Strategies for Improved Stability of Methanol-in-Diesel Emulsions

This study is motivated by the need to present a robust methodology for preparing stable methanol-in-diesel emulsions for use in compression ignition engines with the specific objective of maximizing the methanol content. Specifically, it involved exploring the feasibility of methanol-in-diesel emulsions with conventional surfactants such as Tween-80 and Span-80 and nonconventional surfactants such as 1-dodecanol, pentanol, and butanol. The hydrophilic–lipophilic balance (HLB) values of the surfactant varied from 7 to 15 to investigate the role of the surfactant HLB on the stability of the macroemulsion. It is observed that the macroemulsion with an HLB value of 10 provides the best stability results. Using surfactant HLB value of 10, three macroemulsions with 10 wt%, 15 wt%, and 20 wt% of methanol were prepared using ultrasonication. However, only the macroemulsion with 10 wt% of methanol was observed to be stable for at least 20 days after preparation. Next, the microemulsions of diesel–methanol were produced by using nonconventional surfactants such as 1-dodecanol, pentanol, and butanol. Among these, 1-dodecanol was found out as the most suitable surfactant owing to its ability to form microemulsions with any mixing ratio of diesel–methanol and its high cetane number (63.6). This study has clearly brought out the strategies for preparing both macro and microemulsions. Overall, the results presented in the current work are expected to aid efforts in adapting compression ignition engines for diesel–methanol fuel blends.