Cu and Fe-containing ZSM-5 zeolites as catalysts for wet peroxide oxidation of organic contaminants: reaction kinetics

Abstract

The peroxide oxidation of model substrates (formic acid and phenol) was studied in the presence of copper- and iron-containing catalysts (0.5 % Cu–ZSM-5-30 and 0.65 % Fe–ZSM-5-30). The aim was to develop optimal kinetic models for describing the kinetics of peroxide oxidation. The real kinetics of phenol and formic acid oxidation in the presence of these catalysts at varied reaction parameters (concentrations and temperature) was studied. The copper-containing catalysts were more active to formic acid oxidation than the iron-containing catalyst over all the temperature range studied. The rate of destruction of pollutants decreases with a decrease in the H2O2 concentration and the catalyst weight. The observed rate dependences on the initial substrate concentration appeared to be different for the substrate used. With formic acid, an increase of initial concentration leads to a slight increase in the reaction rate. In the case of phenol peroxide oxidation, the negative order with respect to the substrate concentration was observed. This may be explained by strong inhibition of the reaction rates by phenol and intermediates (hydroquinone, catechol, etc.) of its oxidation. The mathematical modeling of the kinetics was performed for various types of kinetic equations that correspond to different hypotheses on the kinetic reaction scheme. The selected kinetic models based on logical kinetic schemes allowed describing the peroxide oxidation of model substrates at an appropriate accuracy.