Elemental composition and molecular structure of Botryococcus alginite in Westphalian cannel coals from Kentucky

Abstract

Botryococcus-derived alginites from the Westphalian Skyline, No. 5 Block, Leatherwood (eastern Kentucky) and Breckinridge (western Kentucky) coal beds have been analyzed for elemental composition and functional group distribution using an electron microprobe and micro-FTIR, respectively. The alginites from Kentucky show a carbon range of 81.6 to 92% and oxygen content of 3.5 to 9.5%. Sulphur content ranges from 0.66 to 0.84% and Fe, Si, Al and Ca occur in minor quantities. FTIR analysis demonstrates dominant CH 2, CH 3 bands and subordinate aromatic carbon in all alginites. The major differences between alginites are in the ratios of CH 2 and CH 3 groups and ratios between aromatic bands in the out-of-plane region. These differences suggest that, although the ancient Botryococcus derives from a selective preservation of a resistant polymer, it undergoes molecular and some elemental changes through the rank equivalent to vitrinite reflectance of 0.5–0.85%. Other differences, such as intensities of ether bridges and those of carboxyl/carbonyl groups, are attributed to differences in depositional environments.