SYNTHESIS AND CHARACTERIZATION OF VANADIUM (IV) COMPLEXES IN NAY ZEOLITE SUPERCAGES

Encapsulated vanadium complexes with various pyridine-2-carboxylic aci ds and Schiff bases were synthesized from a dehydrated form of VO(2+)- NaY zeolite by a flexible ligand method and a template synthesis metho d. It was suggested by X-ray powder diffraction and X-ray photoelectro n spectroscopy that the complexes were located in the zeolite supercag es. Detailed characterization of the vanadium species was performed by XAFS, FT-IR, ESR and UV-vis spectroscopies in comparison with the cor responding free complexes and reference samples prepared by an impregn ation method. Difference in spectroscopic features of the encapsulated and impregnated VO(pic), samples was explained in terms of coordinati on of zeolite -OH groups to the vanadium complexes. The encapsulated v anadium complexes were active for catalytic selective oxidation of hyd rocarbons with H2O2 and t-BuOOH. (C) 1998 Elsevier Science B.V. All ri ghts reserved.