Structural Composition and Molecular Weight Distribution of Dissolved Organic Matter in Bituminous Oil Sand from Okitipupa, Southern Nigeria

The structural and exact molecular weight composition of the dissolved organic matter present in the oil sand from Okitipupa was investigated. Microscopic and spectroscopic methods were employed to determine the mineral composition and molecular structure of the compounds detected in the extracted bitumen. The extracted composite (dichloromethane/toluene solvent (D:T) ratio was 1:1 (50 mL each) and the sample-to-solvent ratio was 1:2.5 at 60 °C and 300 r/min. Elemental quantification of the oil sand from P1 (Loda) and P2 (Idiopopo) indicated a vast interaction of bitumen with clay minerals through their forms and compositions. The highest extractive quality of the compounds was obtained from P1 using 50:50 D:T extraction. P1 indicated an appreciable percentage of organic compounds with a maximum number of asphaltenes and aromatics as major components of bitumen, saturates, and resin. In P1, high concentrations of heteroatoms like nitrogen, oxygen, sulfur, and metals contributed to an increase in the viscosity and bonding of bitumen with embedded minerals compared to others. Oil sand in this region consists of complex heteroatomic compounds. Meanwhile, the van Krevelen plot revealed that the majority of formulas are in the regions H/C 0.5–2.5 m/z and O/C 0.1–0.5 m/z, which confirmed the diversity in the distribution of mass formulas for the samples. This revealed an important suggestion for understanding the geochemistry and exploitation of bitumen.