Thermodynamics and kinetics of aqueous solution of liquid hydrocarbon mixtures (solutes, petroleum)

• Main Author: Burris, David Robert.
• Format: Others
• Language: English
• Published: W&M ScholarWorks 1985
• Subjects: Geochemistry; Physical Chemistry
• Online Access: https://scholarworks.wm.edu/etd/1539616591; https://scholarworks.wm.edu/cgi/viewcontent.cgi?article=2159&context=etd

Two-phase systems of a liquid hydrocarbon mixture, containing medium molecular weight (C(,7)-C(,12)) aromatic and aliphatic hydrocarbons, and water were examined in both equilibrium and kinetic experiments. Knowledge of the aqueous solution behavior of liquid hydrocarbon mixtures is of importance in determining the fate of hydrocarbon components in such systems of an environmental or geologic nature. Solute concentrations were determined by solvent extraction followed by gas chromatography. The equilibrium solute concentration for a given component i (C(,i)) is related to the pure compound solubility (C(,i)('o)), mole fraction of component i in the hydrocarbon phase (x(,i(h))) and the activity coefficient of component i in the hydrocarbon phase ((gamma)(,i(h))) by the following: C(,i) = x(,i(h))(gamma)(,i(h))C(,i)('o). (gamma)(,i(h)) values determined for binary hydrocarbon mixtures using static vapor pressure measurements (at 20 and 70�C) and (gamma)(,i(h)) values determined using water solubility results (at 20 and 70�C) and the above equation did not differ significantly. This finding indicated that component aqueous phase activity coefficients do not decrease measurably in the presence of hydrocarbon co-solutes, in contradiction to Leinonen and Mackey, 1973 and Leinonen, 1976, and that the presence of water in the hydrocarbon phase is not a significant parameter at these temperatures. Some of the hydrocarbon systems (20�C) examined were: n-octane + 1-methylnaphthalene (also 70�C); tetralin + methylcyclohexane; ethylbenzene + n-octane; methylcyclohexane + 1-methylnaphthalene; 1,4-dimethylnaphthalene + n-octane; methylcyclohexane + n-octane; 1,4-dimethylnaphthalene + 1-methylnaphthalene; a 12-component JP-4 simulated jet fuel mixture and a 12-component JP-8 simulated jet fuel mixture. Methods for predicting multicomponent liquid hydrocarbon mixture solubilities were investigated. Non-equilibrium solutions resulting from water in contact with a liquid hydrocarbon mixture have solute concentration ratios that are essentially the same as those found under equilibrium conditions assuming that the hydrocarbon phase composition did not change substantially in the process. A surface renewal mass transfer model is used to explain this result. The mass transfer model can also be used to help explain non-equilibrium solute concentrations resulting from water in contact with a hydrocarbon phase of changing composition due primarily to evaporation.