The Use of Chelating Agents for the Preparation of Iron Oxide Catalysts for the Selective Oxidation of Hydrogen Sulfide

Abstract

Iron oxide-on-silica catalysts have been prepared for the selective oxidation of hydrogen sulfide to elemental sulfur. Preshaped silica extrudates (Aerosil OX50) were impregnated with aqueous solutions containing different precursors. The precursors used are ammonium iron(III) EDTA, ammonium iron(III) citrate, iron(III) gluconate, iron(III) chloride, iron(III) nitrate, and iron(III) sulfate. After drying and heating in air the resulting iron oxide on silica catalysts were characterized using TEM, SEM, Light Microscopy, XRD, DRIFTS, and Temperature-Programmed Reduction. Moreover, the catalytic properties in the selective oxidation of H 2 S were tested. It is found that catalysts prepared from precursors that do not easily crystallize, such as the above mentioned chelated iron compounds, contain high quantities of small, highly active iron oxide particles (2–5 nm). However, catalysts prepared with precursors that crystallize readily, like most of the simple iron salts, contain large iron oxide particles (>20 nm). Catalysts containing small iron oxide particles exhibit higher activities and selectivities.