Conformation of confined alkanes: n-butane in zeolite Y

Abstract

Articles you may be interested inA constrained maximum entropy method for the interpretation of experimental data: Application to the derivation of single particle orientationconformation distributions from the partially averaged nuclear spin dipolar couplings of nalkanes dissolved in a liquid crystalline solvent Empirical modelling of MFI zeolite synthesis in the presence of fluorides-mastering the characteristics that control usage properties AIP Conf. Proc. 330, 390 (1995); 10.1063/1.47727Sampling the conformational space of oligosaccharides within the framework of macromodel AIP Conf.Configurational-bias Monte Carlo simulation of n-butane in NaY zeolite has been reported at different temperatures and loadings. In contrast to n-butane in silicalite, the gauche conformer population is always found to be higher in zeolite NaY than in pure fluid at the same density. Normally, an increase in adsorbate concentration in gases such as methane, rare gases, etc. leads to an increase in population near the cage centre. In contrast, we find that an increase in n-butane concentration gives rise to an increase in population near the periphery of the cage. Enhancement in gauche conformer population observed for NaY zeolite is attributed to the surface curvature of the ␣-cavity.

Molecular dynamics of n-pentane in NaX zeolite studied by quasi-elastic neutron scattering

“…The isotropic Ó. motion found for n-pentane in NaX, in contrast to n-butane or n-hexane in ZSM-5, is in agreement with the larger gauche conformer population computed by Bandyopadhyay and Yashonath for n-butane in NaY. 13 The larger volume accessible to the molecule on increasing the temperature can be related to the broader distribution of the centre of mass calculated in ref. 13 at higher temperature.…”

“…Furthermore, the simulations were mainly concerned with benzene or aromatic molecules, only one study dealt with an alkane. 13 For a series of n-alkanes absorbed in ZSM-5, the rotational motion measured by QENS was best described by a uniaxial rotation about the main molecular axis, which indicated that the n-alkanes resided mainly in the pore segments, not in the channel intersections,26,27 in good agreement with the simulations performed by June et al 16 and Hernandez and Catlow.19 Further agreement between QENS results and MD simulations was observed for the activation energies and mean jump lengths. 19 In the present work, QENS has been used to study the dynamics of n-pentane adsorbed at low concentration in NaX, at di †erent temperatures.…”

Diffusion mechanisms of normal alkanes in faujasite zeolites

“…They found that conformations inside this relatively open zeolite are very similar to unconfined alkanes. Bandyopadhyay and Yashonath 16 performed similar simulations of n-butane in NaY and attributed a slight enrichment of the gauche conformation to localization of the chains near the pore wall.…”

“…52 FIG. 16. Qualitative representations of the potential energy variations along different paths for chain diffusion in the faujasite structure.…”

Chain Length Effects of Linear Alkanes in Zeolite Ferrierite. 2. Molecular Simulations

“…7,8 Finally, the effect of temperature and n-butane concentration on the conformation of n-butane adsorbed in zeolites NaY and NaCaA was studied by means of CB-MC by Bandyopadhyay and Yashonath. 9,10 The examples mentioned above show the usefulness of molecular simulations. Besides the ability to calculate properties that are not easily accessible by experimental methods, they are also able to obtain a better understanding of the experimental results.…”