Interaction and solubilization of water by petroleum asphaltenes in organic solution

The relation between the often reported micellization of petroleum asphalte nes in organic solvents and the content of trace water in the solvent was i nvestigated using calorimetric titration. The content of trace water in tol uene (ranging from 0 to 0.047%) was found to be the driving force in establ ishing a measurable critical micelle concentration in the concentration ran ge between 0.2 and 8 g/L solvent. It was determined that, for the three dif ferent asphaltenes analyzed, the calorimetric trace in the presence of 0.01 8 water more likely indicates a stepwise association rather than a classica l micelle formation mechanism. On the basis of this result, the solubilizat ion of water into solutions of asphaltenes in toluene was studied, and a qu asi-linear relation between asphaltene concentration and water uptake was o bserved. From this, the Gibbs free energy of the transference of water into the solution or asphaltene micelle was determined to be around -13.4 kJ/mo l at 293 K, which is in the range of hydrogen bonding formation. The solubi lity of asphaltene in toluene was observed to decrease significantly in wat er-saturated toluene at room temperature. Finally, the addition of resins ( petroleum polar components) to the asphaltene system was found to eliminate the break in the curve previously assigned to CMC. These findings are impo rtant for the further understanding of asphaltene self-association, floccul ation, and deposition in the oil industry.