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Ionic liquids (IL) have emerged as a prospective new material for a wide range of industrial applications, owing to their unique structures and properties. Hence, understanding the structure–property relationships of IL is very important for both fundamental and industrial applications. In this study, a series of imidazolium‐based IL with different chain lengths, namely C8mimBF4, C10mimBF4 and C12mimBF4, were synthesized. Their molecular structures were confirmed by proton nuclear magnetic resonance (1H NMR) and Fourier transform infrared (FTIR) analysis. Thermal gravimetric analysis (TGA) revealed that the IL synthesized were thermally stable in the desired temperature range. Dynamic light scattering (DLS) results of IL was analyzed in order to understand the effect of alkyl length on micellar size. Conductivity and surface tension measurements were carried out to determine the adsorption and aggregation characteristics in aqueous solutions. The influences of temperature as well as alkyl chain length on viscosity were also investigated. Surface adsorption parameters such as surface excess, minimum area, effectiveness and efficiency were also determined from equilibrium surface tension data. A careful analysis of the thermodynamic aspects of air‐ionic liquid aqueous systems reveals that free energies of adsorption are favoured over micellization for all systems.

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Carbonate reservoirs contain a significant amount of oil and gas reserves, but the ultimate recovery of these reserves is very low because of higher wettability of the carbonate rock relative to crude oil. Surfactant flooding is the most common method employed to increase the recovery with the main mechanism of wettability alteration, which to an extent depends on the mineralogical attributes of the reservoir. Ionic liquid (IL), which acts as a surface-active chemical, was employed to investigate its potential impact on oil recovery in carbonate reservoirs. X-ray diffraction of the carbonate reservoir rock was done to determine the quantitative mineralogy of rock samples. Fourier transform infrared spectroscopy of carbonate reservoir rock samples and the crude oil sample indicated that the polar components of crude oil are adsorbed onto the surfaces making it oil wet. SARA analysis of the crude oil determined the percentage of heavier fractions (asphaltene and resins), which have a direct impact on altering the wettability toward oil-wet. Experimental investigation revealed that, imidazolium-based ILs were able to alter the wettability from oil-wet to water-wet conditions. In the presence of salt and alkali, IL worked efficiently in reducing the contact angle and altering the wettability toward more water-wet. The loss of IL by adsorption on the carbonate rock was investigated, and the Langmuir isotherm was found to be the best fit. The effect of salt had a detrimental effect on adsorption density of IL, as it increases with increasing salt concentration. On the other hand, the addition of alkali with an optimum concentration of 1.5−2% was found to reduce the adsorption of IL on the rock surface as alkali itself preferentially adsorbs on the rock.

Ionic liquids have emerged as a promising new material for a wide range of industrial applications, because of their unique structures and properties. Ionic liquids possess exceptional properties such as chemical and thermal stability, negligible vapor pressure, or solvency power for different types of molecules. Ionic liquids find their application in different operations in petroleum industry. The purpose of this paper is to review previously published works on the application of the IL in various areas of the petroleum industry and related processes. A detailed discussion of various processes such as enhanced oil recovery, drilling fluids, gas hydrate, CO2 capture, and flow assurance has been provided. This in-depth discussion is intended to aid professional and researchers in understanding the present condition and planning for the future.