Nuclear magnetic resonance (NMR) applications in biodiesel characterization and quality – A review

Abstract

This manuscript highlights the role of nuclear magnetic resonance (NMR) in assessing the quality and purity of biodiesel. NMR has proven to be an indispensable tool for biodiesel characterization, allowing for precise identification of key physicochemical properties such as methyl ester content, oxidative stability, free fatty acids, and glycerin residues. The ability of 1H NMR to detect impurities, adulterants, and structural changes during production and storage ensures compliance with international standards like ASTM D6751 and EN 14214, which are essential for maintaining biodiesel quality and performance. The study comprehensively compares the application of NMR in analyzing biodiesel from various feedstocks, including vegetable oils, animal fats, and waste oils. NMR’s capacity to discriminate biodiesel sources through specific chemical shifts, such as the methoxy group at 3.6 ppm, and identify contaminants, like water and residual catalysts, highlights its superiority over other analytical techniques like gas chromatography (GC) and Fourier-transform infrared spectroscopy (FTIR). Additionally, the manuscript underscores the importance of NMR in optimizing production processes by evaluating conversion efficiency and identifying by-products. The key contributions of this study lie in its detailed comparison of biodiesel from different feedstocks and its focus on the role of impurities and additives in affecting biodiesel quality. This work confirms NMR’s effectiveness as a reliable, non-destructive tool for ensuring biodiesel purity, making it an essential technique in advancing biodiesel production, improving process efficiency, and promoting the use of sustainable biofuels.