Collect. Czech. Chem. Commun. 1992, 57, 675-680

Molecular Mechanics Studies on MFI Type Zeolites. 1. Effect of p-Xylene Adsorption on the Zeolite Structure

Erik de Vos Burchart, Bert van der Linden, Herman van Bekkum and Bastiaan van de Graaf

Laboratory of Organic Chemistry, Delft University of Technology, Julianalaan 136, 2628 BL Delft, The Netherlands


The effect of the adsorption of p-xylene on the all-silica MFI-structure is simulated with our molecular mechanics model. From experimental measurements it is known that the symmetry of the framework changes from monoclinic (space group P21/n.1.1.) towards orthorhombic (space group P212121) upon adsorption of p-xylene up to eight molecules per unit cell. The experimentally observed change in the geometry of the zeolite upon p-xylene adsorption is compared with that calculated by molecular mechanics. For the calculations our force field for all-silica zeolites is used in combination with the MM3 force field for organic molecules. Parameters for the organic-zeolite interactions are obtained by combination of the two force fields.