Abstract: Two kinds of ESR spectra measured from VO²⁺ supported on Y-type zeolites after treatments at various roast temperatures (200~700℃) are reported. Results suggest that the VO(H₂0)₄²⁺ ion in the cage of zeolite has two kinds of probable structures. With the increase of roast temperature, the structure (Ⅰ) turned to structure (Ⅱ) gradually. When the roast temperature was increased over 600℃, the structure (Ⅰ) disappeared entirely, and the parameter A_⊥ of structure (Ⅱ) decreased gradually. This implies that the delocalization of the unpaired electron was enhanced. At last, this unpaired electron was lost and the V⁴⁺ was oxidized to V⁵⁺. The bond parameter and reducible energy level were calculated from the spectral parameters.

Key words: zeolite, ESR, vanadyl