Sequential addition of H2O2, pH and solvent effects as key factors in the oxidation of 2,4,6-trichlorophenol catalyzed by iron tetrasulfophthalocyanine

The efficiency of the H2O2 oxidation of 2,4,6-trichlorophenol (TCP) catalyzed by iron tetrasulfophthalocyanine (FePcS) is highly dependent on the pH value of the reaction mixture, the local hydrogen peroxide concentration and the organization of FePcS molecules in solution. Among the several forms of FePcS in aqueous solutions (dimer or monomer), monomeric FePcS is proposed to be the catalytically active complex. The key role of the organic co-solvent (acetonitrile, acetone, alcohol,...) is to shift the dimer/monomer equilibrium toward monomeric FePcS, the efficient catalyst precursor. A stepwise addition of hydrogen peroxide significantly improves the conversion of TCP and allows a low catalyst loading, below 1% with respect to the pollutant, to be used.