KINETIC-STUDY OF ASPHALTENE DISSOLUTION IN AMPHIPHILE ALKANE SOLUTIONS/

The kinetics of dissolution of pentane-insoluble solid asphaltene prec ipitates by amphiphile/alkane solutions were investigated using a diff erential reactor flow system. Two amphiphiles, dodecylbenzenesulfonic acid and nonylphenol, and five alkane solvents, ranging from hexane to hexadecane, were used. Results showed that the rate of asphaltene dis solution in amphiphile/alkane fluids could be approximated with a firs t-order kinetics with respect to the undissolved asphaltene mass in so lution. The specific dissolution rate constant, k, varied with the con centration of amphiphiles, the type of alkane solvents, the temperatur e, and the fluid flow rate. The rate of asphaltene dissolution display ed a Langmuir-Hinshelwood kinetics with respect to the concentration o f amphiphiles. Increasing the temperature of amphiphile/alkane fluids also enhanced the rate of asphaltene dissolution. The apparent activat ion energy for asphaltene dissolution was approximated to be 4-7 kcal/ mol. The rate of asphaltene dissolution was also greater in amphiphile solutions containing lighter alkanes, such as hexane, with lower visc osities. These trends suggest that both surface reaction and mass tran sfer processes are important to the rate of asphaltene dissolution in amphiphile/alkane fluids.