Regular coal structure and conversion severity

Abstract

In two separate coal conversion studies, one dealing with CO-water conversions of Illinois No. 6 coal, and the other with H 2S addition to conventional tetralin conversions of the lower-rank Wyodak 2, data have been collected over a range of conversion levels. For both studies the degrees of conversion were increased by increasing the reducing power of the medium, while the conversion temperature was kept constant at 400 °C for all runs. The conversion levels for the CO-water runs ranged from 29 to 60%, while the tetralin-H 2S runs yielded conversions from 44 to 67%. Sequential elution solvent chromatography and field ionization mass spectrometry were used for analyses of toluene-soluble fractions from the CO-water runs and THF-soluble fractions from the H 2S-tetralin runs, respectively. The analyses showed that the fraction compositions remained constant with increasing degrees of conversion. This finding suggests that there may be some gross regularity in the structure of coal. Moreover, the results here are in contrast to work reported earlier, in which increased conversion levels, reached through greater conversion temperatures, yielded products with successively increased condensation and aromatization. It is thus suggested that severity be considered in terms of two components. Thermal severity reflects the temperature/time component of conversion chemistry, and derives from simple Arrhenius behaviour of competing reactions, while reduction severity reflects only on the reducing power of the system.