(525f) Understanding the Adsorption Behavior of Asphaltene Molecules at Oil–Rock Interface

Asphaltene deposition on mineral surfaces is one of the major problems in the petroleum industry, impacting the efficiency of injecting fluids, causing pipelines and equipment fouling, and catalyst poisoning. Therefore, a detailed understanding of asphaltene molecules (AMs)-rock interactions and the role of various parts of AM is essential for designing efficient chemical agents for the removal of AMs. Here, we investigated the structural and energetic behavior of AMs near the calcite surface in dodecane solvent using molecular dynamics simulations. We used the umbrella sampling technique to calculate the potential of mean force of five AMs (both island- and archipelago-type) containing a specific heteroatom (oxygen, nitrogen, and sulfur) and different sizes of aromatic core and aliphatic chains. Our findings showed that only certain categories of AMs (containing phenolic, APH; and pyrrolic, APY functional groups) exhibited preferential adsorption to the surface, while others (containing thiophenic, ATH, and TIR; and quinoline, QHP functional groups) encountered substantial barriers to adsorption. We found that the sizes of different components of AMs, their polarity, and the location of heteroatoms in the molecular structure played a crucial role in the adsorption. The APH and APY molecules were anchored to the surface via heteroatoms, supported by hydrogen bonding, leading to strong net interaction energies, which was not the case for ATH, TIR, and QHP molecules. Further, solvent molecules competed with the AMs for surface adsorption, with molecules possessing higher interaction energy outcompeting others. We found that the presence of a polar heteroatom and long aliphatic chains favored AM adsorption with no reliance on the size of the aromatic core. These detailed insights would facilitate the design of chemical agents for effective AM removal from surfaces and crude oil.