Wet peroxide oxidation of phenolic solutions over different iron-containing zeolitic materials

A series of iron-containing zeolitic materials, prepared by different proce dures, have been tested as heterogeneous catalysts for the oxidation of phe nolic solutions with hydrogen peroxide under mild conditions. Fe-TS-1 catal ysts,were synthesized through hydrothermal crystallization of wetness-impre gnated Fe2O3-TiO2-SiO2 xerogels. The iron content within the raw xerogel wa s optimized with the aim, of minimizing the degree of iron leaching into th e solution. For the purpose of comparison, Fe-silicalite and Fe-ZSM-5 zeoli tes free of Ti species, synthesized through hydrothermal crystallization of basic hydrogels and Fe-NaY, Fe-USY, and Fe-ZSM-5 materials prepared by an ion-exchange procedure, were also tested. Heterogeneous catalytic systems s howed a better catalytic performance than homogeneous systems based on diss olved Fe3+ salts. Moreover, Fe-TS-1 zeolite with a moderate Fe content (Si- Fe molar ratio of 76) showed the best results in terms of catalytic activit y and loss of active species into the aqueous solutions. Finally, the stabi lity of Fe species has been shown to be strongly dependent on the Fe enviro nment into the zeolitic framework, the synthetic route, and the temperature of the treatment.