The interaction of different probes with two H-MOR samples has been studied by IR. In the case of the sample with Si/Al = 10 acetonitrile perturbs all the hydroxy groups while 2,2-dimethylpropionitrile (pivalonitrile) perturbs only very few. Pyridine also perturbs all the hydroxy groups but only some of them protonate the pyridine, the others only H-bond to it. n-Hexane and 2,2-dimethylbutane give the same result, perturbing only some of the bridging hydroxy groups. The results are interpreted by assuming that no OHs are located in the 8-ring channels, and that the hydrocarbons cannot interact (due to the steric hindrance of the methyl group) with the OHs located in the side pockets. On the contrary, the at molecule pyridine can enter slightly into the side pockets and H-bond with the OHs there. Pivalonitrile interacts only with the OHs which are well exposed in the main channels. It is concluded that the active sites for alkane isomerization are likely exclusively those that are well exposed in the main channels of H-MOR and that Al substitution in the T3 sites probably does not occur. The sample with Si/Al 45, taken as an example of a dealuminated sample, presents many less bridging OHs which are entirely available for interaction with even pivalonitrile

Samples of beta-zeolite thermally treated at different temperatures and acid leached with diluted hydrochloric acid solution have been investigated by XRD, Al-27 MAS-NMR spectroscopy and FTIR spectroscopy. The results have been used to interpret the behaviour of the samples as catalysts for the acylation of 2-methoxy-naphthalene. It has been shown that the as prepared sample presents two types of extraframework species. These are identified as Al hydroxo-ions highly dispersed in the internal zeolite channels and Al oxide nanoparticles. Calcination causes dealumination of the framework and progressive conversion of the Al hydroxo-ions into Al oxide nanoparticles that reduce the zeolite channels practicability, modifying the shape selectivity effect. The Bronsted acid sites present in the sinusoidal channels (nu(OH)=3608 cm(-1)) can be distinguished from those located in the larger ones (nu(OH)=3620-3612 cm(-1)), due to the inability of the bulky probe molecule pivalonitrile to enter the former. However, internal terminal silanols (nu(OH)=3735 cm(-1)) also apparently display a significant Bronsted acidity, definitely higher than the acidity of those absorbing at 3747 cm(-1), thought to be located at the external crystal surface. The strongest Lewis acidity is displayed by the aluminum hydroxo-ions, while that of alumina nanoparticles is a little weaker. Acid-leached beta-zeolite also displays a medium strength Lewis acidity, likely due to framework Al cations. Thus a partial reinterpretation of the real structure of beta-zeolite and a partial reassignment of the bands due to the surface hydroxy groups are proposed

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