Identification of New Templates for the Synthesis of BEA, BEC, and ISV Zeolites Using Molecular Topology and Monte Carlo Techniques

The
presence of organic structure directing agents (templates)
in the synthesis of zeolites allows the synthesis to be directed,
in many cases, toward structures in which there is a large stabilization
between the template and the zeolite micropore due to dispersion interactions.
Although other factors are also important (temperature, pH, Si/Al
ratio, etc.), systems with strong zeolite–template interactions
are good candidates for an application of new computational algorithms,
for instance those based in molecular topology (MT), that can be used
in combination with large databases of organic molecules. Computational
design of new templates allows the synthesis of existing and new zeolites
to be expanded and refined. Three zeolites with similar 3-D large
pore systems, BEA, BEC, and ISV, were selected with the aim of finding
new templates for their selective syntheses. Using a training set
of active and inactive templates (obtained from the literature) for
the synthesis of target zeolites, it was possible to select chemical
descriptors related to activity, meaning a good candidate template.
With a discriminant function defined upon MT, the screening through
a database of organic molecules led to a small subset (preselection)
of candidate templates for the synthesis of BEA, BEC, and ISV. As
far as we know, this is the first time that topological/topochemical
descriptors, which do not consider 3-D information on the molecules,
have been used to predict the activity of zeolite structure directing
agents (SDAs). Following the prediction of SDAs using MT, an automated
approach of sequential template filling of micropores based on a combination
of Monte Carlo and lattice energy minimization was applied for all
the candidate templates in the three zeolites. Two results can be
obtained from this: an evaluation of the quality of the molecular
topology QSAR models leading to the preselection of templates, and
a final selection of candidate templates for the selective synthesis
of BEA, BEC, and ISV. Regarding the latter, a good template will be
that which maximizes the zeolite–template dispersion interactions
with one, and only one, of the three zeolites. The presented methodology
can be used to find alternative (maybe cheaper or perhaps more selective)
templates than those already known.