Abstract
Abstract Polymer membrane-based gas separation is a superior economical and energy-efficient separation technique over other conventional separation methods. Over the years, different classes of polymers are investigated for their membrane-based applications. The need to search for new polymers for membrane-based applications has been a continuous research challenge. Aromatic polyamides (PAs), a type of high-performance materials, are known for their high thermal and mechanical stability and excellent film-forming ability. However, their insolubility and processing difficulty impede their growth in membrane-based applications. In this review, we will focus on the PAs that are investigated for membrane-based gas separations applications. We will also address the polymer design principal and its effects on the polymer solubility and its gas separation properties. Accordingly, some of the aromatic PAs developed in the authors’ laboratory that showed significant improvement in the gas separation efficiency and placed them in the 2008 Robeson upper bound are also included in this review. This review will serve as a guide to the future design of PA membranes for gas separations.
Highlights
Polymer membrane-based gas separation is a superior economical and energy-efficient separation technique over other conventional separation methods
Different classes of polymers, such as poly(arylene ether)s [13,14,15,16], modified cellulose [17], and polyimides (PIs) [18,19,20,21], have been investigated for membrane-based gas separation applications. Because of their certain outstanding qualities like excellent thermal, mechanical and dimensional stabilities, and low dielectric constant values, aromatic PIs are known as promising candidate for membrane-based gas separation applications [22]
The PAs synthesized from the 4,4′(hexafluoroisopropylidene)bis(benzoic acid) have the best combination of permeability and selectivity (e.g., PCO2 = 157 Barrer and PO2 = 40 Barrer, PCO2/PCH4 = 30.78, PO2/PN2 = 7.69 for PA G-ii) due to disruption of polymer packing and the restricted torsional motion of phenyl rings around the 6F linkage. For all these series of polymers, the PAs synthesized from naphthalene-2,6dicarboxylic acid showed relatively lower permeability, which is attributed to the presence of rigid compact naphthalene unit responsible for the lowest fractional-free volume (FFV) and observed gas permeability
Summary
Abstract: Polymer membrane-based gas separation is a superior economical and energy-efficient separation technique over other conventional separation methods. Different classes of polymers, such as poly(arylene ether)s [13,14,15,16], modified cellulose [17], and polyimides (PIs) [18,19,20,21], have been investigated for membrane-based gas separation applications Because of their certain outstanding qualities like excellent thermal, mechanical and dimensional stabilities, and low dielectric constant values, aromatic PIs are known as promising candidate for membrane-based gas separation applications [22]. PAs are used for several applications, like protective apparel, air filtration, thermal and electrical insulation, as advanced composites in the aerospace and armament industry Difficulties in their processability and solubility due to strong interchain hydrogen bonding that result in dense polymer chain packing restricted their use for the industrial membrane-based gas separations [24]. We will focus on their structural modifications, i.e., strategies employed to overcome their processability issue and improve their gas separation properties
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