Green Biodiesel Production from Various Plant Oils Using Nanobiocatalysts Under Different Conditions

The lipase-immobilized polyethyleneimine (PEI)- and polyacrylic acid (PAA)-coated magnetic silica nanocomposite particles (L-PEI-MS and L-PAA-MS, respectively) were prepared and applied at various transesterification reaction conditions. The reactions were carried out with soybean, sunflower, canola, and palm oils along with methanol or ethanol in the solvent-free and n-hexane systems. The highest fatty acid methyl ester (FAME) and fatty acid ethyl ester (FAEE) synthesis yields were obtained from the transesterification of palm oil, i.e., almost 7.7-10.2% higher than other oils. At the constant reaction conditions, the application of ethanol leads to higher (6.0-8.7%) reaction yields in comparison with methanol. In addition, irrespective of reaction conditions, the best performance was acquired by L-PEI-MS; e.g., the FAME and FAEE synthesis yield values of 81.2% and 88.3% were obtained from transesterification of palm oil in the solvent-free systems, respectively. Addition of n-hexane improved the synthesis of FAME and FAEE yield values to 88.9% and 93.3%, respectively, using L-PEI-MS. The transesterification reactions kinetics follows the Ping-Pong Bi-Bi mechanism with alcohol inhibition effects. The high catalytic performance of L-PEI-MS might be related to its hydrophobic nature, which enhances the accessibility of oil molecules to the immobilized lipases and hampers the deactivating effect of alcohol molecules on them.