ESCA applied to aspects of coal surface chemistry

Abstract

A recent evaluation of the surface sensitive analytical technique, Electron Spectroscopy for Chemical Applications (ESCA), in the analysis of coal, kerogen and gilsonite pitch is reviewed. The ability of ESCA to provide structural information on the materials as studied in their solid state is demonstrated. Comparison has been made of ESCA-derived atomic concentrations with corresponding data from standard elemental analyses for a series of well documented coal samples (Lower Kittanning seam, Ohio and Pennsylvania, USA). For organic oxygen atomic concentrations, ESCA-derived values are shown to be consistently higher than bulk data obtained from the Pennsylvania State University Coal Bank. A rankdependent trend has been noted for the organic oxygen data set, the coal of lowest rank showing the most deviation from a one-to-one, ESCA to bulk relationship. The ability of the ESCA experiment to monitor changes in surface chemistry has been clearly demonstrated with reference to the interaction of gilsonite pitch with u.v. light. Under the mild conditions employed, ESCA was able to detect extensive surface oxidation of both the carbon and sulphur components. Thus the combined use of ESCA and other analytical techniques holds considerable promise in studies of the structure and reactivity of coal and coal-related materials.