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.

SAPO-37 microporous catalysts: revealing the structural transformations during template removal

“…According to the work of Davis and Lobo, templates can be classified into three different types [39]: (i) "true" templates, (ii) structure directing agents (SDAs) and (iii) space-filling species. Simulations using molecular dynamics to investigate the nature of the interaction between the formed zeolite framework and organic template show that the interaction is dominated by van der Waals bonding [40]. The term used by Stevens et al to describe this interaction is "non-bonded" energy.…”

Retrosynthetic Co-Templating Method for the Preparation of Silicoaluminophosphate Molecular Sieves

“…[10][11][12][13][14][15][16][17] The short-range nonbonding interaction energies of these with the oxygen atoms of the framework are found to be crucial in determining which phase crystallises. [18][19][20][21] In most cases, new zeolites have resulted from exploratory crystallisation in the presence of a wide range of OSDAs which are either available commercially or prepared by customised syntheses, with screening of conditions and inorganic gel composition for each OSDA tried.…”

DFT study of the interaction of the HZSM-5 zeolite with the benzene molecule

“…For instance, Monte Carlo simulations to predict positions and orientations of hydrocarbons have been carried out [4]. The formation of carbonium and carbenium ions as intermediates in zeolite-catalyzed reactions has been discussed in terms of transition states stabilized by the zeolite lattice [5].…”