The Effect of Asphaltenes, Naphthenic Acids, and Polymeric Inhibitors on the Pour Point of Paraffins Solutions

Abstract

The influence of asphaltenes and naphthenic acids on wax appearance temperature (WAT), wax crystals morphology, and pour point was estimated for solutions of a commercial paraffin sample dissolved in a solvents mixture. In addition, the performance of copolymers obtained by modification of ethylene‐vinyl acetate copolymers as organic deposition inhibitors (ODI) also was studied. Asphaltenes reduced the pour point and this effect increased with the increase in the asphaltenes concentration, indicating that asphaltenes interact with the paraffins to form particles with a different interaction profile. The observation of the wax crystals using optical microscopy revealed that in the absence of additives the solid wax particles form a homogeneous mass, evenly distributed throughout the whole sample having a plane lamellar structure which favor aggregation. When asphaltenes were incorporated, the particles were smaller and less well defined. At higher asphaltenes concentrations, dark particles whose surface resembled asphaltenes also were observed. Naphthenic acids caused a small increase in the pour point and when both fractions, asphaltenes and naphthenic acids, were added together, the asphaltenes seem to have their pour point reduction effect depressed. The ODI presented some efficiency as pour point reducers but, in the presence of asphaltenes, this efficiency was largely enhanced suggesting that beside the alteration of the particles an efficient dispersion mechanism is also necessary to inhibit the aggregation of the wax particles.