Experimental Study on the Synthesis of Biobased Poly(ethylene-2,5-furandicarboxylate) and Kinetic Modeling on the Esterification of 2,5-Furandicarboxylic Acid and Ethylene Glycol

The esterification of 2,5-furandicarboxylic acid (FDCA) and ethylene glycol (EG) constitutes a critical initial step in the synthesis of poly(ethylene-2,5-furandicarboxylate) (PEF), a promising biobased alternative to the conventional petroleum-based polyethylene terephthalate with superior physiochemical properties. This work presented experimental and kinetic modeling studies on FDCA-EG esterification for the synthesis of PEF using tetrabutyl titanate as a catalyst at 190-220 °C. A reaction network was proposed, incorporating the reversible esterification, transesterification, and, particularly, the decarboxylation of terminal carboxyl groups to elucidate the coloration phenomenon in PEF synthesis. A comprehensive kinetic model, integrating the reaction kinetics and water removal, was developed using the terminal group method from the homogeneous-stage experiments and validated by the reactions in the heterogeneous stage. The model enables accurate prediction of the time to reach a clear point, the esterification rate, and the concentrations and selectivities of key terminal groups and components under varying conditions. Model implication reveals temperature and water removal efficiency (k_La) as dominant kinetic drivers, while equilibrium water concentration governs the minimum level of terminal carboxyl groups and equilibrium esterification rates, which remain unaffected by temperature or k_La. Although all three parameters show negligible effects on ester product selectivity, byproduct selectivity becomes sensitive to these parameters as the system approaches equilibrium, emphasizing the need to avoid equilibrium extremes for decarboxylation mitigation. These insights provide a kinetic framework to balance reaction regulation and byproduct mitigation, enabling optimized FDCA-EG esterification and efficient PEF synthesis through appropriate process intensification.