Inhibition of asphaltene precipitation using hydrophobic deep eutectic solvents and ionic liquid

Precipitation and subsequent deposition of asphaltene in oil reservoirs may cause severe flow assurance problems due to clogging/blocking of pore spaces and wettability alteration of reservoir rocks towards oil-wetness. The present study focuses, for the first time, on the potential application of three hydrophobic deep eutectic solvents (HDESs) prepared by mixing methyltrioctylammonium chloride (N81Cl) as their hydrogen bond acceptor (HBA) with alcoholic hydrogen bond donors (HBDs), namely 1-propanol, 1,3-propanediol, and glycerol. The performance of HDESs was compared with a phosphonium-based hydrophobic ionic liquid (IL), Trihexyltetradecylphosphonium bis(2,4,4-trimethylpentyl)phosphinate (TTPBP), as well as dodecylbenzene sulfonic acid (DBSA), a conventional asphaltene precipitation inhibitor. Initially, the kinetic and onset of asphaltene precipitation were evaluated using an ultraviolet-visible (UV-Vis) spectrophotometer to determine the chemicals' inhibition propensity. Next, Fourier-transform infrared (FTIR) spectroscopy, thermogravimetric (TGA), and elemental analyses were used for the recovered asphaltenes from HDESs and TTPBP solutions to examine their structures. Spectrophotometry results revealed that glycerol-based HDES (HDES 3) and TTPBP could effectively inhibit the asphaltene precipitation, where their performances were comparable to that of DBSA. Besides, aromaticity index, thermal degradation, and H:C and oxygen contents provided evidence that HDES 3 and TTPBP could disrupt the asphaltenes structure, thus stabilizing them in the oleic environment. (C) 2021 Elsevier B.V. All rights reserved.