Sustainable Production of Biodiesel Using Waste <i>Jatropha curcas</i> Shells as a Heterogeneous Catalyst

In this study, the feasibility of using a calcined Jatropha curcas shell (JCS) as a solid catalyst for biodiesel production was investigated. Thermogravimetric analysis (TGA) was applied to the precursor biomass to evaluate the stages of the thermal decomposition processes and to identify proper temperature intervals for biomass calcination, aiming to decarbonize to form oxides that have proven to behave as effective active sites. The kinetic parameters were defined by applying Kissinger's isoconversional method. The activation of the precursor biomass was carried out at three calcination temperatures (700, 800, and 900 °C) and two calcination times (2 and 4 h) in order to evaluate the influence of these operating conditions on the structure, morphology, and catalytic activity of the catalyst. The catalyst was characterized by the Brunauer-Emmett-Teller method (BET), scanning electron microscopy with energy-dispersive X-ray (SEM/EDX), and X-ray diffraction (XRD). The effectiveness of the catalyst was assessed by oil's transesterification at 60 °C, 2 h of reaction, and a 15:1 alcohol/oil molar ratio. The effects of catalyst loading (1, 3, and 5 wt %) and activation temperature of the catalyst on the yield and conversion to fatty acid methyl esters (FAMEs) were studied. The highest values of conversion and FAME yield were obtained with a 3% catalyst load (calcined at 800 °C for 2 h). Ester content and fatty acid profile were obtained by chromatographic analysis. The results of this study demonstrate that calcined JCS has a high potential as a heterogeneous catalyst for biodiesel production.