Selectivity of hydrogen peroxide decomposition towards hydroxyl radicals in catalytic wet peroxide oxidation (CWPO) over Fe/AC catalysts

摘要

Two Fe/AC catalysts prepared with different iron precursors (iron nitrate and iron pentacarbonyl) and the same AC support have been tested in H _2O_2 decomposition in presence and absence of methanol, a known strong scavenger of hydroxyl radicals, to investigate the selectivity towards zOH formation in this reaction and their behavior in the CWPO of phenol. The catalyst prepared with iron nitrate, with the most oxidized surface and the highest Fe surface content, seems to favor a higher selectivity towards ·OH formation in CWPO allowing for complete phenol conversion and a significant TOC removal, with the highest mineralization degree at 508C and atmospheric pressure. Fe/AC catalysts were more efficient in the CWPO of phenol than in methanol presence due to a better use of the oxidant since adsorbed phenol on catalyst surface minimizes inefficient H_2O_2 decomposition to H_2O and O_2(g). The influence of the initial H_2O_2 concentration on phenol oxidation with this catalyst was also studied. A theoretical stoichiometric amount of H _2O_2 for complete oxidation of phenol was chosen as the best starting concentration since auto-scavenging reactions can be minimized and it is sufficient for oxidizing phenol and the aromatic intermediates.