Biodiesel Production From High-free Fatty Acids Podocarpus falcatus Oil and Identification of Fatty Acid Methyl Esters by FT-IR, NMR (¹H and ¹³C) and GC/MS Studies

Biodiesel occupies a prominent place as the alternative fuel to fossil diesel owing to socio-economic and environmental factors. In this present study, Podocarpus falcatus oil (PFO), having undergone a storage effect, was converted into biodiesel. PFO had a high fatty acid content (FFA = 8.19%). For this reason, a two-step transesterification procedure was developed to convert these high-free fatty acid (FFA) oils into their corresponding monoesters. In the initial step, an acid-catalyzed esterification was employed to lower the FFA content of the oil to below 2%. Subsequently, a second step involving an alkaline catalysis transesterification process was used to convert the product obtained in the first step into monoesters and glycerol. The methyl esters obtained were analyzed using nuclear magnetic resonance (¹H, ¹³C NMR), Fourier transform infrared spectroscopy (FT-IR), Thermal gravimetric analysis (TGA), carbon, hydrogen, nitrogen, and sulfur (CHNS), and Gas chromatography-mass spectrometry (GC–MS) analysis. The identity FAME were Hexadecanoic acid, methyl ester (C16:0), 9,11-Octadecadienoic acid, methyl ester, (E, E)- (C18:0), 6-Octadecenoic acid, methyl ester, (Z)- (C18:2), Methyl stearate (C18:1), Methyl (Z)-5,11,14,17-eicosatetraenoate (C20:5), 11,14-Eicosadienoic acid, methyl ester (C20:3), 11-Eicosenoic acid, methyl ester (C20:2). The study examined the thermal stability of synthesized biodiesel, revealing it remained stable up to 189 °C. Furthermore, the physicochemical properties of biodiesel were validated using ASTM6751 standards.