Effect of the Structures of Ionic Liquids and Alkylbenzene-Derived Amphiphiles on the Inhibition of Asphaltene Precipitation from CO2-Injected Reservoir Oils

The inhibition of asphaltene precipitation from high-pressure, CO2-injected reservoir oils by ionic and nonionic amphiphiles, the ionic liquids based on p-alkylpyridinium ([Cnpy]+) and N-butylisoquinolinium ([C4iql]+) cations, and the alkylbenzene-derived amphiphiles p-alkylphenol (Cnphol), p-alkylbenzenesulfonic acid (Cnbsa), and sodium p-alkylbenzenesulfonate (CnbsNa) was investigated for the first time. The influences of the structures of these compounds and the effect of the combination of their cations and anions were studied. The results show that the inhibition abilities of the alkylbenzene-derived amphiphiles first increase when n = 2−8 and then remain almost constant when n ≥8 and that the effectiveness follows the order Cnphol < Cnbsa ≈ CnbsNa. The inverse trend is observed for the ionic liquids [Cnpy][Cl]; that is, their inhibition abilities decrease as n increases from 4 to 8 to 12. [C4iql][Cl] is more effective than [C4py][Cl], but [Cnpy][BF4] and [Cnpy][PF6] have almost no effect on the stab...