Dispersion enhancement of heterodimer antioxidant in palm oil biodiesel

Uncertainty of petroleum supplies and reserves, rise in environmental awareness, and increase of energy consumption have driven the development of renewable energy sources of biodiesel. However, biodiesel tends to be oxidized due to the presence of double bonds in the constituents' fatty acid structure. Utilization of binary antioxidants is one of best option to inhibit biodiesel oxidation as it is more effective than single antioxidant due to the synergistic interactions that take place between each constituent antioxidant. One known interaction is by forming heterodimers that are capable to act as new antioxidant with resembling or even better performance than single antioxidant. Moreover, those heterodimers are also suspected to enhance overall antioxidants dispersion in biodiesel which greatly affects antioxidants effectiveness itself. In this work, dispersion enhancements of 1:1 ratio-PY:TBHQ heterodimers in palm oil biodiesel were then evaluated by comparing the upper-part and lower-part density of the sample and by UV-vis spectrophotometry in one week of storage. Results indicate that heterodimers formed by combination of hydrophilic PY and hydrophobic TBHQ were found to be sufficiently soluble and well-dispersed in biodiesel. Biodiesel treated with PY:TBHQ binary antioxidants was observed had better dispersion than individual PY antioxidant based on increases of density ratio by 0.06344% and 0.07954%, respectively and delta absorbance of 0.023 and 0.041, respectively at 1000 and 2000 ppm. It is concluded that TBHQ moieties of heterodimers existed in binary antioxidants system helped disperse antioxidants better to remarkably improve their performance in inhibiting oxidation.