ABSTRACT
Acknowledgments .............................................................................................................. 284
References .......................................................................................................................... 284
Zeolites are crystalline, aluminosilicate molecular sieves that have pores of molecular dimen-
sions [1, 2]. Zeolites are nontoxic and environmentally benign materials that can be synthe-
sized with a wide range of pore sizes and topologies. The framework structures and properties
of some common zeolites are shown in Figure 11.1 and Table 11.1, respectively. Zeolites are
used in applications such as catalysis, chemical separations, and as ion exchangers [3]. Some
types of zeolites are naturally occurring; there are 40 known naturally occurring zeolites and
over 150 synthetic zeolites [4]. Zeolites are classified as microporous materials that have pore
dimensions in the subnanometer to nanometer size range. The zeolite framework typically
consists of SiO4 4 and AlO4
5 moieties in tetrahedral coordination with shared oxygen atoms. A zeolite composed entirely of SiO4
4 tetrahedral units is neutral, whereas the introduction of aluminum into the framework introduces a negative charge that is charge-compensated by a
cation, such as sodium, to maintain charge neutrality. The charge-compensating cation can be
easily exchanged with other cations to introduce different selectivities or reactivities.
