A KINETIC INVESTIGATION OF COAL-LIQUEFACTION AT SHORT REACTION-TIMES

Coal liquefaction kinetics have been studied at very short reaction ti mes (less than 250 seconds) in order to emphasize the initial underlyi ng physical and chemical processes involved. These studies were made p ossible by the use of a continuous flow stirred tank reactor (CSTR) wh ich avoids the problems of slow heat up and cool down associated with the massive equipment required for running high-temperature and high-p ressure liquefaction reactions. Preliminary physical (NMR and ESR) and chemical analytical results are presented on the coal liquids and rea ction residues from Illinois No. 6 hnu bituminous and Wyodak Black Thu nder subbituminous coals. ESR results showed that radical concentratio n in the solid residue changed during coal liquefaction. These changes were accompanied by changes in the NMR-derived aromaticity. The rate of decrease of organic-based radicals was different for Wyodak Black T hunder and Illinois No. 6 coals, perhaps indicating a different mechan ism for the quenching of radicals in these bituminous and subbituminou s coals. NMR spectra of the liquid products indicated that the initial ly produced material was relatively aromatic, and that subsequent prod ucts had lower aromatic content. This is consistent with secondary hyd rogenation of the primary liquefaction products. Finally, the total ox ygen contents of the coal residues decreased gradually during the firs t three minutes of coal liquefaction at 390-degrees-C. A corresponding decrease in the hydroxyl content of these residues was also noted.