RESEARCH ARTICLE

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

State Key Laboratory of Materials-Oriented Chemical Engineering, College of Chemical Engineering, Nanjing Tech University, Nanjing 211816, China

^* Corresponding authors (emails: liuxiaoling@njtech.edu.cn (Xiaoling Liu); junwang@njtech.edu.cn (Jun Wang); njutzhouyu@njtech.edu.cn (Yu Zhou))

Received: 8 October 2025
Revised: 31 October 2025
Accepted: 3 November 2025

Abstract

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) at 298 K and 1 bar (1 bar = 10⁵ Pa), with an exceptional ideal adsorption solution theory (IAST) C₃H₆/C₃H₈ (50/50, v/v) selectivity exceeding 3000, 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.