Preparation of a garlic peel waste-derived carbon solid acid catalyst with the porous structure for biodiesel production

A waste biomass-derived carbon solid acid catalyst was prepared through the activation of H3PO4-impregnated garlic peel (GP) to enhance the porosity, followed by sulfonation with H2SO4, which was then used to catalyze the esterification reaction with reactants of oleic acid (OA) and methanol. Meanwhile, the influence of the activation temperature on the surface acidity and microstructure of the catalyst and OA conversion has also been determined. Then, the synthesized catalyst was detected using numerous techniques including N2 adsorption–desorption studies, XRD, TG, FTIR spectroscopy, XPS, SEM, Raman spectroscopy, and acid density tests. The catalyst prepared using an activation temperature of 350 °C (PA-GP350-SO3H) exhibited excellent properties by feat of its surface area (469.3 m2/g), pore volume (0.24 cm3/g), and -SO3H density (1.15 mmol/g). FTIR analysis substantiated that the acid functional groups of PA-GP350-SO3H catalyst ware mainly consisted of -COOH, -OH, and -SO3H. In particular, PA-GP350-SO3H catalyst was efficient in the esterification reaction and gave a conversion of 95.2% when the esterification was performed at 60 °C using 5 wt.% catalyst amount and 10:1 of methanol to OA molar ratio for 240 min. The activation energy of the esterification was determined to be 50.4 kJ/mol. Moreover, the reusability and stability of PA-GP350-SO3H catalyst were investigated, which exhibited a 32.3% loss in its activity over to four cycles.