Designing High-Performance Rejuvenators: A Theoretical Approach to Asphaltene Dimer Aggregation and Disaggregation

Abstract

The aging process of asphalt materials encompasses varying levels of oxidation reactions within its components. This process increases the polarity of the molecules, prompting aggregation among asphaltenes. Thus, a thorough examination of asphaltene molecule aggregation and disaggregation patterns holds vital implications for the performance restoration of aged asphalt. According to the density functional theory (DFT), the interaction form between oxidized asphaltene dimers was inferred by electrostatic potential (ESP) and confirmed through the charge density difference. This study identified asphaltene dimers optimal configurations via energy minimization principles and determined the factors influencing aggregation based on interaction energy. On the basis of the molecular structure design theory, the basic structures of three different rejuvenators—chain alkanes, aromatic hydrocarbons, and cycloalkanes—were constructed. Functional groups such as hydroxyl, carboxyl, ether, ester, and amide were incorporated to explore the disaggregation patterns of oxidized asphaltene dimers induced by varying rejuvenator structures. Our results revealed that asphaltene molecules form dimers through the π-π stacking interaction of aromatic rings and the electrostatic interaction between positive-negative ESP regions. Dimer disaggregation predominantly follows two rejuvenation mechanisms: T-shaped and parallel. Parallel rejuvenation is the primary mechanism for chain alkanes, aromatic hydrocarbons, cycloalkanes ether, and ester groups. Here, methyl decyl ether exhibited the most potent disaggregation effect, reducing interaction energy between asphaltene dimers by 61.7%. The conclusions could offer a theoretical foundation for understanding asphaltene molecule aggregation and disaggregation and suggest strategies for high-performance rejuvenator design.