• 멤브레인
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• 제22권1호
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• pp.16-22
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• 2012

팔라듐이 코팅된 $V_{99.8}B_{0.2}$ 합금 분리막을 통해 sweep 가스를 사용하지 않고 수소 투과 시 혼합가스의 영향에 대해 알아보았다. 분리막은 $400^{\circ}C$에서 sweep 가스를 사용하지 않고 순수 수소, 수소/이산화탄소, 수소/일산화탄소의 혼합가스를 1.5~8.0 bar의 압력으로 실험하였다. Sweep 가스를 사용하지 않고 수소만을 공급한 투과 실험에서 팔라듐 코팅된 $V_{99.8}B_{0.2}$ 합금 분리막(두께 : 0.5 mm)의 수소 투과량은 $40.7mL/min/cm^2$였다. 또한 수소/이산화탄소를 공급한 투과실험에서 $V_{99.8}B_{0.2}$ 합금 분리막의 수소 투과량은 $21.4mL/min/cm^2$였다. 수소/이산화탄소 및 수소/일산화탄소 혼합가스를 각각 공급할 때 투과량은 압력에 상관없이 수소 분압 감소 만큼 감소하였고 모든 경우 Sievert 법칙을 잘 만족시켰다. 투과 후 분리막의 XRD, SEM/EDX 결과로부터 $V_{99.8}B_{0.2}$ 합금 분리막은 여러 혼합가스에 대해 안정성과 내구성이 우수하다는 것을 알 수 있었다.

• 한국수소및신에너지학회논문집
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• 제25권3호
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• pp.227-233
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• 2014

Simulated waste-derived synthesis gas has been tested for hydrogen production through water-gas shift (WGS) reaction over supported Cu catalysts prepared by co-precipitation method. $CeO_2$, $ZrO_2$, MgO, and $Al_2O_3$ were employed as supports for WGS reaction in this study. $Cu-CeO_2$ catalyst exhibited excellent catalytic activity as well as 100% $CO_2$ selectivity for WGS in severe conditions ($GHSV=40,206h^{-1}$ and CO concentration = 38.0%). In addition, $Cu-CeO_2$ catalyst showed stable CO conversion for 20h without detectable catalyst deactivation. The high activity and stability of $Cu-CeO_2$ catalyst are correlated to its easier reducibility, high oxygen mobility/storage capacity of $CeO_2$.

• 한국수소및신에너지학회논문집
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• 제28권1호
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• pp.1-8
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• 2017

Cu/Mn/Ce catalysts for water gas shift (WGS) reaction were synthesized by urea-nitrate combustion method with the fixed molar ratio of Cu/Mn as 1:4 and 1:1 with the doping concentration of Ce from 0.3 to 0.8 mol%. The prepared catalysts were characterized with SEM, BET, XRD, XPS, $H_2$-TPR, $CO_2$ TPD, $N_2O$ chemisorption analysis. The catalytic activity tests were carried out at a GHSV of $28,000h^{-1}$ and a temperature range of 200 to $400^{\circ}C$. The Cu/Mn(CM) catalysts formed Cu-Mn mixed oxide of spinel structure ($Cu_{1.5}Mn_{1.5}O_4$) and manganese oxides ($MnO_x$). However, when a small amount of Ce was doped, the growth of $Cu_{1.5}Mn_{1.5}O_4$ was inhibited and the degree of Cu dispersion were increased. Also, the doping of Ce on the CM catalyst reduced the reduction temperature and the base site to induce the active site of the catalyst to be exposed on the catalyst surface. From the XPS analysis, it was confirmed that maintaining the oxidation state of Cu appropriately was a main factor in the WGS reaction. Consequently, Ce as support and dopant in the water gas shift reaction catalysts exhibited the enhanced catalytic activities on CM catalysts. We found that proper amount of Ce by preparing catalysts with different Cu/Mn ratios.

• 한국신재생에너지학회:학술대회논문집
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• 한국신재생에너지학회 2009년도 춘계학술대회 논문집
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• pp.757-760
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• 2009

최근 들어 WGS 반응은 Pt과 같은 귀금속 촉매를 다양한 담체에 담지하여 낮은 온도에서 높은 활성을 지닌 촉매를 제조하기 위한 연구가 활발히 진행되고 있다. WGS 반응에서 귀금속 촉매가 높은 활성을 가지기 위해서 높은 산소저장능력(Oxygen Storage Capacity)과 산화환원능력(Redox)을 지닌 담체 개발이 필요하다. Ce-$ZrO_2$ 담체는 구조적으로 안정하며 높은 산소저장능을 가지고 있는 것으로 알려져 있다. Ce-$ZrO_2$ 구조는 Ce/Zr 비에 따라 다양한 변화가 생긴다. Ce/Zr 비가 6/4, 8/2인 경우 입방구조(Cubic)를 가지며 2/8인 경우 정방입계(Tetragonal)구조를 가진다. 이것은 담체 특성의 변화를 의미한다. 따라서, WGS 반응용 최적 담체를 선정하기 위해 Ce/Zr 비를 제조변수로 하여 담체특성을 분석하였다. 제조된 모든 담체는 공침법(Co-precipitation)을 사용하여 제조하였으며 $500^{\circ}C$에서 6시간 소성하였다. 담체 특성분석은 BET, XRD를 이용하였다. 추가적으로 제조변수를 다양화하여 담체 제조를 마쳤으며 특성분석이 진행 중이다. 분석 결과 $Ce_{0.2}Zr_{0.8}O_2$ 담체가 가장 넓은 표면적을 가지고 있으며 Ce/Zr 비가 높아질수록 표면적이 감소하는 경향을 나타내었다. Ce-$ZrO_2$ 담체의 나노결정크기는 Ce/Zr 비가 작아질수록 결정크기가 감소하는 경향을 나타내었으며 $Ce_{0.2}Zr_{0.8}O_2$가 Ce-$ZrO_2$ 담체 중에서 가장 작은 결정크기를 나타내어 3nm 이하의 나노-담체가 제조되었음을 확인하였다.

• 한국수소및신에너지학회논문집
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• 제30권2호
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• pp.95-102
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• 2019

In order to investigate the effect of water treatment on activity of WGS catalyst, $Cu/ZnO/MgO/Al_2O_3$ (CZMA) catalysts were synthesized by co-precipitation method. The prepared catalysts were water-treated at two different temperature (250, $350^{\circ}C$). Synthesized catalysts were characterized by using BET, SEM, $N_2O$ chemisorption, XRD, $H_2-TPR$ and XPS analysis. The catalytic activity tests were carried out at a GHSV of $28,000h^{-1}$ and a temperature range of $180-320^{\circ}C$. The reduction temperature decreased with water treatment and CZMA_250 catalyst showed the lowest reduction temperature and retained a large amount of $Cu^+$. Water-treated catalysts showed increased reactivity compared to untreated catalyst and the CZMA_250 catalyst showed higher catalytic activity on WGS reaction.

• 한국수소및신에너지학회논문집
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• 제23권6호
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• pp.654-659
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• 2012

The interest in water gas shift (WGS) reaction has grown significantly, as a result of the recent advances in fuel cell technology and the need to develop small-scale fuel processors. Recently, researchers have tried to overcome the disadvantages of the commercial WGS catalysts. As a consequence, supported Pt catalysts have attracted a lot of researchers due to high activity and stability for WGS at low temperatures. In this study, $Pt-Na/Ce_{(1-x)}Zr_{(x)}O_2$ catalysts with various Ce/Zr ratio have been applied to WGS at a gas hourly space velocity (GHSV) of $45,515h^{-1}$. According to TPR patterns of $Pt-Na/Ce_{(1-x)}Zr_{(x)}O_2$ catalysts, the reducibility increases with decreasing the $ZrO_2$ content. As a result, Cubic structure $Pt-Na/Ce_{(1-x)}Zr_{(x)}O_2$ catalysts exhibited higher CO conversion than tetragonal structure $Pt-Na/Ce_{(1-x)}Zr_{(x)}O_2$ catalysts. Expecially, Pt-Na/$CeO_2$ exhibited the highest CO conversion as well as 100% selectivity to $CO_2$. Moreover, Pt-Na/$CeO_2$ catalyst showed relatively stable activity with time on stream. The high activity of cubic structure Pt-Na/$CeO_2$ catalyst was correlated to its higher oxygen storage capacity (OSC) of $CeO_2$ and easier reducibility of Pt/$CeO_2$.

• 한국신재생에너지학회:학술대회논문집
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• 한국신재생에너지학회 2009년도 추계학술대회 논문집
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• pp.232-232
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• 2009

최근 WGS반응용 Pt 촉매의 성능 향상을 위한 다양한 담체 및 조촉매(Promotor) 개발에 대한 연구가 활발하게 진행되고 있다. 선행 연구결과, 입방(Cubic)구조를 가지는 $Ce_{0.8}Zr_{0.2}O_2$ 담체는 정방 입계(Tetragonal)구조를 가지는 $Ce_{0.2}Zr_{0.8}O_2$ 담체 또는 혼합산화물(Mixed oxide)구조를 가지는 $Ce_{0.5}Zr_{0.5}O_2$ 담체 보다 높은 활성과 안전성을 가진다. 이것은 촉매의 성능 향상이 Ce-$ZrO_2$의 결정구조에 의존한다는 것을 나타낸다. 따라서 WGS 반응에서 Ce/Zr 비에 따라 변화된 담체 특성이 Pt 촉매의 활성에 영향이 있을 것으로 예상되며 실험결과 1% Pt/$CeO_2$ 촉매가 가장 높은 활성을 나타내었다. 따라서 Pt/Ce-$ZrO_2$ 촉매의 성능 향상을 위해 Ce-$ZrO_2$ 담체에 조촉매인 Ni을 첨가하여 촉매적 활성을 비교하여 보았다. 촉매는 2%의 Pt과 15%의 Ni로 고정하였고 Ce/Zr 비를 제조변수로 하였다. 제조된 모든 담체는 공침법(Co-precipitation)을 사용하여 제조하였으며 $500^{\circ}C$에서 6시간 소성하였다. Pt 촉매는 함침법 (Incipient wetness impregnation)으로 담지 시켰다. 2% Pt/Ce-$ZrO_2$ 촉매와 2% Pt/15% Ni-Ce-$ZrO_2$ 촉매는 저온영역($200^{\circ}{\sim}320^{\circ}C$)에서 비슷한 CO 전환율을 나타내었으나 고온영역($360^{\circ}C{\sim}400^{\circ}C$)에서는 2% Pt/15% Ni-Ce-$ZrO_2$ 촉매가 더 높은 CO의 전환율을 나타내었다. 이것은 Ni의 영향으로 고온에서 부반응인 메탄화 반응(Methanation reaction)이 생긴 것으로 판단되어 메탄($CH_4$)의 선택도를 살펴본 결과 2% Pt/15% Ni-Ce-$ZrO_2$ 촉매가 고온영역($360^{\circ}{\sim}400^{\circ}C$)에서 급격하게 증가하는 것으로 나타나 메탄화 반응이 일어난 사실을 증명한다.

• 한국수소및신에너지학회논문집
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• 제25권6호
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• pp.577-585
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• 2014

Nanorod and particle shape $CeO_2$ were synthesized via hydrothermal process and precipitation method, respectively, and used as supports of Pt catalyst for water gas shift (WGS) reaction. Three different durations (12, 48, and 96h) for hydrothermal process were applied for the preparation of nanorod type $CeO_2$. 1.0 wt% of Pt was loaded on the prepared supports with incipient wetness method prior to the catalytic activity tests that were carried out at a GHSV of $95,541h^{-1}$, and a temperature range of 200 to $360^{\circ}C$. Varying duration of hydrothermal process led to the difference in physical characteristics of $CeO_2$ nanorods, such as aspect ratio, BET surface area, pore diameter, and pore volume. Consequently, the catalytic activities of Pt/$CeO_2$ nanorods were affected by the physical characteristics of the supports and appeared to be in the order of Pt/$CeO_2$(12) > Pt/$CeO_2$(48) > Pt/$CeO_2$(96). The comparison of the catalytic activities and results of the analysis (XPS, XRD, SEM, BET and TPR) for the supports revealed that the activity of the catalysts depends on chemical states of the Pt and the support materials in the temperature range that is lower than $280^{\circ}C$. However, the activity is rather dependent on the physical characteristic of the supports because the increased gas velocity limits the mass transfer of reactants in micropores of the supports.

• 한국수소및신에너지학회논문집
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• 제26권5호
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• pp.423-430
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• 2015

$Cu/ZnO/Al_2O_3$ catalysts for water gas shift (WGS) reaction were synthesized by co-precipitation method with the fixed molar ratio of Cu/Zn/Al precursors as 45/45/10. Copper and zinc precursor were added into sodium carbonate solution for precipitation and aged for 24h. During the aging period, aluminum precursor was added into the aging solution with different time gap from the precipitation starting point: 6h, 12h, and 18h. The resulting catalysts were characterized with SEM, XRD, BET surface measurement, $N_2O$ chemisorption, TPR, and $NH_3$-TPD analysis. The catalytic activity tests were carried out at a GHSV of $27,986h^{-1}$ and a temperature range of 200 to $400^{\circ}C$. The catalyst morphology and crystalline structures were not affected by aluminum precursor addition time. The Cu dispersion degree, surface area, and pore diameter depended on the aging time of Cu-Zn precipitate without the presence of $Al_2O_3$ precursor. Also, the interaction between the active substance and $Al_2O_3$ became more stronger as aging duration, with Al precursor presented in the solution, increased. Therefore, it was confirmed that aluminum precursor addition time affected the catalytic characteristics and their catalytic activities.