Xanthium strumarium seed as a potential source of heterogeneous catalyst and non-edible oil for biodiesel production

Abstract

A sustainable process has been developed for synthesis of biodiesel by utilizing seed shell ash and non-edible seed oil from Xanthium strumarium seeds. The catalyst prepared by open air burning (UC), calcinations at 550 °C (C550) and 700 °C (C700) was characterized by powder X-ray diffraction (XRD), fourier transform infrared (FT-IR), field emission scaning electron microscope (FESEM), energy dispersive X-ray (EDX), field emission transmission electron microscope (FETEM), X-ray photoelectron spectrometer (XPS), thermogravimetric (TG) and brunauer-emmett-teller (BET) analysis. Elemental analysis by XPS and EDX displayed the presence of potassium (34 wt%) in high concentrations that can contribute effectively to the transesterification process. The derived catalyst provides a high biodiesel yield (98.3%) at optimum operating conditions viz. 6 wt% catalyst concentrations, 9:1 methanol to oil ratio at 60 °C within 70 min. FFA content reduced from 5.63 mg in the oil to 0.28 mg in the biodiesel due to presence of considerable amount of amphoteric SiO2 and acidic P2O5 in the catalyst. The catalyst prepared at 550 °C showed the highest pH value of 11.78. The Hammett indicator test provides higher basicity for C550 (0.513 mmol/g) than that of C700 and uncalcined catalyst. The reaction follows pseudo-first-order kinetics and the activation energy was found to be 37.413 kJ mol−1. The reusability study also showed satisfactory biodiesel yield (82.3%) at 3rd round of transesterification reaction. The prepared biodiesel was characterized by 1H and 13C NMR, GC-MS analysis and the fuel parameters are evaluated by the standard protocols.