High Resolution X-Ray Fluorescence Spectroscopy: A Potentially Useful Technique for Chemical Bonding Studies in Fossil Fuels

摘要

The objective of this paper is to present x-ray fluorescence spectroscopy (XFS) in a new role at high optical resolution, namely, as a potentially useful tool for a direct determination of the valence electron structures around the different kinds of atoms of interest. While it may be premature to assert with any degree of certainty the potential analytical capabilities of XFS for characterizing the nature and amount of different functional groups, a few generalizations are in order. Judging from the position of the oxygen lone pair peaks in squaric acid, it should be feasible to distinguish between -C=O and -C-OH groups. In the case of carboxylic acids the C-K emission is highly simplified and the halfwidth of the lone pairs should provide a handle on the presence and quantity of mono or polycarboxylic acids. An unsaturated ring system provides a unique C/sub 2p/-C/sub 2p/ pi band, and conceivably, the integrated intensity might yield useful information about the extent of unsaturation. XFS to determine sulfur functionality appears to provide a unique capability in determining the degree of saturation in the sulfur heterocyclic substances, as well as the capability in determining the nature of the atoms directly linked to the sulfur atom. While the above fundamental studies appear to be encouraging, clearly it will be necessary to evaluate directly the analytical capabilities of XFS for coal characterization. Preliminary studies are currently under way. 15 refs., 13 figs. (ERA citation 11:025287)