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

摘要

Highlights?Lower Cretaceous lignite samples studied.?Correlation between carbon isotopic composition and chemical structure found.?Mechanism controlling the changes in δ13C value of lignite proposed.AbstractThe results of a combined carbon isotope analysis and NMR study of a set of lignite samples from Mongolia show that a correlation exists between δ13C 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 δ13C values of the lignite are controlled by two mechanisms: (i) Depletion in13C as a result of loss of isotopically enriched O-bonded carbons and (ii) enrichment in13C caused by a loss of isotopically depleted CH4from aliphatic and aromatic carbons. At the rank of lignite, coal is enriched in展开▼