Review of Glycerol Conversion to Glycerol Carbonate via Alkyl Carbonates: Reflections, Future Perspective and Catalytic Roles of Mixed/Promoted Metal Oxides and Mechanistic Insights from DFT

This review summarizes recent progress in the catalytic conversion of glycerol to glycerol carbonate (GC) via transesterification with alkyl carbonates, a sustainable route for valorizing surplus glycerol from biodiesel production. Emphasis is placed on mixed and promoter-modified metal oxide catalysts, which exhibit high activity, selectivity, and stability due to their tunable balance of basic and Lewis acidic sites. Systems such as Mg-Fe, Mg-Al, Mg-Zr, CaO-CeO2, and Mg-Ba oxides have achieved over 90% glycerol conversion and 90–96% GC selectivity under mild, often solvent-free conditions. Mechanistic insights, increasingly supported by density functional theory (DFT), reveal that the reaction proceeds via base-assisted glycerol deprotonation, carbonate activation at Lewis acidic centers, and subsequent cyclization to GC. These findings underscore the importance of acid–base cooperation and promoter effects in enhancing turnover frequency, reducing energy barriers, and mitigating catalyst deactivation due to carbonate deposition or leaching. By integrating experimental results with theoretical modelling, this review provides a comprehensive understanding of catalyst design principles, offering guidance for the development of efficient and robust systems for scalable glycerol upgrading.