Modification of Pyrogallol with Palmitic Acid as a Soluble Biodiesel Additive

Biodiesel, as a promising substitute for fossil diesel oil, has nevertheless a main disadvantage, which is oxidized easily. The oxidation degrades its quality and causes disturbances to the machine during operations. Therefore, antioxidant is commonly used in biodiesel. However, the common antioxidant used, namely pyrogallol, has a poor solubility in biodiesel due to the polarity difference. Therefore, this research focused on the modification of pyrogallol by attaching palmitic acid molecule to the benzene ring of pyrogallol molecule through the Friedel-Crafts acylation. The product was characterized by TLC and ¹H NMR spectroscopy. It was found that the reaction produced a new product, 1.1'-(4,5,6-trihydroxy-1,3-phenylene)bis(hexadecane-1-one). The new product was subjected to a solubility test and an antioxidant activity evaluation. The result showed that the solubility limit of the product was at 2500 ppm, which was significantly higher than pyrogallol analyzed using one sample t-test. However, using DPPH method, it was found that the antioxidant activity of the new product was slightly lower than pyrogallol as the IC50 value of the new product was 18.44 ppm, and pyrogallol's was 3.07 ppm.