High Si/Al zeolites

In zeolite synthesis (ref. 2) an aqueous mixture containing a silicon source, an aluminum source, an alkali source (usually NaOH) is autoclaved and subjected to hydrothermal treatment. Hydrated Na-ions are then filling the pore system in the as-synthesized zeolite. In the case of relatively high Si/Al zeolites an organic template is required which is usually a tetraalkylammonium compound, applied as the bromide or the hydroxide. 

Figure 1. Stylized site placement effects on cetane cracking in high Si/Al zeolites.

Carl PJ, Vaughan DEW, Goldfarb D (2002) Interactions of Cu(II) ions with framework Al in high Si Al zeolite Y as determined from X- and W-band pulsed EPR/ENDOR spectroscopies. J Phys Chem B 106 5428-5437... 

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