Catalytic valorization of biodiesel-derived glycerol to high-value chemicals: advanced catalysts, mechanisms, and process engineering

The growing production of biodiesel has resulted in a substantial surplus of crude glycerol, a low-value byproduct that poses economic and environmental challenges. This review critically examines catalytic valorization strategies that transform crude glycerol into high-value chemicals, thereby enhancing the sustainability and profitability of biodiesel processes. Emphasis is placed on the technical and economic barriers associated with crude glycerol utilization, including impurity-related limitations and energy-intensive purification steps. The paper systematically explores reaction mechanisms governing glycerol oxidation, hydrogenation, and reforming, highlighting advances in heterogeneous, electrochemical, and photocatalytic systems. Particular attention is given to catalyst design innovations such as bimetallic alloys, defect-engineered surfaces, and non-noble metal alternatives that improve selectivity toward C3 products while mitigating C–C bond cleavage. Furthermore, the review addresses process intensification through continuous-flow reactor configurations, which offer superior scalability and operational stability compared to conventional batch systems. Integration of glycerol valorization within biorefinery frameworks is discussed as a pathway to circular bioeconomy models, supported by techno-economic and life-cycle assessments. Finally, future research directions are outlined, focusing on impurity-tolerant catalysts, modular reactor designs, and AI-driven optimization to enable industrial-scale implementation. Collectively, these strategies position glycerol valorization as a critical component for achieving resource efficiency and net-zero emission targets.