An investigation of polar constituents in kerogen and coal using pyrolysis-gas chromatography-mass spectrometry with in situ methylation

Pyrolysis-gas chromatography-mass spectrometry (Py-GC-MS) combined with in situ methylation using aqueous tetramethylammonium hydroxide (TMAH) has been employed in a study of oxygen-containing organic constituents in a solvent-extracted Victorian brown coal (Australia) and two Eocene oil shales (Rundle Formation, Australia and Green River Formation, U.S.A.). Thermally assisted chemolysis of the coal with TMAH yielded assorted products including an homologous series of fatty acid methyl esters (FAMEs), methyl ether derivatives of long-chain alcohols and methylated n-ω-hydroxycarboxylic acids. Alkylated benzenecarboxylic acids and other polyfunctional lignin-derived phenolic moieties were also identified, providing additional compositional information not accessible using conventional Py-GC analysis. FAMEs were the major compounds released after pyrolysis/methylation of the extracted oil shales. Results obtained generally suggest that flash chemolysis/alkylation of macromolecular sedimentary organic materials is especially suitable for the elucidation of hydrolyzable entities, namely, esters, as well as certain other oxygenated species which are prone to defunctionalization under pyrolysis conditions.