Cross-Linked Polymer Nanocomposites for Gas Separations

Gas separation is an important process in the chemical industry, particularly in the separation of the gaseous products resulting from the water-gas shift reaction during steam reformation of hydrocarbons. In this process, hydrogen (H₂) must be separated from a mixed gas stream containing carbon dioxide (CO₂) primarily, but also potential trace amounts of water (H₂O) and carbon monoxide (CO). The hydrogen gas is utilized in many different ways, however in the growing demand for alternative energy sources, hydrogen fuel cells have emerged as one option. It has become industrially important to reduce energy and economic demands of the current separation processes and polymer membranes provide an opportunity to achieve this goal. In this study, we have examined the gas separation properties of a cross-linked polyimide containing palladium (Pd) nanoparticles. Implementation of Pd nanoparticles into these polymer membranes decreases the free volume of the membrane as well as improves the affinity for H₂ over the other gas species. Additionally, chemical cross-linking of the membranes further reduces the free volume and increases chain rigidity, aiding in the prevention of the phenomenon of CO₂ plasticization and disallowing relatively larger gas molecules to penetrate.