Evaluation of Various Structures for PVP Facilitated Transport Membranes Containing Silver Salts and Its Effect on Ethylene-Ethane Separation Process

In this research, two silver salts, AgNO3 and AgBF4 with similar molar concentrations were incorporated into the active layer structure of PES/PVP composite membranes separately. Their different effects on the morphology and performance of ethylene-ethane separation process were investigated through FTIR-ATR, SEM, and gas permeation analysis. FTIR-ATR analysis was performed to survey the variant carbonyl group-silver cations’ complexes. Also, C=O bonds with various weakness and strength cause to create different complexes between carrier cations and non-saturated gas molecules such as ethylene. Therefore, ethylene/ethane separation quality can be affected by carbonyl bond energy. Structure of PVP active layer beside PES support section were observed through scanning electron microscopy. Pure and mixed gas permeation tests were carried out to verification of FTIR analysis and evaluation of separation quality. FTIR experiment demonstrated that Ag+ cations from AgBF4 salt make stronger complexes among polymer chains than cations of other salt and react with higher numbers of PVP active sites, which means AgBF4 salt distribute more effectively in the active layer structure. Permeation test revealed that AgBF4 salt attract ethylene molecules more effectively than AgNO3 salt, which leads to obtain higher ethylene/ethane selectivity. Finally, the maximum ethylene permeation and selectivity was occurred at maximum molar concentration of AgBF4 (50%) and at maximum operational pressure, which were 9.5 GPU and 43 respectively at mixed gas case. These parameters changed to 15 GPU and 64 at pure gas separation test.