Spectroscopic Characterization of Asphaltene Fraction of Nigerian Bitumen

摘要

This research article offers data on the spectroscopic elucidation of the asphaltene fraction of Nigerian bitumen in order to establish its features that might aid the developmental processes of the fossil fuel. Bitumen was extracted from the oil sands obtained from six locations where there were oil sand out-crops in Southwestern Nigeria using toluene via Soxhlet extraction and then deasphalted using n-pentane. The organic components of the precipitated asphaltenes were investigated using Fourier transform infrared spectrometry, while the elemental contents were determined using Inductively coupled plasma atomic emission spectroscopy and carbonitrogen analyzer. The results revealed that the average content (29.15 wt%) of Nigerian bitumen asphaltenes was less than that of Athabasca (40.10 wt%) but slightly higher than that of Cold Lake bitumen (24.40 wt%). The IR spectra of the asphaltenes indicated the presence of various organics and heteroatoms corroborating that asphaltenes composed of high molecular weight polycyclic constituents comprising of nitrogen, sulfur, and oxygen heteroatoms. The results indicated that the values of Cr, Cu, Fe, Mn, Ni, S, V, and Zn were comparatively higher in the asphaltenes than the parent bitumen due to the presence of comparatively high levels of porphyrins in the asphaltenes than the bitumen, while the concentrations of all the elements were higher in the Nigerian bitumen asphaltene than Nigerian crude oil asphaltene (except S and C). Cross plot analysis result between the asphaltenes and bitumen using their elemental mean concentrations as variables indicates that significant and positive correlation (R-2 = 0.975) exists between them, indicating very strong interelement and geochemical relationships between them. The elements showed close clustering, indicating similar sources because the elements were known to associate with petroleum hydrocarbon formation. Also, apart from N, S, and C, other elements are transition metals with similar chemical affinity.