2022 Annual Meeting
Synthesis Process and Variation of Triptycene Structures for Membrane-Assisted Gas Separation of H2/CO2 at High Temperatures
As environmental awareness grows, and cost-effectiveness continues to be a goal to achieve, low cost and good processability have made polymeric membranes promising candidates for industrial gas separation applications. Furthermore, smaller carbon footprints and operational simplicity cause polymer membranes to be great candidates when compared to other processes. However, most existing conventional polymer materials are not ideal for high-temperature H2/CO2 applications which demand high thermal stability and strong size-sieving capability. Of particular interest are polybenzimidazoles (PBI), such as m-PBI (Cerazole ), capable of reliably accomplishing H2/CO2 separation at elevated temperatures. The problem with m-PBI is the low permeability it exhibits. Triptycene-based PBI (TPBI) polymers contain triptycene structures desired for their structural integrity and dependable free volume that assist with the issues intrinsic to polymer membranes. Research, therefore, focused on the development of TPBI polymers capable of preventing a high degree of polymer packing and assisting with the natural low permeability intrinsic to organic polymers. Moreover, by systematically varying the content of triptycene unit, structure-property relationships of this novel triptycene-based PBI (TPBI) could be investigated. In this work, a triptycene-based dicarboxylic acid (TP-COOH) has been synthesized and purified. Within the multistep TP-COOH synthesis, nuclear magnetic resonance (NMR) permitted the verification of the structural makeup analyzed at any step of the synthesis, along with impurities that exist. Moreover, a series of TPBI copolymers with systematically varied triptycene content (25%-50%) have been produced. The copolymersâ molecular weight was therefore adjusted through reaction time and adding sequence. Results convey that high-molecular-weight TPBI with 50% triptycene units (TPBI-50) could be consistently synthesized. Moreover, modification of reaction conditions to produce TPBI with 25% triptycene units (TPBI-25) is still ongoing. The research into triptycene structures in polymer membranes has great value and potential for high-temperature H2/CO2 separation with much exploration and improvements left to be made.