Vacuum pyrolysis of Recent sedimentary humic acids and kerogens.

Abstract

Humic acid and kerogen samples isolated from some Recent sediments of different environments were analyzed by vacuum pyrolysis to characterize their chemical nature. The samples were pyrolysed at 500°C in vacuo (about 10-2 Torr.). Gravimetric and elemental analyses of the pyrolysis residue indicated that the pyrolytic degradation resulted in the loss of carbon and nitrogen in the range of 35–53% and 53–68%, respectively. The pyrolysate was trapped and extracted with chloroform. It was fractionated using silica gel and Ag+-impregnated silica gel column chromatography. Subsequent gas chromatographic analyses enabled quantification of n-alkane and n-alkene homologues. Generated straight-chain hydrocarbons (≥C14) amounted to about 1–4mg per g carbon in the humic acids and to about 2–20mg per g carbon in the kerogens. The potential of the technique to characterize the chemical nature of the humic materials is discussed.