Solvent-free synthesis of renewable FDCA-based bis-cyclic carbonate using a metal-free heterogeneous catalyst

Abstract

In this work, we developed a new catalytic strategy to synthesise an industrially relevant, fully renewable  cyclic carbonate: 2,5-bis-dicarboxyl furan cyclic carbonate (BDFCC). This compound contains two terminal cyclic carbonate groups, which makes it attractive for application as a building block for green polymers. BDFCC was prepared from two renewable compounds: the methyl ester of 2,5-furandicarboxylic acid and glycerol carbonate, via a transesterification reaction at mild temperature (80 °C) using a novel, metal-free dual catalytic system consisting of commercially available ion-exchange resin beads (Amberlite IRA-900-Cl) and glycidol. Under conditions previously reported for homogeneous catalysis, involving n-hexane as solvent, only a moderate yield of BDFCC was achieved (42%). An improvement in both performance and sustainability of the process was achieved by implementing an equilibrium-shifting solvent-free strategy, which overcomes the thermodynamic limit of the reaction (Δ_rG° = +25 kJ mol⁻¹ based on DFT calculations). This approach, combined with an optimisation of the reaction conditions, allowed increasing the BDFCC yield to 86%. Furthermore, the heterogeneous resin bead catalyst was recyclable over multiple runs without experiencing loss of activity. Control experiments allowed to gain insight in the reaction mechanism and revealed the crucial role played by glycidol in promoting the catalytic activity of the Amberlite resin beads.