Engineering the Si/Al ratio of MWW zeolites for propylene/propane separation

Propylene/propane (C₃H₆/C₃H₈) separation is critical to the petrochemical industry but remains highly energy-consuming. Adsorption-based strategies provide a promising energy-efficient alternative, yet developing adsorbents combining both high capacity and selectivity is challenging due to the nearly identical physicochemical properties of C₃H₆ and C₃H₈. Here, we systematically investigated MCM-22 zeolites (MWW topology) with varying Si/Al ratios (9.6−36.5) for C₃H₆/C₃H₈ separation. Gas adsorption isotherms, cyclic sorption tests, and dynamic breakthrough experiments revealed that the Si/Al ratio significantly regulated the separation performance. Remarkably, MCM-22(30) with a moderate Si/Al ratio of 18.7 achieved the best performance, achieving a high C₃H₆ uptake (6.28 mmol g⁻¹) and an exceptional C₃H₆/C₃H₈ (50/50, v/v) selectivity exceeding 3000 at 298 K, while maintaining favorable regenerability and structural stability over multiple cycles. Breakthrough experiments further demonstrated the superior dynamic separation efficiency of MCM-22(30) compared with its higher- or lower-Si/Al counterparts.