Phosphotungstic acid-supported alumina as a catalyst for glycerol monolaurate synthesis: process parameter optimization and reaction kinetics

Abstract

Esterification of lauric acid with glycerol is an efficient way to valorize the excess glycerol produced as a by-product of biodiesel production. A phosphotungstic acid incorporated alumina (10HPW/Al₂O₃) catalyst was synthesized and employed as a heterogeneous catalyst for esterification of lauric acid with glycerol. The catalyst displayed potent catalytic activity even at a low catalyst dose of 0.5 wt%. The reaction temperature influenced catalytic activity as a two-fold increase in the conversion was observed with a rise in temperature from 403 K to 443 K. The catalyst showed catalytic activity for 4 reaction cycles without any substantial decrease in conversion. Kinetics models such as nucleophilic substitution (NS), Langmuir–Hinshelwood (LH) and Eley–Rideal (ER) models were investigated. Activation energy and pre-exponential factor for NS and LH models were calculated using the Arrhenius equation. Higher activation energy indicated that the mass transfer limitations were negligible for this catalyst. The synthesized catalysts can be used for up to 4 reaction cycles without any significant decline in the catalytic activity.