Acid-catalyzed pretreatment
The Jatropha oil used had an initial acid value of 6.2 mg KOH/g corresponding to a free fatty acid (FFA) level of 3.1%, which is above the 1% limit for a satisfactory transesterification reaction using an alkaline catalyst [16]. Therefore, FFAs were first converted to esters in a pretreatment process with methanol (molar ratio methanol/oil = 6.5:1) using H2SO4 as catalyst (0.3%) in 90 min reaction time at 60 °C [6].
Base-catalyzed transesterification using the conventional technique
The method applied for the production of biodiesel from Jatropha oil in this research is base-catalyzed transesterification in a laboratory-scale setup. The reaction was performed using methanol as alcohol and KOH as catalyst. The transesterification process was studied at two catalyst loadings (1 and 1.5 wt.% KOH) and three alcohol to oil molar ratios (4.5:1, 6:1, and 7.5:1).