The optimation of reaction time on biodiesel production from palm oil and waste cooking oil catalyzed by silica-titania has been investigated. The reaction time varied in the range of 2-6 hs. The optimum condition has been obtained by flow rate, density, and acid number analysis of biodiesel product. The results show that biodiesel product from palm oil has optimum reaction time of 4-5 h with percentage of conversion of 33.33%. The same optimum reaction time is also shown for biodiesel product from waste cooking oil, however, the percentage of conversion is higher, i.e. 57.14%. The higher reaction time (6h) yields lower percentage of conversion due to back reaction of hydrolysis of fatty acid ester.

Keywords : Biodiesel; FAME; FFA; Percentage of Conversion; Silica-Titania Catalyst.