Transesterification of Rubber-Seed Oil (RSO) to Biodiesel Using an Empty Palm Kernel Bunch (EFB) Catalyst: Kinetics, Thermodynamic and Biodiesel Yield Prediction

Abstract

Kinetics of transesterification reaction of rubber seed oil (RSO) using empty palm kernel bunch (EPB) was carried out to correlate kinetic data, the rate constants, order of reaction with the thermodynamic parameters such as enthalpy, entropy, activation energy, and free energy of conversion. The study was aimed to determine the effect of EPB on methyl-ester conversion while examining the variation of biodiesel properties with experimental variables at methanol to oil molar ratio. Optimum methanol to oil molar ratio of 6:1 was selected for the transesterification at varied temperatures 20C to 60C and reaction time 10minutes-120minutes respectively. The chromatography technique was applied to determine the methyl-ester concentration at varied catalyst weights of 0.2wt%, 0.3wt%, and 0.5wt %, respectively. The analysis of the results shows that; the reaction in terms of methyl-ester conversion followed predominantly 1st order kinetics. The enthalpy (ΔH‡), entropy (ΔS‡), and activation energy (Ea) values increased as catalyst weights and temperature increases intermittently with the reaction time, which translates to; 16.15kjmol‒1, ‒ 350kjmol‒1, and 17.43kjmol‒1 respectively at 0.5wt% of EPB. The maximum rate constantk = 4.8x10‒3kmol/min with a correlation coefficient: R2 = 0.999 was obtained for the conversion. The prediction results obtained with the Multiple Linear Regression (MLR) algorithm shows that; corresponding values of (ΔH‡) and yield increase consistently with the increase of the concentrations of catalyst (EPB). The MLR results established that; higher yield ≥ 80% and quality of RSO is feasible at the temperature ≥ 400C, catalyst weight ≥ 0.5wt% and maintains considerable values of enthalpy at the optimal ratio of 6:1.