Solid-state1H NMR studies of the acidity of mordenites

Abstract
The interaction of known numbers of water molecules with the acidic OH groups of H-form commercial mordenites, giving H3O+ and H2O⋯HO, is studied using 1H broad-line NMR at 4 K and MAS NMR at 300 K. The H3O+ concentration for one adsorbed water molecule per Brønsted-acid site is related to the Si/Al ratio. The differences between the H3O+ concentrations for the two samples at a higher water concentration is associated, semi-quantitatively, with synergy between Brønsted- and Lewis-acid sites.