Ferrate(VI) as an iron source for the synthesis of a silica aerogel-supported iron oxide catalyst for sulfide oxidation

Potassium ferrate(VI), K 2 FeO 4 , was used as the iron precursor to prepare iron (hydr)oxide (FeH y O x ) supported on silica aerogel by an aqueous hydrothermal method. Electron microscopy and elemental analysis supported the incorporation and dispersion of iron-containing species within the porous silica framework, while X-ray diffraction (XRD) was consistent with a poorly crystalline or amorphous Fe-containing phase. The catalyst contained 5 wt% Fe and retained a Brunauer–Emmett–Teller (BET) specific surface area of 221.9 m² g⁻¹, although silica aerogel accessible porosity decreased substantially during preparation. Using H 2 O 2 in ethanol at room temperature, the catalyst afforded substrate conversions from (59 ± 2)% to (100 ± 2)% and sulfoxide selectivities from (88 ± 2)% to (98–100)%. Under the optimized conditions, methyl phenyl sulfide conversion and sulfoxide selectivity were (98–100)% and (91 ± 2)%, respectively. The catalyst was evaluated over six consecutive runs, with conversion decreasing from (98–100)% to (75 ± 2)% while sulfoxide selectivity remained high. Solution-phase atomic absorption spectroscopy (AAS) detected no increase in Fe above the reported background. These results establish ferrate(VI) as a useful precursor for supported iron-based oxidation catalysts and identify catalyst durability and synthesis resource consumption as priorities for further development.