▎ 摘　　要

Biodiesel has gained much more attention as an alternative and renewable energy source due to the continuous exhaustion of petroleum reserves and their inauspicious environmental effects. Non-edible feedstocks are economically viable for the production of biodiesel but the presence of higher amount of free fatty acids (FFAs) in these oils is a main hurdle for getting good quality biodiesel. This issue can be addressed through esterification prior to transesterification of oil. This work was designed to evaluate soapnut oil as a source for biodiesel production. Moreover, the catalytic activity of two sunlight active photocatalysts; BiVO(4)and RGO/BiVO(4)was also compared for the esterification of higher FFA content present in soapnut oil. BiVO(4)and RGO/BiVO(4)were characterized through SEM, XRD and FT-IR. Experimental results revealed that RGO/BiVO(4)exhibited higher catalytic activity as compare to BiVO(4)for the esterification of FFA under sunlight irradiation. Different process variables were optimized and maximum conversion of FFA (88 %) was obtained at 3 : 1 methanol to oil ratio, 5 % catalyst dose, 300 rpm stirring speed and 3 h of reaction time. Esterified oil was then transesterified by using MgO-KOH heterogeneous catalyst and maximum yield (94 %) of soapnut methyl esters (SNMEs) was obtained at 9 : 1 methanol to oil ratio, 3 % catalyst dose, 2 h reaction time, 80 degrees C temperature and at 300 rpm stirring speed. The physic-chemical analysis of synthesized biodiesel revealed that it meets ASTM standards.