Experimental evaluation over the effects of natural antioxidants on oxidation stability of binary biodiesel blend

Prolonged storage of biodiesel leads to deterioration of fuel properties and its usage in engines results in drop-in performance characteristics. The present study deals with the effect of natural antioxidants on the storage stability of binary biodiesel blend of Jatropha biodiesel and lemongrass oil, which are synthesized through transesterification and steam distillation process, respectively. Natural antioxidants such as sesame, horse gram, sweet basil, coffee, and peas were employed in the current study. Thermal analysis of the antioxidants was carried out utilizing differential scanning calorimetry and thermogravimetric analysis to study the effect of temperature on antioxidants. Ethanol extract of natural antioxidants was prepared at various concentrations such as 500, 1000, and 1500 ppm. Total phenol content in the antioxidant extracts was determined through the Folin-Ciocalteu method in terms of gallic acid equivalent (GAE). The oxidation stability of fuel samples with the addition of antioxidant extracts was estimated by the Rancimat method in terms of the induction period (IP). As a result, the scavenging effect in percentage for sesame, horse gram, sweet basil, coffee, and peas were 88.76%, 86.51%, 75.28%, 74.15%, and 70.78% at 1500 ppm, respectively. Besides, the total phenol content (mg GAE/100 g) for sesame, horse gram, sweet basil, coffee, and peas observed are 97.37, 39.99, 35.07, 30.15, and 25.25, respectively. More interestingly, adding antioxidants extracted from sesame, horse gram, sweet basil, coffee, and peas could increase the IP of the Jatropha biodiesel-lemongrass oil binary blend to 9.92, 8.10, 7.74, 7.10, and 4.10 hours, respectively compared to the case of binary blend without antioxidant (only 2.06 hours). In general, the inclusion of natural antioxidants additives increased the oxidation stability of biodiesel, promoting its prolonged storage, and the overall effectiveness of selected natural antioxidants was found to be in the order of sesame > horse gram > sweet basil > coffee > peas. Highlights: The incorporation of a binary biodiesel blend reduces the cost of biodiesel synthesis. Replacement of synthetic antioxidant additive with natural antioxidant additive. Natural antioxidant addition enhances the storage stability of binary biodiesel blend.