Comparison of molecular properties of saturate and aromatic fractions of Turkish and Iraqi crude oil residues

Abstract

The chemical characterization of crude oil fractions is important for the petroleum research and complex structure of crude oil residue keeps studies ongoing. An analytical method which gives the composition of residue is not available yet and a combination of facile methods that elucidates the structure of residue is the most important in the petroleum research.This work reveals the detailed analyses of saturate and aromatic fractions of the selected crude oil atmospheric residues (ARs). Molecular structure of the saturate and the aromatic fractions was investigated by a combination of High-Performance Liquid Chromatography (HPLC) and nuclear magnetic resonance (NMR) spectroscopy techniques. In this study, saturate and aromatic fractions were physically divided into sub-fractions by HPLC and sub-fractions were examined in depth according to the hydrogen type using 1H NMR. Moreover, AR maltenes and their saturates were analyzed by High Temperature-Simulated Distillation (HT-SIMDIS), in order to deduce carbon number (CN) ranges of the AR distillation cut points in weight percentages. The study revealed the distribution of aliphatic and aromatic hydrogen types in sub-fractions of the saturates and the aromatics of the selected ARs. Mono, di- and tri-aromatic hydrogen types of each sub-fraction were also disclosed. For all sub-fractions, total aromaticity increases in the order of increasing elution sequence. Celikli AR maltene fraction has molecules that have CN in the range of 14–30 or less for half of its total weight and contains mostly low boiling structures.