The purpose of this work is to evaluate the performance of Ni 0.5 Zn 0.5 Fe 2 O 4 ferrite doped with 0.1 and 0.4 mol of Cu as a catalyst for the transesterification of soybean oil to biodiesel, using methanol. The samples were characterized by X-ray diffraction, nitrogen adsorption and scanning electron microscopy. The reaction was performed for 2 hours at a temperature of 160 °C, using 10 g of soybean oil, a molar ratio of oil: alcohol of 1:20, and 4% (w/w) of catalyst. The product of the reaction was characterized by gas chromatography, which confirmed conversion to methyl esters. The diffraction patterns showed the presence only of Ni 0.5 Zn 0.5 Fe 2 O 4 ferrite phase with a crystallite size of 29 nm. The samples doped with 0.1 and 0.4 mol of Cu showed a surface area and particle size of 22.17 m 2 g -1 and 50.47 nm; and 23.49 m 2 g -1 and 47.64 nm, respectively. The morphology of both samples consisted of brittle block-shaped agglomerates with a wide particle size distribution. A comparative analysis of the two catalysts indicated that the catalyst doped with 0.4 mol of Cu showed the better performance, with a conversion rate of 50.25%, while the catalyst doped with 0.1 mol of Cu showed 42.71% conversion.

Ni0.5Zn0.5Fe2O4, Mn0.5Zn0.5Fe2O4and Ni0.2Cu0.3Zn0.5Fe2O4nanoferrites were synthesized, characterized and evaluated in terms of their performance as catalysts in the methyl esterification reaction of soybean oil. The nanoferrites were synthesized by combustion and characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDX). The XRD patterns show the presence of inverse spinel B(AB)2O4phase. The EDX results confirmed the stoichiometry of the nanoferrite systems, whose morphology consisted of large block-like agglomerates with a brittle aspect and a wide agglomerate size distribution. The results indicate that the Ni0.5Zn0.5Fe2O4nanoferrite was the most active catalyst in the esterification reaction, with conversion rates ranging from 40 to 91%.