Structural study on the Al distribution in zeolites Nu-6(1) and Nu-6(2)

This work describes the preparation of zeolites Nu-6(1) and Nu-6(2) with different Si/Al atomic ratios (24, 45, 90 and ∞) followed by the study of the Al distribution in the different available Si or Al (T atom in the zeolite) positions. Nu-6(1) is a layered zeolite that can be converted by topotactic condensation (achieved by calcination) into the framework zeolite Nu-6(2). Several Si/Al ratio samples were submitted to synchrotron radiation and to subsequent structural refinement. The results suggest that two of six possible T positions are preferred for Al from the point of view of simulated formation energy. These two positions are in terminal situation in the gallery space of the layered zeolite, i.e., near the positively charged amine template molecules. The results were corroborated by 29Si and 27Al solid-state NMR observations.

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► Nu-6(1) is a layered zeolite that can be converted by calcination into the framework zeolite Nu-6(2).
► Zeolites Nu-6(1) and Nu-6(2) were synthesized with different Si/Al ratios (24, 45, 90 and ∞).
► The samples were submitted to synchrotron radiation and to structural refinement.
► From six possible T positions, two are preferred for Al atoms.
► The two preferred positions are in terminal situation in the gallery space of the layered zeolite.