ZIF-8 membrane-based cryo-stripping of trace impurities towards electronic grade C3H6 production

Electronic-grade (EG) C3H6 represents an essential feedstock for semiconductor manufacturing, yet its purification remains energy-intensive due to the difficulty in removing trace C3H8 impurities via conventional cryogenic distillation, which requires high pressure and low temperature operation conditions. In this study, we demonstrate efficient C3H6/C3H8 separation under practical operation conditions using a ZIF-8 membrane prepared at near-freezing temperature. Gas permeation results show that the C3H6/C3H8 separation factor (SF) increases as temperature decreases, reaching 607 at −40 °C and remaining independent of operating pressure. Under industry-relevant conditions (−20 °C, 3 bar), the membrane achieved a SF of 362 with C3H6 flux of 135.3× 10-5 mol m-2 s-1, enabling one-step reduction of C3H8 from 2998 ppm to 8 ppm and complete removal of C4H10 from polymer-grade C3H6 feed. Adsorption-diffusion analysis reveals that enhanced separation at subfreezing temperature originates from increased diffusion selectivity caused by contraction and rigidification of ZIF-8 window. Process analysis further shows that integrating the membrane with distillation column can upgrade 99.5% C3H6 to ~5 N purity while reducing operating cost by 56.57% (1.34 US$ kg-1 EG C3H6). Purifying electronic-grade propylene is challenging due to trace impurities. Here, authors demonstrate a ZIF-8 membrane that efficiently removes impurities at low temperatures, enabling high-purity propylene production with reduced energy and cost.