Effect Of N-Alkane Precipitants On Aggregation Kinetics Of Asphaltenes

The effect of different n-alkane precipitants on the kinetics of asphaltene aggregation is investigated in this study. When the chain length of the n-alkane precipitant, i.e., the carbon number, is increased, both the viscosity and solubility parameter of the solution increase and, as a result, the aggregation rate is expected to decrease. However, the actual behavior of the system is more subtle, and the aggregation rate can remain constant, increase, or pass through a maximum as the carbon number, n, increases. This behavior can be explained by the polydispersity of asphaltenes and the weaker precipitating power of longer chain n-alkanes. The polidispersity of asphaltenes is successfully characterized using their solubility parameter and the model developed in our previous study (Haji-Akbari, N., Masirisuk, P., Hoepfner, M. P., and Fogler, H. S. Energy Fuels 2013, 27, 2497-2505), where a universal relationship between the detection time and the differences in solubility parameters was established. The solubility parameter of the precipitated asphaltenes is shown to increase with increasing the chain length of the n-alkane precipitants and is successfully used to predict the aggregation rate of asphaltenes in blends of up to five different n-alkane precipitants.