SYNTHESIS AND CHARACTERIZATION OF A GALLOSILICATE ANALOG OF ZEOLITE MORDENITE

The gallosilicate analog of zeolite mordenite has been synthesized and characterized. Evidence for the presence of gallium in the lattice fr amework is obtained from chemical analysis, XRD, framework i.r., FTi.r ., and Ga-71 MAS n.m.r. spectroscopies, d.t.a./t.g., and catalytic act ivity data. Chemical analysis and n.m.r. confirm the absence of signif icant amounts of Al in the zeolite (SiO2/Al2O3 > 1000). Lattice Ga lea ds to an increase in the X-ray ''d'' values. The framework i.r. bands are shifted to lower frequencies on Ga incorporation in the lattice. T he gallomordenite sample exhibits both product-shape selectivity and r estricted transition-shape selectivity comparable to Al-mordenite, whe reas disproportionation was found to be more for Ga-mordenite than for Al-mordenite due to higher ratio of Lewis to Bronsted acid sites, as could be inferred from the FTi.r. spectra on chemisorption of pyridine molecules.