Acid Value Reduction of Calophyllum inophyllum Oil by Oilseeds In situ Esterification Using Sulfuric Acid Catalyzed Methanol and Isopropyl Alcohol Mixture

Abstract

Non-edible oilseed can be used in biodiesel preparation as a low-cost feedstock. However, it contains a high free fatty acid or a high acid value, which causes a problematic biodiesel reaction. The investigation of acid value reduction of Calophyllum inophyllum oilseed by in situ esterification using sulfuric acid-catalyzed methanol and isopropyl alcohol has been conducted. Calophyllum inophyllum oil was extracted by n-hexane in the Soxhlet apparatus to determine the oil content. In situ esterification using methanol-isopropyl alcohol and the sulfuric acid as a catalyst was carried out in a reflux three-neck rounded bottom flask batch process to decrease free fatty acid or acid value. Four independent reaction variables, including the ratio of mixture volume to seed weight, the ratio of methanol to mixture volume, catalyst percentage, and reaction time, were varied. The experiments utilized by the response surface methodology with central composite design configuration to obtain the optimum conditions. The oil content of Calophyllum inophyllum oilseed extraction was 57.94% and an acid value was 90.38 mg KOH/g. The maximum esterified oil yield of 91.00% and 3.81 mg KOH/g minimum acid value were achieved in the optimum reaction conditions.