Issue 24, 1998

Modelling aromatics in siliceous zeolites: a new forcefield from thermochemical studies

Abstract

A new forcefield for the modelling of interactions between aromatics and siliceous zeolites has been derived by fitting to calorimetric data on the sorption of benzene in siliceous faujasite. The calometric measurements suggest a heat of sorption of 55 kJ mol−1 at densities lower than 22 molecules per unit cell. Monte Carlo docking calculations have been carried out, using the new forcefield, to predict the most favourable binding sites for sorption of benzene in this zeolite. They show a relatively flat potential-energy surface as compared to Na-Y with a wide variety of different mainly low-symmetry binding sites. The sites are to be classified as being either near to 4-rings (58.4 kJ mol−1), 6-rings (50.0 kJ mol−1) or in the 12-ring window (43.7 kJ mol−1). These results are consistent with neutron diffraction measurements on the same system. Molecular dynamics calculations with the new forcefield suggest that two processes contribute to the motion of benzene molecules in the pore system. At low temperatures, the benzene molecules tend to be confined to a single supercage by sliding around the walls. However, at higher temperatures, the molecules have sufficient kinetic energy to move through the 12 ring window into an adjacent supercage. Minimum-energy pathways have also been calculated, based on the docking binding sites, which correlate well with this rationalisation of the transport mechanism.

Article information

Article type
Paper

J. Chem. Soc., Faraday Trans., 1998,94, 3759-3768

Modelling aromatics in siliceous zeolites: a new forcefield from thermochemical studies

N. J. Henson, A. K. Cheetham, M. Stockenhuber and J. A. Lercher, J. Chem. Soc., Faraday Trans., 1998, 94, 3759 DOI: 10.1039/A806175K

To request permission to reproduce material from this article, please go to the Copyright Clearance Center request page.

If you are an author contributing to an RSC publication, you do not need to request permission provided correct acknowledgement is given.

If you are the author of this article, you do not need to request permission to reproduce figures and diagrams provided correct acknowledgement is given. If you want to reproduce the whole article in a third-party publication (excluding your thesis/dissertation for which permission is not required) please go to the Copyright Clearance Center request page.

Read more about how to correctly acknowledge RSC content.

Spotlight

Advertisements