In situ solid-state H-1 NMR studies of hydration of the solid acid catalyst ZSM-5 in its ammonium form

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 H-1 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-H center dot center dot center dot O hydrogen bonding with the water molecules. Studies of the adsorption of deuterated water, and dehydration of the hydrated material, are also reported. (C) 2009 Elsevier Inc. All rights reserved.