Influence of alkyl chain length of imidazolium-based ionic liquid on the crude oil-aqueous solution IFT under different ionic strengths

Abstract

Due to the unique potentials of ionic liquid (ILs) for interfacial tension (IFT) reduction, a large number of studies concentrated on the applications of these chemicals. In this way, the current study compares the IFT of 1-dodecyl-3-methylimidazolium chloride ([C12mim]Cl) and 1-octadecyl-3-methylimidazolium chloride ([C18mim]Cl) in the presence and absence of NaCl, to investigate the effect of alkyl chain length on the ILs performance. The measured IFTs reveal that, [C18mim]Cl has a higher influence on the IFT reduction in comparison to [C12mim]Cl, in the absence of ions. However, in the presence of NaCl, longer alkyl chain has a destructive effect on the IFT reduction which means the better efficiency of [C12mim]Cl for IFT reduction compared to [C18mim]Cl. According to the findings, the critical micelle concentrations (CMC), the functionality of IFT and the alkyl chain length of imidazolium based ILs depend not only on the number of methyl presented in the cationic part of the IL, but also on the ionic strength of the aqueous solution. The common effect of alkyl chain length (i.e. reduction of surface activity as a function of cation chain length) can be reversed at the presence of the salt, as the surface activity of shorter cation chain length is higher in the presence of NaCl.