Chemical characterization of insoluble macromolecules (Kerogen) from marine and lacustrine sediments –Molecular distribution of aliphatic dicarboxylic acids in alkaline KMnO₄ oxidation products–

Abstract

Insoluble macromolecules (kerogen) were isolated from 7 marine and 10 lacustrine sediment samples and subjected to alkaline KMnO₄ oxidation, followed by analysis of organic acids in the oxidation products. The major compounds consist of aliphatic C₄-C₁₅α, ω-dicarboxylic acids, n-C₇-C₂₈ monocarboxylic acids and benzene mono-to-polycarboxylic acids. The α, ω-dicarboxylic acids from lacustrine kerogens have a maximum at C₈ or C₉. Whereas those from marine ones show a shoulder in this carbon range, have a maximum at C₄ and decrease with increasing carbon number. This difference in the relative abundance of C₄ and C₈, C₉ α, ω-dicarboxylic acids may be due to different precursory materials in the different environments. This result is in accordance with our previous findindg, suggesting strongly that a portion of the chemical structures of kerogens from marine and lake environments is generally different from each other. A mathematical expression was proposed to visualize the feature of molecular distribution of α, ω- dicarboxylic acids from kerogens. In addition, it is shown by both alkaline CuO oxidation and KMnO₄ experiments that polymerized structure of polyhydroxy acids can be one of the precursors for α, ω-dicarboxylic acids from kerogens.