Comparison of Photo‐Esterification Capability of Bismuth Vanadate with Reduced Graphene Oxide Bismuth Vanadate (RGO/BiVO 4 ) Composite for Biodiesel Production from High Free Fatty Acid Containing Non‐Edible Oil

Abstract 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 °C temperature and at 300 rpm stirring speed. The physic‐chemical analysis of synthesized biodiesel revealed that it meets ASTM standards.