• Carbon letters
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• 제13권2호
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• pp.99-108
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• 2012

The sol-gel technique has been studied to fabricate a homogeneous Fe-Mo/MgO catalyst. Ambient effects (air, Ar, and $H_2$) on thermal decomposition of the citrate precursor have been systematically investigated to fabricate an Fe-Mo/MgO catalyst. Severe agglomeration of metal catalyst was observed under thermal decomposition of citrate precursor in air atmosphere. Ar/$H_2$ atmosphere effectively restricted agglomeration of bimetallic catalyst and formation of highly-dispersed Fe-Mo/MgO catalyst with high specific surface-area due to the formation of Fe-Mo nanoclusters within MgO support. High-quality thin-multiwalled carbon nanotubes (t-MWCNTs) with uniform diameters were achieved on a large scale by catalytic decomposition of methane over Fe-Mo/MgO catalyst prepared under Ar-atmosphere. The produced t-MWCNTs had outer diameters in the range of 4-8 nm (average diameter ~6.6 nm) and wall numbers in the range of 4-7 graphenes. The as-synthesized t-MWCNTs showed product yields over 450% relative to the utilized Fe-Mo/MgO catalyst, and indicated a purity of about 85%.

• Bulletin of the Korean Chemical Society
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• 제26권2호
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• pp.281-284
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• 2005

The Fe/MgO catalysts with different Fe loadings (1, 4, 6, 15 and 30 wt% Fe) were prepared by a wet impregnation with iron nitrate as precursor. All of the catalysts were characterized by BET surface analyzer, X-ray diffraction (XRD), temperature-programmed reduction (TPR), and X-ray photoelectron spectroscopy (XPS). The maximum removal capacity of $H_2S$ was obtained with 15 wt% Fe/MgO catalyst which had the highest BET surface area among the measured catalysts. XRD of Fe/MgO catalysts showed that well dispersed Fe particles could be present on Fe/MgO with Fe loadings below 15 wt%. The crystallites of bulk $\alpha$-$Fe_2O_3$ became evident on 30 wt% Fe/MgO, which were confirmed by XRD. TPR profiles showed that the reducibility of Fe/MgO was strongly related to the loaded amounts of Fe on MgO support. Therefore, the highest removal efficiency of $H_2S$ in wet oxidation could be ascribed to a good dispersion and high reducibility of Fe/MgO catalyst. XPS studies indicated that the $H_2S$ oxidation with Fe/MgO could proceed via the redox mechanism ($Fe^{3+}\;{\leftrightarrow}\;Fe^{2+}$).

• Carbon letters
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• 제5권3호
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• pp.133-141
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• 2004

The synthetic behaviors of carbon nanotubes (CNTs) by Fe/MgO catalysts were investigated in 0~90 wt.% range of MgO mixture ratios by catalytic chemical vapor deposition (CCVD) process. The CNTs were synthesized with 40 minutes of synthetic time, and 923 K of synthetic temperature using 0.1 L/min of ethylene gas and 1.0 L/min of hydrogen gas as synthetic and carrier gas, respectively. As the increase of synthetic temperatures and times, the diameters of CNTs become thicker. The carbon yield showed in a parabolic curve as MgO content increased and the maximum carbon yield was obtained at 30 wt.% of MgO. There were no obvious changes in the diameters of CNTs respect to the change of MgO content. Fe/MgO CNTs showed good crystalinity by High Resolution Transmission Electron microscope (HR-TEM) analysis. The behaviors of Fe/MgO CNTs have a tendency of depending on synthetic time and temperature rather than MgO content.

• 대한환경공학회지
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• 제27권4호
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• pp.402-408
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• 2005

Fenton 산화공정을 매립지 침출수에 적용하여 최적의 촉매를 선정하고 최적의 반응조건을 도출하기 위해 Lab scale로 상온에서 실험하였다 본 실험의 연구 결과, 다음의 결과를 얻을 수 있었다. 1) TOC의 제거효율로 최적 pH를 살펴본 결과 $Fe^{2+}$는 pH 3.0, $Fe^{3+}$는 pH 4.5, $Fe^0$는 pH 4.0으로 각각 관찰되었다. 2) 각 촉매별 최적 주입량을 결정하고 반응특성을 살펴보기 위하여 TOC, $COD_{Cr}$, $UV_{254}$를 변수로 보았고, 2가철의 경우 $H_2O_2$ : $Fe^{2+}\;=\;1,200\;mg/L$ : 1,200\;mg/L로 결정되었다 또한 3가철의 경우 $H_2O_2$ : $Fe^{3+}\;=\;1,200\;mg/L$ : 1,200 mg/L, 0가철의 경우 $H_2O_2$ : $Fe^0\;=\;900\;mg/L$ : 1,200 mg/L로 각각 결정되었다. 3) 최적조건에서 3가철($Fe^{3+}$)이 TOC와 $COD_{Cr}$에서 가장 높은 제거효율을 나타냈지만 0가철($Fe^0$)과 큰 제거율 차이를 나타내지 않았다. 이에 따라 경제적인 측면을 고려할 때 0가철($Fe^0$)이 동일한 철염주입량에서 가장 적은 과산화수소 주입량이 필요하므로 상대적으로 우수한 것으로 나타났다. 4) 실험에 적용된 최적 pH를 검증하기 위해 처리수를 pH 중화제(NaOH)로 적정했을 때 각 촉매별로 실험에 사용된 pH가 최적조건임을 확인할 수 있었다. 5) 촉매별로 시간에 따른 redox potential을 사용하여 모든 촉매에 대해 산화반응의 정도 및 반응이 일어나고 있는 계의 산화환원력을 간접적으로 측정할 수 있었다. 이에 따라 실제 Fenton 공정을 적용할 때 "on-line monitoring"의 기초 자료로써 산화환원전위를 활용할 수 있을 것으로 판단된다.

• 한국수소및신에너지학회논문집
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• 제15권4호
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• pp.274-282
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• 2004

This study focused on the development of high performance catalyst for autothermal reforming (ATR) of gasoline to produce hydrogen. The ATR was carried out over MgO/Al2O3 supported metal catalysts prepared under various experimental conditions. The catalysts before and after reaction were characterized by N2-physisorption, CO-chemisorption, SEM and XRD. The performance of supported multi-metal catalysts were better than that of supported mono-metal catalysts. Especially, it was observed that the conversion of iso-octane over prepared Ni/Fe/MgO/Al2O3 catalyst was 99.9 % comparable with commercial catalyst (ICI) and the selectivity of hydrogen over the prepared catalyst was 65% higher than ICI catalyst. Furthermore, it was identified that the sulfur tolerance of prepared catalyst was much better than ICI catalyst based on the ATR reaction of iso-octane containing sulfur of 100 ppm. Therefore, Ni/Fe/MgO/Al2O3 catalyst can be applied for a fuel reformer, hydrogen station and on-board reformer in furl cell powered vehicles.

• 한국신재생에너지학회:학술대회논문집
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• 한국신재생에너지학회 2007년도 추계학술대회 논문집
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• pp.457-460
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• 2007

석탄가스화 기술은 석탄을 고온/고압 조건에서 가스화 반응시켜 CO와 $H_2$가 주성분인 합성가스(syngas)로 전환시키는 기술이다. 그러나 가스화 반응으로 인해 합성가스 내에는 불순물인 $H_2S$, COS, $NH_3$ 등의 오염 물질이 발생하게 되며, 가스터빈의 부식, 촉매의 피독, 전극의 성능 저하 현상 등을 일으켜 효율을 저하시키게 된다. 이에 본 연구에서는 FeMgO 촉매를 제거용매로 사용하여 $H_2S$를 효과적으로 제거하기 위하여 Lab-scale 탈황 설비를 제작하였으며, 석탄 가스화 운전에 연계하여 합성가스 내 포함된 산성가스 정제 특성에 관한 연구를 진행하였다.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2006년도 제37회 하계학술대회 논문집 C
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• pp.1378-1379
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• 2006

Carbon nanotubes (CNTs) with few defects and very small amount of amorphous carbon coating have been synthesized by catalytic decomposition of acetylene in $H_2$ over well-dispersed metal particles supported on MgO. The yield, quality and diameters of CNTs were obtained by control of catalyst metal compositions to be used. The optimization condition of carbon nanotubes with high yield is when Co and Mo are in a 1:1 ratio and Fe metal contents to Co is increased on magnesium oxide support. It is also found that the diameter of the as-prepared CNTs can be controlled mainly by adjusting the molar ratio of Fe-Mo, Co-Fe, and Co-Mo versus the MgO support. Our results indicated that desired diameter distribution of CNTs is obtained by choosing or combining the catalyst to be employed.

• 한국수소및신에너지학회논문집
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• 제21권6호
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• pp.500-506
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• 2010

The metal monolith catalyst coated with 15wt% Ni/$MgAl_2O_4$ is applied to the natural gas steam reforming for hydrogen production. To address the improvement of adherence between metal monolith and catalyst coating layer, the pre-calcination temperature as well as the coating conditions of $Al_2O_3$ sol are optimized. When the Fe-Cr alloy monolith is pre-calcined at $900^{\circ}C$ for 6 h, $Al_2O_3$ layer was formed uniformly on the entire surface of the metal substrate. It is seen that the formation of $Al_2O_3$ layer on the monolith surface is essential for the uniform coating of $Al_2O_3$ sol onto the monolith substrate. The monolith catalyst coated with 10wt% $Al_2O_3$ sol shows high $CH_4$ conversion and good thermal stability as compared with the monolith catalyst without $Al_2O_3$ sol coating under severe reaction conditions with high GHSV of 30,000 $h^{-1}$ at $700^{\circ}C$. In addition, the metal monolith catalyst shows higher catalytic activity and better thermal conductivity than 15wt% Ni/$MgAl_2O_4$ pellet catalyst.

• Environmental Engineering Research
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• 제25권3호
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• pp.316-323
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• 2020

The degradation of aqueous oxytetracycline (OTC) from an aqueous solution antibiotic using H₂O₂/Fe²⁺ process was studied in one 1 L batch chemical reactor. The extent of OTC degradation (20 mg/L) was investigated from a known initial pH solution, temperature and the type of catalyst (Fe²⁺, Fe³⁺) and for various initial concentrations of OTC, H₂O₂ and Fe²⁺. The degradation efficiency achieved was found to be very important (90.82% and 90.63%) at initial pH solution of 3 and 4, respectively. However, the type of catalyst and the reaction temperature had a slight impact on the final degradation of OTC. The results showed that the OTC removal increased with increasing initial H₂O₂ concentration in the range of 70 to 150 mg/L and initial Fe²⁺ concentrations in the range of 2 to 5 mg/L. The highest degradation efficiency obtained at ambient temperature was 90.95% with initial concentration of OTC of 10 mg/L, H₂O₂ = 150 mg/L and Fe²⁺ = 5 mg/L. Moreover, biodegradability improved from 0.04 to 0.36 and chemical oxygen demand degradation was 78.35% after 60 min of treatment. This study proved that Fenton process can be used for pretreatment of wastewater contaminated by OTC before a biological treatment.

• 공업화학
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• 제8권4호
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• pp.582-588
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• 1997

고체산 촉매인 헤테로폴리산 촉매를 이용하여 대기오염 방지를 위한 옥탄가 향상제인 TAME, ETBE 및 MTBE 합성반응에 대한 실험을 고정층 상압유통식 반응장치에서 수행하였다. 일반적으로 TAME, ETBE 및 MTBE 합성반응에서 헤테로폴리산에 hetero원자와 poly원자를 치환시켜 비교한 결과, 배위된 poly원자가 W, hetero원자가 Si인 $H_4SiW_{12}O_{40}$ 촉매의 활성이 가장 우수하였고, 또한 치환된 금속에 따라 촉매의 활성이 달랐으며 이는 촉매의 산성질과 관련이 있음을 알 수 있었다. 헤테로폴리산 촉매를 이용한 합성반응에서 TAME 경우는 $FeHPW_{12}O_{40}$과 $K_3PM_{o12}O_{40}$이 비교적 활성이 좋았으나, ETBE나 MTBE 경우에 비해서는 다소 활성이 낮았다. 그리하여 본 연구에서는 활성이 좋은 헤테로폴리산 촉매들을 선정하여 각각에 대하여 1:1로 다음과 같이 혼합하여 $H_4SiW_{12}O_{40}$ : $Sr_2SiW_{12}O_{40}$, $H_4SiW_{12}O_{40}$ : $NaH_2PW_{12}O_{40}$, $Fe_{1.5}PW_{12}O_{40}$ : $Mg_2SiW_{12}O_{40}$ 및 $Mg_2SiW_{12}O_{40}$ : $Ba_2SiW_{12}O_{40}$ 실험한 결과, 혼합촉매들이 각각의 단일성분 촉매때보다 TBA의 전화율과 ETBE나 MTBE의 선택율이 더욱 향상되었음을 알 수 있었다.