Kinetic and Thermodynamic Studies of Transesterification Catalysed by Black Pepper Seed-Potassium Hydroxide Catalyst

Abstract

This study proposed biodiesel production from refined, bleached, and deodorised palm oil via transesterification using black pepper seed-KOH catalyst. A heterogeneous industrial waste catalyst, notably black pepper seed-KOH, was proposed because it can offer sustainability in biodiesel production. While among first generation oil feedstocks, palm oil stands out due to its high productivity because more palm oil can be generated per land area than others. Despite the most common use of the pseudo-first-order kinetic model in biodiesel studies, limited attention has been given to the second-order and reversible kinetics studies. Therefore, catalyst characterization encompassed SEM, EDX, TGA, PSA, FTIR, and basicity tests were first performed. Then, transesterification was executed at different temperatures (50–70 °C), 240-minute reaction time, 6:1 methanol-to-oil ratio, 5 wt% catalyst loading, and 200 rpm to obtain the best fit kinetic model and thermodynamic data. The results displayed a pseudo-irreversible first-order kinetics. Activation energy and pre-exponential factor were determined as 61.5195 kJ mol⁻¹ and 1.1367 × 107 min⁻¹. While, thermodynamic value was calculated, ΔH = 58.7528 kJ mol⁻¹, ΔS = − 0.0850 kJ mol⁻¹ K⁻¹ and ΔG = 86.2157 to 87.9162 kJ mol⁻¹. Therefore, the transesterification was defined as an endothermic, endogenic, and non-spontaneous reaction. This study demonstrates the black pepper seed-KOH’s efficacy in biodiesel production and enhances understanding of kinetic and thermodynamic parameters governing the transesterification process.