Prediction of template location via a combined Monte Carlo–simulated annealing approach

Abstract

A combined Monte Carlo–simulated annealing approach has been developed to predict the location and orientation adopted by organic molecules within a zeolite host. Periodic boundary conditions were used throughout the simulations in order to permit a full treatment of organic–organic interactions within a densely packed system. This approach has been used to investigate the relationship between zeolite products and the organic template molecules used in their synthesis. The results are shown to reproduce experimentally determined locations accurately, including important disordering effects. Previous experimental work has shown that some template molecules can effect the synthesis of more than one type of zeolite framework when experimental conditions are varied and also that many zeolites can be synthesised by an apparently diverse range of templates. Our results show that both these observations can still be rationalised via the ‘templating theory’ of zeolite synthesis. A mechanism for faulting is proposed which is shown to be consistent for NU-86 and the industrially important zeolite beta.