Phase Behaviors of Vegetable Oil-Based Microemulsion Fuels: The Effects of Temperatures, Surfactants, Oils, and Water in Ethanol

Vegetable oil-based microemulsification not only reduces the high viscosity of vegetable oils but also enhances the miscibility of polar and oil phases. In addition, vegetable oil-based microemulsion fuels produce lower pollutant emissions compared to neat No.2 diesel. Since the stability of microemulsion fuels is temperature sensitive, the effect of temperature on the microemulsion phase behavior should be evaluated. The overall goal of this study is to formulate temperature-robust microemulsion fuels by studying the effect of temperature on phase behaviors of different systems of vegetable oil-based reverse micelle microemulsions. Our results demonstrate that, when using an alcohol ethoxylate surfactant as a renewable surfactant, it is possible to formulate microemulsion fuels with comparable properties to nonionic surfactant evaluated in previous studies. Further, mixtures of nonedible oil (algae mixed with castor) were found to have comparable properties to edible oil (canola) used to produce microemulsion fuels. Moreover, microemulsion fuels can be obtained using bioethanol although the bioethanol systems required a higher amount of surfactant than anhydrous ethanol. All microemulsion fuel systems were able to function at low temperature without phase separation. Thus, this study provides useful information and alternatives of optimum microemulsion fuel formulations based on surfactants and oils not evaluated in previous research and thus demonstrates the robustness of this approach.