Investigation of competitive sorption and plasticization of hyperaged CANAL ladder polymers for acid gas purification

Abstract

Identifying membrane materials that have exceptional separation performance and stability to complex CO₂-containing mixtures is a pressing topic in separation science. In this work, the membrane separation performance for a recently discovered class of contorted polymers synthesized via catalytic arene-norbornene annulation (CANAL) polymerization is presented. These CANAL polymers achieve high CO₂/CH₄ selectivity of 68 after physical aging (up to ∼1 year), which significantly augments the size-sieving capabilities of the membranes. Binary CO₂/CH₄ and ternary H₂S/CO₂/CH₄ testing result in a 41 % and 50 % enhancement in selectivities, respectively, for hyperaged (∼1 year) contorted CANAL polymers, highlighting their size-sieving capabilities. The remarkably high CO₂/CH₄ mixed-gas and combined acid gas (CAG, (CO₂+H₂S)/CH₄) selectivities of 88 and 95, respectively, for CANAL-Me-S₅F in particular surpass both the 2018 CO₂/CH₄ mixed-gas and CAG upper bounds. Performance stability was also investigated for high concentrations of CO₂, revealing a reduction in CO₂/CH₄ mixed-gas selectivity without compromising CO₂ permeability, suggesting strong sorption of CO₂ but minimal plasticization effects for short testing periods. Conversely, time-dependent plasticization shows negligible effects on CO₂/CH₄ mixed-gas selectivity despite an increase in CO₂ permeability when exposed to high concentrations of plasticizing CO₂ over an extended period of 170 h. This study provides valuable insights into hyperaged CANAL polymers and their performance in practical industrial processes.