- Email: [email protected]
16-P-13 - Characterisation of hypothetical zeolite frameworks
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16-P-12 - M o n t e Carlo simulation of isobutane in silicalite D. Paschek and R. Krishna
University of Amsterdam, paschek@its, chem. uva.nl, The Netherlands Recent experimental work on transport diffusion of alkanes in zeolite Silicalite [B. Millot et al., J. Phys. Chem. B, 103 (1999) 1096; B. Millot et al., Micropor. Mesopor. Mater., 38 (2000) 85] indicates a possible change of the diffusion mechanism of branched components when approaching higher loadings. Therefore, we report kinetic Monte Carlo (KMC) simulations of diffusion of isobutane adsorbed in Silicalite. By using configurational-biased Monte Carlo (CBMC) simulations we get evidence for the presence of repulsive interactions between molecules adsorbed at adjacent intersection and straight channel sites. Our KMC simulations reveal that even weak repulsive interactions have a rather strong influence on the diffusivities at higher loadings and therefore could serve as a possible explanation for the experimentally observed behavior.
16-P-13 - Characterisation of hypothetical zeolite f r a m e w o r k s M.D. Foster (a), R.G. Bell (a) and J. Klinowski (b)
a DFRL, Royal Institution of GB, London, UK, [email protected], [email protected]. b Dept. of Chemistry, Univ. Cambridge, UK A series of hypothetical zeolite structures has been evaluated on the basis of calculated lattice energies and structural properties. The structures were those generated by Delgado and coworkers, using recent advances in tiling theory. Over 900 structures are currently under evaluation, from which results are presented of the 157 uninodal structures based on a quasisimple tiling unit, which include all 18 presently known uninodal zeolite structures. Treating each structure as a silica polymorph, we have calculated relative lattice energies, framework densities and coordination sequences. An automated procedure uses these quantities and correlations between them, to make an initial selection of likely candidate zeolite structures.
16-P-14 - Cation mobility and the sorption of chloroform in zeolite NaY: a molecular d y n a m i c s study N.A. Ramsahye and R.G. Bell
DFRL, Royal Institution of Great Britain, London, UK;[email protected] Molecular dynamics simulations at temperatures of 270 K, 330 K and 390 K have been carried out in order to address the question of cation migration upon chloroform sorption in zeolite NaY. The results show that the cations located in different sites exhibit different types of mobility. These may be summarised as follows: 1. SII cations migrate towards the centre of the supercage upon sorption, due to interactions with the polar sorbate molecules. 2. SI' cations migrate from the sodalite cage into the supercage to fill vacant SII sites. 3. The SI cations are able to migrate across double six rings and sodalite cages in order to fill another vacant SI' site. SI' cations can also migrate to fill another vacant SI' site.
16-P-12 - M o n t e Carlo simulation of isobutane in silicalite D. Paschek and R. Krishna
University of Amsterdam, paschek@its, chem. uva.nl, The Netherlands Recent experimental work on transport diffusion of alkanes in zeolite Silicalite [B. Millot et al., J. Phys. Chem. B, 103 (1999) 1096; B. Millot et al., Micropor. Mesopor. Mater., 38 (2000) 85] indicates a possible change of the diffusion mechanism of branched components when approaching higher loadings. Therefore, we report kinetic Monte Carlo (KMC) simulations of diffusion of isobutane adsorbed in Silicalite. By using configurational-biased Monte Carlo (CBMC) simulations we get evidence for the presence of repulsive interactions between molecules adsorbed at adjacent intersection and straight channel sites. Our KMC simulations reveal that even weak repulsive interactions have a rather strong influence on the diffusivities at higher loadings and therefore could serve as a possible explanation for the experimentally observed behavior.
16-P-13 - Characterisation of hypothetical zeolite f r a m e w o r k s M.D. Foster (a), R.G. Bell (a) and J. Klinowski (b)
a DFRL, Royal Institution of GB, London, UK, [email protected], [email protected]. b Dept. of Chemistry, Univ. Cambridge, UK A series of hypothetical zeolite structures has been evaluated on the basis of calculated lattice energies and structural properties. The structures were those generated by Delgado and coworkers, using recent advances in tiling theory. Over 900 structures are currently under evaluation, from which results are presented of the 157 uninodal structures based on a quasisimple tiling unit, which include all 18 presently known uninodal zeolite structures. Treating each structure as a silica polymorph, we have calculated relative lattice energies, framework densities and coordination sequences. An automated procedure uses these quantities and correlations between them, to make an initial selection of likely candidate zeolite structures.
16-P-14 - Cation mobility and the sorption of chloroform in zeolite NaY: a molecular d y n a m i c s study N.A. Ramsahye and R.G. Bell
DFRL, Royal Institution of Great Britain, London, UK;[email protected] Molecular dynamics simulations at temperatures of 270 K, 330 K and 390 K have been carried out in order to address the question of cation migration upon chloroform sorption in zeolite NaY. The results show that the cations located in different sites exhibit different types of mobility. These may be summarised as follows: 1. SII cations migrate towards the centre of the supercage upon sorption, due to interactions with the polar sorbate molecules. 2. SI' cations migrate from the sodalite cage into the supercage to fill vacant SII sites. 3. The SI cations are able to migrate across double six rings and sodalite cages in order to fill another vacant SI' site. SI' cations can also migrate to fill another vacant SI' site.