Biodiesel is a renewable, with high combustion efficiency but low emission as a replacement of limited reserves of petrodiesel. On the other hand, biodiesel as a fuel has a problem caused by its instability against oxidative degradation. This reaction might decrease the quality of biodiesel as the product of the reaction potentially harm the diesel engine during combustion. Therefore, antioxidant additive should be added to biodiesel to prevent the oxidative degradation. Among several phenolic antioxidants, pyrogallol has been known/mentioned as one of the best antioxidant additive for biodiesel. However, the solubility of pyrogallol in biodiesel is relatively low. In the previous study, the addition of alkyl group to pyrogallol's benzene ring has been done in order to increase the solubility of pyrogallol in biodiesel. Pyrogallol was reacted with methyl linoleate through oxidative coupling reaction using 2,2-diphenyl-1-picryhidazyl (DPPH) resulting a new synthesized product. Unfortunately, the reaction resulted a mixture of products containing unreacted pyrogallol, DPPH, dimer of pyrogallol, and low concentration of the synthesized product. The synthesized product was separated from the mixture to get the higher concentration. The difference in molecular size led to the separation of synthesized product from the mixture through molecular sieve zeolites. Zeolites has been widely used as molecular sieve to separate the mixture based on molecular size. In this research, the product mixture was separated based on the molecular size through adsorption using 3 types of zeolites which has different pore sizes: SAPO34 (4Å), Na-Y (7Å) and 13X(10Å). The result confirmed that different pore size of zeolites could successfully separate the synthesized product from other components in the mixture.