Understanding the role of iron (III) tosylate on heavy oil viscosity reduction

• Published in: Fuel (Guildford) 2020-08, Vol.274, p.117808, Article 117808
• Main Authors: Xu, Yan, Ayala-Orozco, Ciceron, Chiang, Pinn-Tsong, Shammai, Michael, Wong, Michael S.
• Format: Article
• Language: English
• Subjects: Asphaltenes; Catalyst; Crude oil; Energy recovery; Energy sources; Enhanced oil recovery; Heat treatment; Heavy metals; Heavy oil; Iron; iron (III) tosylate; Ligands; Mechanism; Oil; Oil recovery; Reaction products; Thermal recovery; Viscometry; Viscosity; Viscosity reduction; X ray photoelectron spectroscopy
• ISSN: 0016-2361; 1873-7153
• DOI: 10.1016/j.fuel.2020.117808

Heavy oil is an abundant energy resource, but its recovery remains challenging primarily due to its high viscosity. Thermally enhanced oil recovery in the presence of metal-ligand compounds (MLCs) has been studied as a promising method for in situ viscosity reduction and oil quality upgrading. In spite of its importance, the interactions between MLCs and crude oil components at the molecular-level are poorly understood, and their mechanistic details for viscosity reduction are unclear. Here we studied viscosity changes of Peace River oil in the range of 80–295 °C in the presence and absence of iron (III) tosylate (para-toluenesulfonate) MLC and analyzed reaction products via viscometry, TGA-MS, XPS, GC-MS, SARA analysis, and elemental analysis. Whereas thermal treatment lowered viscosity at 190 °C and above, thermal treatment with the iron tosylate MLC decreased viscosity only at temperatures above 230 °C. The MLC effect was most substantial at 280 °C, at which viscosity decreased by 58% (compared to 39% in absence of the MLC at the same temperature). The MLC likely lowered oil viscosity by catalytically reacting with the asphaltene to decrease its total content in oil, and by releasing a ligand to form 4-methylbenzenethiol (MBT) that interfered with asphaltene intermolecular interactions. At temperatures below 230 °C, the MLC unexpectedly raised oil viscosity, likely due to bridging interactions with asphaltene. This understanding of MLC-induced deviscosification provides a selection rationale for appropriate metals and ligands for enhancing heavy oil recovery.