Thesis (Ph.D.)--Chulalongkorn University, 2013

The use of palm oil-diesel microemulsion fuels with ethanol (ME50) has been considered as a very promising renewable fuel for reducing high viscosities of palm oil as well as a feasible substitute for diesel fuel. This work demonstrates for the first time that microemulsion fuel can be formulated from a mixture of palm oil-diesel blends as the oil phase, ethanol as the polar phase and viscosity reducer, surfactant and cosurfactant as the mixed surfactant system. The objective of this research is to study the effects of surfactant, cosurfactant, ethanol, surfactant/cosurfactant ratio, and palm oil-diesel blends on the phase behavior, kinematic viscosity, and microemulsion-droplet size with the goal of formulating optimized microemulsion-based fuel. Four nonionic surfactants, stearyl alcohol, oleyl alcohol, methyl oleate, and Brij-010, were investigated in this research. It was found that the mixture of methyl oleate/1-octanol (22 vol. %), ethanol (20 vol. %), and the palm oil-diesel (1:1 v/v) blends (58 vol. %) can greatly reduce the bulk viscosity and produce uniformly size of microemulsion droplets while use the least amount of surfactant for solubilizing ethanol-in-oil in the system. As consider the exhaust emissions from ME50 after used in an unmodified direct-injection (DI) diesel engine, the results showed that nitrogen oxide emissions, the exhaust gas temperature, and carbon dioxide from microemulsion fuels were gradually reduced while fuel consumption increased; however, there is no significant difference in carbon monoxide emissions when compared to those of regular diesel. In conclusion, the microemulsion fuel displays the competitive advantages in term of the environmentally friendly fuel production and the exhaust gas emission reduction which leads to an improvement of overall environmental performance of the biofuel technology.