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

Abstract

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.