Comprehensive two-dimensional liquid chromatography of heavy oil

Heavy oil refers to the part of crude oil that is not amenable to further distillation. Processing of these materials to useful products provides added value, but requires advanced technology as well as extensive characterization in order to optimize the yield of the most profitable products. The use of comprehensive two-dimensional liquid chromatography (LC × LC) was investigated for the characterization of de-asphalted short residue, also called maltenes. Initial studies were performed on a polycyclic aromatic hydrocarbon standard, an aromatic extract of hydrowax, and the fractions obtained after solvent fractionation of the maltenes. Cyanopropyl- and octadecyl-silica were used as first-dimension and second-dimension columns, respectively. The analysis of the maltenes and fractions thereof required a change in first-dimension stationary phase to biphenyl as well as an increase in modifier strength to improve recovery. The extensive characterization of maltenes with LC × LC within four hours was demonstrated. The Program for the Interpretive Optimization of Two-dimensional Resolution (PIOTR) has been applied to aid the method development, but due to the absence of specific peaks in the chromatograms it was challenging to apply to the maltenes or its fractions. Nonetheless, an approach is suggested for resolution optimization in cases such as the present one, in which regions of co-elution are observed, rather than clearly separated peaks.