Vanadium complex catalysts encapsulated in Y-zeolite (VPA-Y), which are prepared by the "ship in a bottle" method, are investigated as heterogeneous catalysts for the liquid-phase oxidation of benzene to phenol with molecular oxygen. Phenol is the major product of the process, and the catalyst can be easily separated from the product solution after the reaction. These encapsulated catalysts are characterized by thermogravimetric analysis, demonstrating that the vanadium complexes are formed in the Y-zeolite cages.