An inverse liquid chromatography (ILC) technique was applied to evaluating the porous structure of coals. Swollen Morwell coal (C = 65 wt %, daf) or Pocahontas coal (C = 91 wt %, daf) particles were packed in a ILC column as the stationary phase, and -hexane (HEX) or tetrahydrofuran (THF) was used as the mobile phase. For any combinations of coals and carrier solvents, n-alkanes of C5-C22 that were used as the molecular probes eluted in the size-exclusion region. In the Pocahontas-HEX system, all probes eluted nearly at the size-exclusion limit. This indicates that there were few pores of 1-10 nm in that coal. In the Morwell-HEX and Morwell-THF systems, however, the elution volume was varied by the chain length of probes. Under the assumption that the elution was controlled by the steric-exclusion mechanism alone, the volume of pores into which pentane could penetrate was 0.04 and 0.83 cm3/g of coal for the Morwell-HEX and Morwell-THF systems, respectively. The swelling of Morwell coal by THF (swelling ratio = 2.15) created micro- and mesopores accessible to n-alkane molecules.
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