SOURCE:

Faculty: Physical Sciences
Department: Pure And Industrial Chemistry

CONTRIBUTORS:

Anekwe, O. J.
Ajiwe, V.I.E

ABSTRACT:

The depletion and price fluctuations of fossil fuel in the international market have been a major source of concern in total dependence on diesel fuel hence use of biodiesel produced from vegetable oil is a good substitute or additive fuel. Studies were carried out to investigate the fuel properties of Cyperus esculentus, Colocynthus vulgaris, Sesamum indicum ethylesters, methylesters and their corresponding methyl/ethyl ester blends. Ethylesters and methylesters of these oils were prepared by H2SO4 catalyzed transesterification reaction between the oils and ethanol/methanol. The fuel properties such as kinematic viscosity, flash points, pour point and water crackle were determined using ASTM methods. GC-MS was used to determine the fatty acid profile of the transesterified oils. Fourier Transform Infra Red (FTIR) was used to identify the chemical bond functional groups on all the biodiesel, their blends and petrodiesel was carried out at different temperatures 28oC, 100oC, 150oC and 200oC to determine the bond stability. The heavy metal present in the samples were analyzed using atomic absorption spectrometer and flame absorption spectrometry. The kinetics of transesterification was tested using zero order, 1st order and second order kinetic models on the methyl/ethyl esters. Engine emission / performance tests were carried out on a TECHNO R175A diesel engine. Pearson correlation was used to measure the linear relationship between the biofuel properties and fatty acid variables of the biofuel samples. It was observed that the density of most of the ethyl/methyl esters and their blends were higher than that of the petrodiesel, this is as a result of the fatty acid composition and molecular weight of the oil and the biodiesel. The flash points and pour points of all the samples were within ASTM limits. The FFA results showed that the oils were rich in saturated fatty acids (66.67%), appreciable value of monounsaturated fatty acids (33.33%) and (33.33%) polyunsaturated fatty acids. The fatty acid chain lengths that were predominant in Cyperus esculentus, Colocynthus vulgaris, Sesamum indicum were C16, C17, C18 and C20 for the ethylesters while those in the methylesters were C16, C17, C18, C19 and C21. From the FTIR results, it was observed that the wavenumbers slightly increased with increase in temperature which showed that the esters, ester blends and the petrodiesel were thermally stable at those temperatures and had good resistance to thermal degradation and polymerisation. The heavy metal compositions of the esters were lower than that of the corresponding oils which showed that the esters were purified during the esterification process. The optimum temperature for the ethylation and methylation of the samples was 40oC except for Cyperus esculentus methyl ester and Colocynthus vulgaris ethyl ester that had 70oC as the optimum temperature. The values of correlation coefficients R2 obtained from trend line indicated that the experimental data in this study fitted well with the pseudo second order kinetic model. The engine emission / performance tests carried out showed that the biofuels and the oils could power a TECHNO R175A diesel engine used for the test and the fumes from the biofuels were less acidic than the hydrocarbon diesel hence more environmentally friendly. It was observed from the pearson correlation that %MUFAs had strong correlations with pour point and relative density r = 0.984 and 0.885 respectively. The kinematic viscosities at various temperatures had very strong correlations between each other, the viscosity at 700C had strong correlations with the viscosity at 1000C (r=0.970), Weak correlations was also observed between %PUFAs and pour point, %MUFAs and viscosities at different temperatures. Transeserification of these vegetable oils enhanced the fuel properties of the oils and these esterified oils can be better alternatives to fossil diesel.