Crystallization Kinetics of Silicalite-1: Use of Tetrapropylammonium Bromide and Chloride as Templates

Silicalite-1, the aluminum-free end number of the ZSM-5 zeolites, was synthesized from a batch composition of 3.25 Na₂O · 40.0 SiO₂ · 552 H₂O · 2.00 TPA by using tetrapropylammonium bromide (TPA-Br) or chloride (TPA-Cl) as templates in the temperature range of 100 to 175 °C in a batch system. Conversion of silica in the starting batch composition into silicalite-1 in the product was followed quantitatively. The activation energies of nucleation and crystallization were determined as 37.2 and 66.5 kJ/mol, respectively. The use of TPA-Cl as the template instead of TPA-Br results in longer induction period for crystallization to start and a larger crystal size in product.