In this work, it was described the preparation and the characterization of a solid acid catalyst obtained by the mixture of Cr/Al oxides (CRAL). The catalyst was tested in the transesterification reaction of babassu oil with 5% of free fatty acid (FFA). The results of textural and acidity characteristics of CRAL were: area (56 m2 g-1), pore size (7.0 µm), total acidity (182.28 µmol g-1), wherein Brönsted sites are the most active. Powder X-ray diffractometry (XRD), scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDX) show three phases of the catalyst (Cr2O3/Na2Cr2O3/Al2O3), 0.25:0.25:0.50, respectively. The reaction reached conversion about 98.6% under the conditions: alcohol/oil molar ratio (24:1), catalyst to oil mass ratio of 3.0%, 15 h and 70 ºC. The turnover frequency (TOF) found was 24.5 × 10-4 s-1. Kinetic of the reaction was researched over a temperature range of 60-80 ºC. A pseudo first-order model was proposed with the activation energy (Ea) of 49.18 kJ mol-1. CRAL is active in the biodiesel production for just one cycle, because in the second one it loses its activity. The leaching of catalyst is about 13%, demonstrating that the catalyst is not totally heterogeneous.
Keywords:
biodiesel; catalyst; babassu oil; kinetic; reusability; leaching; heterogeneity
