Structural characterization of vitrinite-rich and inertinite-rich Permian-aged South African bituminous coals

✍ Scribed by Daniel Van Niekerk; Ronald J. Pugmire; Mark S. Solum; Paul C. Painter; Jonathan P. Mathews

• Publisher: Elsevier Science
• Year: 2008
• Tongue: English
• Weight: 721 KB
• Volume: 76
• Category: Article
• ISSN: 0166-5162
• DOI: 10.1016/j.coal.2008.08.014

✦ Synopsis

Two South African coals of the same rank and age, but different in maceral composition were subjected to extensive structural analyses. Inertinite-rich Highveld coal (dominated by semifusinite) and vitrinite-rich Waterberg coal were studied to determine structural differences and similarities. The two coals had similar carbon content (∼ 84%, dmmf) and vitrinite reflectance (mean-maximum 0.71% for vitrinite-rich vs. 0.75% for inertinite-rich), but differed in hydrogen content (6.23% for vitrinite-rich and 4.53% for inertinite-rich). The inertinite-rich coal was more aromatic (86% for inertinite-rich and 76% for vitrinite-rich) and more polycondensed (indicated by a higher bridgehead carbon content). The inertinite-rich coal was structurally more ordered, with a higher degree of crystalline stacking. Both coals had similar average aromatic cluster sizes (16 carbons for vitrinite-rich and 18 carbons for inertinite-rich) and number of cluster attachments (6 attachments for vitriniterich and 5 attachments for inertinite-rich). Mass spectrometry showed that both coals consist of similar molecular weight distributions; ranging to approximately 1700 m/z with a maximum abundance of ∼450 m/z for the vitrinite-rich coal and ∼550 m/z for the inertinite-rich coal. Compared to the Argonne Premium coals the South African vitrinite-rich Waterberg coal was comparable to the coals in the high-volatile bituminous range and inertinite-rich Highveld was closer to the medium-to low-volatile bituminous range. Both coals were surprisingly similar in bulk characterization, although inertinite-rich Highveld coal was structurally more ordered, hydrogen deficient, and more aromatic.