Comparative spectroscopic analysis, performance and emissions evaluation of Madhuca longifolia and Jatropha curcas produced biodiesel.

Abstract

In order to fulfil the growing need to replace fossil fuels, investigations exploring the production of biodiesel from agricultural biomass have gained attention. In this study, biodiesels were produced from Madhuca longifolia and Jatropha curcas by means of pre-treatment followed by a two-step acid-base homogeneous catalyst method. These biodiesels were blended with diesel at different percentages. The efficacy of the process was examined using various characterization methods while the efficiency of the produced biodiesels was examined by their engine performance and emission tests. Both Madhuca and Jatropha-based biodiesels exhibited physiochemical properties like that of diesel. Biodiesels were produced by pre-treating with orthophosphoric acid and toluene. The second step involves acid esterification, followed by base transesterification. Raman spectra exhibited C=O stretching at 1725 cm-1 indicating conversion of Madhuca and Jatropha oil into biodiesel. Fourier transform infrared spectroscopy showed a strong presence of fatty acid profile and triglyceride ester linkage at 1744 cm-1. Ultraviolet-visible (UV) spectra confirmed the presence of conjugated dienes in the extracted biodiesels. UV absorbance at 320 nm decreased linearly with blend percentage. 1H and 13C nuclear magnetic resonance (NMR) confirmed the presence of methyl ester moiety at 3.6 δ (ppm) and methoxy carbon at 51.2 δ in biodiesel, distinguishing it from diesel. In the engine performance tests, the variations of brake specific fuel consumption, exhaust gas temperature and brake thermal efficiency versus brake power were studied. The emission tests of different blends were done in terms of carbon monoxide, nitrous oxide and unburnt hydrocarbon. The Jatropha biodiesel exhibited lower mean brake specific fuel consumption, exhaust gas temperature, emitted less carbon monoxide and unburnt hydrocarbon than Madhuca biodiesel. The average decrease in brake thermal efficiency was more in Jatropha biodiesel than Madhuca biodiesel. The present work uses for the first time treatment of ortho phosphoric acid and toluene to produce biodiesel followed by a two-step homogeneous acid-base catalyst method, drastically reducing free fatty acid value.