Immobilized different amines on modified magnetic nanoparticles as catalyst for biodiesel production from soybean oil

Fe₃O₄ nanoparticles were modified with tetraethylorthosilicate (TEOS) and (3-chloropropyl)trimethoxysilane (CPTMS) followed by immobilization with different amines such as guanine, piperazine, methylamine, morpholine, aniline, ethylenediamine, 3-aminopropyltriethoxysilane, and melamine, designated as Fe₃O₄@SiO₂@CPTMS@amine (nanocatalyst). The prepared nanocatalysts were characterized by means of FTIR, XRD, VSM, SEM, and TEM. Trans-esterification reactions of soybean oil with methanol were then carried out in the presence of the Fe₃O₄@SiO₂@CPTMS@amine as a nanocatalyst. Optimization of the reaction parameters revealed that the fatty acid methyl esters (FAMEs or biodiesel) is obtained in 6–96% yields by using methanol to oil molar ratio of 36 in the presence of 6% of nanocatalysts containing melamine and guanine, respectively, at 160 °C within 3 h. The stability and reusability of the catalyst as well as the effect of reaction parameters on the FAME yield are described in this paper.