Hydration of the ammonium form of the solid acid catalyst ZSM-5 is investigated by applying a technique that has been developed recently for carrying out in situ solid-state NMR studies of adsorption processes. From (1)H MAS NMR spectra recorded as a function of time and temperature during the hydration process, insights are established on the nature of the interaction between the adsorbed water molecules and the ammonium cations in the ZSM-5 material. The change in isotropic chemical shift for the ammonium cations is consistent with the formation of N-Hcdots, three dots, centeredO hydrogen bonding with the water molecules. Studies of the adsorption of deuterated water, and dehydration of the hydrated material, are also reported.
Acids Computer Simulation