Quadrupole nutation n.m.r. reveals the presence of a new aluminium species in hydrothermally treated zeolites

27 Al Quadrupole nutation n.m.r. reveals the presence of four kinds of aluminium in dealuminated zeolite Y; we suggest that distorted framework tetrahedral (DFT) aluminium, which is reported for the first time here, is bonded to hydroxyl groups formed during dealumination.