Site selectivity of calcium ions in dehydrated zeolite A: xenon-129 NMR spectroscopy

Na{sub x}Ca{sub y}-A zeolite samples with various calcium loadings are examined with NMR spectroscopy of sorbed xenon gas. The chemical shift extrapolated to zero pressure changes with the amount of calcium per unit cell. The results indicate that the first four or five Ca{sup 2+} ions reside in the {alpha}-cage (probably at site II) and the remaining exchanged Ca{sup 2+} resides outside the {alpha}-cage, which is in agreement with X-ray and neutron scattering data and theoretical calculations.