Effect of Antioxidants and Additives on the Oxidation Stability of Jatropha Biodiesel

Abstract

Jatropha biodiesel was produced by a transesterification reaction, using potassium hydroxide at 1.5% by weight of Jatropha oil as a catalyst. The mole ratio of methanol and Jatropha oil was 7:1. The temperature, speed of mixing and reaction time used were 45°C, 600 rpm and 1.5 h, respectively. Antioxidants and additives were added to Jatropha biodiesel. The range of antioxidant and additive concentrations was 0-750 and 0-1,000 ppm, respectively. The three antioxidants used were PG (3,4,5-trihydroxybenzoic acid propyl ester, propyl gallate), TBHQ (t-butyl hydroquinone) and BHA (butylated hydroxyanisole). The three commercial additives used were ZEP additive, NITROX and L-power. The induction time of biodiesel with either antioxidant or additive was measured according to EN14112, using a Rancimat instrument. The results showed that PG was the best antioxidant for the production of Jatropha biodiesel at concentrations of 50, 150, 250, 350, 500, 650 and 750 ppm, which improved the induction time from 4.21 with no additive to 18.93, 26.35, 30.20 32.98, 34.04, 36.01 and 37.55 h respectively. Regarding the effect on storage for 20 weeks, Jatropha biodiesel with PG added at a concentration of 150 ppm, resulted in an induction time from the first week storage of 26.35 h and this reduced to 23.59 h in the final week (10.47% reduction from the first week). The Jatropha biodiesel properties that resulted from the addition of PG at a concentration of 150 ppm were within the acceptable range, according to ASTM and EN Standards.