The Effect of solvent type on wex precipitaion

Abstract

Wax depostion in sub-sea petroleum transportation pipelines causes significant operational problems. Paraffinic waxes precipitate at low temperatures from the crude oil which consist of various types of compounds. The preciptiation of wax in various solvent types was studied systematically in order to develop prediction model for wax precipitation temperature. Onset wax in various solvent types was studied systematically in order to develop prediction model for wax preciptiation temperature. Onset wax precipitation temperatures or clous point temperatures of both paraffinic wax and octacosane (n-C28) were measured in aromatic, cyclic and n-alkane solvents. For comparable solvent carbon numbers, cloud point temperatures are highest in aromatic solvents and lowest in cyclic solvents. The observed paraffin solubility behavior is a result of the dissimilarity of intermolecular interactions between aromatic solvent and n-alkane solute and the destruction of liquid phase orientational order by cycloalkane solvents. Thermodynamic model proposed by Coutinho (1999) was sound to provide the accurate cloud point temperature predictions for only the n-alkane solvent systems. A model modification was made in the liquid phase residual activity coefficient calculated from modified UNIFAC in order to improve the predictions in non-normal alkane solvents. The group interaction parameters for non-normal alkane solvents were estimated from n-C28 cloud point temperature data providing good prediction for both binary and multi-component systems.