate that enhanced methanation activity is obtained when the adsorption strength between carbon dioxide and nickel is stroing. As the reduction temperature increases, the methantion activity of the catalyst increase. From this result the larger size nickel particle seems advantageous for $CO_2$ methanation reaction. The maximum activity is obtained when nickel loading is 3.3wt%. Carbon monoxide is produced as a by-product throughout the reaction temperature range, and as the contact time increases, the selectivity to methane increases and the selectivity to carbon monoxide decreases steadily. Thus methane seems to be produced from $CO_2$ via CO as an intermediate species. In the temperature range of $410{\sim}450^{\circ}C$, the methane production rate is found to be dependent on the orders of 3.3~-0.5 and 1.4~3.6 with respect to $CO_2$ and $H_2$ partial pressures, respectively. This clearly shows that $CO_2$ and $H_2$ are competing for adsorption sites and as the reaction temperature increases, it becomes increasingly difficult for $H_2$ to be adsorbed on the catalyst surface.