Biodiesel production through transesterification of a mixture of non-edible oils over lithium supported on activated carbon derived from scrap tires

Abstract

Transesterification of a mixture of non-edible oils with methanol was achieved over lithium impregnated waste tires derived activated carbon (WTAC), as a novel solid base catalyst. The WTAC was impregnated with lithium hydroxide, to prepare the solid base catalyst (Li/WTAC). The catalyst was examined through various techniques, such as the surface area, scanning electron microscope (SEM), Thermo-gravimetric analysis (TGA), Hammett indicator method, and x-ray diffraction (XRD). The non-edible oils mixture transesterification to fatty acid methyl esters (FAME) using the so-developed catalyst was found to be 92.23 ± 2.0% under typical reaction conditions of 3.0 wt% amount of the catalyst, 9/1 methanol/oil molar ratio, 40 °C reaction temperature and 60 min reaction period. The superior merits of the so-prepared solid base catalyst are cheap, easily acquired, simple work-up, and the reusability without a significant decline in catalytic activity. The FTIR and 1HNMR spectroscopy affirmed the transesterification of the non-edible oil mixture to FAME. The physicochemical properties of the produced FAME were specified following ASTM standard methods and found to be corresponding to the quality necessities established by ASTM 6751 and EN 14214. Furthermore, the so-synthesized catalyst (40Li/WTAC) exhibited sustained activity after being recycled and reused for 4 times with FAME content > 80%. The pseudo-first order model with 0.0405 min−1 rate constant (at 40 °C) and 19.01 kJ/mol activation energy was the best fitted to demonstrate the methanolysis kinetic of the non-edible oils mixture. The catalytic activity of the catalyst 40Li/WTAC was very effective as it produced a high yield of FAME at mild reaction conditions compared to other solid base catalysts announced in the literature.