Acid-catalyzed esterification of karanja (Pongamia pinnata) oil with high free fatty acids for biodiesel production

Abstract

We report the production of a biodiesel fuel by acid-catalyzed esterification of high free fatty acid (FFA) karanja oil (KO). Pretreated KO was converted to biodiesel by a process of alkaline catalyzed transesterification. Optimum acid-catalyzed esterification was achieved using 1% Sulfated Zirconia (SZ) as a solid acid catalyst with a methanol-to-oil ratio of 9:1, temperature at 60°C and reaction time of 2h. During this process, FFA were converted into fatty acid methyl esters. The acid value of karanja oil was reduced to 1.3mg KOH/g from 12.27mg KOH/g, which confirmed the conversion. Consequently, this pretreatment reduces the overall complexity of the process and reduces the cost of producing biodiesel fuel.