High yield and conversion of biodiesel from a nonedible feedstock (Pongamia pinnata).

An efficient approach has been adopted for the synthesis of biodiesel developed from karanja, a nonedible oil feedstock. A two-step reaction was followed for synthesis of biodiesel. Karanja oil possessing a high free fatty acid content was esterified with sulfuric acid, and the product obtained was further converted to fatty acid alkyl esters (biodiesel) by transesterification reactions. A moderate molar ratio of 6:1 (methanol/oil) was efficient for acid esterification with 1.5% v/v H2SO4 and 1 h of reaction time at 60+/-0.5 degrees C, which resulted in reduction of FFA from 19.88 to 1.86 mg of KOH/g. During alkaline transesterification, 8:1 molar ratio (methanol/oil), 0.8 wt % sodium hydroxide (NaOH), 1.0 wt % sodium methoxide (CH3ONa), or 1.0 wt % potassium hydroxide (KOH) as catalyst at 60+/-0.5 degrees C gave optimized yield (90-95%) and high conversion (96-100%). Optimum times for alkaline transesterification were 45 min for CH3ONa and 1 h for NaOH and KOH. Conversion of karanja oil feedstock to its respective fatty acid methyl esters was identified on a gas chromatograph-mass spectrometer and determined by 1H nuclear magnetic resonance and gas chromatography. The fuel properties, such as cetane number of the methyl ester synthesized, were studied and found to be within the limits and specification of ASTM D 6751 and EN 14112 except for oxidation stability.