Investigations on the Oxidation Stability of Biodiesel Synthesized from Different Vegetable Oils

Abstract

In the present work, different vegetable oils such as sunflower oil, olive oil, corn oil, peanuts oil, palm oil and grape seeds oil were used as feedstocks for catalytic transesterification with methanol to produce biodiesel. The main drawback of biodiesel is a high susceptibility to oxidation or autoxidation during long-term storage than conventional petrodiesel, because of the presence of varying double bonds in the free fatty acid molecules. The objective of this study was to investigate the oxidation stability of biodiesel by Rancimat method. It was found that oxidation stability of all methyl esters investigated (SFME-Sunflower Oil Methyl Ester, OMEOlive Oil Methyl Ester, CME-Corn Oil Methyl Ester, PME-Peanuts Oil Methyl Ester, PaME-Palm Oil Methyl Ester, GsME-Grape Seed Oil Methyl Ester) did not meet the requirements of EN 14214 (6 hours), therefore the efficiency of two antioxidant additives: ascorbic acid and tert-butylhydroquinone (TBHQ), was investigated on oxidation stability of peanuts oil methyl ester and sunflower oil methyl ester. It was found that both additives improve the oxidation stability of biodiesel but tert-butylhydroquinone is more efficient than ascorbic acid. The physico-chemical properties of vegetable oils and biodiesel such as acid value, density, viscosity, lubricity, cloud point, flash point and heating value were determined according to ASTM standards.