DETERMINATION OF THE AL-H AND H-H INTERNUCLEAR DISTANCES IN ZSM-5 USING NMR-SPECTROSCOPY

NMR spectroscopic techniques are used to determine the structure of Bronsted acid sites in zeolite ZSM-5. The internuclear distance between aluminum and proton nuclei associated with Bronsted acid sites is measured directly using spin echo double resonance (SEDOR) techniques. This distance is determined to be 0.243 +/- 0.003 nm, consistent with the value of 0.246 nm determined by applying the method of moments to the H-1 spectrum of ZSM-5. The method of moments is applied to the H-1 spectrum of silicalite, and the internuclear distance between protons associated with an internal silanol pair is measured as 0.26 nm.