PROTON-TRANSFER BETWEEN BRONSTED SITES AND BENZENE MOLECULES IN ZEOLITES H-Y STUDIES BY IN-SITU MAS NMR

In situ H-1 MAS NMR spectroscopy of the proton, transfer between bridg ing hydroxyl groups and benzene molecules yields temperature-dependent exchange rates over more than five orders of magnitude. H-D exchange and NOESY MAS NMR experiments were performed by conventional and laser heating up to 600 K. It is shown that the dealumination of the zeolit e has a strong influence on this exchange rate, which represents a dyn amic measure of Bronsted acidity. (C) 1998 Academic Press.