Synthesis and Characterization of Nb2O3 by Combustion Reaction for Catalytic Application in Biodiesel Production

This work presents the synthesis and characterization of niobium pentoxide (Nb₂O₅) obtained by combustion reaction, as well as its application as a heterogeneous catalyst in the production of biodiesel via simultaneous transesterification and esterification reaction (TES). The choice of Nb2O5 is justified by the fact that it is a material with wide applications, as a catalyst for biodiesel production; few reports in the literature can be explored. The vast majority of natural Nb2O5 is extracted in Brazil, in the city of Araxá in Minas Gerais (MG) by the Brazilian Metallurgy and Mining Company (CBMM), as it holds 98.2% of the world’s reserves. The synthesis of Nb2O5 was carried out on a laboratory scale using urea as fuel and niobium ammonium oxalate as precursor. The material obtained was characterized by XRD, FTIR, DG, BET, and SEM, showing a polyphasic structure (T-orthorhombic and TT-pseudohexagonal), polydisperse particle size distribution, surface area of 14.59 m2·g, and predominance of mesopores with a mean diameter of 7.16 nm. Subsequently, Nb2O5 was applied as a catalyst in the production of biodiesel from soybean vegetable oil and residual frying oil, using ethanol and methanol. The conversions into ethyl and methyl esters, densities, and acidity values were analyzed and compared with the standards of the National Petroleum Agency (ANP). The highest conversions were observed for soybean oil using methanol (34.74±0.79%) and residual frying oil using methanol (42.54±1.09%). Although the parameters obtained were below regulatory requirements, the results demonstrated the potential of Nb2O5 as an efficient and low-cost catalyst. The production of biodiesel using alternative and renewable materials highlights the feasibility of applying Nb2O5 in sustainable processes, with the possibility of future optimizations in synthetic routes and reaction conditions.