Optimization and kinetic study of N-methyldiethanolamine-based esterquats production

Abstract

A sustainable alternative process for the production of bio-based esterquats via heterogeneous transesterification of palm methyl ester and N-methyldiethanolamine was developed. The transesterification process conditions over CaO/γ-Al₂O₃ catalyst were optimized using Response Surface Methodology (RSM). At 146°C, 83.2% di-ester yield was obtained after 6 h when 4.1 wt% of the synthesized catalyst was used with 1.8:1 methyl ester/N-methyldiethanolamine molar ratio. CaO/γ-Al₂O₃ was able to be reused for 3 cycles without a significant deactivation. A kinetic model was proposed based on irreversible second-order kinetics and it was the best-fitted experimental data with an overall reaction rate constants ranging between 0.0892 and 0.695 L/mol.min and an activation energy of 48 kJ/mol. The first experimental investigation on kinetic can be applied to provide insights on large scale reactor design for bio-based esterquats production. The synthesized esterquats was found to be readily biodegradable, as it reached the pass level of 60% of biodegradation within the period of incubation (28 days). It exhibits similar chemical and physical properties to the commercially available tallow-based esterquats, thus offering a potential substitute for the animal fat-based feedstock with the most abundantly available and renewable palm-based oleochemicals.