Removal of free fatty acids in neem oil using diphenylamine functionalized magnetic mesoporous silica SBA-15 for biodiesel production

Abstract

Biodiesel is produced from edible/non-edible plants oil. However, alkaline transesterification of these oils makes the process challenging due to the presence of large amount of free fatty acids (FFA), which forms soap on reaction with alkali. Hence, it is necessary to reduce FFA present so that alkaline catalyzed transesterification can be carried out. In this work, biodiesel fuel was produced using diphenylamine functionalized magnetic mesoporous silica SBA-15 as catalyst for the esterification of free fatty acid (FFA) present in neem oil (NO) and its effect on esterification reaction was studied. Optimum catalyzed esterification was achieved using 1 g diphenylamine functionalized magnetic mesoporous silica SBA-15 as a solid base catalyst with a methanol to oil ratio of 9:1, at 60°C and reaction time of 1.25 h. During this process, FFA was converted into fatty acid methyl esters. The acid value of NO oil was reduced to 7.34 mg KOH/g from 52.45 mg KOH/g, accounting for 86% conversion efficiency. Consequently, this pretreatment reduces the overall complexity of the process and reduces the cost of producing biodiesel fuel. Pretreated NO was converted to biodiesel by a process of alkaline catalyzed transesterification using 1% KOH in methanol.