Activated Ag ions and enhanced gas transport by incorporation of KIT-6 for facilitated olefin transport membranes

• Olefin/paraffin separation membranes were composed of poly(ethylene oxide) (PEO)/AgBF4/Al(NO3)3/KIT-6.
• Activated Ag ions and enhanced gas diffusivity by KIT-6 were confirmed.
• Facilitated olefin transport membranes with long-term stability were successfully prepared.

Facilitated olefin transport membranes consisting of polymer/Ag salt/Al(NO3)3 have shown long-term stability, increasing the possibility of being used in practical applications. However, even though they show excellent separation performance over a long duration, the need for significant amounts of Ag salts acts as an obstacle, owing to relatively high cost of Ag. Thus, reduction in the amount of Ag salts in the membranes is required for practical applications in the industry. However, since the separation performance is directly related to the amount of Ag salts, it has been difficult to reduce the amount of Ag salts. In this study, we succeeded in preparing polymer/Ag salts/Al(NO3)3 membranes with 30% reduction in the amount of Ag salts by utilizing KIT-6, which is a porous material. When KIT-6 was incorporated into the polymer/Ag salts/Al(NO3)3 membrane, the separation performance for propylene/propane mixed gas increased with a propylene over propane selectivity of 20 and mixed gas permeance of 10 GPU. These values of selectivity and permeance amounted to 154% and 133% enhancement, respectively, compared to the performance without KIT-6. The enhanced separation performance is attributed to both the coordination of hydroxyl groups in KIT-6 with Ag ions and the porous properties of KIT-6, which leads to increased diffusivity. The coordination behavior of polymer/Ag salts/Al(NO3)3 containing KIT-6 was investigated by FT-IR, FT-Raman, and XPS analyses.