Study of 5A exchange NaCa-zeolites by 27Al MAS and MQMAS NMR

Na x Ca y -A zeolite samples with various calcium loading and treated in various conditions are examined with 27 Al magic-angle-spinning (MAS) NMR and MQMAS measurements, in order to study the framework structure evolution. Properties of zeolites are greatly influenced by their framework and extra-framework composition. The aluminum content of the zeolite framework can be modified by thermal treatments. These procedures are believed to increase the framework Si/Al ratio by effecting a migration of framework aluminum into non lattice positions. The formation of a extra-framework tetrahedral aluminum species due to dealumination by thermal treatment of ion-exchanged zeolite A was characterized by 27 Al MAS and MQMAS NMR.