Carbon isotope analysis and a solid state 13C NMR study of Mongolian lignite: Changes in stable carbon isotopic composition during diagenesis. (November 2017)

• Record Type: Journal Article
• Authors: Erdenetsogt, Bat-Orshikh; Lee, Insung; Ko, Yoon-Joo
• Is Part Of: Organic geochemistry. Volume 113(2017:Dec.)
• Page Start: 293
• Page End: 302
• Publication Date: 2017-11
• Subjects: Coal -- Carbon isotope -- NMR -- Mongolia; Organic geochemistry -- Periodicals; Biogeochemistry -- Periodicals; Géochimie organique -- Périodiques; 553.205
• DOI: 10.1016/j.orggeochem.2017.07.014
• Languages: English
• ISSNs: 0146-6380

Abstract

Highlights: Lower Cretaceous lignite samples studied. Correlation between carbon isotopic composition and chemical structure found. Mechanism controlling the changes in δ 13 C value of lignite proposed. Abstract: The results of a combined carbon isotope analysis and NMR study of a set of lignite samples from Mongolia show that a correlation exists between δ 13 C value and the ratios of oxygenated carbon (O-aliphatic, carboxyl/carbonyl and O-aromatic carbons) over protonated and carbon substituted aliphatic and aromatic carbons. The results indicate that the δ 13 C values of the lignite are controlled by two mechanisms: (i) Depletion in 13 C as a result of loss of isotopically enriched O-bonded carbons and (ii) enrichment in 13 C caused by a loss of isotopically depleted CH4 from aliphatic and aromatic carbons. At the rank of lignite, coal is enriched in 13 C because the amount of isotopically enriched CO2 and CO, released from coal as a result of change in chemical structure, is less than that of isotopically depleted CH4 .