Long-term oxidative stability of Jatropha biodiesel and its diesel blends: A comprehensive evaluation using advanced analytical techniques

This study aims to fill the research gap by extensively evaluating the oxidative stability of Jatropha biodiesel and its blends with conventional diesel over a prolonged storage period of 180 days. Initially, Jatropha oil was extracted using mechanical and chemical methods and then converted into biodiesel via an alkaline-catalysed transesterification process with ethanol. We subjected the resultant ethyl esters to a 180-day storage test in pure form and mixed them with 5 %, 10 %, and 20 % diesel. A comprehensive array of analytical techniques was employed to monitor oxidation effects, including Fourier transform infrared spectroscopy, UV–visible spectroscopy, thermogravimetric analysis, rheological assessment, and pressurised differential scanning calorimetry. The results indicated a gradual increase in oxidation markers suggesting biodiesel degradation over the storage period. UV–visible spectroscopy detected the formation of conjugated dienes, trienes, and ketones. Oxidative induction time, as measured by P-DSC, significantly decreased from 41.3 minutes to 7.72 minutes at the end of the 180 days, indicating diminished oxidation stability. Infrared spectra revealed new peaks corresponding to peroxides and dimers, confirming oxidation.The study also observed that diesel-biodiesel blends exhibited a relative increase in oxidation proportional to the concentration of Jatropha biodiesel in the blend. However, these blends displayed longer induction times and greater thermal stability than pure B100 biodiesel. By the study's conclusion, Jatropha biodiesel showed a reduction in oxidation stability by up to 55 %, yet its fuel properties remained within the acceptable range for diesel blend usage, underlining its potential viability as a diesel blend component even after long-term storage.