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Site percolation is studied in 13 tetrahedral frameworks of zeolitic materials. The percolation threshold, p c , has been calculated by numerical simulation and is found to be dependent on the network topology. The obtained p c values range from 0.442 for bikitaite to 0.493 for faujasite, which means a relative difference of about 10%. These percolation thresholds correlate well with...
Ti-containing mesoporous silicas have been synthesized at ambient temperature using amines with alkyl chains of 10–16 carbon atoms as templating surfactant. Following this synthesis route, it was possible to prepare materials with more than 2 wt% Ti without forming extrawall TiO 2 . Physicochemical characterization of the samples showed that Ti atoms were probably tetrahedrally coordinated,...
Zeolite MCM-22 has been studied by infrared (i.r.) spectroscopy, thermoprogrammed desorption (t.p.d.) of NH 3 , and 27 Al n.m.r. with magic angle spinning (MAS). It has been found that zeolites MCM-22 and ZSM-5 both have framework i.r. bands at about 1,245 and 550 cm −1 , and zeolites MCM-22 and Y both have two pore opening i.r. bands at about 380 and 317 cm −1 . In...
The room temperature aging process in a solution phase ZSM-5 preparation has been studied by scattering and n.m.r. techniques. Small-angle X-ray scattering detected particles growing in the 1–10 nm size domain, and their evolution was followed over a period of 4 days; the most dramatic changes occurred in the first 24 h. A contrast variation small-angle neutron scattering experiment was performed...
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