Synthesis of Tert-butylhydroquinone Derivative as a Soluble Biodiesel Antioxidant

Biodiesel has been widely used as a substitution for petroleum diesel for years. It offers some various advantages such as higher cetane number, higher efficiency, and low sulfur content. Despite the advantages, biodiesel has one major drawback which is prone to oxidation. The oxidation degrades its quality and causes disturbances to the machine during operations. Therefore, antioxidant was added into biodiesel. However, Tert-butylhydroquinone (TBHQ), as the most effective antioxidant for biodiesel, has low oil solubility. Hence, in this research, TBHQ was modified with methyl linoleate via coupling reaction using benzoyl peroxide. TLC, HPLC, and LC-MS results confirmed that the reaction had successfully produced a new product and its isomer, methyl (10E,12Z)-9-(4-(tert-butyl)-2,5-dihydroxyphenyl)octadeca-10,12-dienoate and methyl (9Z,nE)-13-(4-(tert-butyl)-2,5-dihydroxyphenyl)octadeca-9,n-dienoate. The yield was found to be 10.4%. The product mixture was subjected to a solubility test and an antioxidant activity evaluation. The result showed that the reaction product had higher oil solubility than TBHQ indicated by a steady increase in product absorbance up to 7000 ppm. TBHQ had reached its solubility limit at 5500 ppm. DPPH dot-blot assay, acid value, and rancimat test results revealed that the product mixture had antioxidant activity.