Asphaltene Adsorption on Different Solid Surfaces from Organic Solvents

Abstract

Adsorption of asphaltenes at liquid-liquid and solid-liquid interfaces is an undesirable phenomenon and considered to be the major contributor to several complications found in petroleum industry. Although the adsorption of asphaltenes on mineral surfaces has been extensively studied, little work has been performed on the adsorption of asphaltenes on metal surfaces. There remain some inconsistencies in findings reported in the literature and several unanswered questions regarding these topics. In this study, the adsorption of asphaltenes on different solid surfaces from toluene and heptane/toluene (1:1 volume mixture) solutions was investigated. UV-Vis spectrophotometry was used to study the adsorption of asphaltenes on particles with different surface areas, chemical compositions and morphology (SiO2, Al2O3, kaolinite, and stainless steel). Adsorption of asphaltenes on solid particles was found to be highly sensitive to the aromaticity of organic solvents and the type of particles. In toluene, the equilibrium adsorption data were fitted better by the Langmuir isotherm model. In heptol, asphaltene adsorption on particles studied showed a continuous increase with asphaltene concentrations and exhibited Freundlich type adsorption isotherms. To investigate the adsorption kinetics of asphaltenes and the structural properties of the adsorbed layer(s) onto different surfaces (SiO2, Al2O3, Fe3O4, and stainless steel) coated on quartz crystals surfaces, a sensitive technique of Quartz Crystal Microbalance with Dissipation (QCM-D) was used. The adsorption process was identified as being rapid and able to form rigid film(s). It was found that the amount of asphaltenes desorbed represents less than 10 % of the mass of asphaltenes adsorbed. The adsorption capacity of asphaltenes on the surfaces investigated was also found to be strongly dependent on the quality of the solvent and type of solid surfaces. Carboxylic, pyrrolic, and thiophenic functional groups were identified to play a critical role in the interactions between asphaltenes and the solid surfaces investigated.