Chemical stability of olefin carrier based on silver cations and metallic silver nanoparticles against the formation of silver acetylide for facilitated transport membranes

Facilitated transport membranes containing silver cations and metallic Ag nanoparticles (NPs) as an olefin carrier have high olefin permeability and selectivity over propane. Silver ions are known to readily react with acetylene in aqueous conditions to produce silver acetylide, which can explosively decompose at temperatures over 160 °C, and therefore its formation should be avoided. In this regard, we examined whether silver acetylide from olefin carriers such as free silver cations and surface-activated Ag NPs by 7,7,8,8-tetracyanoquinodimethane (TCNQ) is formed upon exposure to acetylene, which is present as a minor impurity in many petrochemical feeds. The results showed that silver acetylide was not formed from the activated Ag NPs under the current experimental conditions, while free silver cations of polymer electrolyte produced silver acetylide by reacting with acetylene. Therefore, it is concluded that the activated Ag NPs showed superior chemical stability, compared to free silver cations.