Comparison of crystallization rates of [Al]-and [Ga]-MFI-type zeolites

Abstract The crystallization rates of [Al]- and [Ga]-MFI-type zeolites were studied at 170°C and autogeneous pressure. Samples were characterized by XRD, FT i.r. solid-state 27 Al and 71 Ga MAS n.m.r., and X.p.s. techniques. Results clearly show that the crystallization rate of [Ga]-ZSM-5 is much faster than that observed for [AI]-ZSM-5. Whereas [Ga]-ZSM-5 is synthesized in just 4 h, [AI]-ZSM-5 is synthesized in 40 h under the same conditions. This is probably due to the fact that, under alkaline conditions, free gallate ions are more stable than are aluminate ions.