LAUSR

Abstract Zeolites Y from organic-free system with adjustable Si/Al ratios (2.15–2.87) were synthesized and compared to the commercial zeolite Y (HSZ-320NAA, Tosoh Co., Japan). We found that the as-synthesized and commercial zeolites with similar X-ray crystallinity and Si/Al ratios tend to show different susceptibility to removal of framework aluminium. Furthermore, our study indicates that increased extraction of framework aluminium atoms not always result in lower crystallinity. We attribute this behaviour to different distribution of Si(nAl) building units and structural defects as revealed by 29Si MAS-NMR, 27Al MAS-NMR and powder XRD analyses. We also found that the progressively increasing amount of extra-framework aluminium is inversely related with the Si/Al ratios of the dealuminated samples and contributes to higher catalytic activity. Finally, we evaluated the influence of X-ray crystallinity and Si/Al ratios on the catalytic performance of the as-synthesized and commercial samples.