A Novel Solid-Liquid Equilibrium Model for Describing the Adsorption of Associating Asphaltene Molecules onto Solid Surfaces Based on the "Chemical Theory"

Asphaltenes exhibit an amphiphlic behavior and tend to form colloidal i-mers, because of their chemical structure. The formation of colloidal aggregates can generate formation damage for the precipitation and/or deposition of asphaltenes, because of the degree of self-association, altering the wettability of rock surface and significantly affect crude oil viscosity and specific gravity. This study aims at introducing a novel model for describing, at the macroscopic level, the adsorption equilibria of self-associating molecules such as asphaltenes in solution onto solid surfaces based on the "chemical theory". The model describes the adsorption isotherms temperature-dependent using three parameters, namely, maximum amount adsorbed, constant of i-mer reactions, and Henry's law constant. Furthermore, a temperature-independent model of five parameters, based on the modifications of the constants of reaction and Henry's law using an Arrhenius-type equation was proposed for estimating the thermodynamics parameters, such as Delta G(ads)(o), Delta H-ads(o), and Delta S-ads(o) of the adsorption process. This model improves the understanding of interactions asphaltene-asphaltene and asphaltene-solid surface on the adsorption-equilibrium process. The theoretical predictions of isotherms were validated successfully by determining the root mean-square errors (RSM%) between data obtained from published literature and values predicted for asphaltenes and surfaces with differing chemical natures. More than 40 experimental data taken from literature have been used for validating the solid-liquid equilibrium (SLE) model for describing the adsorption isotherm of asphaltenes from different origins on surfaces with different chemical nature, which shows the model robustness due to the complexity of the liquid phase adsorption for those complex molecules.