Low temperature swelling of Argonne premium coal samples: effect on micropore shape and size

Changes in the pore structure of Argonne premium coal samples (APCS) upon slurrying at different temperatures with either toluene, nitrobenzene or pyridine were followed using an electron paramagnetic resonance (e.p.r.)-spin probe method. Coals swelled in toluene at 298 K and 333 K exhibited both spherical and cylindrical pores. Upon swelling with polar solvents, spherical pores disappeared due to pore elongation. The degree of pore elongation increased with swelling temperature and swelling solvent polarity. This change in pore structure was attributed to break-up of the hydrogen bonding network in coal by polar solvents. The change in pore shape from spherical to cylindrical was attributed to anisotropy in hydrogen bond densities, and a model was developed to show this change.