Sustainable Mg-promoted biochar from pomegranate peel for glycerol carbonate synthesis: Response surface methodology optimization

Mesoporous Mg-promoted pomegranate peel biochar was developed as a low-cost and sustainable heterogeneous catalyst for glycerol carbonate (GC) synthesis via transesterification of glycerol with dimethyl carbonate (DMC). The biochar was calcined at 700–800 °C and modified with 1–5 wt.% magnesium nitrate to introduce basic active sites. Physicochemical characterization identified the sample calcined at 750 °C and impregnated with 3 wt.% magnesium nitrate as the most active catalyst, with a basicity of 1.06 mmol g -1 . Response surface methodology (RSM) was employed to optimize catalyst loading (2–10 wt.%), reaction temperature (60–100 °C), and reaction time (60–180 min). The model predicted optimal conditions of 79.5 °C, 6.33 wt.% catalyst loading, 121 min, and a 3:1 DMC to glycerol molar ratio, affording a GC yield 50.67% GC yield, 53.35% glycerol conversion, and 95% GC selectivity. Catalyst reusability tests revealed a decrease in GC yield to 23.39% after three cycles, likely due to reversible surface fouling. Structure–activity analysis suggests that Mg–O species and inherent alkali components (e.g., K, Ca) contribute to the formation of moderate-strength basic sites associated with catalytic activity. These findings highlight the potential of Mg-promoted biochar as a sustainable catalyst for glycerol valorization. • Waste-derived pomegranate peel valorized into Mg-promoted mesoporous biochar catalyst • Sustainable and low-cost heterogeneous catalyst for glycerol carbonate production • Structure–activity relationships established between basicity, porosity, and catalytic performance • RSM optimization achieves 50.67% GC yield with 95% selectivity under mild conditions • Deactivation mechanism identified as reversible surface fouling with stable catalyst framework