Temperature and concentration dependence of adsorption properties of methane in NaY: a molecular dynamics study

Yashonath , Subramanian and Demontis, Pierfranco and Klein, Michael L (1991) Temperature and concentration dependence of adsorption properties of methane in NaY: a molecular dynamics study. In: Journal of Physical Chemistry, 95 (15). 5881 -5889.

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Abstract

Molecular dynamics calculations on methane sorbed in NaY (Si/Al = 3.0) employing realistic methane-methane and methane-zeolite intermolecular potential functions at different temperatures (50, 150, 220, and 300 K) and concentrations (2, 4, 6, and 8 molecules/cage) are reported. The thermodynamic results are in agreement with the available experimental data. Guest-guest and guest-host radial distribution functions (rdfs), energy distribution functions, distribution of cage occupancy, center-of-cage-center-of-mass (coc-com) rdfs, velocity autocorrelation functions for com and angular motion and the Fourier transformed power spectra, and diffusion coefficients are presented as a function of temperature and concentration. At 50 K, methane is localized near the adsorption site. Site-site migration and essentially free rotational motion are observed at 150 K. Molecules preferentially occupy the region near the inner surface of the alpha-cage. The vibrational frequencies for the com of methane shift toward higher values with decreasing temperature and increasing adsorbate concentration. The observed frequencies for com motion are 36, 53, and 85 cm-1 and for rotational motion at 50 K, 95 and 150 cm-1 in agreement with neutron scattering data. The diffusion coefficients show a type I behavior as a function of loading in agreement with NMR measurements. Cage-to-cage diffusion is found to be always mediated by the surface.

Item Type:	Journal Article
Publication:	Journal of Physical Chemistry
Publisher:	American Chemical Society
Additional Information:	Copyright of this article belongs to American Chemical Society.
Keywords:	Atom-Atom Approximation;Statistical Calculation; Self-Diffusion;Zeolite-X;Hydrocarbons;Energetics;Mobility; Sorption;Neutron;Sieves.
Department/Centre:	Division of Chemical Sciences > Solid State & Structural Chemistry Unit Division of Interdisciplinary Sciences > Supercomputer Education & Research Centre
Date Deposited:	14 Dec 2010 05:01
Last Modified:	14 Dec 2010 05:01
URI:	http://eprints.iisc.ac.in/id/eprint/34223

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