Chemical compositional and structural characteristics of Late Permian bark coals from Southern China

The characteristics of an unusual liptinitic component, known in Chinese petrographic nomenclature as barkinite, have been studied over the past 80 years. The chemical characteristics of barkinite have been studied for many years, but there has been little progress in establishing the chemical structural differences between barkinite and other liptinitic macerals of the same rank and age. In this paper, aspects of the chemical composition and structural characteristics of bark coal/barkinite are discussed. Bark coal is high volatile bituminous coal and has high volatile matter yield (>37%, daf, dry-ash free). The hydrogen content and H/C atomic ratio of barkinite are higher than those of vitrinite. The classification of barkinite would be type I–II kerogen. In addition, the chemical structure of barkinite is characterized by rich aliphatic structure concentration although dominated by aromatic structure. Chemical structural characteristics of barkinite seem close to vitrinite.