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Abstract: The grand canonical Monte Carlo (GCMC) simulation study on the separation performance of zeolites (MFI, MOR, CFI and DON) and carbon nanotubes (CNTs) to ethanol–water mixtures is reported. The calculation is performed with different bulk percentage under the ambient temperature and pressure. The results show zeolites prefer water to ethanol and could be used for ethanol dehydration. Only water can enter CNT55, but for other CNTs, because the CNT is more hydrophobic than zeolite, the selectivity of CNTs to ethanol is larger than 1, and CNT77 is very fit to condense dilute ethanol solution. CNT77 show excellent performance for its special nanoscale. It prefers ethanol to water in all fraction range. [Copyright &y& Elsevier]

This work investigates the effect of zwitterionic molecules on ionic association in ethylene oxide (EO)-based electrolytes using molecular dynamics simulations. Zwitterionic molecules can associate with cations and anions because they possess both positively and negatively charged groups. This unique feature can be leveraged to develop electrolytes with high ionic conductivity if we understand how zwitterionic molecules influence ionic associations. We investigate the ionic associations in the electrolytes composed of oligo(ethylene oxide) (EO) (EO x , x = 2, 3, 4, and 5), LiTFSI and zwitterionic molecules containing cationic imidazole group and anionic sulfonate group using molecular dynamics simulations. The analyzed properties include the radial distribution functions between Li+, [TFSI]-, EO x and zwitterionic molecules, the structures and dynamics of Li+-[TFSI]-, Li+- EO x and Li+-zwitterion associations, and the diffusion coefficients of Li+, [TFSI]-, EO x and zwitterionic molecules. The simulation results show two distinct effects of zwitterionic molecules on ionic associations in the electrolytes. First, they could release Li+ from the trapping effect of EO x chains and accelerate Li+ transport. Second, they can associate with Li+ themselves and slow down the Li+ transport. The competition between these two effects relates to the length of the EO x chains. Our simulations suggest that zwitterionic molecules could help manipulate the ionic conductivity of polyethylene oxide electrolytes. Image 1 [ABSTRACT FROM AUTHOR]

Abstract: The behaviors of the ionic hydration in nanopore are of both biological and chemical interests. Using carbon nanotube (CNT) as the 1-D nanopore model, we investigated the effect of the modified groups (Cing on the pore inner wall on the hydration of Li+, Na+ and K+ with molecular dynamics simulation. The structures of the water molecules around the cations confined in the modified CNTs were compared with their counterparts in the pristine CNTs. Among the three cations, the sequence of the sensitivity for the spatial and orientation distributions of the water molecules in the first coordination shells is: K+ >Na+ >Li+. The same modification results in the opposite effects for the ionic hydration inside the (10, 10) and (8, 8) CNTs. Inside the (10, 10) CNT, the modification enhances the ionic hydration, whereas inside the (8, 8) CNT, the ionic hydration is weakened by the modification of CNT wall. [ABSTRACT FROM AUTHOR]

Abstract: Grand canonical Monte Carlo and configurational bias Monte Carlo techniques were employed to simulate the adsorption of binary mixtures of butane isomers and quaternary mixtures in nine zeolites at 300K. For binary mixtures the results show there is a critical pore size, which is 10-membered-ring about 5.6Å. The channel sizes of BEA, ISV, MOR and CFI are larger than this critical pore size, they prefer i-butane than n-butane, whereas TON with smaller channel size than critical pore size prefers n-butane than i-butane, but its selectivity decreases with pressure increasing. MFI, MEL and TER prefer i-butane than n-butane at low pressure, but with pressure increasing, the selectivity is reversed. BOG prefers i-butane than n-butane but the selectivity decreased with pressure increasing. It demonstrates that the adsorption and selectivity are controlled by both pore size and pore structure. The n-butane–i-butane–n-pentane–2-methylbutane quaternary mixtures adsorbed in these nine zeolites were studied, and the results show alkane chain length dependence at low pressure, but the adsorption is controlled by pore size and structure with pressure increasing in all the zeolites except for TON and BOG. [Copyright &y& Elsevier]