Oxidation of 2,4,6-trichlorophenol by hydrogen peroxide. Comparison of different iron-based catalysts

Abstract

A systematic study of the stoichiometric and kinetic efficiencies of catalysts in the oxidation of 2,4,6-trichlorophenol by hydrogen peroxide was carried out. Six different iron-based activators were used: Fe³⁺(aq), Fe(TPPS)⁺, cis-[(cyclam)Fe]³⁺, trans-[(cyclam)Fe]³⁺, [Fe(TPA)]²⁺, and [Fe(6-Me₂-TPA)²⁺ (ligand abbreviations: TPPS = meso-tetra(4-sulfonatophenyl) porphine, cyclam = 1,4,8,11-tetraazacyclotetradecane, TPA = tris(2-pyridylmethyl)amine, 6-Me₂-TPA = bis[(6-methyl-2-pyridyl)methyl](2-pyridylmethyl)amine). The stoichiometric efficiencies of the catalyst were characterized by comparing the total organic carbon content, chloride ion concentration, and remaining oxidant concentration to the ideal stoichiometry where carbon dioxide, water and inorganic chloride are the only products. The kinetic efficiencies of the catalysts were compared using the rate of chloride ion formation and H₂O₂ consumption. It was shown that Fe(TPPS)⁺ is the best catalyst. Illumination by visible light significantly enhances the rate of oxidation.