Application of a BPH zeolite for the transesterification of glycerol to glycerol carbonate: effect of morphology, cation type and reaction conditions

Valorization of glycerol (Gly) to high-value chemicals is the key to unlocking economic and sustainable biodiesel production. The transesterification of Gly with dimethyl carbonate (DMC) to glycerol carbonate (GC) requires a catalyst with high basicity and uniform pore size for high product selectivity. BPH-type zeolite (Linde Q) nanosheets are promising catalysts for overcoming diffusion transport limitations inside the pore network and inhibiting the formation of glycidol as a side product. As-prepared BPH nanosheets (nano-sized CsBPH_AP, 192 nm size) and micron-sized BPH (micron-sized KBPH_AP, 600 nm size) were prepared by hydrothermal treatment with different Si/Al ratios. With a morphology-dependent reaction, the nano-sized CsBPH_AP demonstrates superior performance in the transesterification of Gly to GC as compared to micron-sized KBPH_AP. Ion-exchange of the nano-sized CsBPH_AP and micron-sized BPH_AP, with potassium and cesium precursors respectively, to afford nano-sized K-CsBPH_IE and micron-sized Cs-KBPH_IE resulted in similar thermal properties but different basicity and catalytic activity compared to the parent samples; higher basicity resulted in better catalytic performance. The nano-sized CsBPH_AP with a catalyst loading of 6 wt% shows good catalytic performance over four runs under optimized reaction conditions at 120 degrees C for 3 h and the Gly : DMC molar ratio of 1 : 5. This study reveals the crucial effect of catalyst morphology and size on the conversion of Gly to GC.

Automated summary

This study investigates the morphology and size effect of catalysts on the conversion of glycerol to glycerol carbonate. Nano-sized CsBPH_AP catalysts show superior performance compared to micron-sized KBPH_AP. Ion-exchange of the catalysts leads to different basicity and catalytic activity. The study highlights the importance of catalyst morphology and size in the valorization of glycerol.