Weathering Effects on Structure and Reactivity of US Coals. Second Quarterly Report, Year 2

摘要

In previous reports it was shown that the main gaseous components of the products evolving during mild coal oxidation (e.g. at 80 deg C in air) were carbon dioxide and water. Although the total amount evolving as carbon dioxide or water can be measured quantitatively by gas chromatography, the actual fraction of these components directly derived from reactions with ambient air as opposed to CO sub 2 and H sub 2 O produced by existing oxygen functionalities in the coal cannot be determined by this approach. In order to determine this value and to measure subtle structural changes, Anderson lignite was weathered at 80 sup 0 C under two different atmospheres composed of (21% sup 16 O sub 2 + 79% N sub 2 ) and (21% sup 18 O sub 2 + 79% N sub 2 ) and the oxidized coal samples subsequently analyzed by means of pyrolysis mass spectrometry (Py-MS). Two different Py-MS methods were used; namely time-integrated Py-MS and time-resolved Py-MS. Furthermore, computerized multivariate analysis methods such as factor and discriminant analysis were used for data reduction as well as for the numerical extraction of underlying chemical tendencies in the data. The purpose of the experiments reported here is therefore to determine the fate of oxygen incorporated into the coal from the simulated ambient air as well as the role of preexisting oxygen functionalities in coal and to elucidate the structural changes due to the weathering process. 2 refs., 6 figs., 1 tab. (ERA citation 12:000030)