Characterization of Virgin Asphaltenes and its Subfractions using UV-Visible and FTIRSpectroscopy

Abstract

Spectroscopic characterization of asphaltene is necessary in order to understand the changes it undergoes when heavy and extra-heavy oil types such as bitumen are subjected to catalytic aquathermolysis. The structural composition of asphaltene and its subfractions were investigated using UV/Visible and FTIR Spectroscopy. Raw bitumen sample was obtained from the bitumen deposit at Mile 2 in Odigbo, Ondo State, Nigeria. The sample was purified and the asphaltene fraction was precipitated with n-hexane, the precipitated asphaltene was fractionated into fractions A and B based on their difference in solubility and polarity with hexane/toluene mixture at a fixed ratio. The results showed that virgin asphaltene and their subfractions absorbed light of a longer wavelength in the range (465 640 nm), indicating that they are made up of polynuclear aromatic compounds. The results also revealed the presence of alkyl side chains and major oxygenated groups in both virgin asphaltene and its subfractions (A and B). In general, asphaltene are a complex molecular compound that consists of aromatic moieties with alkyl side chains, polar groups (esther, ether, and carbonyl), acidic and basic groups (carboxylic and pyridine) which can interact at a certain pH range by accepting or donating protons.