On the optimization of activated carbon-supported iron catalysts in catalytic wet peroxide oxidation process

Abstract

Different homemade iron-activated carbon catalysts (Fe/AC) have been studied in the CWPO of phenol at mild conditions (atmospheric pressure and 50°C). Both iron content and the way to introduce iron active phase in Fe/AC catalysts were analyzed to select the most stable and efficient activated carbon-supported iron catalyst. The major differences were found on their surface properties, mainly those related to iron distribution and iron particle size. Catalysts prepared by two-consecutive steps of impregnation, regardless of iron content, always presented lower leaching phenomena of iron to the reaction medium than those prepared by one-step wetness impregnation. This higher stability could be indicating an improved metal-support interaction as a consequence of the two-step methodology used to incorporate the iron, which leads to the formation of small iron particles very homogeneous in size (≈3nm). The best performance balanced between activity and stability was obtained with 2% iron 2-steps catalyst (2sFe/CN) which gave rise to complete removal of phenol after 60min, maximal reduction of TOC content and optimal use of the stoichiometric amount of H2O2 added during batch experiments at 50°C, atmospheric pressure, 500 mgL−1 catalyst loading, 100 mgL−1 and 500 mgL−1 of phenol and hydrogen peroxide concentrations, respectively, at pH0=3.The study of H2O2 decomposition in the presence of an excess of MeOH, a well-known OH scavenger, has been an useful tool to analyze the behavior of heterogeneous catalysts in CWPO reactions. 2sFe/CN catalyst led to a better and efficient use of H2O2 with higher hydroxyl radical yield in the presence of phenol instead of methanol, as a consequence of phenol adsorption onto the catalyst surface which minimizes the inefficient decomposition of H2O2 at the same operating conditions.