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