title: A model to calculate the average interaction energy and adhesion force between petroleum asphaltenes and some metallic surfaces.
abstract: A model is proposed to account for the interaction energy and adhesion force between petroleum asphaltenes and metallic surfaces. It is assumed that the total molecule-surface interaction potential may be constructed through superposition of corresponding interactions with a relevant number of atomic layers forming the substrate and resorting to the Lindhard continuum planar potential (CPP) approximation, which requires only of knowledge of binary molecule-atom interactions. Molecular mechanics (MM) calculations are performed to generate the average binary interaction between the asphaltene molecule and an atom in the substrate, which in turn is represented by a parameterized analytical--physically sound--expression. The resulting CPP yields an analytical expression representing the interaction between the asphaltene molecule and each substrate layer. To validate the method, pilot calculations are performed for a sample asphaltene molecule with a fixed orientation relative to metallic surfaces of iron, aluminum, and chromium. Comparison between corresponding CPP and MM calculations for the asphaltene-plane (A-P) and asphaltene-substrate (A-S) interactions indicate reasonable agreement pointing to the adequacy of the CPP method to represent molecule-surface interactions. Also, the effect of a surrounding (i.e., solvent) medium is addressed with the use of a dielectric constant, epsilon, incorporated in the molecule-atom potential. Finally, a discussion is presented on the applicability of the method to generate an analytical universal expression for asphaltene-metallic wall interactions.
authors.affiliation: Mexican Institute of Petroleum, Eje Central Lazaro Cardenas 152, Mexico 07730, Mexico.
authors.forename: A
authors.initials: A
authors.lastname: Ortega-Rodriguez
authors.forename: F
authors.initials: F
authors.lastname: Alvarez-Ramirez
authors.forename: S A
authors.initials: SA
authors.lastname: Cruz
authors.forename: C
authors.initials: C
authors.lastname: Lira-Galeana