The synergistic effect of pyrogallol based binary antioxidants in the oxidative stability of palm oil biodiesel

Abstract

Biodiesel is one of the renewable alternative fuels consists of mono alkyl ester fatty acids derived from vegetable oils or animal fats. Due to its high availability, palm oil become the main source of Indonesian biodiesel production. Nevertheless, one of the drawbacks in the use of biodiesel is that biodiesel is prone to quality degradation due to its oxidative instability especially on the unsaturated based methyl ester content in the presence of air, heat, metal elements, peroxides, and storage conditions. The oxidation of biodiesel might lead to some problems such as filter plugging, fouling on the injector, deposits development on the combustion engine, and malfunctions in the diesel engine fuel system. Biodiesel oxidation can be prevented by the addition of antioxidants. The application of binary antioxidants has been reported in extending the induction periode and the improvement of biodiesel quality due to its synergistic effect. In this study, pyrogallol is used as the main component in several binary mixtures with other antioxidants. There are three pyrogallol binary antioxidant that have synergistic effect, PY:TBHQ (1:3), PY:TBHQ (1:1), and PY:BHA (1:1), with their induction periode of 26.88 hours, 38.48 hours, and 31.24 hours, respectively. PY:TBHQ (1:1) has the highest induction periode among the other binary antioxidants. For the iodine value and acid number, all of the samples are within the specification of biodiesel (max. 115 g-I2/100 g) and (max. 0.5 KOH mg/g).