• Journal of Ceramic Processing Research
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• 제21권5호
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• pp.602-608
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• 2020

Bioelectromethanation was tested using an isolated strain, Methanothermobacter sp., for biogas upgrading. The investigated method showed faster bioelectrochemical conversion of carbon dioxide to methane with higher coulombic efficiency than previously reported without additional hydrogen and mediator supplementation. Bioelectromethanation can utilize carbon dioxide, unlike gas separation methods, and actually requires a less negative potential than in water electrolysis. The isolated methanogens showed a relatively fast conversion to methane compared to the previously reported methane production rate and current intensity. Through further research on electroactive methanogens and the development of operation technology, bioelectromethanation can be applied for biogas upgrading with a lower energy requirement but without CO2 emissions.

• Korean Chemical Engineering Research
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• 제56권6호
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• pp.871-877
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• 2018

전 세계적으로 재생에너지의 비율이 증가함에 따라, 재생에너지로부터 생산되는 불연속적이고 간헐적인 에너지 저장 문제가 주목을 받고 있다. 다양한 에너지 저장 시스템(ESS) 중에서 $CO_2$ 메탄화 기술은 타 시스템에 비해 높은 저장 용량과 저장 기간으로 각광 받고 있다. $CO_2$ 메탄화 반응은 발열반응이며, 촉매가 낮은 온도 범위($250-500^{\circ}C$)에서 높은 활성 및 메탄 선택도를 갖는다. 기존의 고정층 방식에 비하여 유동층 반응기는 높은 열전달 특성으로 인해 발열반응에 적합하며, 열전달과 물질 전달이 유리한 장점을 갖고 있다. 본 연구에서는, 촉매 특성 평가를 위해 기포유동층 반응기(Diameter: 0.025 m, Height: 0.35 m)와 $Ni/{\gamma}-Al_2O_3$ (Ni 70% and ${\gamma}-Al_2O_3$ 30%) 촉매를 사용하였다. 반응 조건은 $H_2/CO_2$ mole ratio: 4.0-6.0, 조업온도 $300-420^{\circ}C$, 조업 압력 1-9 bar 및 $U_o/U_{mf}$ 1-5이었다. 생성 가스의 조성은 NDIR를 통해 분석하였으며, $CO_2$ 전환율은 $H_2/CO_2$ ratio, 압력, 온도가 증가함에 따라 높아지는 경향을 보였다. 이에 반해 가스유속이 빨라질수록 $CO_2$ 전환율은 떨어졌다. 최적의 운전 조건은 $H_2/CO_2$ ratio: 5, 조업온도 $400^{\circ}C$, 조업 압력 9 bar 및 $1.4-3U_{mf}$이었으며 이 때 $CO_2$ 전환율은 99.6%로 나타났다. 본 실험 촉매의 경우 장기 운전 시 촉매 성능 저하가 없이 $CO_2$ 전환율이 일정하게 유지하는 것을 확인하였다.

• 한국수소및신에너지학회논문집
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• 제20권2호
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• pp.151-160
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• 2009

Natural gas combustion characteristics of mass produced oxygen carrier particles were investigated in a batch type bubbling fluidized bed reactor. Five particles, NiO/bentonite, OCN601-650, OCN702-1100, OCN703-950, OCN703-1100 were used as oxygen carrier particles. Natural gas and air were used as reactants for reduction and oxidation, respectively. During reduction reaction, high fuel conversion and high $CO_2$ selectivity were achieved for most of oxygen carriers. During oxidation, NO emission was very low. These results indicate that inherent $CO_2$ separation and low NOx combustion are feasible for the natural gas fueled chemical-looping combustion system. Among the five oxygen carriers, OCN703-1100 particle was selected as the best candidate for demonstration of long-term operation in large-scale chemical-looping combustor from the viewpoints of fuel conversion, $CO_2$ selectivity, $CH_4$ concentration, and CO concentration.

• Journal of Electrochemical Science and Technology
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• 제13권3호
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• pp.398-406
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• 2022

To satisfy the growing demand for high-performance batteries, diverse novel anode materials with high specific capacities have been developed to replace commercial graphite. Among them, cobalt hydroxides have received considerable attention as promising anode materials for lithium-ion batteries as they exhibit a high reversible capacity owing to the additional reaction of LiOH, followed by conversion reaction. In this study, we introduced graphene in the fabrication of Co(OH)₂-based anode materials to further improve electrochemical performance. The resultant Co(OH)₂/graphene composite exhibited a larger reversible capacity of ~1090 mAh g^-1, compared with ~705 mAh g^-1 for bare Co(OH)₂. Synchrotron-based analyses were conducted to explore the beneficial effects of graphene on the composite material. The experimental results demonstrate that introducing graphene into Co(OH)₂ facilitates both the conversion and reaction of the LiOH phase and provides additional lithium storage sites. In addition to insights into how the electrochemical performance of composite materials can be improved, this study also provides an effective strategy for designing composite materials.

• 공업화학
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• 제29권4호
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• pp.382-387
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• 2018

본 연구에서는 Pd-Ni-YSZ 촉매의 형태 및 공급되는 가스 조성에 따른 수증기-이산화탄소 복합개질 반응 특성을 평가하였다. 촉매는 분말 형태와 다공성 디스크 형태로 제조되었으며 주입 가스는 $CH_4/CO_2/H_2O$ ratio를 각각 다르게 하여 공급하였다. 그 결과 분말 형태의 촉매와 비교하여 다공성 디스크 형태 촉매를 사용하였을 때 $CH_4$와 $CO_2$ 전환율이 전반적으로 향상되었으며, 공급가스의 $CH_4/CO_2/H_2O$ ratio를 1 : 0.5 : 0.5로 하였을 때 $H_2/CO$ ratio가 2에 가깝게 조절되었다. 하지만 탄소침적에 의해 반응 시작 6 h 이후 $CH_4$ 전환율이 일부 감소하였으며 압력 강하가 0.1에서 0.8로 증가하였다. 이를 해결하기 위하여 공급되는 가스의 $CH_4/CO_2/H_2O$ ratio를 조절하여 수분 비율을 최적화한 결과, 1 : 0.5 : 1의 비율로 가스를 공급할 경우 탄소 침적 방지를 통한 내구성 확보가 가능하였으며 전환율 역시 비교적 높은 수준으로 유지됨을 확인하였다.

• 한국수소및신에너지학회논문집
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• 제18권2호
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• pp.116-123
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• 2007

[ $La_{0.5}Ce_{0.5}Co_{1-x}Cu_xO_{3-{\alpha}}$ ](X=0, 0.1, 0.3, 0.5) perovskites were prepared by coprecipitation method at pH 7 or pH 11 and its catalytic activity of selective CO oxidation was investigated. The characteristics of these catalysts were analyzed by $N_2$ adsorption, X-ray diffraction(XRD), SEM, $O_2$-temperature programmed desorption(TPD). The pH value at a preparation step made effect on particle morphology. The smaller particle was obtained with a condition of pH 7. The better catalytic activity was observed using catalysts prepared at pH 7 than pH 11. The maximum CO conversion of 98% was observed over $La_{0.5}Ce_{0.5}Co_{0.7}Cu_{0.3}O_{3-{\alpha}}$ at $320^{\circ}C$. Below $200^{\circ}C$, the most active catalyst was $La_{0.5}Ce_{0.5}Co_{0.9}Cu_{0.1}O_{3-{\alpha}}$, of which conversion was 92% at $200^{\circ}C$. By the substitution of Cu, the evolution of ${\alpha}$-oxygen was remarkably enhanced regardless of pH value at preparation step according to $O_2$-TPD. Among the different ${\alpha}$-oxygen species, the oxygen species evolved between $400^{\circ}C$ and $500^{\circ}C$, gave the better catalytic performance for selective CO oxidation including $La_{0.5}Ce_{0.5}CoO_3$ in which Cu was absent.

• 대한기계학회논문집B
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• 제39권10호
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• pp.787-793
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• 2015

초임계 이산화탄소($S-CO_2$) 사이클은 소형화된 터보기계 및 열교환기를 통해서 작은 공간에서도 높은 열효율로 전력을 생산할 수 있는 잠재력을 가진 것으로 평가되고 있으며, 최근 이에 대한 관심이 증가하고 있다. 원자력 및 태양열(CSP) 분야에서 $S-CO_2$ 사이클에 대한 연구 결과가 다수 소개되어 온 반면, 폐열 분야에 대한 연구 결과는 상대적으로 많지 않다. 본 연구에서는 폐열 회수 응용 분야에 있어서, 예열에 의한 $S-CO_2$ 사이클의 성능 향상 가능성을 살피기 위하여, 재생 $S-CO_2$ 브레이튼 사이클과 예열기를 갖는 재생 $S-CO_2$ 브레이튼 사이클을 모델링하고 시뮬레이션 하였다. 시뮬레이션 결과, 순출력을 극대화시키는 최적 $CO_2$ 분기율이 존재함을 확인하였다. 본 연구의 시뮬레이션 조건 하에서, 예열기에 의한 순출력 향상은 약 16-26%로 계산되었다.

• 한국수소및신에너지학회논문집
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• 제25권2호
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• pp.114-121
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• 2014

The synthesis of Fischer-Tropsch oil is the catalytic hydrogenation of CO to give a range of products, which can be used for the production of high-quality diesel fuel, gasoline and linear chemicals. Our cobalt catalyst was prepared Co/alumina, Co/silica and Co/titania by the incipient wetness impregnation of the nitrates of cobalt with supports. Co-based catalysts was calcined at $400^{\circ}C$ before being loaded into the FT reactors. After the reduction of catalyst has carried out under $450^{\circ}C$, FT reaction of the catalyst has carried out at GHSV of 4,000 under $200^{\circ}C$ and 20atm. From test results, the order of increasing activity for the catalyst was Co/alumina > Co/silica > Co/titania. When the content of Co metal such as 5, 12, 20 and 30wt% was changed, an CO conversion increased as the content of Co metal increased. The activity of catalyst has obtained the best value at 12wt% Co content.

• 한국수소및신에너지학회논문집
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• 제26권5호
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• pp.402-408
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• 2015

In D-T fusion reaction, $D_2$ (duterium) and $T_2$(tritium) are used as fuel gas. The exhaust gas of nuclear fusion includes hydrogen isotopes $Q_2$ (Q means H, D or T), tritiated components ($CQ_4$ and $Q_2O$), CO, $CO_2$, etc. All of hydrogen isotopes should be recovered before released to the atmosphere. This study focused on the recovery of hydrogen isotopes from $CQ_4$ and $Q_2O$. Two kinds of experiments were conducted to investigate the catalytic reaction characteristics of SMR (Steam Methane Reforming) and WGS (Water Gas Shift) reactions using Pt catalyst. First test was performed to convert $CH_4$ into $H_2$ using 6% $CH_4$, 6% CO/Ar feed gas. In the other test, 100% CO gas was used to convert $H_2O$ into $H_2$ at various reaction conditions (reaction temperature, S/C ratio, GHSV). As a result of the first test, $CH_4$ and CO conversion were 41.6%, 57.8% respectively at $600^{\circ}C$, S/C ratio 3, GHSV $2000hr^{-1}$. And CO conversion was 72% at $400^{\circ}C$, S/C ratio 0.95, GHSV $333hr^{-1}$ in the second test.

• 한국세라믹학회지
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• 제39권9호
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• pp.835-839
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• 2002

Micro-Pulling Down(${\mu}$-PD)법을 이용하여 직경 1 mm, 길이 30∼35 mm의 $Er_2O_3$와 MgO가 첨가된 화학양론조성 $LiNbO_3$단결정을 성장하였다. 성장된 결정의 $Er_2O_3$와 MgO 첨가에 따른 up-conversion 특성의 변화 및 MgO 첨가량이 광손상에 미치는 영향을 관찰하기 위해 투과율을 측정하였다. 또한 $LiNbO_3$ 단결정 내의 결함유무를 광학현미경을 이용하여 관찰하였고, Electron Probe Micro Analysis(EPMA)를 이용하여 결정 내에 $Er_2O_3$와 MgO가 균일하게 분포되어있음을 확인하였다.