Development of Functionalized Polymer of Intrinsic Microporosity Membrane with Reversible Preferential Interaction for Olefin-Paraffin Separation

Olefin-paraffin separation had faced challenges due to the similarities in its physical properties. The petroleum and natural gas industry relies on thermal energy intensive process to achieve sufficient separation performance. It is estimated that membrane gas separation can reduce energy consumption by up to 90%. Current research direction in membrane development for olefin-paraffin separation focus on the use of additives to enhance the preferential interaction with olefin species. For example, silver ion has been one the material of interest due to its unique electron orbital overlap with olefin p-bonds. However, silver ion faces challenges such as life time stability and deactivation under reductive conditions. To overcome these challenges, the author proposed the development of functionalized PIM-membranes with preferential and reversible interaction with olefin gas species. The author had identified two possible routes for performance enhancement: incorporating silver nanoclusters and the addition of functional group on PIM-1 backbone. Silver nanoclusters were a material of interest due to its unique properties of being thermodynamically stable and exhibiting molecule-like properties. The initial investigation of Ag44 nanoclusters to be shelf stable and also stable under the exposure to hydrogen gas. However, Ag44 nanoclusters were incompatible to PIM-1 and PIM-NH2 polymers. At the same time, further investigation of PIM-NH2 membrane revealed that it exhibits preferential interaction with olefins. A thorough analysis of hydrogen bonding-inducing functional groups, such as NH2 and COOH, in PIM-type polymers and its effect on propylene/propane separation was examined. It was shown that PIM-1 type polymer containing hydrogen-bonding has denser polymer packing and overall lower permeability. On the other hand, the hydrogen bonding donor groups exhibit preferential interaction towards the p-bond in olefine due to a specific type of weak hydrogen bonding force. Furthermore, PIM-NH2 demonstrates an interesting aging pattern, where the selectivity was more intensively affected. Aging mitigation method of PIM-NH2 focus on the development of controlled crosslinking using esterification of COOH groups. The results showed successful aging mitigation, as crosslinked PIM-NH2 was able to retain detectable permeability after 1 month of aging. At the same time, variables such as COOH concentration and linker type were altered to optimize the mitigation results.