N-Octylaminopropan-2-ol surfactant for crude-oil asphaltene dispersion: Integrated experimental and modeling insights

Abstract

This study provides the first-reported evidence that aliphatic structured surfactant, N-octylaminopropan-2-ol (OSI), is a novel and effective inhibitor of the aggregation of acidic, island-structured crude oil asphaltenes (A-ZO). The molecular mechanisms of OSI’s effective dispersion were elucidated using a combination of advanced spectroscopic techniques and Density Functional Theory (DFT) calculations. Fourier Transform Infrared Spectroscopy (FT-IR) and Nuclear Magnetic Resonance (NMR) analyses revealed strong interactions between OSI and A-ZO, including hydrogen bonding and acid-base interactions, which prevent asphaltene precipitation in crude oil. Differential Thermal Analysis (DTA) confirmed the chemisorption of 12.5 % OSI onto A-ZO. Dynamic Light Scattering (DLS) measurements showed a significant reduction in the average nanosize of A-ZO in hexane, decreasing from 583 nm to 76 nm after treatment with OSI. Scanning Electron Microscopy (SEM) images of the A-ZO and OSI mixture revealed the filling of deep grooves and cracks on the rough surface of the asphaltene agglomerates, demonstrating the resin-like dispersion effect of OSI. DFT simulation reveals a binding energy of −28.2 kcal/mol for A-ZO and OSI complex formation. Noncovalent interaction (NCI) analysis shows that van der Waals interactions occur [sign(λ₂)ρ ≈ −0.015 to +0.005 au] in a large region between the OSI saturated tail and the A-ZO polycyclic aromatic fragment, which explains experimentally observed well-disperssed state of the hexane + A-ZO mixture after the addition a certain amount of OSI. The detailed, data-driven analysis offers unique molecular-level insights into asphaltene stabilization, presenting OSI as a significant alternative to traditional inhibitors for the oil industry.