Homogeneous catalyzed transesterification of neem seed oil to biodiesel and its kinetic modeling

Abstract

AbstractThis study focuses on the kinetic modeling of homogeneous catalyzed transesterification of neem seed oil and the determination of the rate‐limiting step (RLS). The oil was extracted from the seeds by cold solvent extraction and it was characterized to determine its physicochemical properties. The effect of factors such as time, amount of catalyst, temperature, methanol / oil molar ratio, and agitation speed on the biodiesel yield were investigated. The kinetic experiments for the transesterification reaction were carried out by batch process, assuming a pseudo second‐order reaction. Rate equations for the arrays of reversible reactions of triglyceride to glycerol and biodiesel were developed to determine the RLS. The oil yield extracted was 34%. The extracted oil contained 60.2% monounsaturated fatty acid and the dominant monosaturated fatty acid is oleic acid having 40.6% of total composition of monosaturated fatty acid in the oil. The biodiesel yield produced by transesterification of pretreated neem oil was 90% and biodiesel properties were within the limits of American Society for Testing and Materials (ASTM) (D6751‐02) standards. The kinetic modeling of the reaction revealed that the rate constant values for forward reactions (transesterification) (k1, k3, and k5) were higher than those of backward reactions (k2, k4 and k6) at temperatures of 45, 55, and 65 °C. The rate constant (k1) for the conversion of triglyceride to diglyceride was the least among the rate constants of forward reactions at all the studied temperatures showing the RLS. The rate constants for the RLS are 0.0174, 0.0208, and 0.0303 min−1 at temperatures of 45, 55, and 65 °C respectively and the activation energy is 24.9 kJ mol−1. © 2020 Society of Industrial Chemistry and John Wiley & Sons Ltd