Excellent gas separation performance of hybrid carbon molecular sieve membrane derived from polyimide/10X zeolite for hydrogen purification

Abstract

Membrane-based gas separation is attracting more and more attention in hydrogen purification and CO2 separation. One critical challenging remaining for large-scale production is fabricating a high-performance membrane with both inexpensive and excellent separation performance. In this work, a novel hybrid-carbon molecular sieve (CMS) membranes were reported for hydrogen purification by pyrolysis of commercial polyimide precursor (PMDA-ODA) with incorporation of modified 10X zeolite. The addition of modified 10X zeolite provided additional gas transport channels to the CMS mixed matrix membrane (MMM), and contained a significant fraction of micropores within the 0.6–0.8 nm range, which greatly enhance hydrogen adsorption capacity. Interestingly, despite this, the selectivity for H2/N2 and H2/CH4 also increases with higher zeolite content. This unexpected phenomenon may be attributed to the partial blocking of zeolite pores by CMS strand, which narrows the 10X pore size to a dimension smaller than CH4 and N2, enabling differentiation between H2 and CH4 gas pairs. Therefore, the permeability and selectivity of H2 was significantly enhanced. The CMS/10X-7.5 (with 7.5 wt % 10X zeolite) exhibited an advanced H2 permeability (1709 Barrer) and high gas selectivity of 551 for H2/CH4 and 105 for H2/N2, respectively, which is higher than other samples and exceed the 2015 trade-off lines. Furthermore, the CMS/10X-7.5 delivered excellent stability after 20 cycles. Therefore, this hybrid CMS/10X-7.5 obtained by carbonization of zeolite-doped polymer precursors has great potential for larger industrial applications.