• Asian-Australasian Journal of Animal Sciences
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• 제17권1호
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• pp.68-72
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• 2004

The effects of the addition of yeast on in vitro roughage degradability and methane production were investigated in order to clarify the effects of yeast on the rumen microbes and to establish methods of rumen manipulation. Three roughages (whole crop corn, rice straw and Italian ryegrass) were incubated for 3, 6, 12 and 24 h with or without dried beer yeast following the method described by Tilley and Terry. Using the same method, these roughages were incubated with or without yeast extract, albumin or purified DNA. In vitro methane production was measured with or without dried beer yeast at 12 and 24 h. The degradability of yeast was found to be 57 and 80% at 12 and 24 h, respectively. The rate of degradation of fraction b was 6.16%/h. There was a significant increase in roughage degradability at 6 h (p<0.05), 12 h (p<0.05) and 24 h (p<0.01) by dried yeast addition. The degradability of all three roughages was higher in the samples treated with yeast extract than in the no addition samples except in the case of rice straw incubated for 12 h. Nevertheless, the magnitude of increment was smaller with the addition of yeast extract than without the addition of yeast. With the addition of purified DNA, there were significant increases in roughage degradability at 6 h (p<0.01), 12 h (p<0.01) and 24 h (p<0.05); however, higher degradability values were detected in the samples to which albumin was added, particularly at 6 h. If the degradability values of the no addition samples with those of samples containing yeast, yeast extract, DNA and albumin were compared, the largest difference was found in the samples to which yeast was added, although it is worth noting that higher values were observed in the yeast extract samples than in the DNA or albumin samples, with the exception of the case of rice straw incubated for 24 h. Methane production was significantly increased at both 12 and 24 h incubation. The increment of roughage degradation and methane production brought about by the addition of dried beer yeast to the samples was thought to be due to the activation of rumen microbes. Water soluble fraction of yeast also seemed to play a role in ruminal microbe activation. The increment of degradability is thought to be partially due to the addition of crude protein or nucleic acid but it is expected that other factors play a greater role. And those factors may responsible for the different effects of individual yeast on ruminal microbes.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2004년도 하계학술대회 논문집 Vol.5 No.2
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• pp.1270-1273
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• 2004

The combination of methane-chemical activation and Self-propagating High-temperature synthesis (SHS) has widened the possibilities for both methods. For YBCO systems the investigation showed that a short-term mechano-chemical activation of initial powders before SHS leads to single-phase and ultra-fine products. A new technique for preparation ultra-fine high-temperature superconductors of YBCO composition with a grain size d < $1{\mu}m$ is developed. The specific feature of the technique is formation of the $YBa_2Cu_3O_{7-x}$ crystalline lattice directly from an X-ray amorphous state arising as a result of mechanical activation of the original oxide mixture. The technique allows the stage of formation of any intermediate reaction products to be ruled out. X-ray and magnetic studies of ultra-fine high temperature superconductors (HTS) are carried out. Dimension effects associated with the microstructure peculiarities are revealed. A considerable enhancement of inter-grain critical currents is found to take place in the ultra-fine samples investigated.

• 한국산학기술학회논문지
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• 제22권2호
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• pp.644-650
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• 2021

본 연구는 지구 온난화의 주요 원인인 이산화탄소를 이용하여 메탄의 개질반응 특성을 수행하였다. 이산화탄소와의 메탄 분해 반응을 전이금속 촉매인 주석을 사용하여 수행되었으며, 주석의 분해 반응성은 니켈, 철과 같은 전이 금속보다 낮으며, 대부분의 분해 반응은 고체 상태 촉매하에 수행된다. 반면에 주석의 녹는점은 505.03K로 액상 촉매하에서 분해가 발생된다. 주석을 사용하는 경우 액상으로 반응하며 메탄이 분해되어 생성되는 고체상 탄소가 촉매에 침적되어 비활성화되는 것을 것을 방지하는 장점이 있다. 이산화탄소를 사용하여 메탄을 분해하는 경우 일산화탄소와 수소를 생성한다. 촉매의 활성과 수명을 높이기 위해 Ni를 사용한 경우 촉매 활성이 향상되었다. 본 연구에서는 과잉습식함침법을 이용하여 촉매를 합성하였으며, 반응 온도, 공간 속도에 따른 활성과 촉매 재생 가능성을 타진하였다. 탄소가 침적된 주석의 촉매 재생 온도는 1023 K로 나타났으며, 니켈을 조촉매로 사용하고 물을 공급하므로써 반응성이 향상되는 것으로 나타났다.

• Korean Journal of Chemical Engineering
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• 제35권11호
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• pp.2185-2190
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• 2018

Methane activation through oxychlorination is in the spotlight due to the relatively mild reaction conditions at atmospheric pressure and in the temperature range of $450-550^{\circ}C$. Although $CeO_2$ is known to exhibit good activity for methane oxychlorination, significant amounts of by-products such as $CO_2$, CO and carbon deposits are produced during the reaction over $CeO_2$. We investigated the effect of iron in $FeO_x/CeO_2$ catalysts on methane oxychlorination. $FeO_x/CeO_2$ with 3 wt% iron shows the maximum yield at $510^{\circ}C$ with 23% conversion of methane and 65% selectivity of chloromethane. XRD and $H_2$ TPR results indicate that iron-cerium solid solution was formed, resulting in the production of more easily reduced cerium oxide and the suppression of catalysts sintering during the reaction. Furthermore, the selectivity of by-products decreased more significantly over $FeO_x/CeO_2$ than cerium oxide, which can be attributed to the facilitation of HCl oxidation arising from the enhanced reducibility of the former sample.

• 한국산학기술학회논문지
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• 제12권1호
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• pp.537-544
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• 2011

본 연구에서는 탄화수소가스 중에서 가장 발화온도가 높은 메탄을 대상으로 전이금속 촉매의 산화반응 특성을 수행하였다. 망간의 경우 MnO, $MnO_2$, $Mn_2O_3$, $Mn_3O_4$, $Mn_4O_5$와 같이 다양한 산화가를 나타내므로 산화망간을 선택하여 메탄산화반응실험을 실시하였다. 메탄의 산화를 위한 전이금속 촉매중 망간을 산화물형태로 $Al_2O_3$, $TiO_2$에 담지하였으며, 조촉매로는 Ni, Co 등을 이용하여 활성능과 수명의 향상을 연구하였다. 본 연구에서 촉매 제조는 과잉용액 함침법을 사용하였다. 촉매의 활성화에너지, $T_{50}$, $T_{90}$을 계산하기 위하여 온도와 공간속도에 대한 전환율을 측정하였다. Mn-Co, Mn-Ni의 두성분의 전이금속촉매의 수명이 망간촉매에 비하여 10%이상 증가하고 활성은 약간 감소함을 알 수 있었다.

• 공업화학
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• 제3권2호
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• pp.256-265
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• 1992

NaCl(30wt%)/ZnO(60wt%)/${\alpha}-Al_2O_3$ 촉매상에서 메탄의 oxidative coupling 반응의 속도식을 연구하여 활성 산소종에 관하여 고찰하였다. 반응온도 $650^{\circ}C$에서 $750^{\circ}C$까지 메탄의 전화율 10%미만의 범위에서 메탄과 산소의 분압을 변화시켜 가면서 메탄의 전환속도를 측정하여 속도식을 검증하였다. 제안된 메틸라디칼의 생성반응은 Langmuir-Hinshelwood형 반응기구를 따른다. 촉매표면의 서로 다른 활성점에 흡착된 메탄분자와 산소분자가 반응하여 메틸라디칼이 생성되는 반응이 속도결정단계이며, 이때 활성화 에너지는 약 39kcal/mol이었다. 메탄의 C-H 결합의 해리에 관여하는 산소종은 표면상의 이원자 산소인 $O{_2}{^{2-}}$나 $O_2{^-}$로 제시할 수 있었다.

• Nuclear Engineering and Technology
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• 제11권2호
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• pp.119-126
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• 1979

전자선경화성 prepolymer를 합성하기 위해서 4,4'-Dihydroxydiphenyl methane (4,4'-DPM) 과 메타크릴산 글리시딜 (GMA)과의 반응을 염화벤질 트리에틸 암모늄(TEBAC)을 촉매로 하여 진행시키고 그 반응 메카니즘을 고찰하였다. 반응은 3차 속도식 진행시키고 그 반응 메카니즘을 고찰하였다. 반응은 3차 속도식 (equation omitted) 에 해당하였고 활성화 에너지는 33.4kca1/mole 이었다. 그러나 혼합물을 상온에서 24시간 방치한 후의 반응은 빠른 속도로 진행되었다. 촉매효과 및 2,2'-DPM 과 4,4'-DPH의 GMA에 대한 반응성을 비교 검토하였다. 얻어진 데이타를 기초로 하여 가능한 반응기구를 제시하였다.

• 한국세라믹학회지
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• 제51권4호
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• pp.367-373
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• 2014

In this study, the reducing agent hydrazine and precipitator NaOH were used with $NiCl_2$ as a starting material in order to compound Ni-based material with spherical nano characteristics; resulting material was used as an anode for SOFC. Synthetic temperature, pH, and solvent amounts were experimentally optimized and the synthesis conditions were confirmed. Also, a 0 ~ 0.15 mole ratio of metal(Co, Fe) was alloyed in order to increase the catalyst activation performance of Ni and finally, spherical nano $Ni_{(1-x)}-M_{(x=0{\sim}0.15)}$(M = Co, Fe) alloy materials were compounded. In order to evaluate the catalyst activation for hydrocarbon fuel, fuel gas(10%/$CH_4$+10%/Air) was added and the responding gas was analyzed with GC(Gas Chromatography). Catalyst activation improvement was confirmed from the 3% hydrogen selectivity and 2.4% methane conversion rate in $Ni_{0.95}-Co_{0.05}$ alloy; those values were 4.4% and 19%, respectively, in $Ni_{0.95}-Fe_{0.05}$ alloy.

• 공업화학
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• 제5권1호
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• pp.139-148
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• 1994

실리카에 담지된 헤테로폴리산 촉매에서 아산화질소에 의한 메탄의 부분산화반응을 연구하였다. 여러 가지의 반응조건, 즉 반응온도, 반응물의 분압, 접촉시간, 촉매의 담지량 및 전처리온도 등이 전환율이나 생성물의 선택도 및 속도론에 미치는 영향이 연구되었다. 20 wt%로 담지된 촉매가 전환율과 포름알데히드의 수율에 있어서 가장 높은 값을 보여 주었다. 메탄은 전환반응에서의 속도식을 구한 결과, 메탄에 대해서는 1차식을 보여 주었고, 아산화질소에 대한 반응차수는 약 0.4였다. 또한 전체반응의 겉보기 활성화에너지는 30.78 kcal/mole 이었다. 반응물 중에 첨가된 소량의 사염화탄소는 메탄의 산화반응에서 실리카 담지 HPMo 촉매의 활성을 증가시키는 반면에, 반응물에 첨가된 물은 오히려 활성을 감소시키는 것을 볼 수 있었다.

• 한국복합재료학회:학술대회논문집
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• 한국복합재료학회 2002년도 추계학술발표대회 논문집
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• pp.273-275
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• 2002

In this studies, curing behavior and mechanical properties of tetrafunctional epoxy resin (4EP)/ fluorine-containing epoxy resin (FEP) blend systems was investigated with 4, 4'-diaminodiphenol methane (DDM) as a curing agent. The cure activation energies $(E_a)$) were studied by Flynn-Wall-Ozawa's equation with dynamic DSC method. For the fracture toughness of the casting specimens, the critical stress intensity factor ($K_{IC}$) and the specific fracture energy ($G_{IC}$) were determined by fracture toughness test.