QUANTITATIVE ELECTRON SPECTROSCOPIC ANALYSIS OF ARGONNE PREMIUM COALS

The eight Argonne Premium Coal Samples were analyzed by electron spectroscopy for chemical analysis (ESCA or XPS). The surface elemental compositions were determined. Quantities of elements are reported as percent surface atomic concentrations. Analyses were performed upon opening the sample vials and 3 24 h after opening to evaluate oxidation due to air exposure. Two samples were also analyzed 10 months after opening and after severe oxidation by radio-frequency glow discharge (RFGD). Two methods are discussed for quantifying organic oxidation products present at the surface of the coal. One method uses curve fitting of the C 1s envelope to determine types and amounts of carbon functional groups. The second method involves the stoichiometric subtraction of the inorganic oxygen content from the total oxygen content to quantify the organic oxygen present at the surface. The oxygen/carbon ratios were compared between the two methods, and it was concluded the stoichiometric technique is the more precise method to quantify the degree of oxidation of coal.