Trióxido de tungstênio obtido pelo método Pechini modificado, aplicado como catalisador nas reações de transesterificação e esterificação simultâneas

Abstract

Tungsten (WO3) for use in biodiesel catalysis, by the reaction processes of transesterification, esterification and these two simultaneous reactions (TES). This oxide was obtained at 800°C and characterized by X-ray diffraction (XRD) and XRD with in situ heating, infrared spectroscopy (IR), IR spectroscopy using probe molecule, UV-visible (UV-VIS) spectroscopy, Raman spectroscopy, scanning electron microscopy (SEM), zeta potential measurement and surface area measurement (SBET). The diffractograms confirmed the monoclinic phase, and the IR and Raman spectra confirmed the presence of different W-O bonds in the material. The micrographs exhibited hexagonal morphologies and agglomerated particles, corroborating the surface area of 0.99 m2 g-1

. WO3 was used in the reactions with refined and crude palm oil, soybean oil and oleic acid, using a molar ratio of methanol:fatty matter (12:1), catalyst concentration of 3% w/w, varying temperature and reaction time. The reaction products were characterized by kinematic viscosity, acid number (AI), gas chromatography (GC), and nuclear magnetic resonance spectroscopy (1H and 13C NMR). The reduction in kinematic viscosity and acid number in all catalytic tests indicated that both transesterification and esterification occurred, but with very different activities. The highest conversion to methyl esters was achieved using a temperature of 200 °C/120 min, obtaining 14.5% for the transesterification reaction of OPR according to GC; and 88.8% for esterification of oleic acid by 1H NMR characterization. For soybean oil, the highest conversion by methyl transesterification (30.4%) was obtained at 200°C for 240 min. The reactions (TES) using refined palm oil (RPO), with the addition of 10% oleic acid (OA), showed a maximum conversion in EM observed by GC of 70% after 2 hours of reaction, indicating a synergy with the acidification of the reaction medium. The tests with 4 hours of reaction involving soybean oil with 20% OA, resulted in a conversion of 76.1%, and for crude palm oil (CPO), 85.3% according to CG. These results confirm the catalytic potential of this oxide in biodiesel production.