Promotion of Salinity to Protonation of Amidine-based CO2-switchable Surfactant

Abstract

Abstract Amidine-based switchable surfactants, whose surface activity is enabled by protonation, are a desirable candidate for the development of enhanced oil recovery methods. However, studies on the influence of salt components on the protonation of amidine-based surfactants are still very limited. In this study, it has been found that inorganic salts can induce the protonation of amidine-based surfactants, using N’-dodecyl-N and N-dimethyl acetamidine (C12-DMAA) as an example. The feasibility predictions of protonation of C12-DMAA in pure water and brines were attained by quantum chemical simulation. The occurrence of partial protonation is determined by Nuclear Magnetic Resonance (NMR). In the dispersion test, variation in conductivity and pH indicated that the water molecule plays the role of proton donor in the protonation process, and the protonation level is unaffected by the presence of cationic species. Overall, this research enhances the understanding of the switchable ability, as well as the efficient utilization of amidine-based surfactants in salt-containing systems.