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금속 산화물 촉매의 크기와 형태에 따른 질소산화물의 탄화수소 선택적 촉매환원 특성
임태헌(Tae-Heon Ihm),조진오(Jin-Oh Jo),현영진(Young Jin Hyun),목영선(Young Sun Mok) 한국가스학회 2015 한국가스학회지 Vol.19 No.5
탄화수소 선택적 촉매환원공정에서 γ-알루미나에 지지된 금속 산화물 촉매의 크기 및 형태에 따른 질소산화물 (NO<SUB>x</SUB>) 저감 특성에 대해 조사하였다. 환원촉매로는 Ag, Cu 및 Ru를 사용하였으며, n-heptane을 환원제로 사용하였다. Ag/γ-Al₂O₃ 촉매의 경우 온도범위 250~400℃에서 20 nm>50 nm>80 nm 순으로 Ag의 크기가 작을수록 NO<SUB>x</SUB> 전환효율이 높게 나타났다. 금속 산화물 촉매의 형태에 따른 영향은 구형과 선형에 대해 살펴보았다. Ag와 Cu는 동일한 조건에서 선형이 구형보다 NO<SUB>x</SUB> 전환효율이 높은 것으로 나타났으나, Ru의 경우에는 형태에 따른 영향이 거의 관찰되지 않았다. 사용된 금속산화물 촉매 중에서 Ag를 사용했을 때 NO<SUB>x</SUB> 저감효율이 가장 높았으며, 선형의 Ag를 사용했을 때 300℃의 반응온도에서 대부분의 NOx를 제거할 수 있었다. Cu와 Ru 촉매상에서는 NO가 환원되기보다는 NO₂로의 산화반응이 우세하여 전체적으로 NO<SUB>x</SUB> 저감효율이 낮게 나타났다. This work investigated the size and shape effect of γ-alumina-supported metal oxides on the hydrocarbon selective catalytic reduction of nitrogen oxides. Several metal oxides including Ag, Cu and Ru were used as the catalysts, and n-heptane as the reducing agent. For the Ag/γ-alumina catalyst, the NO<SUB>x</SUB> reduction efficiency in the range of 250 ~ 400℃ increased as the size of Ag decreased (20 nm>50 nm>80 nm). The shape effect of metal oxides on the NO<SUB>x</SUB> reduction was examined with spherical- and wire-shape nanoparticles. Under identical condition, higher catalytic activity for NOx reduction was observed with Ag and Cu wires than with the spheres, while spherical- and wire-shape Ru exhibited similar NO<SUB>x</SUB> reduction efficiency to each other. Among the metal oxides examined, the best catalytic activity for NO<SUB>x</SUB> reduction was obtained with Ag wire, showing almost complete NOx removal at a temperature of 300℃. For Cu and Ru catalysts, considerable amount of NO was oxidized to NO₂, rather than reduced to N₂, leading to lower NO<SUB>x</SUB> reduction efficiency.
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플라즈마가 결합된 탄화수소 선택적 촉매환원 공정에서 질소산화물(NOx)의 저감
임태헌 ( Tae Heon Ihm ),조진오 ( Jin Oh Jo ),현영진 ( Young Jin Hyun ),목영선 ( Young Sun Mok ) 한국공업화학회 2016 공업화학 Vol.27 No.1
Low-temperature conversion of nitrogen oxides using plasma-assisted hydrocarbon selective catalytic reduction of (HC-SCR) was investigated. Plasma was created in the catalyst-packed bed so that it could directly interact with the catalyst. The effect of the reaction temperature, the shape of catalyst, the concentration of n-heptane as a reducing agent, the oxygen content, the water vapor content and the energy density on NOx removal was examined. NOx conversion efficiencies achieved with the plasma-catalytic hybrid process at a temperature of 250 ℃ and an specific energy input (SIE) of 42 J L-1 were 83% and 69% for one-dimensional Ag catalyst (Ag (nanowire)/γ-Al2O3) and spherical Ag catalyst (Ag (sphere)/γ-Al2O3), respectively, whereas that obtained with the catalyst-alone was considerably lower (about 30%) even with Ag (nanowire)/γ-Al2O3 under the same condition. The enhanced catalytic activity towards NOx conversion in the presence of plasma can be explained by the formation of more reactive NO2 species and partially oxidized hydrocarbon intermediates from the oxidation of NO and n-heptane under plasma discharge. Increasing the SIE tended to improve NOx conversion efficiency, and so did the increase in the n-heptane concentration; however, a further increase in the n-heptane concentration beyond C1/NOx ratio of 5 did not improve the NOx conversion efficiency any more. The increase in the humidity affected negatively the NOx conversion efficiency, resulting in lowering the NOx conversion efficiency at the higher water vapor content, because water molecules competed with NOx species for the same active site. The NOx conversion efficiency increased with increasing the oxygen content from 3 to 15%, in particular at low SIE values, because the formation of NO2 and partially oxidized hydrocarbon intermediates was facilitated.
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대기압 유전체배리어방전 플라즈마를 이용한 형광체 분말 코팅
장두일 ( Doo Il Jang ),임태헌 ( Tae Heon Ihm ),쿠앙흥트린 ( Quang Hung Trinh ),조진오 ( Jin Oh Jo ),목영선 ( Young Sun Mok ),이상백 ( Sang Baek Lee ),헨리J라모스 ( Henry J Ramos ) 한국공업화학회 2014 공업화학 Vol.25 No.5
This work investigated the hydrophobic coating of silicate yellow phosphor powder in the form of divalent europium-activated strontium orthosilicate (Sr2SiO4:Eu2+) by using an atmospheric pressure dielectric barrier discharge (DBD) plasma with argon asa carrier and hexamethyldisiloxane (HMDSO), toluene and n-hexane as precursors. After the plasma treatment of the phosphorpowder, the lattice structure of orthosilicate was not altered, as confirmed by an X-ray diffract ometer. The coated phosphor powderwas characterized by scanning electron microscopy, fluorescence spectrophotometry and contact angle analysis (CAA). The CAA of the phosphor powder coated with the HMDSO precursor revealed that the water contact angle increased from 21.3° to139.5° (max. 148.7°) and the glycerol contact angle from 55° to 143.5° (max. 145.3°) as a result of the hydrophobic coating,which indicated that hydrophobic layers were successfully formed on the phosphor powder surfaces. Further surface characterizationswere performed by Fourier transform infrared spectroscopy and X-ray photoelectron spectrometry, which also evidencedthe formation of hydrophobic coating layers. The phosphor coated with HMDSO exhibited a photoluminescence (PL) enhancement,but the use of toluene or n-hexane somewhat decreased the PL intensity. The results of this work suggest that the DBDplasma may be a viable method for the preparation of hydrophobic coating layer on phosphor powder.
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