High-Performance Carbon Molecular Sieve Membrane Derived from a Crown Ether-Containing Co-Polyimide Precursor for Gas Separation

Abstract

A carbon molecular sieve (CMS) membrane was prepared via a co-polyimide precursor containing a crown ether segment. Two elements ensured that the CMS membrane achieved both high permeability and selectivity: (1) preferential decomposition of the crown ether segment at relative low temperature and (2) the transformation of a pore structure from a micropore (>7 Å) to an ultra-micropore (<7 Å) at a higher-temperature pyrolysis. A BET analysis showed the CMS membrane formed a micropore below 500 °C. Then, the micropore structure gradually transformed to an ultra-micropore when the heat-treatment temperature raised to 500 and 650 °C, followed by formation of a single-distribution ultra-micropore pyrolyzed at 800 °C. The performance of membranes treated at 650 and 800 °C surpassed the 2015 upper bound for H2 separation and the 2019 upper bound for CO2 separation. Furthermore, the membrane treated at 650 °C exhibited remarkable mixed-gas separation performance and possessed a CO2 permeability of 7266.4 ± 22.85 to 7496.3 ± 22.34 barrer and a CO2/N2 (20/80, vol%) and CO2/CH4 (10/90, vol%) selectivity of ∼60.

Next-generation carbon molecule sieve membranes derived from polyimides and polymers of intrinsic microporosity for key energy intensive gas separations and carbon capture

“…In addition to directly heating polymers to the desired carbonization temperature with a certain heating rate, in many studies, step-wise temperature increasing protocols have also been used to fabricate CMS membranes. 120,121 For instance, precursors with the potential of having thermal rearrangement ( e.g. , TR polymers) can be treated at a temperature significantly lower than the carbonization temperature ( e.g.…”

“…This pre-heating treatment can be applied to regulate the pore structure of CMS membranes thus tuning their gas transport properties. 120 In addition, during the pyrolysis process, the edges of CMS membranes tended to curl due to internal stress or chain orientation of the polymer, leading to relatively poor mechanical properties. In addition, polymers transform into carbon after pyrolysis, resulting in a membrane that is more rigid and sacrifice their flexibility and mechanical properties.…”

2D Zeolite-Based Thin Film Nanocomposite Membranes for Efficient CO2 Separation

“…CO 2 capture is a critical step in the CCUS processes; in the past decades, there have been many different methods have been developed for CO 2 capture (such as absorption, adsorption, and membrane separation); among these technologies, membrane separation stands out due to its small footprint, effective separation capabilities, ease of maintenance, and environmental friendliness . Commonly utilized membranes include polymeric membranes, inorganic membranes, carbon molecular sieve (CMS) membranes, and mixed matrix membranes (MMMs) . MMMs integrate the processability of polymer membranes with the excellent gas separation properties of inorganic nanofillers, aiming to address the trade-off between gas permeability and selectivity .…”

Mixed Matrix Membranes Based on MFI Zeolite Nanosheets with Tunable Thickness for CO2/CH4 and H2/CH4 Separation

“…Among them, membrane separation has been considered as a promising alternative to conventional absorption processes, thanks to its small footprint, high separation efficiency, and easy maintenance . At present, many different membrane materials have been developed for NG purification, including polymeric membranes, , inorganic membranes, carbon molecular sieve (CMS) membranes, and mixed matrix membranes (MMMs). , Polymer membranes have a “trade-off” effect in gas permeability and selectivity that greatly limit their application in practical industrial conditions . Inorganic membranes present better gas separation performance but the complicated membrane fabrication process as well as the high cost hindered their industrial applications .…”