Detection of active sites for paraffin cracking on USY zeolite by 27Al MQMAS NMR operated at high magnetic field 16 T

27Al MAS and 3QMAS NMR at a high magnetic field (16 T) detected a tetra-coordinated species of extra-framework Al with a large structural anisotropy (IVb), which was a candidate of active species for paraffin cracking on USY zeolite.