Towards a molecular understanding of shape selectivity

Cracking zeolite catalysis Zeolites are crystalline materials with ordered pore structures that are widely used as industrial catalysts. They are particularly important in oil refining, where the outcome of chemical transformations is strongly influenced by the pore topology of the zeolite catalyst. In a review, Berend Smit and Theo Maesen argue that this so-called shape selectivity can be rationalized using a straightforward thermodynamic analysis of how pore topology affects the free energies of formation of the reactants, intermediates and products. Despite the need for drastic simplifications, the approach can explain experimental observations and even guide the search for zeolite structures optimized for specific catalytic applications.