Impact of ferrocene on the nanostructure and functional groups of soot in a propane/oxygen diffusion flame

Abstract

This study presents the effect of ferrocene ((C₅H₅)₂Fe) on the soot oxidation activity by influencing the nanostructure and molecular structure of soot. Soot particles were obtained at different heights from propane/oxygen flames without and with ferrocene added to the fuel, respectively. The fringe properties of soot were compared using the skeleton images extracted from the high-resolution transmission electron microscopy images of soot particles. Near-edge X-ray absorption fine structure spectroscopy was used to characterize the carbon chemistry of soot particles. It was found that ferrocene reduced the degree of graphitization of soot by changing its fringe length, tortuosity, and separation distance, and these effects were much more obvious near the flame terminus. These changes may be related to ferrocene dropping the flame temperature there. Fe from (C₅H₅)₂Fe reacting with OH and O radicals decreased the oxygen-containing functional groups of soot and affected its aromatic structure after the addition of (C₅H₅)₂Fe to the flame. The inner cores of soot particles were also much bigger due to partial oxidation. Thermogravimetric analysis revealed that ferrocene promoted the soot oxidation at low temperatures.