Reactivity and Nature of Free Radicals in Catalytic Coal Oxidation: Final Report, September 1, 1984-August 31, 1987

摘要

Pyrolytic and oxidative treatments of three coals, Illinois No. 6, Montour, and Adaville No. 1, have been performed between 349 and 583 K. Free radical concentrations were followed by electron spin resonance as a function of time of treatment at a given temperature. Initial increases in the organic free radical concentrations were observed at all temperatures, but at the higher temperatures termination reactions caused the increase to be transient. The decay of free radicals generated at 583 K in the Illinois No. 6 coal proceeded by a first order reaction, in contrast to the second order free radical decay under near-ambient conditions. With a low mineral-containing subbituminous Adaville No. 1 coal, the process of flowing air over the coal at low temperatures, 349-418 K, resulted in the generation of about twice as many free radicals as when the treatment gas was nitrogen. The mild oxidation of Montour coal by air in a fluidized-bed reactor has been studied by utilizing XRD, scanning electron microscopy accompanied by energy dispersive x-ray analysis, and Moessbauer spectroscopy. These techniques show that some of minerals in Montour undergo changes concurrently with the reactions of the coal matter. Oxidative transformations of iron minerals in a heavily weathered Illinois No. 6 coal were investigated by Moessbauer spectroscopy and x-ray powder diffraction (XRD). Temperature ranges were determined for the conversions of pyrite to ferrous sulfate and ferric hydroxysulfate and of ferric hydroxysulfate to ferric oxysulfate and ferric oxide. Most pronounced mineral transformations occurred at temperatures greater than or equal to563 K. This is the temperature range at which extensive weight loss of the organic coal matter began. 129 refs., 62 figs., 7 tabs. (ERA citation 13:024068)