PYROLYSIS-GAS CHROMATOGRAPHY MASS-SPECTROMETRY OF ASPHALTENE FRACTIONS

Two n-heptane-precipitated asphaltene samples, characterized by elemental analysis and nuclear magnetic resonance spectrometry, were fractionated according to relative molecular size by gel permeation chromatography (GPC). Both the whole asphaltene samples and their fractions were analysed by pryolysis/gas chromatography/mass spectrometry. The data obtained from the pyrograms (average side-chain length, aromaticity index, sulphur compounds vs. aliphatic compounds, presence of SO2 and CO2) demonstrated that, in the case of asphaltenes, GPC fractionation results in the separation of different chemical structures ranging from lower molecular mass, highly aromatic and polar compounds to higher molecular mass, less polar and aromatic compounds.