AN INVESTIGATION OF BRONSTED ACIDITY IN GALLOSILICATE-MFI (GA-ZSM-5)

The hydrogen form of gallosilicate-MFI is characterised by H-1 MAS n.m.r. in various stages of hydration. For the dehydrated sample, the chemical shift of the peak associated with Bronsted acidity is similar to that observed in the aluminosilicate analog (HZSM-5) and to higher frequency of the shift reported for the boron-containing analog. The presence of strong acid sites is independently confirmed by temperature-programmed desorption of ammonia and is also probed by C-13 CP MAS n.m.r. studies of an as-synthesized sample containing a diethanolamine template.