Highly Selective and Permeable Microporous Polymer Membranes for Hydrogen Purification and CO₂ Removal from Natural Gas

Abstract

This paper reports a new macromolecular design that incorporates hierarchical triptycene unit into thermally rearranged polybenzoxazole (TR-PBO) structures for highly selective and permeable gas separation membranes with great potential for H 2 purification and CO 2 removal from natural gas. We demonstrate that triptycene moieties not only effectively disrupt chain packing enabling microporous structure for fast mass transport, but also introduce ultrafine microporosity via the unique internal free volume intrinsic to triptycene unit that allows for superior molecular sieving capability in resulting PBO membranes. Consequently, these triptycene-based polybenzoxazole (TPBO) membranes display among the highest gas selectivities for H 2 separations (i.e., α(H 2 /N 2 ) = 96; α(H 2 /CH 4 ) = 203) and CO 2 removal from natural gas (i.e., α(CO 2 /CH 4 ) = 68) among existing glassy polymeric membranes. It is also demonstrated that microporous structure and gas transport properties of TPBO films are highly tailorable by adjusting the triptycene content and the ortho-functionality of the precursors. The highly diverse tunability, along with the excellent resistance toward membrane plasticization and physical aging, render the TPBO membranes with extremely versatile separation capability applicable for a wide range of important industrial processes to get clean or low carbon fuels and reduce carbon footprint.

Advances in Organic Solvent Nanofiltration Rely on Physical Chemistry and Polymer Chemistry

“…Another possible approach for the design of polymers with controlled free volume architecture relies on using monomers bearing triptycene moieties. Recently, this approach has been successfully used to design gas separation membranes (Luo et al, 2016 , 2018 ; Weidman and Guo, 2017 ; Weidman et al, 2017 ) endowed with unprecedented levels of permeability and selectivity. Triptycenes are three-dimensional, paddlewheel-like structures formed by three aromatic rings arranged at 120° on three different planes.…”

“…Moreover, unlike ordinary glassy polymers, whose free volume is purely conformational, the internal free volume of triptycene units is configurational and, as such, it is not collapsible. According to this physical picture, iptycene-based polymers exhibit uncommon resistance to physical aging (Luo et al, 2016 , 2018 ; Weidman and Guo, 2017 ; Weidman et al, 2017 ). Potential use of such materials in OSN is fairly unexplored.…”

Modelling Mixed-Gas Sorption in Glassy Polymers for CO2 Removal: A Sensitivity Analysis of the Dual Mode Sorption Model

“…Despite the fact that CO 2 removal from natural gas with membranes has found industrial application since the 1980s [3], nowadays this technology has only about 10% of the market, which is dominated by solvent absorption using amines [1]. In membrane materials design research, countless structural and molecular modifications have been investigated in order to achieve a better separation performance, that would make membranes more competitive, in addition to being more energy-efficient and environmentally friendly [4,5,6,7,8,9,10]. However, one of the greatest challenges faced in membrane materials design is the existence of a trade-off between permeability and selectivity: for every gas pair the logarithm of the selectivity versus the logarithm of the permeability of the most permeable gas has been shown to lie below a limiting line, customarily referred to as the Robeson upper bound [11,12].…”

Intermediate thermal manipulation of polymers of intrinsic microporous (PIMs) membranes for gas separations

“…Colorful sphere: Data in this work (black for PIM‐1, blue for PIM‐1‐400, and red for PIM‐1‐450, with the thickness of 44 μm, 35 μm, and 33 μm, respectively). Open shapes: Data of TR‐PIM, UV rearranged PIM, thermal oxidative crosslinking PIM, thermal crosslinking PIM, photo oxide PIM, PIM‐based MMMs, and other polymeric TR membranes and CMS membranes, et al, from Reference 32, 34, 37, 38, 40, and 49–59 [Color figure can be viewed at wileyonlinelibrary.com]…”