Effect of Hydrophobic Tail and Amine Groups on the Thermal and Interfacial Properties of Protic Ionic Liquids for Oilfield Application

Heat tolerance and solubility in high-salt water are crucial factors in oilfields. Commercially available material undergoes degradation at high temperatures, and continuous heating intensifies this phenomenon, causing considerable difficulties for the petroleum sector. To solve these problems, the oil industry is still developing new materials for use in oil recovery at high temperatures and salinity environments. In this study, we synthesized six new protic ionic liquids (ILs) to efficiently solve the issue caused by high temperature and high salinity. The synthesized ILs were characterized by NMR and FTIR spectroscopies. The thermogravimetric analysis (TGA) and surface tension measurements were examined to see the effect of alkyl chain and amine types on the thermal stability and surface characteristics. The results demonstrate that all protic ILs have thermal stability above the reservoir temperature (90 °C). The surface-activity findings depicted that as the alkyl chain increases from C₄ to C₉, the critical micelle concentration reduces abruptly. The thermodynamic properties demonstrated that the micelle process for these ILs is spontaneous and thermally stable. The synthesized ILs demonstrated solubility and stability in high-salinity (0- 241,688 ppm) and high-temperature (90 °C) conditions. These results proved that the synthesized protic ILs are suitable for the oilfield sector, having high-saline and high-temperature environments.