Stability of carbon-supported iron catalysts for catalytic wet peroxide oxidation of ionic liquids

The stability of two carbon-supported Fe catalysts in the catalytic wet peroxide oxidation (CWPO) of 1-Butyl-3-methylimidazolium acetate (BmimAc) was examined. One catalyst (Fe/AS) was obtained by chemical activation of dried sewage sludge with iron chloride at a FeCl3:sewage sludge mass ratio of 3 and the other (Fe/HTCS) by hydrothermal carbonization of the sludge in the presence of FeCl3 at a mass ratio of also 3. Fe/AS catalyst exhibited a well-developed porosity, whereas Fe/HTCS one did not show porosity. The carbon content was high in both catalysts, with a total Fe content of 5.2 and 6.6% (w/w) for Fe/AS and Fe/HTCS catalysts, respectively. An aditional Fe catalyst prepared by incipient wetness impregnation on a commercial active carbon support (Fe/AC) was used for comparison with the previous two. All catalysts were active in experiments of H2O2 decomposition and long-term CWPO runs (0.133 kg(Fe) h mol(BmimAc)(-1) at 80 degrees C). Whereas Fe/AC catalyst lost activity largely due to Fe leaching (90% of Fe-Bulk), Fe/AS and Fe/HTCS catalysts exhibited virtually no Fe leaching and hence fairly good stability. Fe/AS catalyst, which afforded complete removal of Bmim(+) and TOC conversion values around 30%, proved the most efficient catalyst.