New insights into effect of the electrostatic properties on the interfacial behavior of asphaltene and resin: An experimental study of molecular structure

Abstract

Regardless of many attempts to identify asphaltene and resin interfacial phenomena, the complexity of their molecular structure increases the uncertainty about their interfacial behavior. This study aims to examine the effect of physicochemical properties of asphaltenes and resins and the concentration and type of dissolved ions in the aqueous phase on the interfacial interactions. First, the molecular structure parameters of the examined asphaltene and resin were compared using FTIR-ATR and elemental analyses. These results illustrate that the resin molecules rapidly occupy the interface because of the lower relative molecular mass and size. Next, the electrostatic properties of asphaltene and resin molecules were studied via zeta potential and (Isoelectric point) IEP measurements. From the generated laboratory data, new indexes were developed to provide a new understanding of polar sites on their surfaces. We showed that the activity of negative polar sites on the asphaltene and resin structure was higher than positive sites, which confirms that the effect of cations is crucial in the interfacial mechanisms. The interfacial tension (IFT) and zeta potential of the resin and asphaltene fraction were measured in solutions with different concertation of the MgCl2, CaCl2, and Na2SO4. It was observed that the ability of Mg2+ to reduce the IFT of the resin was more than that for Ca2+. This behavior was vice versa for asphaltene fractions.