Improved Fe2O3/Al2O3 as heterogeneous Fenton catalysts for the oxidation of phenol solutions in a continuous reactor

BACKGROUND: Improved Fe2O3/Al2O3 catalysts were studied for the catalytic oxidation of concentrated phenol solutions (5 g L-1) with H2O2. To enhance catalyst stability, two strategies were investigated: the use of a high calcination temperature and a step of immersion into an organic acid solution. The reaction runs were performed in a continuous reactor at 70 degrees C and atmospheric pressure. RESULTS: For all the catalysts, almost complete phenol degradation was achieved. The mineralization levels were incomplete, reaching 60 and 50% for the catalysts treated with acetic and oxalic acid, respectively. The leaching levels were reduced from 25% (for the untreated catalyst) to 11% after the immersion in oxalic acid. In all cases, the formation of reversible carbonaceous deposits was observed during reaction and a progressive decay in phenol, TOC and H2O2 conversions was registered. CONCLUSION: Catalyst resistance to leaching was significantly enhanced by combining both thermal and acidic treatments. These procedures did not affect the catalytic wet hydrogen peroxide oxidation (CWHPO) performance in terms of mineralization levels. The lixiviation levels were acceptable, taking into account the strong acidic reaction medium. Deactivation processes might be primarily associated with the formation of reversible carbonaceous deposits due to intermediates accumulation onto the catalyst surface. (C) 2014 Society of Chemical Industry