Phase Behavior of Castor Oil-Based Ionic Liquid Microemulsions: Effects of Ionic Liquids, Surfactants, and Cosurfactants

Abstract

Castor oil-based ionic liquid microemulsions are promising alternatives for petroleum-based biolubricant basestocks. This study presents the phase behavior of castor oil-based ionic liquid microemulsions through phase manifestation, and the areas of the single-phase domain (S ME ) were calculated accordingly to further illustrate the phase-forming capacities of the designed microemulsions. The results indicated that the phase-forming capacities of castor oil-based ionic liquid microemulsions depended largely on the ionic liquid ions, surfactant types, and cosurfactant chain lengths. The S ME of different anion-based ionic liquid microemulsions showed the following sequences: [BMIM][Tf 2 N]-based > [BMIM][PF 6 ]-based > [BMIM][BF 4 ]-based. The longer carbon chain of ionic liquid cations in single surfactant-based systems and the larger percentage of ionic liquid-based surfactant in mixed surfactants-based systems both gave rise to the phase-forming capacities of castor oil-based ionic liquid microemulsions. Given the presence of ionic liquid−castor oil amphiphilic balance in the designed systems, the castor oil−surfactant micelles achieved maximum solubilization capacity for [BMIM][BF 4 ] when the ethoxylated groups' number of surfactant was about eight in single surfactant microemulsion.In addition, n-hexanol donated a higher phase-forming capacity than n-butanol, while n-octanol brought about a different phase behavior due to the spontaneous curvature effect and oil nature of long-chain alcohols (C ≥ 7) in the castor-oil based ionic liquid microemulsions. Thus, this study presented useful information for formulating optimum castor oil-based ionic liquid microemulsion biolubricants based on different ionic liquids, surfactants, and cosurfactants, which were not evaluated in previous research.

Effect of Cosolvent Ethanol on Solubilization of Ionic Liquids in Supercritical CO2Microemulsions: Experiments and Simulations

“…Therefore, the results proved that EtOH could exist as a cosolvent in the [Emim]­[Tf 2 N]/CO 2 microemulsion system. The addition of EtOH reduced the radius of the spontaneous curvature, so the construction of the microemulsion became easier …”

“…The addition of EtOH reduced the radius of the spontaneous curvature, so the construction of the microemulsion became easier. 55 For the Ls-45 system, it was found that the higher the temperature, the smaller the effect of EtOH concentration on the CPP. For example, at 35 °C, when the concentration of [Emim][Tf 2 N] was 1.0 mmol/L, the gap in CPP between W E = 1.5 and 3 was about 0.5 MPa.…”