• Bulletin of the Korean Chemical Society
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• v.28 no.8
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• pp.1265-1272
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• 2007

A solid acid catalyst, NiSO4/CeO2-ZrO2 was prepared simply by promoting ZrO2 with CeO2 and supporting nickel sulfate on CeO2-ZrO2. The support of NiSO4 on ZrO2 shifted the phase transition of ZrO2 from amorphous to tetragonal to higher temperatures because of the interaction between NiSO4 and ZrO2. The surface area of 10-NiSO4/1-CeO2-ZrO2 promoted with CeO2 and calcined at 600 oC was very high (83 m2/g) compared to that of unpromoted 10-NiSO4/ZrO2 (45 m2/g). This high surface area of 10-NiSO4/1-CeO2-ZrO2 was due to the promoting effect of CeO2 which makes zirconia a stable tetragonal phase as confirmed by XRD. The role of CeO2 was to form a thermally stable solid solution with zirconia and consequently to give high surface area and acidity of the sample, and high thermal stability of the surface sulfate species. 10-NiSO4/1- CeO2-ZrO2 containing 1 mol% CeO2 and 10 wt% NiSO4, and calcined at 600 oC exhibited maximum catalytic activities for both reactions, 2-propanol dehydration and cumene dealkylation.

• 한국전기화학회:학술대회논문집
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• 2005.07a
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• pp.317-322
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• 2005

[ $Pt/CeO_2$ ] 촉매에 Zr을 첨가하여 우수한 저온 수성가스전화반응의 활성을 가진 촉매를 만들었다. $Pt/ZrO_2-CeO_2$ 촉매는 $Pt/ZrO_2$나 $Pt/CeO_2$ 촉매에 비해 Ce와 Zr의 상호작용에 의한 시너지 효과로 인해 CO chemisorption으로 측정한 Pt area가 증가하고 담체에 Pt가 잘 분산되었다. 또한, Zr이 첨가된 $Pt/CeO_2$는 Ce의 redox 능력을 향상시켜 support의 reducibility를 향상시켰다. 담체에 고르게 잘 분산되고 support의 산소저장능력과 reducibility가 향상된 $3\;wt\%\;Pt/ZrO_2-CeO_2$ 촉매들은 반응물에 수소와 이산화탄소의 첨가 유무와 상관없이 $3\;wt\%\;Pt/ZrO_2$나 $3\;wt\%\;Pt/CeO_2$ 촉매보다 우수한 활성을 보였다.

• Korean Chemical Engineering Research
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• v.62 no.1
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• pp.125-131
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• 2024

In this study, synthesized Ni/Ce_xZr_1-xO₂ catalysts were coated on the surface of honeycomb metalic monoliths to investigate catalytic activity in steam reforming of methane reactions. Supports with varying Ce/Zr ratios were synthesized to observe their behavior in the reforming reaction, and catalysts with Ni contents ranging from 5 wt% to 20 wt% were prepared to analyze the effect of Ni loading contents on catalytic activity. The catalysts were characterized by XRD, BET, TPR, and SEM. The TPR analysis indicated the formation of Ni-Ce-Zr oxide with a strong interaction between the active metal Ni and CeO₂-ZrO₂ support. The 15 wt% Ni/Ce_0.80Zr_0.20O₂ catalyst exhibited the highest activity and stability in the steam reforming of methane reaction. Catalysts with enhanced activity and stability were synthesized by manufacturing composite materials using excellent oxygen storage and donor properties of CeO₂ and the thermal properties of ZrO₂.

• Bulletin of the Korean Chemical Society
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• v.27 no.12
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• pp.1989-1996
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• 2006

The $NiSO_4/CeO_2-ZrO_2 $catalysts containing different nickel sulfate and $CeO_2$ contents were prepared by the impregnation method, where support, $CeO_2-ZrO_2$was prepared by the coprecipitation method using a mixed aqueous solution of zirconium oxychloride and cerium nitrate solution followed by adding an aqueous ammonia solution. No diffraction line of nickel sulfate was observed up to 20 wt %, indicating good dispersion of nickel sulfate on the surface of $CeO_2-ZrO_2$. The addition of nickel sulfate (or $CeO_2$) to $ZrO_2$ shifted the phase transition of $ZrO_2$ from amorphous to tetragonal to higher temperatures because of the interaction between nickel sulfate (or $CeO_2$) and $ZrO_2$. A catalyst (10-$NiSO_4/1-CeO_2-ZrO_2$) containing 10 wt % $NiSO_4$ and 1 mole % $CeO_2$, and calcined at $600{^{\circ}C}$ exhibited a maximum catalytic activity for ethylene dimerization. The catalytic activities were correlated with the acidity of catalysts measured by the ammonia chemisorption method. The role of $CeO_2$was to form a thermally stable solid solution with zirconia and consequently to give high surface area, thermal stability and acidity of the sample.

• 한국신재생에너지학회:학술대회논문집
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• 2009.06a
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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.

• Journal of the Korean Ceramic Society
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• v.34 no.1
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• pp.102-108
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• 1997

ZrO2 powders stabilized with Y2O3 and CeO2 of various compositions were prepared by the coprecipitation of water-soluble ZrOCl2.8H2O, YCl3.6H2O and Ce(NO3)3.6H2O, and their compacts were pressurelessly sintered at 1400 and 150$0^{\circ}C$ for 2hrs in air. 2mol% Y2O3-ZrO3 showed the most superior strength (1003MPa) and microhardness (12.6GPa), while 10 mol%CeO2-ZrO2 had the hightest toughness (13.3 MPa.m1/2) after sintering at 140$0^{\circ}C$. The addition of Y2O3 into Y2O3-ZrO3 decreased mean grain size and increased strength and hardness but decrease toughness. On the other hand, the addition of CeO2 into Y2O3-ZrO2 enhanced the stability of tetragonal phase during low-temperature aging for a long time under hydrothermal atmosphere.

• Journal of the Korean Ceramic Society
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• v.36 no.12
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• pp.1390-1395
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• 1999

Zr(Y,Ce)O2 TZP ceramics were prepared by sintering compacts of 3 mol% Y2O3-TZP(3Y-TZP) powders with different amount of 12 mol% CeO2-TZP(12Ce-TZP) in air at 140$0^{\circ}C$ for 2 h. The phase changes microstructure and mechanical properties of Zr(Y. Ce)O2 TZP after hydrothermal aging(20$0^{\circ}C$ 5h) were investigated. Although an addition of 12Ce-TZP accelerated the grain growth of Zr(Y, Ce)O2 TZP it restrained the transformation of tetragonal to the monoclinic phase during aging. The degradation in mechanical properties of sintered bodies was governed by the formed monoclinic phase and chemical composition. Induced Vickers indentation crack was propagated intergranually. From SEM observation of the fracture surfaces the pull-out of individual grain was confirmed.

• Transactions of the Korean hydrogen and new energy society
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• v.23 no.6
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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/$CeO_2$.

• Economic and Environmental Geology
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• v.37 no.6 s.169
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• pp.603-612
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• 2004

Pyrochlore is known as one of the most promising materials for the immobilization of radionuclide in high level waste. This study included the synthesis, phase relation and characteristics of $pyrochlore(CaCeZr_xTi_{2-x}O_{7,\;x=0.2\~2.0)$ in the system of Ca-Ce-Zr-Ti-O. Using the CPS(Cold pressing and sintering) method, the mixtures of $CaCO3_,\;CeO_2,\;ZrO_2\;and\;TiO_2$ oxides were pressed, and sintered at $1100\~1600^{\circ}C$ for 20 hours. The optimal synthetic conditions at various compositions were differed from 1300 to $1600^{\circ}C$ Even in the optimal temperatures, pyrochlore or fluorite coexisted with minor amount of perovskite, $CeO_2\;or\;Ce_{0.75}Zr_{0.25}O_2$. It was confirmed that pyrochlore and fluorite structures were stable at $x\leq0.6\;and\;x\geq1.0$, respectively. Especially, the compositions of pyrochlore or fluorite showed non-stoichiometric compositions in that contents of Ca and Ti were more deficient and those of Zr and Ce were more excess than batch compositions with the increase of x value. These characteristics stemmed from the behavior of elements occupied at eight- and six-coordinated site, and then caused the coexistence of perovskite, $CeO_2\;or\;Ce_{0.75}Zr_{0.25}O_2$ along with pyrochlore or fluorite.

• Journal of the Korean Ceramic Society
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• v.28 no.7
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• pp.541-548
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• 1991

Sinterability and stability of TZP ceramics co-stabilized by 12 mol% CeO2 and divalent or trivalent oxides less than 1 mol% were investigated. Divalent and trivalent oxides increased stability of tetragonal ZrO2. 100% tetragonal ZrO2 phase was obtained by doping 12 mol% CeO2 and 0.2 mol% CaO and MgO respectively when sintering was carried out at 1500$^{\circ}C$ for 2 hours. Divalent and trivalent oxides improved sinterability and inhibit grain growth of ZrO2. And it was found that CaO was the most effective sintering aid and grain growth inhibitor for ZrO2 in this study. Incorporation of divalent and trivalent oxides into 12Ce-TZP increased the strength of 12Ce-TZP and particulary 12Ce, 0.4Ca-TZP exhibited a flexural strength of about twofold greater than 12Ce-TZP.