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RISS 인기검색어
- 검색키워드
- 저자 : Saman Alavi (검색결과 3 건)
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Alavi, Saman,Shin, Kyuchul,Ripmeester, John A. American Chemical Society 2015 Journal of chemical and engineering data Vol.60 No.2
<P>We performed molecular dynamics simulations of the ammonia and methanol-based clathrate hydrates with the emphasis on characterizing hydrogen-bonding interactions of these guest molecules with the water lattice. Systems studied include structure II (sII) binary clathrate hydrates of tetrahydrofuran (THF) (large cage, L) + NH<SUB>3</SUB> (small cage, S) and THF (L) + CH<SUB>3</SUB>OH (S), the structure I (sI) pure NH<SUB>3</SUB> (L), pure CH<SUB>3</SUB>OH (L), the binary NH<SUB>3</SUB> (L) + CH<SUB>4</SUB> (S), and binary CH<SUB>3</SUB>OH (L) + CH<SUB>4</SUB> (S) clathrate hydrates. We simulated these clathrate hydrates with the transferable intermolecular potential with four point changes (TIP4P) water potential and the TIP4P/ice water potential to determine the effect of the water potential on the predicted hydrogen bonding of the guest molecules. Simulations show that, despite strongly hydrogen bonding with the framework water molecules, clathrate hydrate phases with NH<SUB>3</SUB> and CH<SUB>3</SUB>OH can be stable within temperatures ranges up to 240 K. Indeed, a limited number of thermodynamic integration free energy calculations show that both NH<SUB>3</SUB> and CH<SUB>3</SUB>OH molecules give more stable guest–host configurations in the large sI clathrate hydrate cages than methane guests. Predictions of hydrogen bonding from simulations with the two different water potentials used can differ substantially. To study the effect of proton transfer from water to the basic NH<SUB>3</SUB> guests, simulations were performed on a binary NH<SUB>3</SUB> + CH<SUB>4</SUB> sI clathrate hydrate where less than 10 % of the ammonia guests in the large cages were converted to NH<SUB>4</SUB><SUP>+</SUP> and a water molecule of the hydrate lattice in the same large cage was converted to OH<SUP>–</SUP>. The small percentage of proton transfer to ammonia guests in the large cages did not affect the stability of the resultant hydrate. The structural perturbations in the lattice that result from this proton transfer are characterized.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/jceaax/2015/jceaax.2015.60.issue-2/je5006517/production/images/medium/je-2014-006517_0011.gif'></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/je5006517'>ACS Electronic Supporting Info</A></P>
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Hironori D. Nagashima,Saman Alavi,Ryo Ohmura 한국공업화학회 2017 Journal of Industrial and Engineering Chemistry Vol.54 No.-
To investigate the preservation of CO2 clathrate hydrate in the presence of fructose or glucose and absence of sugars, CO2 hydrate samples were preserved at 238.2 K, 253.2 K and 258.2 K under atmospheric pressure for three weeks. The preservations of CO2 hydrate with those two monosaccharide sugars at both 238.2 K and 253.2 K were lower than that of the pure CO2 hydrate without the sugars. The results indicated that the viscosity of super-cooled or stable sugar aqueous solution and occurrence of super-cooled water in the sample hydrate particles are significant factors in the preservation of CO2 hydrate.
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Masamichi Kodera,Kosuke Watanabe,Maxence Lassiège,Saman Alavi,Ryo Ohmura 한국공업화학회 2020 Journal of Industrial and Engineering Chemistry Vol.81 No.-
Interfacial tension is one of the most important physical properties for high-precision simulations todevelop the methods of preventing plugging of pipelines in the oil and natural gas industry. This paperreports experimental data with the pendant drop method for the interfacial tension of adecane + methane + water system at temperatures between 278.2 K to 298.2 K and pressures up to10 MPa. The data show that in this temperature range the interfacial tension in the decane + methane+ water system decreases almost linearly with increasing temperature. The results also show that byincreasing the pressure of methane, the interfacial tension decreases from 53.98 mN m 1 to50.23 mN m 1 at 283.2 K and 52.23 mN m 1 to 49.74 mN m 1 at 288.2 K. The nature of the methanepressure dependence of the interfacial tension changes for pressures above around 2.00 MPa. Theinterfacial tension decreases with the pressure up to 2.00 MPa, but has no pressure dependence above2.00 MPa. It may be inferred that the decane/water interface is saturated with methane at pressuresaround 2.00 MPa and at higher pressure the interfacial tension is no longer affected by the presence ofmethane.
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