Modeling of zeolite L crystallization using continuum time Monte Carlo simulations

A model to investigate a gel-to-zeolite transformation as a possible growth mechanism through association and rearrangements of extended precursor str uctures is developed and solved via continuum time lattice Monte Carlo simu lations. The model is used to study the morphology of zeolite L nanocrystal s grown from an initial amorphous microporous precursor gel. The model cons iders gel dissolution to release growth precursor extended structures, prec ursor migration, precursor-precursor association, precursor incorporation i nto zeolite nanoparticles, and zeolite dissolution. It is shown that the ge l-to-zeolite transformation can occur when dissolved precursor migration is slow compared to precursor incorporation and zeolite dissolution. Under th ese conditions, the initial gel microstructure (intraparticle porosity) has a significant effect on the zeolite morphology and on the crystallization kinetics. This transformation proceeds in two stages: A zeolitic framework forms initially without long-range order, followed by slow rearrangement of building units into nanocrystalline particles with possible defects. Final ly different growth modes are identified as a function of microkinetic para meters and gel morphology. (C) 1999 American Institute of Physics. [S0021-9 606(99)71229-8].