Evaluation of the characteristics of non-oxidative biodiesels: a FAME composition, thermogravimetric and IR analysis

Abstract

This experiment evaluates the effects of non-oxidative biodiesel (low oxygen content biodiesels) characteristics and their engine performances. Biodiesels produced from different feedstocks typically contains 10% to 15% oxygen by weight, which enhances the combustion quality and reduces the emissions of hydrocarbons (HCs) and carbon monoxide (CO). However, it produces a higher amount of nitrogen oxides (NO_x) due to an increasing number of combustion products, resulting in a higher cylinder temperature. In addition, lean air–fuel mixtures can contribute to higher NO_x emissions because biodiesel is more oxygenated than diesel. In this study, biodiesels produced from different feedstocks by a transesterification process were used to reduce the oxygen content by dipping an iron bar in the biodiesels, which absorbs oxygen and gets oxidized. Then, the oil characteristics, such as the percentage of saturated and unsaturated fatty acids, thermal degradation, stability and existing functional groups, were analyzed using fatty acid methyl ester (FAME) composition analysis, thermogravimetric analysis (TGA), differential scanning calorimetry (DSC) and Fourier transform infrared (FT-IR) spectroscopy analysis of neat biodiesel and non-oxidative biodiesel. Herein, Pongamia and Moringa biodiesels, containing normal and reduced weight percentages of oxygen, were evaluated to improve the quality and stability of biodiesels used in the diesel engine, which will also reduce the NO_x emissions. Non-oxidative biodiesels had some positive effect on their properties, which can further reduce the NO_x emissions. Herein, non-oxidative Pongamia and Moringa had quite similar characteristics and the former was observed to perform better in the reduction of NO_x and other emissions as well.