Molecular accessibility in oxidized and dried coals. Quarterly report, [January 1, 1996--March 31, 1996]

The objective of this research project is to determine the molecular and structural changes that occur in swelled coal as a result of oxidation and moisture loss both in the presence and absence of light using our newly developed EPR spin probe method. The proposed study will make it possible to deduce the molecular accessibility distribution in swelled, oxidized Argonne Premium Coal Samples (APCS) for each rank as a function of (1) size (up to 6nm) and shape, (2) the relative acidic/basic reactive site distributions, and (3) the role of hydrogen bonding as a function of swelling solvents. The advantage of the EPR method is that it permits molecules of selected shape, size and chemical reactivity to be used as probes of molecular accessible regions of swelled coal. From such data an optimum catalyst can be designed to convert oxidized coal into a more convenient form and methods can be devised to lessen the detrimental weathering processes. Results of current study on changes in molecular accessibility in APCS coal oxidized in presence of sunlight show that accessibility to spin probes upon O-alkylation of the oxidized coal depends on the percent oxygen present before alkylation. An increase in microporosity occurs upon alkylation and this increase is more pronounced in higher rank than lower ranked coals. It was also observed that the increase in microporosity depends on the structure of each coal