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)nand the same AC support have been tested in H2O2 decomposition in presence and absence ofnmethanol, a known strong scavenger of hydroxyl radicals, to investigate the selectivity towardsnzOH formation in this reaction and their behavior in the CWPO of phenol. The catalyst preparednwith iron nitrate, with the most oxidized surface and the highest Fe surface content, seemsnto favor a higher selectivity towards zOH formation in CWPO allowing for complete phenolnconversion and a significant TOC removal, with the highest mineralization degree at 508C andnatmospheric pressure. Fe/AC catalysts were more efficient in the CWPO of phenol than innmethanol presence due to a better use of the oxidant since adsorbed phenol on catalystnsurface minimizes inefficient H2O2 decomposition to H2O and O2(g). The influence of the initialnH2O2 concentration on phenol oxidation with this catalyst was also studied. A theoreticalnstoichiometric amount of H2O2 for complete oxidation of phenol was chosen as the bestnstarting concentration since auto-scavenging reactions can be minimized and it isnsufficient for oxidizing phenol and the aromatic intermediates.