PHYSICOCHEMICAL CHARACTERIZATION OF BORO-SILICATE AND GALLO-SILICATE ISOMORPHS OF BETA-ZEOLITE

The crystalline isomorphs of beta-zeolite containing boron or gallium in the framework positions have been synthesized and the products char acterized by comparing them with Al-beta zeolite. Evidence for the pre sence of B or Ga in the zeolite lattice framework has been confirmed b y spectroscopic (XRD, IR and Si-29, Al-27 and B-11 MASNMR), DTA/TG, io n exchange, sorption and catalytic activity results. Chemical analysis and NMR confirm the absence of any significant amount of Al in the ze olite (SiO2/Al2O3 = 2000). The XRD pattern of the as-synthesized B-bet a Ga-beta compounds matched well with that of Al-beta zeolite. Lattice B and Ga leads to a change in the X-ray d values. Framework and bridg ing hydroxyl stretching IR bands of beta-zeolite are shifted due to in corporation of gallium and boron into the zeolitic framework. MASNMR s pectra of B-11 and Si-29 also suggest the presence of tetrahedrally co ordinated B(III)) or Ga(III)) ions in the beta-zeolite framework. B an d Ga beta-zeolites exhibit significant ion exchange capacity and catal ytic activity in the m-xylene isomerization reaction. The shifts in th e IR bands towards higher frequency in B-beta and lower frequency in G a-beta, the observed ion exchange capacities and catalytic properties, indicate the presence of B3+ or Ga3+ ions in the framework of beta-ze olite.