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- 저자 : Alexis T. Bell (검색결과 6 건)
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FTIR 을 이용한 Cu/SiO2 촉매상에서의 메탄올 분해반응 연구
이동근,Bell,Alexis T 한국화학공학회 1996 Korean Chemical Engineering Research(HWAHAK KONGHA Vol.34 No.3
Cu/SiO₂촉매에서의 메탄올 분해반응을 연구하기 위하여 FTIR실험을 행하였다. 촉매 표면에 존재하는 메탄올 분해반응 중간물질로는 메탄올, methoxy, formaldehyde, methylenebis(oxy) 및 formate 그룹이 IR 실험결과 나타났으며, 구리의 표면상태가 이들 표면중간물질의 특성에 영향을 주었다. 환원된 촉매의 경우 methoxy가 매우 불안정하고 bidentate formate가 존재한 반면, 부분산화된 촉매의 경우 methoxy의 생성이 두드러졌고 unidentate formate가 존재하였다. 상온에서부터 300℃까지의 승온 FTIR 스펙트럼 결과로부터 Cu/SiO₂촉매상에서의 메탄올 분해반응 메카니즘을 제시하였다. Methanol decomposition on Cu/SiO₂ has been investigated by means of Fourier transform infrared spectroscopy. Infrared spectroscopy experiments showed the following surface methanol decomposition intermediates on Cu/SiO₂: methanol, methoxy, formaldehyde, methylenebis(oxy), and formate groups. The characteristics of surface intermediates were affected by the oxidation state of copper. On reduced copper methoxy was highly unstable and bidentate formate was formed., while on oxidized copper methoxy was stable and unidentate formate was formed. A mechanism of methanol decomposition was also proposed based on temperature programmed infrared experiment from 20 to 300℃.
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I발표장 : 촉매 및 반응공학3 ; I-63 : N2O decomposition over FeZSM5 catalyst
박주형,정종현,남인식,함성원,( Alexis T. Bell ) 한국화학공학회 2007 화학공학의이론과응용 Vol.10 No.1
The N2O decomposition activity of FeZSM5 is known to be strongly dependent on the iron content and the preparation methods including wet ion exchange (WIE), and solid state ion exchange (SSIE). However, the peculiar characteristics of FeZSM5 for N2O decomposition have not been clearly identified yet from the view of the active reaction site on the catalyst surface. The present study has been investigated to correlate the state of Fe species based upon the preparation method with their role for N2O decomposition activity. The decomposition activity of FeZSM5-SSIE mostly appears to be higher than that of FeZSM5-WIE, indicating the formation of a distinctive local structure of Fe, which is confirmed by EXAFS and XANES spectra. The neighbor shells in Fourier transformed Fe kedgeEXAFS spectra for FeZSM5-SSIE and WIE catalysts are estimated to be ca. 4×Fe-O / 1×Fe- Fe, and 6×Fe-O / 6×Fe-Fe respectively. It reveals that the most of Fe species of FeZSM5-SSIE are well dispersed in the form of oxygen-bridged binuclear Fe species. It can be concluded that the high performance of FeZSM5-SSIE is mainly due to the fine dispersion of Fe species onto its surface during the preparation of the catalyst.
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FTIR 을 이용한 Cu / SiO2 촉매상에서의 메탄올 분해반응 연구
이동근 ( Dong Keun Lee ),Alexis T . Bell 한국화학공학회 1996 Korean Chemical Engineering Research(HWAHAK KONGHA Vol.34 No.3
Cu/SiO₂촉매에서의 메탄올 분해반응을 연구하기 위하여 FTIR실험을 행하였다. 촉매 표면에 존재하는 메탄올 분해반응 중간물질로는 메탄올, methoxy, formaldehyde, methylenebis(oxy) 및 formate 그룹이 IR 실험결과 나타났으며, 구리의 표면상태가 이들 표면중간물질의 특성에 영향을 주었다. 환원된 촉매의 경우 methoxy가 매우 불안정하고 bidentate formate가 존재한 반면, 부분산화된 촉매의 경우 methoxy의 생성이 두드러졌고 unidentate formate가 존재하였다. 상온에서부터 300℃까지의 승온 FTIR 스펙트럼 결과로부터 Cu/SiO₂촉매상에서의 메탄올 분해반응 메카니즘을 제시하였다. Methanol decomposition on Cu/SiO₂ has been investigated by means of Fourier transform infrared spectroscopy. Infrared spectroscopy experiments showed the following surface methanol decomposition intermediates on Cu/SiO₂: methanol, methoxy, formaldehyde, methylenebis(oxy), and formate groups. The characteristics of surface intermediates were affected by the oxidation state of copper. On reduced copper methoxy was highly unstable and bidentate formate was formed., while on oxidized copper methoxy was stable and unidentate formate was formed. A mechanism of methanol decomposition was also proposed based on temperature programmed infrared experiment from 20 to 300℃.
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Singh, Meenesh R.,Kwon, Youngkook,Lum, Yanwei,Ager, Joel W.,Bell, Alexis T. American Chemical Society 2016 JOURNAL OF THE AMERICAN CHEMICAL SOCIETY - Vol.138 No.39
<P>Electrolyte cation size is known to influence the electrochemical reduction of CO2 over metals; however, a satisfactory explanation for this phenomenon has not been developed. We report here that these effects can be attributed to a previously unrecognized consequence of cation hydrolysis occurring in the vicinity of the cathode. With increasing cation size, the pKa for cation hydrolysis decreases and is sufficiently low for hydrated K+, Rb+, and Cs+ to serve as buffering agents. Buffering lowers the pH near the cathode, leading to an increase in the local concentration of dissolved CO2. The consequences of these changes are an increase in cathode activity, a decrease in Faradaic efficiencies for H-2 and CH4, and an increase in Faradaic efficiencies for CO, C2H4, and C2H5OH, in full agreement with experimental observations for CO2 reduction over Ag and Cu.</P>
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Nitric-acid Hydrolysis of Miscanthus giganteus to Sugars Fermented to Bioethanol
Fuxin Yang,Waheed Afzal,Kun Cheng,Nian Liu,Markus Pauly,Alexis T. Bell,Zhigang Liu,John M. Prausnitz 한국생물공학회 2015 Biotechnology and Bioprocess Engineering Vol.20 No.2
Miscanthus giganteus (M. giganteus) is a promising feedstock for the production of bioethanol or biochemicals. Using only dilute nitric acid, this work describes a two-step process for hydrolyzing hemicellulose and cellulose to fermentable sugars. Primary variables were temperature and reaction time. The solid-to-liquid mass ratio was 1:8. No enzymes were used. In the first step, M. giganteus was contacted with 0.5 wt.% nitric acid at temperatures between 120 and 160°C for 5 to 40 min. The second step used 0.5 or 0.75 wt.% nitric acid at temperatures between 180 and 210°C for less than 6 min. Under selected conditions, almost all hemicellulose and 58% cellulose were transferred to the liquid phase. Small amounts of degradation products were observed. The xylose solution obtained from the nitric-acid hydrolysis was fermented for 96 h and the glucose solution for 48 h to yield 0.41 g ethanol/g xylose and 0.46 g ethanol/g glucose. To characterize residual solids and the liquor from both steps, nuclear-magneticresonance (NMR) spectroscopy was performed for each fraction. The analytical data indicate that the liquid phase from Steps 1 and 2 contain little lignin or lignin derivatives.
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