Venkatesh Kamath, H.Iyyaswami, I.Saidutta, M.B.2026-02-052011Fuel Processing Technology, 2011, 92, 1, pp. 100-1053783820https://doi.org/10.1016/j.fuproc.2010.09.003https://idr.nitk.ac.in/handle/123456789/27363The free fatty acid of crude karanja oil (Pongamia pinnata) was reduced and biodiesel was synthesized from pretreated oil under microwave irradiation. The process variables such as irradiation time, methanol-oil ratio and sulfuric acid concentration for pretreatment step; irradiation time, methanol-oil ratio and KOH concentration were optimized through the Box-Behnken experimental design. The free fatty acid of crude karanja oil was reduced to 1.11 ± 0.07% with an optimal combination of 190 s irradiation time (180 W), 33.83 (w/w)% methanol-oil ratio and 3.73 (w/w)% sulfuric acid concentration. An optimal combination of 150 s irradiation time, 33.4 (w/w)% methanol-oil ratio and 1.33 (w/w)% KOH concentration yielded 89.9 ± 0.3% biodiesel. The model was validated by conducting experiments at optimal design conditions. The present work confirmed that the microwave energy has a significant effect on esterification and transesterification reaction. © 2010 Elsevier B.V. All rights reserved.Acid concentrationsBiodiesel synthesisBox-Behnken experimental designFree fatty acidIrradiation timeKaranjaKaranja oilKOH concentrationMicrowave energiesOil ratioOptimal combinationOptimal designPongamia pinnataPre-TreatmentProcess VariablesTransesterification reactionBiodieselConcentration (process)Design of experimentsEstersFatty acidsIrradiationMethanolOptimizationPotassium hydroxideRadiationSulfur determinationSulfuric acidSynthesis (chemical)Synthetic fuelsTransesterificationMicrowave irradiation