Robust models are useful to predict
the properties of biodiesel
to facilitate the careful choice of feedstock for producing biodiesel
for automotive engine applications. In the present work, a Fourier
transform infrared spectroscopy (FTIR)-based approach is used to predict
the kinematic viscosity, density, cetane number, and the higher calorific
value of biodiesels. Unlike the standard partial least-squares (PLS)
regression performed over a complete infrared spectrum, a novel approach
involving few independent variables based on the functional groups
present in biodiesel and correlating them with the properties of biodiesel
is explored in the present study. To mimic a wide range and the type
of methyl esters present in biodiesels, five biodiesels of significantly
different compositions, namely, camelina, coconut, karanja, linseed,
and palm, are chosen and are mixed in different volumetric proportions
to obtain 70 biodiesel blends. The peak absorbance ratios of 70 biodiesel
blends obtained from FTIR are correlated with the measured kinematic
viscosity, density, cetane number, and the higher calorific value.
The property prediction models are developed using multilinear regression
and an artificial neural network whose performance is compared with
that of standard full spectrum PLS regression. The results obtained
show that the proposed approach is simple, reliable, and direct and
provides better prediction with mean absolute percentage errors of
4.62%, 1.04%, 2.75%, and 6.85%, respectively, for the kinematic viscosity,
density, higher calorific value, and cetane number of biodiesels.