Fourier transform infrared spectroscopy models to predict cetane number of different biodiesels and their blends. 2020-01-0617
The ignition quality of a fuel is described by its Cetane number. Experimental methods used to determine cetane number employ Co-operative fuel research (CFR) engine and Ignition quality tester (IQT) which have less repeatability and require skilled operation, and hence least preferred. There are many prediction models reported, which involve number of double bonds and number of carbon atoms whose determination is not-direct. Usage of models relating biodiesel composition to its cetane number is limited by the range of esters involved. Hence, a model to predict cetane number of biodiesels that addresses the limitations of the existing models, without ignoring the influence of factors such as degree of unsaturation and number of carbon atoms is needed. Employing Fourier transform infrared spectroscopy (FTIR) could be one such method. Five biodiesels with significant compositional variations were prepared from Camelina, Coconut, Karanja, Linseed and Palm oils which were blended in different volume proportions to 70 samples. The range of cetane number covered was from 42.2 to 66.6. Peak absorbance of different functional groups of these samples was determined using FTIR which was correlated to their cetane number and prediction models were developed using regression. These models were validated using biodiesels not used to develop them. Mean absolute deviation and Mean absolute percentage error were the statistical parameters used to compare the proposed model with the existing models whose values turned out to be reasonably good.