A striaght channel system is intersected by a sinusoidal channel system. The diagram on the right shows the view down the striaght channel system. The pore diameter is in the order of 5.4 Angstroms. Zeolites therefore can be seen as the perfect microporous material. They are fairly simple in their synthesis and they can be produced in a number of thermodynamically stable crystalline forms.
Zeolites also have other hidden powers.
Molecules which are too large to diffuse into the pores are excluded, whereas molecules which have a kinetic diameter smaller than the pore size, diffuse into the pores, adsorb and under certain conditions are capable of undergoing catalytic reactions. An example of this is in the sieving of striaght and branched chained hydrocarbons to increase the octane number of gasoline. Introduction of Al atoms into the framework produce a charge imbalance due to the difference in valance of Si and Al. The introduction of Al into the framework has several effects. Introduction of an electric field - Makes the zeolite more hydrophillic.