Characterization of Aluminum in Cation-Exchanged NH4NaY and USY Zeolites by 27Al MAS NMR Spectroscopy

The effects of cations on the local electromagnetic environments of catalytic sites in Y-zeolites are studied as a function of cation type and concentration. Quadrupolar coupling parameters measurable using ²⁷Al MAS NMR at multiple field strengths, provide a window to study aluminum’s local electronic structure. Quadrupolar parameters calculated for framework tetrahedral aluminum are related to cation concentration and Brønsted acidity for potassium-, zinc-, and lanthanum-exchanged NH₄NaY and USY zeolites.