27Al quadrupole nutation and 1H27Al cross-polarization solid-state NMR studies of ultrastable zeolite Y with fast magic-angle spinning

Abstract 1 H 27 Al cross-polarization magic-angle spinning (PC/MAS) NMR has been used to monitor selectively the non-framework aluminium (Al NF ) species in dealuminated zeolite Y (Si/Al=4.0–14). 27 Al quadrupole nutation with fast (12.5 kHz) MAS and radiofrequency excitation fields up to 220 kHz reveals resonances of 0, 30, 56 and 62 ppm, all of which have been assigned. The quadrupole coupling constant, C Q , of the site responsible for the 30 ppm signal changes significantly with the degree of dealumination, from 4.5–5 MHz (at Si/Al=4.0) to > 6 MHz (at Si/Al=9). The corresponding isotropic chemical shifts are in the range 41–57 ppm. We conclude that the non-framework matter contains four-,five-and six-coordinated aluminium.