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RISS 인기검색어
- 검색키워드
- 저자 : Moudrakovski, Igor L. (검색결과 5 건)
- 무료
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<SUP>13</SUP>C NMR을 이용한 질소 및 이산화탄소 혼합 가스의 메탄 하이드레이트 치환 속도 규명 연구
Igor L Moudrakovski,John A. Ripmeester,서유택(Yutaek Seo),강성필(Seong-Pil Kang),이재구(Jae Goo Lee) 한국신재생에너지학회 2008 한국신재생에너지학회 학술대회논문집 Vol.2008 No.05
지구 온난화 문제의 심각성이 대두되면서 이산화탄소 저감 기술에 대한 관심이 증폭되고 있다. 가장 이상적인 방법은 탄소가 포함되지 않은 청정 재생 에너지원이지만, 에너지 공급 규모 면에서 보면 근 미래에도 화석 연료가 에너지 수요에 대한 주요 공급원으로 남아있을 것이라는 의견이 지배적이다. 많은 화석 연료 중 천연가스는 탄소 배출량이 가장 적은 청정 연료로 지난 10년간 수요가 폭발적으로 증가해왔다. 이를 고려해볼 때 탄소 배출량이 적은 천연가스를 생산하면서 이산화탄소를 격리 시킬수있는 기술은 매우 매력적 이다. 본 연구에서는 심해저의 메탄 하이드레이트로부터 천연가스를 생산하는 기술로서 이산화탄소와 질소의 혼합 가스를 사용하는 기술 개발의 일환으로 혼합 가스에 의한 메탄 하이드레이트 해리 속도를 13C NMR을 이용해 측정한 결과를 제시하고자 한다.
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Crystal engineering and characterization of a structure-H ionic clathrate hydrate
Shin, Kyuchul,Moudrakovski, Igor L.,Udachin, Konstantin A.,Ratcliffe, Christopher I.,Ripmeester, John A. National Research Council 2015 Canadian journal of chemistry Vol.93 No.8
<P> Ionic hydrates are known to form numerous clathrate structures in which either the cations or anions sit in cages and the counterions are incorporated into the water framework. Due to the inclusion of the ionic species, such ionic clathrate hydrates not only show many peculiar features such as metal ion encagement and superoxide ion generation, but also exhibit notable physicochemical properties such as outstanding ionic conductivity and thermal stability. Thus, the ionic clathrate hydrates are considered for their potential applicability in various fields, including those that involve solid electrolytes, gas sensors, and energy storage. In this study, we report the design, synthesis, and characterization of the first ionic clathrate hydrate of the hexagonal structure-H (Str.H) crystal type. Diethyl-dimethyl-ammonium hydroxide hydrate was synthesized with CH4 and Xe as help gases, and the crystal structure was identified by powder X-ray diffraction analysis. Further confirmation of the formation of Str.H was obtained from Raman spectroscopy and <SUP>13</SUP>C, <SUP>129</SUP>Xe, and <SUP>2</SUP>H solid-state NMR spectroscopy. From <SUP>13</SUP>C NMR and ab initio calculations, it was shown that the quaternary ion occupies the large cage of Str.H with a conformation different from that in solution, due to constraints imposed by the dimensions of the cage. The H deficiency introduced by substitution of OH<SUP>-</SUP> for a water molecule appears, from <SUP>129</SUP>Xe NMR, to be disordered over the framework, and, from <SUP>2</SUP>H NMR, to substantially increase the rate of reorientational mobility of the D atoms in the framework, over that observed for a Str.I hydrate and for ice. The Str.H hydrates are commonly more stable than other structures, thus the present findings on the ionic Str.H clathrate hydrate may offer a new approach for improving the stability of ionic clathrate hydrates for their practical application. </P>
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Cha, Minjun,Shin, Kyuchul,Lee, Huen,Moudrakovski, Igor L.,Ripmeester, John A.,Seo, Yutaek American Chemical Society 2015 Environmental science & technology Vol.49 No.3
<P>In this study, the kinetics of methane replacement with carbon dioxide and nitrogen gas in methane gas hydrate prepared in porous silica gel matrices has been studied by in situ H-1 and C-13 NMR spectroscopy. The replacement process was monitored by in situ H-1 NMR spectra, where about 42 mol % of the methane in the hydrate cages was replaced in 65 h. Large amounts of free water were not observed during the replacement process, indicating a spontaneous replacement reaction upon exposing methane hydrate to carbon dioxide and nitrogen gas mixture. From in situ C-13 NMR spectra, we confirmed that the replacement ratio was slightly higher in small cages, but due to the composition of structure I hydrate, the amount of methane evolved from the large cages was larger than that of the small cages. Compositional analysis of vapor and hydrate phases was also carried out after the replacement reaction ceased. Notably, the composition changes in hydrate phases after the replacement reaction would be affected by the difference in the chemical potential between the vapor phase and hydrate surface rather than a pore size effect. These results suggest that the replacement technique provides methane recovery as well as stabilization of the resulting carbon dioxide hydrate phase without melting.</P>
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n-Pentane & n-Hexane as Coguests of sH Hydrates in the Mixture with 2,2-Dimethylbutane and Methane
이종원(Lee, Jong-Won),Lu, Hailong,Moudrakovski, Igor L.,Ripmeester, Christopher I. Rat 한국신재생에너지학회 2006 한국신재생에너지학회 학술대회논문집 Vol.2006 No.11
n-Pentane and n-hexane, previously regarded as non-hydrate formers, are found to form structure H hydrate in mixtures with 2,2-dimethylbutane. Even though they are thought to be too large to fit into the largest cage of the structure H hydrate, powder XRD and NMR measurements show that they form gas hydrates in mixtures with other sH hydrate former. These findings are of fundamental interest and also will impact the composition and location of natural gas hydrates and their potential as global energy resource and climate change materials.
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Seo, Yutaek,Lee, Jong-Won,Kumar, Rajnish,Moudrakovski, Igor L.,Lee, Huen,Ripmeester, John A. Wiley (John WileySons) 2009 Chemistry - An Asian Journal Vol.4 No.8
<P>Gas hydrates represent an attractive way of storing large quantities of gas such as methane and carbon dioxide, although to date there has been little effort to optimize the storage capacity and to understand the trade-offs between storage conditions and storage capacity. In this work, we present estimates for gas storage based on the ideal structures, and show how these must be modified given the little data available on hydrate composition. We then examine the hypothesis based on solid-solution theory for clathrate hydrates as to how storage capacity may be improved for structure II hydrates, and test the hypothesis for a structure II hydrate of THF and methane, paying special attention to the synthetic approach used. Phase equilibrium data are used to map the region of stability of the double hydrate in P-T space as a function of the concentration of THF. In situ high-pressure NMR experiments were used to measure the kinetics of reaction between frozen THF solutions and methane gas, and (13)C MAS NMR experiments were used to measure the distribution of the guests over the cage sites. As known from previous work, at high concentrations of THF, methane only occupies the small cages in structure II hydrate, and in accordance with the hypothesis posed, we confirm that methane can be introduced into the large cage of structure II hydrate by lowering the concentration of THF to below 1.0 mol %. We note that in some preparations the cage occupancies appear to fluctuate with time and are not necessarily homogeneous over the sample. Although the tuning mechanism is generally valid, the composition and homogeneity of the product vary with the details of the synthetic procedure. The best results, those obtained from the gas-liquid reaction, are in good agreement with thermodynamic predictions; those obtained for the gas-solid reaction do not agree nearly as well.</P>
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