Abstract
The present work reports the results of the study of the effect of metal contaminants on the oxidation, thermal, and storage stability of Jatropha curcas biodiesel (JCB) with and without antioxidants. Taking Pyrogallol (PY) as the most effective antioxidant based on the earlier work of the authors, JCB was mixed with different transition metals—Fe, Ni, Mn, Co, and Cu in different concentrations. Induction period (IP) was measured using Rancimat method (EN 14112). The ASTM D6468 and thermogravimetric analysis (TGA) methods are used for evaluating the thermal behavior of JCB. Based on results, several correlations are developed for assessing the oxidation, thermal, and storage stability. For the purpose of optimization, response surface methodology (RSM) is used. A comparison between the experimental values and those predicted by the correlation shows that all the data points lie within ±10% deviation lines of the experimental results. The optimized concentration of PY for 2 ppm metal-contaminated biodiesel to have an IP of 6 hr is 326.96, 361.64, 386.15, 417.24, and 600 ppm for Fe, Ni, Mn, Co, and Cu, respectively. From the experiments it is found that if metal concentration is 0, then, 200 ppm of PY is sufficient to make biodiesel stable for 6 months. If metal (Fe) concentration is 2 ppm or more, then 800 ppm PY is sufficient to make biodiesel stable for 5.5 months. This is the first study of its kind being reported in the literature in which RSM is used for design of experiment for developing the correlation for oxidation, thermal, and storage stability. The models developed by RSM will be highly useful for predicting the optimum antioxidant concentration to impart maximum fuel stability in JCB.
Highlights
Stability of biodiesel may be affected by its interaction with contaminants, light, temperature, factors causing sediments formation, changes in color, and other changes that reduce the cleanliness of the fuel [1]
A comparison between the Induction period (IP) obtained from experimental investigation and those predicted by the correlation shows that all the predicted data points lie within ±10% deviation lines of the experimental results
For the objective Jatropha curcas biodiesel (JCB) was mixed with PY and different metal contaminants, subjected to open air storage exposed to sunlight condition
Summary
Stability of biodiesel may be affected by its interaction with contaminants, light, temperature, factors causing sediments formation, changes in color, and other changes that reduce the cleanliness of the fuel [1]. Most of the plant-derived fatty oils like soybean and rapeseed contain poly-unsaturated fatty acids that are methylene interrupted rather than conjugated. This structural feature is key to understanding both oxidative and thermal instability. India imports about 40–50% of total domestic edible oil demand, and it is impossible to divert these resources for biodiesel production [2]. Attention has been focused to the use of nonedible oil resources like Jatropha, pongamia, neem, and so forth for biodiesel production in the country. The oil from the seeds of the Jatropha curcas plant would become the source of biodiesel
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