SOLID-STATE NMR-STUDIES OF ZEOLITE [SI,B]-ZSM-5 SYNTHESIZED BY THE FLUORIDE METHOD

Crystalline zeolite [Si,B]-ZSM-5 synthesized via the ''fluoride method'' has been characterized by solid-state NMR. In as-prepared samples, boron resides in the zeolitic framework and remains there upon calcination, although its coordination with respect to oxygen changes from tetrahedral to trigonal. Similar coordination changes occur upon exposing a calcined sample to anhydrous alcohols, but not to aprotic solvents such as benzene. B-11 quadrupole nutation NMR shows that both coordinations of boron coexist in a partially hydrated sample, although trigonal B is not observed by conventional B-11 MAS NMR.