TITANIUM IN MFI-TYPE ZEOLITES - A CHARACTERIZATION BY XANES, EXAFS, IR, AND TI-74, TI-49 AND O-17 MAS NMR-SPECTROSCOPY AND H2O ADSORPTION

The location and chemical environment of titanium in MFI-type zeolites synthesized in OH or in F-media was determined by XANES, EXAFS, IR, and 47, 49 Ti and 17O MAS-NMR spectroscopy. Water adsorption and its influence on the coordination of Ti was studied in the calcined zeolites. Titanium is incorporated into the framework by substitution for silicon, but a significant amount of Ti can also be present in the form of extracrystalline or intracrystalline inclusions of TiO2 depending on the F/Ti ratio in the synthesis mixture. In the absence of water. Ti in the framework is essentially tetrahedrally coordinated; in the presence of water its coordination becomes octahedral. © 1993 Academic Press, Inc.