Comparative QENS and PFG NMR diffusion studies of water in zeolite NaCaA

Quasi-elastic neutron scattering and pulsed field gradient NMR, in combination with temperature-programmed desorption, were applied to study water diffusion in NaCaA samples obtained by exchange from a batch of NaA zeolite of commercial origin. Both techniques exhibit similar trends, viz. increasing water diffusivities with increasing loading (at least up to medium pore filling factors) and with decreasing calcium content. There are, however, notable differences in both the absolute values of the diffusivities and their temperature dependencies. These differences are explained by the real structure of the zeolite samples and the different sensitivity of the measuring techniques to the deviations from ideal crystallinity.