• Applied Chemistry for Engineering
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• v.18 no.1
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• pp.94-97
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• 2007

Carbon nanotubes and nanowires were prepared by methane pyrolysis over Pd(5)/SPK catalyst by changing oxygen molar ratio in a fixed bed flow reactor under atmospheric condition and also analyzed by SEM and TEM. When the $CH_4/O_2$ molar ratio was 1, carbons were not almost deposited on the catalyst bed support, but when it was 2, carbons were deposited as much as plugging reactor. TEM and SEM images for the deposited carbons showed a number of single-walled carbon nanotubes and carbon nanowires. The growth mechanism of carbon nanotubes produced on the catalyst surface was the tip growth mode. It should be played an important role in carbon nanotubes and nanowires produced on the catalyst bed support to formate the carbon growth velocity vectors and nuclei of ring structure of carbon nanowires. SPK carrier was $N_2$ isotherm of IV type with mesopores, and excellent in the thermal stability.

• 한국신재생에너지학회:학술대회논문집
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• 2009.11a
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• pp.208-208
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• 2009

메탄의 수증기-이산화탄소 복합개질반응에서 니켈 촉매의 탄소 침적 저항성에대한 Ce 증진 효과를 살펴보기 위해, Ni-Ce/${\alpha}-Al_2O_3$ 촉매를 제조하였다. Ce/Ni 비율 변화에 따른 촉매 비표면적, Ni 입자 분산도 및 촉매 활성 변화를 살펴보았고, Ce 첨가량을 최적화 할 수 있었다. Ce/Ni 비율 증가에 따라 NiO 결정크기가 감소하고 표면적과 Ni 분산도는 증가하였다. 특히, Ce/Ni=0.5 첨가 시, 촉매는 가장 넓은 비표면적과 Ni 분산도를 가졌으며, 우수한 촉매 활성 및 높은 탄소 침적 저항성을 보였다. 또한, 본 연구에서는 Ni과 Ce 담지 방법에 따른 Ni 분산도 향상과 Ni과 Ce간의 접촉 면적 극대화를 통한 활성산소 공급 향상에 대한 영향을 함께 살펴보았다. Ni과 Ce를 동시 함침법과 연속 함침법으로 담지하여 비교한 결과, 동시 함침법으로 제조한 Ni-Ce/${\alpha}-Al_2O_3$ (Ce/Ni=0.5) 촉매가 가장 우수한 촉매 성능 및 높은 탄소 침적 저항성을 보였다. 이는 동시 함침법으로 고분산된 Ni 입자와 담체간의 강한 상호작용 형성과 원활한 활성 산소 공급에 기인한 것이다.

• Applied Chemistry for Engineering
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• v.2 no.1
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• pp.47-55
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• 1991

Regeneration of carbon-deposited Ni catalyst used for hydrogenation reaction was studied. Deposited carbon was removed by oxidation with various concentrations of oxygen. Activity of the catalysts was tested on aniline hydrogenation as a model reaction. When a carbon-deposited catalyst was treated under oxygen atmosphere, the specific surface area of the catalyst increased and then decreased with the increase of treatment temperature. The treatment temperature which gives maximum specific surface area increased with the decrease of oxygen concentration. Pore size of the support was decreased and sintering of nickel particles was more significant with the increase of oxygen concentration. The catalyst treated under 5 % oxygen concentration recovered its catalytic activity up to 90 % of the initial value, but the treatment under 20 % oxygen concentration gave no significant increase of the catalytic activity. Catalytic activity increased with treatment time when the catalyst was treated under 5 % oxygen concentration, but nearly constant after 1 hour.

• 한국신재생에너지학회:학술대회논문집
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• 2008.10a
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• pp.387-390
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• 2008

Ni/MgAl 촉매상에서 LPG의 수증기 개질반응을 반응온도 $700{\sim}800^{\circ}C$, 공간속도 $20,000h^{-1}$, 수증기/탄소 비율 $1.0{\sim}3.0$인 조건으로 대기압하에서 수행하였다. 본 연구에서 사용된 촉매들은 공침법으로 제조하였으며, 하이드로탈사이트 구조에서 Ni-MgO 구조로 변환되는 과정에서 활성금속인 니켈이 고분산되는 장점을 지니고 있다. 제조된 촉매는 함침법으로 제조된 촉매보다 활성이 잘 유지되었으며 탄소침적에 대한 내구성 또한 향상되었으나 완벽하게 해결되지는 못하였다. 따라서 이와 같은 문제점을 해결하기 위해 귀금속이 modified된 Ni/MgAl 촉매를 제조하고 반응 특성을 비교하였다. Rh-Ni/MgAl 촉매는 LPG 수증기 개질 반응에서 1024시간동안 활성이 유지됨을 확인하였을 뿐만 아니라 탄소침적 또한 발생하지 않음을 확인하였다.

• 한국신재생에너지학회:학술대회논문집
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• 2008.05a
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• pp.263-265
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• 2008

자원 재활용 및 에너지 생산관점에서 폐유지로부터 환경친화적인 연료인 바이오디젤에 대한 연구가 활발히 진행되고 있다. 특히 폐유지내 함유된 유리지방산 및 수분에 의해 효율적인 에스테르화 반응이 어렵기 때문에 이를 전처리 단계에서 제거되어야 한다. 본 연구에서는 폐유지내 유리지방산을 효과적으로 제거하기 위하여 회분식 반응기에서 제올라이트 촉매의 종류에 의한 세공구조와 산성도 변화에 따른 유리지방산 전환반응에 미치는 영향을 조사해 보았다. 제올라이트 촉매의 유리지방산 전환율은 세공구조와 산성도에 따라 큰 차이를 나타내었다. 유리지방산 전환율은 FAU < MOR < MFI < BEA의 순으로 높았다. 제올라이트의 세공구조는 1차원적인 구조를 가질 경우 탄소침적이 일어나지만 3차원적인 세공구조를 가지는 경우 탄소침적에 의한 촉매의 활성저하가 감소된다. 또한 제올라이트의 산성도에 따른 특성으로는 유리지방산의 전환반응에는 중간정도의 산세기를 가진 촉매가 유리함을 확인하였다. 그러므로 폐유지로부터 유리지방산을 제거하기 위한 우수한 제올라이트 촉매로는 BEA 제올라이트 촉매임을 확인하였다.

• 한국신재생에너지학회:학술대회논문집
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• 2008.05a
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• pp.487-490
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• 2008

Temperature programmed oxidation (TPO) is used to characterize coke species deposited on commercial nickel catalyst, C11-PR during propane pre-reforming. Propane pre-reforming performed under various condition, S/C from 1.5 to 2.5 and temperature from $350^{\circ}C$ to $450^{\circ}C$. There are three kinds of coke species detected by TPO: (i) reactive coke, (ii) coke deposited on metal site and (iii) coke deposited on acid support. Coke deposited on metal and support are minimized although reactive coke is generated at temperature of $400^{\circ}C$ and S/C of 2.0. Reactive coke is expected to remove easily below temperature of $200^{\circ}C$. Therefore, optimized pre-reforming condition for propane is $400^{\circ}C$ and S/C of 2.0.

• 한국신재생에너지학회:학술대회논문집
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• 2008.05a
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• pp.9-12
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• 2008

The internal reforming of n-Butane on Ni-YSZ and Cu-Ceria-YSZ was investigated with anode granule at steam to carbon ratio from 0 to 3 and at temperature of $750^{\circ}C$. Although hydrogen production was lager at Ni-YSZ, resistivity for carbon deposition was better at Cu-Ceria-YSZ. These phenomena occur because unwanted side reaction go on with reforming reaction for hydrogen production at Ni-YSZ.

• 한국신재생에너지학회:학술대회논문집
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• 2007.06a
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• pp.37-40
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• 2007

Diesel autothermal reforming(ATR) is an effective method for hydrogen production. But, diesel ATR has several problems such as the sulfur poisoning of catalyst and carbon deposition during reforming reactor. Especially, carbon deposition is a severe problem, which causes rapid performance degradation, in the reforming reaction. Ethylene among the reformate gas is a carbon precursor. Effective decomposition of ethylene is an important issue. In this paper, we investigated the carbon deposition from ethylene in the reforming reaction for proper reaction condition of diesel ATR. We achieved relatively high performance of diesel ATR under $H_{2}O/C=0.8$, $O_{2}/C=3$ condition that was based on the experiment of ethylene reforming reaction.

• 한국신재생에너지학회:학술대회논문집
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• 2007.11a
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• pp.67-70
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• 2007

Diesel autothermal reforming has several problems such as carbon deposition in reforming reactor, sulfur poisoning of catalyst, difficulty of aromatics decomposition and mixing problems of reactants(diesel, steam, oxygen). Severe carbon deposition causes the rapid performance degradation of reformer. Carbon deposition is formed from ethylene, carbon precursor. Ethylene was generated at the homogeneous reaction zone of the reactor entrance. This phenomenon is closely linked to the mixing of reactants. In this investigation, we try to minimize the ethylene generation at the reactor entrance atomization technique.

• Applied Chemistry for Engineering
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• v.2 no.1
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• pp.38-46
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• 1991

Regeneration of Ni catalyst deactivated by carbon-deposition and sulfur-poisoning was studied. When a carbon-deposited catalyst was regenerated by hydrogen, the final recovery of catalytic activity for benzene hydrogenation was large but relatively long period of regeneration was required, and futhermore the deposited carbon could not be removed completely. In case of oxygen-treatment, the regeneration rate was high and the deposited carbon could be removed almost completely after a subsequent reduction treatment. When a sulfur-poisoned catalyst was regenerated by hydrogen and water vapor, the catalytic activity was not recovered. The regeneration treatment with oxygen at $650^{\circ}C$ recovered the catalytic activity up to 60 % of the initial value. When $Cl^-$ was added to oxygen, the activity was easily recovered to 45 % of the initial value even after treatment at $500^{\circ}C$. Sintering of the dispersed Ni particles was enhanced by water vapor but was hindered by oxygen and chlorine addition.