This research studied on the emulsion formation problem in biodiesel washing step after transesterification reaction of spent vegetable oil with methanol catalyzed by sodium hydroxide. The studied variables were transesterification reaction time (5, 15, 30, 45, 60, 120, 180 and 300 minutes), spent vegetable oil washed and not washed by water before transesterification reaction, stirring speed (210 and 594 rpm) and washing water temperature (24 and 60C). Gas Chromatography analysis demonstrated that there was no significant difference of the amount of monoglyceride, diglyceride and triglyceride synthesized at the different reaction times above. The quantitative analysis of sodium hydroxide and free fatty acid soap showed that when the reaction time increased, the quantities of sodium hydroxide and free fatty acid soap were decreased and would form less emulsion because free fatty acid soap was emulsifier. Spent vegetable oil being washed with water provided less sodium hydroxide and free fatty acid soap than another one not being washed with water. Experiments of biodiesel after transesterification showed that biodiesel synthesized for 5 hours and being washed with water at 60 C at the stirring speed of 210 rpm would form less emulsion than biodiesel synthesized at the same period and being washed with water at 24 C at the stirring speed of 594 rpm, respectively.
By
Thanawattana Uttamaroop
Thiti Thienparithi
