Molecular Structure: The First and Most Significant Factor in the Precipitation of Asphaltenes

Abstract

Summary For decades, asphaltene deposits have been one of the most common problems in the oil industry in production, transportation, refining, processes, and storage. To find a solution, researchers have always faced three intertwined challenges of accurate structure determination, properties investigation, and precipitation prediction because asphaltenes in one oil sample are “a spectrum of complex molecular structures with very close masses.” Various models and theories of the inherent self-association of asphaltenes have been presented. All of them confirm the role of the unique molecular structure of asphaltenes as “the initiator” of the precipitation process. The driving factor for self-association is π-π stacking of aromatic rings. Recent advances in molecular dynamics (MD) calculations confirm the results of recent models. After the molecular structure, thermodynamic parameters (P, T, and composition) are the influencing agents on precipitation. Any change in these parameters causes an increase or decrease in the intensity of the precipitation. Due to the greater importance of molecular structure over other parameters, until the great challenge of characterization of asphaltenes is not specific, the validation of sediment prediction models will undoubtedly be accompanied by errors. In this paper, we review essential types of asphaltene self-association models and precipitation prediction methods. As an introduction and emphasis on the understanding of this inherent phenomenon, the weight, molecular structures, analysis methods, and ambiguities are investigated.

Mechanistic Study on the Effect of Molecular Structure Characteristics of Asphaltene on the Synergistic Modification with EVA on Model Waxy Oil

“…As the most polar substances in the oil phase, asphaltenes tend to self-aggregate, leading to an increase in particle size and the formation of solid precipitates. ,− Factors affecting the self-aggregation tendency of asphaltenes include solvent composition, active substances in the oil phase, and the molecular structure of the asphaltenes themselves. ,, As a surfactant, EVA’s molecular structure contains both polar and nonpolar portions, allowing it to adsorb onto asphaltene particles and reduce asphaltene particle size, thereby enhancing asphaltene dispersion stability. Therefore, we tested the particle size of the oil samples containing asphaltene before and after the addition of EVA, and indirectly reflected the adsorption of EVA on the surface of asphaltene through the change of the particle size.…”

“…Pour point depressant (PPD), serving as a disruptive agent in the wax crystallization process, has been the subject of investigation for several decades, giving rise to the concept of “additive delivery” widely implemented in global crude oil pipeline transportation. − Nonetheless, a notable compatibility issue exists between PPD and waxy oil, with the modification effect closely intertwined with the constituents of waxy crude oils, including waxes, resins, and asphaltenes. ,− Among these constituents, asphaltene, recognized as the most polar component within crude oil, ,− has garnered considerable academic scrutiny in recent years.…”

Asphaltene Precipitation/Deposition Estimation and Inhibition through Nanotechnology: A Comprehensive Review

“…Asphaltenes tend to thermally decompose and form solid carbonaceous deposits, known as coke, on the surfaces of refining equipment. The accumulation of coke restricts the flow of fluids and heat transfer, leading to reduced efficiency and operational problems [8,9].…”