Investigation of the catalytic activity and reaction kinetic modeling of two antimony catalysts in the synthesis of poly(ethylene furanoate)†
In the last few decades, the interest in the synthesis and development of novel biobased polymers with interesting properties, able to compete with the existing petroleum-based polymers, has grown exponentially. 2,5-Furandicarboxylic acid (FDCA) is among the most studied biobased monomers and is currently the only aromatic one, when aromaticity is mandatory to obtain polymers with superior properties. However, furan-based polyesters are mainly prepared from 2,5-dimethyl furandicarboxylate (DMFD), by transesterification, adding a supplementary step in the synthesis and an extra barrier towards industrialization. Herein, we present the study of the polymerization of high-purity FDCA with EG using two different antimony catalysts (antimony oxide, Sb2O3, and antimony acetate, Sb(CH3COO)3) and different esterification and polycondensation temperatures by the traditional two-step polycondensation method. Each step was monitored by suitable characterization techniques, such as intrinsic viscosity measurements, carboxylic acid end-group analysis, nuclear magnetic resonance spectroscopy, infra-red spectroscopy and differential scanning calorimetry. Additionally, for the first time, liquid chromatography (LC) coupled with high resolution mass spectrometry (HRMS) was used in the study of FDCA polymerization. PEF oligomers produced during the esterification step were precisely identified by HRMS, providing new insights into the evolution of this step. Finally, theoretical studies were conducted to model the kinetics of the polymerization of PEF during both esterification and polycondensation stages.