LAUSR

The current study concentrates on chemical kinetics, thermodynamic, and overall mass transfer studies on production of biodiesel from waste cooking sunflower oil in transesterification reaction using bentonite-supported sodium methoxide catalyst. The kinetics and thermodynamics analysis of biodiesel from waste cooking sunflower oil was studied at three different temperatures, namely, as 50, 55, and 60 °C using bentonite-supported sodium methoxide catalyst at optimized conditions of methanol-to-oil molar ratio of 12:1 and reaction time of 70 min. It was found that transesterification of waste cooking sunflower oil follows the first-order reaction. The calculated activation energy and pre-exponential factor were found to be 40.98 kJ mol−1 and 1.4 × 105, respectively. The positive values of Gibbs free energy (∆G = 89.66 kJ mol−1), enthalpy (∆H = 38.05 kJ mol−1), and negative entropy (∆S =  − 0.15 kJ K−1 mol−1) values revealed that the transesterification process is non-spontaneous and endothermic in nature. The reaction rate is a function of two resistances: the surface chemical reaction on the catalyst surface and the mass transfer of triglycerides to the catalyst. The overall calculated parameters of triglyceride volumetric mass transfer coefficient, kmt,TG is 1.18 × 103 min−1, and effective pseudo-first-order reaction rate constant, k, is 0.0525 kJ mol−1 min. The used kinetic model accurately represents the entire transesterification mechanism, involving triglyceride conversion to fatty acid methyl ester (FAME) and reaction-controlled on the catalyst. It is observed that the overall volumetric mass transfer depends mainly on the triglyceride conversion rate.