Potential of Nb₂O₅ as a Catalyst in Biodiesel Production: A Study with Different Feedstock

The objective of this study was to evaluate the catalytic performance of commercial Nb₂O₅, supplied by CBMM, in the production of biodiesel by transesterification and esterification, using different feedstocks (soybean, corn, sunflower, and waste oils) and both methyl and ethyl routes. For this, the catalyst was characterized in terms of its crystal structure by X-ray diffraction (XRD), specific surface area using the Brunauer-Emmett-Teller (BET) technique, thermal stability by thermogravimetric analysis (TGA), morphology by scanning electron microscopy (SEM), acidity by ammonia desorption at programmed temperature (TPD-NH₃), and catalytic activity by gas chromatography. The results from the structural analyses indicated that Nb₂O₅ has a single monoclinic phase and a morphology consisting of irregular agglomerates. The specific surface area was 1.3 m²/g, and its density was 4.639 g/cm³. The thermogravimetric analysis showed that the material has thermal stability, maintaining its structural integrity up to temperatures as high as 1000 °C. The total acidity reached 301 μmol NH₃/g, indicating the presence of Brønsted and Lewis acidic sites. In catalytic tests, Nb₂O₅ showed higher efficiency in the methyl route, achieving an initial conversion of 96.43% in esters with soybean oil, outperforming other feedstocks. However, catalyst reuse over five cycles revealed a progressive decrease in catalytic activity, possibly due to blocking active sites by adsorbed products, as confirmed by FTIR and XRD analyses conducted on the catalyst. Despite decreased activity after the cycles, the catalyst maintained its crystal structure, indicating structural stability. These results demonstrate the potential of Nb₂O₅ as a heterogeneous catalyst for biodiesel production, particularly with the methyl route and high-quality oils. This study highlights the relevance of Nb₂O₅ in biodiesel synthesis, contributing to sustainable practices and technological advancement in the renewable energy sector.