Synthesis of Pyrogallol Derivative as a Soluble Antioxidant for Biodiesel Additive

Biodiesel as a promising alternative fuel has a major technical drawback which is its instability during storage. One of the solutions to this problem is the addition of antioxidants to improve storage stability. However, the commonly used antioxidant, pyrogallol, has poor solubility in biodiesel due to its polarity difference with biodiesel. Hence this research is focused on modification of pyrogallol with methyl linoleate through a free radical mechanism using benzoyl peroxide as the radical initiator to increase pyrogallol solubility. The presence of the proposed product (10E,12Z)-9-(2,3,4-trihydroxyphenyl) octadeca-10,12-dienoate and its isomer methyl (9Z,11E)-13-(2,3,4-trihydroxyphenyl) octadeca-9,11-dienoate was confirmed using TLC, HPLC and LC-MS/MS which yielded 0.2%. UV-Vis Spectrophotometer was used for the solubility test and the result showed that the solubility limit of the product 2500ppm which was higher than pyrogallol. For the antioxidant activity, the Rancimat test was performed to see the product's performance in accelerated oxidation as well as acid value determination during four weeks of storage. The Rancimat test result shows the product has higher induction period compared to pyrogallol and fulfilled the oxidation test standard. However, the product showed lower acid value stability compared to pyrogallol and biodiesel.