Reactivity of USY extraframework alumina in alkaline medium

Two ultrastable Y zeolites with different degrees of dealumination were treated with NaOH solution al various temperatures and contact limes. Filtrate analysis showed the transference of the solubilized nonframework aluminum species to the solid phase, at a rate that increases with both increasing temperature and dealumination degree. The reinsertion of this aluminum in the lattice was verified by the reduction in the structural silica-to-alumina ratios (SAR) determined by Si-29 n.m.r. and FT i.r. The mesoporosity reduction points to a reinsertion in the structural defects, An estimate of the activation energy for the reinsertion process was obtained from the data fitting to a basic zeolite crystallization model.