The relation between some electrical properties and thermodynamic properties of adsorbed water has been studied for two montmorillonites, a silica gel, and a window glass powder at room temperature. A relationship has been found between electrical conduction and the mobility of water molecules in the monolayer. These molecules are immobile on the hydroxylic surface of silica gel and mobile on the oxygen internal surface of montmorillonite. The electrical conduction in the monolayer is believed to be mainly protonic. The dissociation degree of water molecules in this situation seems to be of the order of magnitude of 1%.

The acidity of a series of commercial dealuminated H−Y zeolites was studied by means of MAS NMR and XPS spectroscopy. 27Al MAS NMR has shown the presence of three types of Al in the dealuminated samples:  framework tetrahedral Al, nonframework octahedral Al, and a third type of Al. As inferred from the framework Si/Al ratio obtained by 29Si MAS NMR spectra and from the evolution of the unit cell parameter determined by XRD, this third type of Al may be localized into the zeolite framework. XPS characterization of the samples in their acid form has allowed us to establish the relative concentration of Al at the outer surface of the particles. Upon adsorption of ammonia on the dealuminated zeolites, three types of acid sites have been evidenced by XPS. The analysis of the XPS data indicates that the strength of the acid sites associated with tetrahedral framework Al atoms is not influenced by the other types of Al. The catalytic results of heptane and decane hydroisomerization have evidenced that the acid sites of certain dealuminated H−Y zeolites may be very efficient. The information provided by MAS NMR, combined with the XPS results and literature data, has allowed us to partially elucidate the origin of the high activity of some dealuminated H−Y zeolites.

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Abstract--Beidellite was synthesized hydrothermally from a noncrystalline gel at 320~ and 130 bar pressure. The beidellitic character of the product was verified by infrared spectroscopy on the NH4 § exchanged form. Intercalation was achieved with hydroxy-aluminum solutions having different OH/A1 molar ratios. The solutions were investigated by several methods, including 27A1 nuclear magnetic resonance. Essentially, two Al species were detected: monomeric A1 and a polymerized form containing A1 in four-fold coordination. This latter species was found to be selectively fixed in the interlamellar region, which resulted in a stable spacing of 18 ,~ at 110~ and 16.2 ~ at 700~ The pillared beidellites had specific surface areas of > 300 m2/g, mainly due to micropores. Both Br6nsted and Lewis acid sites were evidenced by infrared spectroscopy using pyridine as a probe molecule.

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