Characterization of a high-loaded intercalate of p-xylene with a highly siliceous form of ZSM-5 by high resolution 29Si solid-state NMR spectroscopy

High-resolution solid-state 29Si MAS NMR spectra of zeolite ZSM-5 with 4–8 molecules of sorbed p-xylene per unit cell reveal the presence of a ‘high-loaded’ phase for this system in which there are 24 T sites in the asymmetric unit; proton decoupling must be used to obtain good resolution in this phase and this is an indication for considerable dipolar interaction between the p-xylene protons and the 29Si nuclei in the zeolite lattice, in contrast to the case of the ‘low-loaded’ form with two molecules per unit cell previously observed and described; thus, cross-polarization may be used to discriminate in favour of the ‘high-loaded’ phase.