Proton magic angle spinning nuclear magnetic resonance and temperature programmed desorption studies of ammonia on the acidity of the framework hydroxyl groups in the zeolite H-ZSM-5 and in H-boralite

Abstract

The acidity of the framework hydroxyl groups of H-ZSM-5 and H-boralite is investigated by proton magic angle spinning NMR and temp. programmed desorption (TPD) of NH3. The acidity decreases from Si-OH-Al, the Broensted acidic site in H-ZSM-5, to Si-OH-B, the Broensted acidic site in H-boralite, to Si-OH, the terminating OH group of the zeolite lattice (silanol group). This sequence agrees with the NH3-TPD results.