Structural relationships between humic fractions from peat and lignites from the Miocene Granada basin

Abstract

Fulvic acids, humic acids and humins, isolated from two closely situated peat and lignite deposits, have been examined by solid-state 13C NMR and analytical pyrolysis. No marked structural differences were found between the humic fractions from the various deposits, suggesting a common origin. Within each deposit some distinguishing structural characteristics were observed between the humic fractions. The differences observed showed that the loss of carbohydrate and lignin during the early coalification process led to the accumulation of a predominantly polyalkyl, kerogen-like residue. The humin fractions from both materials contain the greatest amounts of aromatic structures, although they also present high proportions of aliphatic components. Thus, their NMR spectra consist almost exclusively of alkyl and aromatic hydrocarbon entities. This agreed with the results of pyrolysis, which reflected the presence in humins of condensed alkyl material.