Characterization of Petroleum Heavy Oil Fractions Prepared by Preparatory Liquid Chromatography with Thin-Layer Chromatography, High-Resolution Mass Spectrometry, and Gas Chromatography with an Atomic Emission Detector

In this study, a preparatory-scale fractionation method was developed. To verify the effectiveness of this method, an oil sample was fractionated into five fractions, referred to as saturate, aro1, aro2, polar1, and polar2; these fractions were completely characterized by thin-layer chromatography-flame ionization detection (TLC-FID), field desorption (FD) and (+) atmospheric pressure photoionization (APPI) high-resolution mass spectrometry (HR-MS), and gas chromatography with an atomic emission detector (GC-AED). TLC-FID analysis was used to compare the results obtained by the fractionation method to those obtained from the conventional saturates, aromatics, resins, and asphaltenes (SARA) method. FD-MS was employed to characterize the hydrocarbon class compounds in the saturate and aro1 fractions. As observed from the FD-MS spectra, non-aromatic hydrocarbon compounds were abundant in saturates, while mono- and diaromatic compounds were abundant in the aro1 fraction. This result is in good agreement with those obtained by HR-MS. (+) APPI HR-MS analysis of fractions showed that aromaticity increases from saturates to the polar1 fraction but decreases in the polar2 fraction. Heteroatom class distributions investigated by (+) APPI HR-MS showed that non-basic nitrogen compounds were abundant in polar1, while non-aromatic sulfur compounds were abundant in the polar2 fraction. From the results obtained by the GC-AED analysis of fractions, nickel porphyrin compounds were concentrated in the polar1 fraction. Hence, the combined results clearly demonstrate that the fractionation method is effective for isolating fractions on a preparative scale.