A New Quaternized Chitosan-Based Catalyst Obtained by an Environmentally-Friendly Synthesis Route for Green Production of Carbonated Molecules from Terminal Epoxides

Using CO₂ as a building block to produce monomers through carbonation (cycloaddition reaction) provides an attractive approach to carbon dioxide valorization. The design of an efficient, cheap, and reusable catalyst for epoxide carbonation remains a challenge. In this paper, a new quaternized chitosan catalyst, useful for the cycloaddition of CO₂ to epoxides, was developed. The new catalyst was obtained using a short and straightforward route, including the use of non-depolymerized chitosan and benign reactants such as succinic anhydride (a food additive), at room temperature. The catalyst allowed the carbonation of glycidyl methacrylate at 100 °C, 2 MPa, and 6 h reaction without any solvent required, with 98% epoxide conversion and 87% selectivity to the carbonated product. The catalyst was reused during 3 cycles showing stable values of conversion and selectivity to the carbonated GMA. The selectivity to the carbonated GMA remained stable at 87% during seven recycles. The use of non-depolymerized chitosan as a precursor is a key point that brought durability to the catalyst in comparison to depolymerized chitosan. The catalyst was also used in the carbonation of two di-epoxides (1,4-butanediol diglycidyl ether and bisphenol A diglycidyl ether) at 100 °C and 2 MPa affording high yields to the carbonated products.