Thermally assisted hydrolysis and methylation of kerogen-like organic matter in a recent sediment off the Danube delta (northwestern Black Sea)

Abstract

The kerogen-like organic matter (KL) isolated from the surface section of a recent sediment core off the Danube delta was analysed by flash pyrolysis in the presence of tetramethylammonium hydroxide (TMAH). The main compounds released from KL were lignin-derived phenols arising from the cleavage of the β-O-4 ether bonds. Aromatic units — methyl esters of benzenecarboxylic acids — occurred in major amounts and corresponded to cinnamyl, guaiacyl and syringyl units. The thermal degradation products also consisted of aliphatic series such as methyl esters of C 5–C 30 fatty acids, branched aliphatic acids, and α,ω-alkanoic diacids. Several nitrogen-containing compounds identified as both nitrogenous heterocycles and methylated amino acids were detected in the TMAH thermochemolysate. These results are compared to those of conventional flash pyrolysis previously performed, and the important qualitative and quantitative differences thus noted are discussed along with additional information on the chemical structure of KL and sources derived from thermally assisted hydrolysis and methylation (THM) with TMAH.