Iron and Zinc Metallates Supported on Ion Exchange Resins: Synergistic Catalysts for the Solvent-Free Cyclic Carbonate Synthesis from Epoxides and CO2

Abstract

Despite extensive research into developing efficient and environmentally friendly catalysts for converting CO₂ over the last decade, the search for a robust and cost-effective catalytic system is ongoing. This study describes developing and applying a new catalytic system using inexpensive ferrate and zincate anions immobilized on easily available commercial ion exchange resins (IER) to produce cyclic carbonates from CO₂ with high efficiency and low cost. Two polystyrene-based anion exchange resins, Amberlyst^TM A26-Cl (A26-Cl) and Amberlite^TM IRA-400-Cl (IRA400-Cl), were compared. The results demonstrated the catalysts’ remarkable activity under mild conditions and demonstrated the synergistic effect between the polystyrene support and the active ammonium metallates, presenting a scalable, eco-friendly method for cyclic carbonate production using waste CO₂. A Design of Experiment (DoE) approach was implemented to optimize the catalytic cycloaddition of CO₂. The reaction scale-up to produce a 5 g batch of propylene oxide and conducting recycling tests demonstrated that the catalyst retained its activity over four cycles. The research also explored the use of various epoxides and found that terminal epoxides produced very good yields. In summary, this study introduces a cost-effective, scalable method for converting CO₂ into valuable cyclic carbonates, leveraging the synergistic effects of polystyrene supports and active ammonium metallates.