Optimization of Conversion of High Free Fatty Acid Jatropha curcas Oil to Biodiesel Using Response Surface Methodology

A five-level-four-factor central composite design (CCD) with 54 assays was employed to study the effect of catalyst concentration (NaOH), reaction temperature, reaction time, and methanol/oil molar ratio on the methyl esters yield from Jatropha curcas oil (JCO) during its transesterification. Using response surface methodology (RSM), a quadratic polynomial equation was obtained for Jatropha curcas biodiesel (JCB) yield by regression analysis. Verification experiments confirmed the validity of the predicted model. The high free fatty acids (FFAs) (14.6%) of JCO could be reduced to 0.34% by acid-catalyzed esterification and a JCB yield of 98.3% was obtained with methanol/oil ratio (11 : 1) using NaOH as catalyst (1% w/w) in 110 min time at 55°C temperature. The predicted value of JCB yield is found to be in good agreement with the experimental value at the optimum level of input parameters. The properties of the biodiesel, thus, produced conform to the ASTM and IS specifications, making it an ideal alternative fuel for diesel engines. The model can be effectively used in oil industry to maximize the biodiesel yield from given oil.