Mechanochemically Prepared Supported Ionic Liquids for Efficient Glycerol Valorization to Glycerol Carbonate

Abstract

The valorization of glycerol, a major byproduct of the biodiesel industry, into high value chemicals offers a sustainable pathway to support circular economy objectives within biorefineries. Among various transformation routes, the transesterification of glycerol with dimethyl carbonate (DMC) to produce glycerol carbonate (GC) is particularly attractive due to its green chemistry credentials and industrial relevance. In this study, supported ionic liquids (SILs) based on imidazolium cations with intrinsic basicity were synthesized and immobilized onto solid supports to develop efficient and reusable catalysts for this process. A solvent-free mechanochemical approach using ball milling was employed to immobilize the ionic liquids on CeO2, SiO2, Al2O3, MCM-41, and SBA-15 supports. The resulting catalysts were extensively characterized using XRD, FTIR, N2 physisorption, CO2-TPD, solid state NMR and SEM techniques. Among the tested catalysts, the N(CH3)2-[Im][HCO3]@SiO2 exhibited the highest activity, achieving 97% glycerol conversion and 94% GC yield at 90 °C in 60 min with a glycerol to DMC molar ratio of 1:3. Moreover, the SiO2 supported ionic liquid catalyst demonstrated greater stability and reusability over multiple cycles compared to its CeO2 based counterpart. These results highlight the potential of immobilized SILs as robust and sustainable catalysts for the efficient valorization of glycerol to glycerol carbonate.