Aging-resistant carbon molecular sieve membrane derived from pre-crosslinked Matrimid® for propylene/propane separation

Despite the well-recognized potential of carbon molecular sieve (CMS) membranes for olefin/paraffin separation, its gradual performance degradation has been the main bottleneck to reach commercialization. Particularly, the structural transformation of CMS membranes has recently been identified as an additional challenge to be resolved. Herein, we systematically studied the aging phenomenon under nitrogen and helium atmosphere, as well as the aging of CMS membranes during propylene separation under oxygen-free dry conditions. In order to minimize this structural transformation, the shift of carbon structure must be prevented by fastening the chains. We implemented a pre-crosslinking step on Matrimid (R) polymer precursors with various contents of crosslinking agent prior to pyrolysis to establish firm networks, resulting in a remarkable improvement of long-term stability nearly 18-fold when tested in long-term (500 h) at 7 barg and 50 degrees C. Moreover, it was found that there exists an optimal pre-crosslinking density of CMS membrane for aging suppression.