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

Abstract

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^-5mol 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).