Characterization of paraffinic hydrocarbon fraction of Nigerian bitumen using multivariate analytical techniques

Abstract

Nigerian bitumen paraffinic hydrocarbon (PH) fraction was analyzed to establish the characteristics which might aid the developmental processes of the natural resource. Bitumen samples extracted from the oil sands were deasphalted and paraffinic hydrocarbons (PHs) eluted by column chromatography. The organic components of the PHs were investigated using Fourier transform infrared (FT-IR) spectrometry and Gas chromatography (GC); elemental concentration was determined using Atomic absorption spectrometry, while physical properties by standard methods. The IR spectra showed mainly the presence of CH(CH₃) and CH(CH₂) functional groups, indicating high purity of the samples. Thirty-one organic compounds were identified and quantified by GC. The PHs had a mean carbon preference index value of 1.035, indicating that the PHs were thermally matured and of petrogenic origin. Principal component analysis using the organics’ concentrations as variables indicated that the compounds had similar chemical properties, common sources, and/or maturation age. Elemental concentrations of the PHs were generally low compared with other fraction of Nigerian bitumen and were confirmed by their T-test values which indicated significant difference. Elemental cluster analysis showed two groups which were fairly correlated indicating similar sources and/or chemical affinity. The PHs V/Ni ratio 0.10–1.88 (1.12 was close to that of Nigerian bitumen 0.45–2.28 (1.12) which was higher than the average value (0.16) obtained for Nigerian crude oil, while V/V + Ni ratio 0.09–0.65 (0.50) obtained in this study is also close to 0.31–070 (0.50) obtained for Nigerian bitumen. Color of the PHs ranged from colorless to off-white. Values of the analyzed physical parameters confirmed that the PHs contained relatively high concentration of carbon and would tend to burn slower in the combustion chamber of an engine. The study also provided useful information on conversion mechanism and environmental implications of the development of the fossil fuel.