Kinetics and Thermodynamics Studies of the Transesterification of Waste Cooking Oil Using Biochar-Based Catalyst Derived from Rubber Seed Shells

Abstract

Biodiesel, a renewable and environmentally friendly fuel, has gained significant attention as an alternative to conventional diesel due to its numerous advantages, such as reduced greenhouse gas emissions, biodegradability, and sustainability. In this study, the kinetics and thermodynamics of the transesterification of Waste Cooking Oil (WCO) using a recently developed biochar-based catalyst derived from rubber seed shells were investigated. Experimental kinetic data were obtained using UV-spectrophotometric analysis of glycerol concentration. Three kinetic models- power law, Eley-Rideal, and Langmuir-Hinshelwood, were fitted to the experimental data, and their fitness and suitability were assessed using statistical parameters such as coefficient of determination (R²), adjusted R², root mean square error (E_RMS), and variance. The results show that the reaction kinetics of the transesterification of WCO over the developed catalyst is best described by the irreversible pseudo-first-order kinetic model, having a rate constant of 0.0164 min^-1 at 65 ^oC. The exponential factor and the activation energy of the reaction were 7139.5 min^-1 and 36.6 kJ/mol respectively. The thermodynamic parameters of the reaction include a change in enthalpy (∆H) of 33.9 kJ/mol and a change in entropy (∆S) of -0.180 kJ/mol. K, with positive Gibb’s free energy (∆G) values. The results, therefore, imply that the transesterification of WCO catalyzed by the recently developed biochar-based catalyst derived from rubber seed shells is an endothermic process and a non-spontaneous reaction.