New alternative biodiesel (fatty acid butyl ester) production using microwave-assisted transesterification: kinetics and optimization

Abstract

Microwave-assisted transesterification represents a promising intensification strategy for rapid biodiesel processing. This study investigates the production of fatty acid butyl esters (FABE) from coconut oil via microwave-assisted butanolysis as an alternative to conventional methanol- or ethanol-based ester systems. Process optimization was performed using a face-centered central composite design (FCCD), with reaction time, temperature, and butanol-to-oil molar ratio as the principal variables. Under the optimized conditions, an approximately 98 % gravimetric product-recovery yield was obtained in less than three minutes. Kinetic analysis showed that the experimental data were better described by an apparent pseudo-second-order model under the investigated conditions; this model is interpreted as a lumped empirical description rather than proof of an elementary reaction mechanism. The evaluated fuel properties—density, kinematic viscosity, flash point, and cetane number—were within the corresponding limits specified by SNI 7182:2015 for those measured parameters only. Full SNI compliance and standardized quantitative total ester content were not established. Overall, the results demonstrate the feasibility of rapid microwave-assisted coconut-oil butanolysis while identifying important needs for improved feedstock characterization, quantitative ester analysis, replicated screening experiments, direct total-energy measurement, microwave-compatible temperature sensing, and solvent-recovery mass balancing.