Kinetic modeling and optimization of biodiesel production from white mustard (Sinapis alba L.) seed oil by quicklime-catalyzed transesterification

The biodiesel production from white mustard (Sinapis alba L.) seed oil (WMSO) by transesterification with methanol over the quicklime powder was investigated in a batch stirred reactor. Two independent first-order models with respect to triacylglycerols (TAGs) or a more complex model that combined the changing mechanism and the first-order rate law with respect to TAGs and fatty acid methyl esters (FAMEs), respectively described successfully the kinetics of this transesterification reaction. Besides that, the response surface methodology coupled with a full factorial design with replication was applied to model and optimize esters content with methanol-to-WMSO molar ratio, catalyst amount and reaction time (X1, X2 and X3, respectively). The analysis of variance indicated that all individual process factors, the interactions X1-X2 and X2-X3 and the quadratic term X22 influenced significantly FAME content at the 95% confidence level. According to the reduced quadratic model, complete conversion could be achieved with the catalyst loading of 9.8%-10% and the methanol-to-WMSO molar ratio in the range between 6.1:1 and 11.6:1 in 50 min. WMSO was transesterified even faster than sunflower oil in the presence of both quicklime and KOH, due to higher total content of unsaturated fatty acids.