Microwave-assisted valorization of biodiesel byproduct glycerol to solketal over Musa acuminata peel waste derived solid acid catalyst: process optimization, kinetics, and thermodynamics

Abstract

The massive quantity of glycerol produced due to the rapid expansion of biodiesel production requires its transformation into value-added products utilizing novel and sustainable methods. Here we report the microwave-induced production of solketal from glycerol using banana (Musa acuminata) peel waste functionalized with sulfonic acid as a heterogeneous catalyst. FTIR, PXRD, TGA, SEM-EDX, and TEM techniques were used to examine the chemical composition and morphology of the catalyst. The four parameters, the glycerol to acetone molar ratio (GTAR), reaction time, catalyst wt.%, and reaction temperature, were optimized using central composite design (CCD). 94.89% glycerol conversion to solketal was observed with a catalyst loading of 7 wt.%, a GTAR of 1 : 4, a reaction temperature of 65 °C, and a reaction time of 12 min. The catalyst showed remarkable stability when used repeatedly and could be reused at least five times without substantial reduction in its activity. With an activation energy of 40.23 kJ mol⁻¹, the reaction followed pseudo-first-order kinetics. The thermodynamic analysis established the endothermic and non-spontaneous nature of the acetalization reaction. Therefore, this technique of glycerol valorization could be applied to the production of solketal as a biofuel additive on an industrial scale with further optimization.