• Journal of the Korean Institute of Gas
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• v.13 no.5
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• pp.33-38
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• 2009

Synthetic natural gas was producd by the reaction of carbon monoxide and hydrogen via methanation. Ni-Co bimetallic catalyst supported on $Al_2O_3$ for methanation was prepared using deposition-precipitation method. For the comparison, Ni, Co monometallic catalyst was prepared using the same method. The prepared catalysts were characterized by TEM, XRD and TPR and applied to methanation reaction. The catalysts prepared using deposition-precipitation method showed the high metal dispersion. The activity of Ni-Co bimetallic catalyst was higher than that of Ni, Co monometallic catalyst. TPR measurements indicated that Ni-Co bimetallic catalyst had more active hydrogen species than Ni, Co monometallic catalyst due to the synergetic effect in the presence of Ni and Co.

• New & Renewable Energy
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• v.9 no.1
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• pp.51-59
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• 2013

Tantalum carbide crystallites which is to be used for $H_2$ fuel cell has been synthesized via a temperature-programmed reduction of $Ta_2O_5$ with pure $CH_4$. The resultant Ta carbide crystallites prepared using two different heating rates and space velocity exhibit the different surface areas. The $O_2$ uptake has a linear relation with surface area, corresponding to an oxygen capacity of $1.36{\times}10^{13}\;O\;cm^{-2}$. Tantalum carbide crystallites are very active for hydrogen production form ammonia decomposition reaction. Tantalum carbides are as much as two orders of magnitude more active than Pt/C catalyst (Engelhard). The highest activity has been observed at a ratio of $C_1/Ta^{{\delta}+}=0.85$, suggesting the presence of electron transfer between metals and carbon in metal carbides.

• Clean Technology
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• v.19 no.2
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• pp.128-133
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• 2013

Catalytic combustion of benzene over $CeO_2$-supported copper oxides has been investigated. The supported copper oxides catalysts were prepared using ball mill method and characterized by XRD, FT-IR, TEM and TPR. In the CuO/$CeO_2$ catalysts prepared using ball mill method, highly dispersed copper oxide species were shown at high loading ratio. The CuO/$CeO_2$ prepared using ball mill method showed the higher activity than those prepared using impregnation method. The catalytic activity increased with an increase in the CuO loading ratio, 10 wt% loaded CuO/$CeO_2$ catalyst giving the highest activity. In addition, the promoting of 10 wt% loaded CuO/$CeO_2$ catalyst with $Fe_2O_3$ and CoO enhanced the dispersion of CuO and then increased the catalytic activity.

• Applied Chemistry for Engineering
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• v.3 no.1
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• pp.24-34
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• 1992

Recent studies dealing with the fundamental understanding and applications of bimetallic catalysts are discussed. Bimetallic catalysts have had a major industrial impact, specifically for the reforming of petroleum naphtha, for the hydrogen reduction of carbon monoxide, and for the three way catalytic converter system. The action of the bimetallic catalysts in these reactions may be interpreted in terms of ensembles, electronic influences and surface structure. Various combinations of metal pairs have been considered in order to evaluate the role played by the added metals. For catalyst selectivity control, the possibility of surface enrichment of one element has been recognised. More generally, the influence of preparative variables on the formation of supported catalysts has been clarified, In particular by temperature programmed reduction (TPR). Information on the structure of bimetallic catalysts has been obtained with chemical probes, such as chemisorption and reaction rate measurement and physical probes, such as extended X-ray absorption fine structure (EXAFS), scanning transmission electron microscopy (STEM) and Xe-NMR.

• 한국신재생에너지학회:학술대회논문집
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• 2011.05a
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• pp.157.1-157.1
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• 2011

선택적 CO 산화반응(PrOx)에 사용되는 촉매 중 Pt, Ru, Rh 등의 귀금속 계 촉매들은 비귀금속 계 촉매에 비해 활성이 좋은 반면 가격이 비싸다는 경제적인 제한점이 있다. 따라서 소량의 귀금속을 사용하여 높은 활성의 촉매를 제조하고자 활성금속의 고분산 담지 방법에 대한 연구가 이루어지고 있다. 본 연구에서는 담체인 ${\gamma}-Al_2O_3$ 표면에 활성금속인 Pt의 고분산 담지를 위해 증착-침전법(Deposition-precipitation)을 적용하였으며 용액의 pH 변화에 따른 Pt 금속 입자의 분산도에 대한 영향을 살펴보았다. Pt의 함량은 1wt%로 고정하였고 침전제로 NaOH를 사용하여 용액의 pH를 pH 7.5 ~ 10.5로 변화시켰다. 제조된 촉매는 세척 후 $400^{\circ}C$, 3시간 소성 하였다. 제조된 1wt% Pt/$Al_2O_3$ 촉매의 특성분석을 위해 BET, TPR, CO-chemisorption을 수행하였다. PrOx 반응 실험은 GHSV=60,000 $ml/g_{cat}{\cdot}h$, $T=100{\sim}200^{\circ}C$, ${\lambda}$=4 조건에서 수행되었으며 반응 전에 촉매는 $400^{\circ}C$, 3시간 환원 후 사용하였다. 촉매의 특성분석과 PrOx 반응 실험 결과를 통해 촉매가 담체 위에 고분산 되는 최적의 pH를 확인할 수 있었으며, 기존의 함침법으로 제조된 촉매와 성능 비교를 통해 제조방법에 따른 영향을 살펴보았다.

• Korean Chemical Engineering Research
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• v.55 no.5
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• pp.679-684
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• 2017

The influence of catalytic activity on Fe loading methods over Fe/BEA zeolite catalyst in the simultaneous reduction of $N_2O/NO$ has been studied. The Fe/BEA zeolite catalysts were prepared by ion exchange and impregnation. Catalytic tests were carried out in the selective catalytic reduction using ammonia as a reductant to identify the activity of prepared catalysts. The results show that the ion exchanged catalyst exhibited higher NO and $N_2O$ conversions than the impregnated catalysts did. To investigate the difference in catalytic activity, we performed various analyses such as XRD, $H_2-TPR$, $O_2-TPD$ and XPS. It is considered that the increase in the activity of the ion exchange catalyst is due to improved reducibility and increased oxygen desorption rate. In addition, the ion exchange catalyst was found through the XPS analysis that $Fe^{2+}$, which is related to the catalytic activity, is formed about 1.6 times more than the impregnated catalyst.

• Clean Technology
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• v.24 no.3
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• pp.198-205
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• 2018

This study investigated the influence of catalyst preparation on the activity of $Co-CeO_2$ catalyst for $N_2O$ decomposition. $Co-CeO_2$ catalysts were synthesized by co-precipitation and incipient wetness impregnation. In order to estimate the performance of the as prepared catalysts, direct catalytic $N_2O$ decomposition test was carried out under $250{\sim}375^{\circ}C$. As a result, the catalyst prepared by co-precipitation (CoCe-CP) showed an enhanced performance on $N_2O$ decomposition reaction even in the presence of $O_2$ and/or $H_2O$, whereas the impregnation catalyst (CoCe-IM) did not. In order to investigate the difference in catalytic activity, characterization such as XRD, BET, TEM, $H_2-TPR$, $O_2-TPD$, and XPS was conducted. It is confirmed that the particle size and specific surface area were changed depending on the catalyst preparation method and the synthesis process influenced the physical properties of the catalysts. In addition, the improvement in the activity of the catalyst prepared by co-precipitation is due to the enhanced reduction from $Co^{3+}$ to $Co^{2+}$ and the improved oxygen desorption rate. However, it has been confirmed that the surface electron state and binding energy, which are related to $N_2O$ decomposition, do not change depending on the preparation method.

• Clean Technology
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• v.21 no.4
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• pp.248-256
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• 2015

MnO₂ was prepared by a hydrothermal process method in the range of 120-200 ℃ and 0.5-5 h, calcined at 300 ℃ after induction of precipitation using KMnO₄ and MnCl₂･4H₂O, and its catalytic activity was compared for CO oxidation. The catalysts were characterized using by X-ray diffraction, N₂-sorption, scanning electron microscopy, and temperature programmed reduction of H₂ or CO. The crystalline structure of pure α-MnO₂ or hybrid α/β-MnO₂ was controlled by the preparation conditions. The pure α-MnO₂ showed better catalytic activity and thermal stability than hybrid α/β-MnO₂. Especially, α-MnO₂ prepared at 150 ℃ for 1 h has the highest specific surface area 214 m² g^-1, reducibility and labile lattice oxygen species analyzed by H₂, CO-TPR, respectively. It also showed the best CO oxidation activity in both conditions of temperature programmed and isothermal reaction. The results came from the physicochemical properties of catalysts like the crystalline structure, specific surface area, reducibility and lattice oxygen species, and which are correlated with catalytic performance.

• 한국신재생에너지학회:학술대회논문집
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• 2010.06a
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• pp.228.1-228.1
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• 2010

선택적 CO 산화반응(PrOx)을 위한 Ru이 고분산 담지된 $Ru/{\alpha}-Al_2O_3$ 촉매를 증착-침전법(deposition-precipitation)으로 제조하였다. 용액의 pH와 aging 시간에 따른 Ru 입자의 크기 변화와 분산도의 영향을 살펴보았으며 함침법(impregnation)으로 비교 촉매를 제조하였다. 촉매의 특성분석은 BET, TPR, CO-Chemisorption분석을 수행하여 촉매의 비표면적, 환원특성, 분산도를 알 수 있었다. 특성분석결과, 증착-침전법으로 제조한 $Ru/{\alpha}-Al_2O_3$ 촉매가 함침법으로 제조한 촉매에 비해 분산도가 높았으며, pH별 촉매 제조에서는 pH6.5로 제조한 촉매가 22.06%로 가장 높은 분산도를 보였다. 또한, 담체의 비표면적 영향에 따른 Ru 입자의 분산도를 살펴보기 위해 ${\gamma}-Al_2O_3$와 ${\alpha}-Al_2O_3$ 담체를 적용한 결과, 비표면적이 작은 ${\alpha}-Al_2O_3$ 담체 표면에서 Ru 분산도가 ${\gamma}-Al_2O_3$ 담체에 비해 높았다. 이는 기공이 발달하여 비표면적이 넓은 ${\gamma}-Al_2O_3$ 담체는 소량의 Ru을 고분산 담지 시 담체 표면보다는 기공 내에 담지 되는 양이 많아 실제 반응 시 반응에 참여하는 표면 활성 금속양이 적음을 알 수 있다. 특히, 선택적 산화반응과 같이 표면에서 빠른 반응이 일어나는 경우, 기공 내부의 활성금속이 반응에 참여하기 어려워 반응 활성이 낮음을 PrOx 반응실험을 통해 확인할 수 있었다. PrOx test 조건은 GHSV 250000~60000, 온도는 80~200도, 람다값은 2~4로 성능 비교하여 실험 하였다. PrOx의 성능평가 결과 담체를 ${\alpha}-Al_2O_3$를 사용하여 deposition-precipitation방법으로 제조한 pH6.5 촉매에서 $100{\sim}160^{\circ}C$에서 90%의 가장 높은 CO conversion을 가지고 18%의 선택도를 가졌다.

• Applied Chemistry for Engineering
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• v.5 no.2
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• pp.295-304
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• 1994

$Mo-V-O/SnO_2$(VM/Sn) and $SnO_2/Mo-V-O$(Sn/VM) catalysts have been prepared and characterized by XRD, BET, SEM and TPD of ammonia. The catalytic reaction of acrolein oxidation with these catalysts, in a continuous-flow fixed-bed reactor, showed that they had higher conversion of acrolein and higher yield of acrylic acid than those of Mo-V-O itself. The origin of the observed synergy studied by TPD, TPR and TPO is explained by the cooperation of $SnO_2$ and Mo-V-O at their interfaces where electrons flow from Mo-V-O phase to $SnO_2$ and $SnO_2$ produces spill-over oxygens, which, by being transported onto the surface of Mo-V-O, reoxidize the partially reduced active sites.