Energy & Fuels, Vol.22, No.4, 2429-2436, 2008
Variations in bulk kinetic parameters of sulfur-rich asphaltenes isolated with different n-alkane solvents from heavy crude oils
Asphaltenes from three heavy sulfur-rich crude oils from southern Italy were precipitated using n-pentane, n-hexane, and n-heptane to investigate the influence of alkane solvent chain length on asphaltene kinetics and resulting geological predictions. These asphaltenes were subjected to artificial open-system maturation experiments. The chain length of the solvent has an effect on the properties of precipitated asphaltenes from sulfur-rich crude oils that impact geological predictions of hydrocarbon generation. Asphaltenes isolated with n-heptane yield kinetic models with lower activation energies and lower predicted temperatures of hydrocarbon generation under geological conditions compared to the other n-alkane solvents. Asphaltenes isolated with different n-alkane solvents show slight changes in pyrolysate concentrations of GC-unresolved compounds and the amount of organic sulfur compound upon pyrolysis. These observed slight differences in asphaltene pyrolysates cannot directly explain the differences in bulk kinetics found for those asphaltenes. The study shows at least that differences exist in kinetic models that are associated with sulfur-rich asphaltenes from the same and related oils and that these differences may have a significant impact upon using such models in geologic predictions.