Molecular accessibility in solvent swelled coals. Quarterly report, [September--November, 1993]

This quarter, experiments were performed on the use of binary swelling solvents in molecular accessibility in coal conversion. These experiments consisted of accessibility measurements of spin probe VII (TEMPAMINE) in Toluene swelled Illinois No. 6 APCS coal. The toluene was spiked with amounts of pyridine which ranged in concentration from 500 ppm to 10%. The experiments were done in triplicate to gain information about the experimental error involved in the procedure. It was shown that oscillations occur in the concentration of spin probe retained as the amount of pyridine that is added to the swelling solvent is increased. These oscillations decrease in intensity as the concentration of pyridine in the solvent solution is increased up to 2% pyridine (0.2mLs pyridine in 10mLs toluene). From a 2% pyridine concentration to a 5% concentration, there is no significant change in the retention of spin probe VII. An increase in retention is observed when the concentration of pyridine is increased to 6% and 7% successively, followed by a large decrease at 8% and 9% pyridine. The largest changes in spin probe retention are observed for concentrations of pyridine less than 0.5%. A three fold increase in spin probe retention is observed upon the addition of 500 ppm pyridine in the toluene swelling solvent, which indicates that small amounts of a strong swelling solvent could be used to improve molecular accessibility 91% in coals swelled in an otherwise weak swelling solvent.