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

A series of iron-containing zeolitic materials, prepared by different procedures, have been tested as heterogeneous catalysts for the oxidation of phenolic solutions with hydrogen peroxide under mild conditions. Fe-TS-1 catalysts,were synthesized through hydrothermal crystallization of wetness-impregnated Fe2O3-TiO2-SiO2 xerogels. The iron content within the raw xerogel was optimized with the aim, of minimizing the degree of iron leaching into the solution. For the purpose of comparison, Fe-silicalite and Fe-ZSM-5 zeolites 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 showed a better catalytic performance than homogeneous systems based on dissolved 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 activity and loss of active species into the aqueous solutions. Finally, the stability of Fe species has been shown to be strongly dependent on the Fe environment into the zeolitic framework, the synthetic route, and the temperature of the treatment.