This work allows the gathering of information during the process design to assist in the choice of the solvent and technology to use.

The nonideal behavior of polymeric membranes during separation of gas mixtures can be quantified via the solution-diffusion theory from experimental mixed-gas solubility and permeability coefficients. In this study, CO2-CH4 mixtures were sorbed at 35 °C in 4,4′-(hexafluoroisopropylidene)diphthalic dianhydride (6FDA)-m-phenylenediamine (mPDA)—a polyimide of remarkable performance. The existence of a linear trend for all data of mixed-gas CO2 versus CH4 solubility coefficients—regardless of mixture concentration—was observed for 6FDA-mPDA and other polymeric films; the slope of this trend was identified as the ratio of gas solubilities at infinite dilution. The CO2/CH4 mixed-gas solubility selectivity of 6FDA-mPDA and previously reported polymers was higher than the equimolar pure-gas value and increased with pressure from the infinite dilution value. The analysis of CO2-CH4 mixed-gas concentration-averaged effective diffusion coefficients of equimolar feeds showed that CO2 diffusivity was not affected by CH4. Our data indicate that the decrease of CO2/CH4 mixed-gas diffusion, and permeability selectivity from the pure-gas values, resulted from an increase in the methane diffusion coefficient in mixtures. This effect was the result of an alteration of the size sieving properties of 6FDA-mPDA as a consequence of CO2 presence in the 6FDA-mPDA film matrix.

promising energy efficient separation processes in the chemical separation industry. Its continued growth can be attributed to lower energy requirements translating to lower capital and operating cost as well as significantly reduced environmental impact compared to conventional thermal separation processes. Additionally, membrane technology offers the advantages of continuous process operation, modular design, and small system footprint and is predicted to be a main contributor to global energy-and carbon-reduction initiatives in the coming decades. [2] In 2008, the global membrane market was valued at ≈12 billion USD with a compound annual growth rate (CAGR) of ≈10%. [3] Reverse osmosis (RO) and nanofiltration (NF) membranes contribute significantly to the total global membrane sales with the majority of products comprising of variations of thin-film composite (TFC) membranes made by interfacial polymerization. Such highly crosslinked aromatic submicroporous (i.e., pore size < 4 Å) [4] polyamide TFC membranes-pioneered by John Cadotte-revolutionized the desalination industry due to their unprecedented combination of high water flux and salt rejection. [5][6][7][8] Surprisingly, despite their immense commercial success for aqueous RO and NF applications, the IP membrane formation process has not been implemented in other large-scale fluid separation processes, especially organic solvent nanofiltration (OSN) and gas separations. [9][10][11] Polymers of intrinsic microporosity (PIMs) are an emerging group of solution processible amorphous microporous materials (pore size < 20 Å) gaining significant attention in membranebased separations due to their ability to transcend the conventional permeability/selectivity trade-off relationships. [12][13][14][15] Such materials exhibit exceptionally high free volumes as a result of inefficient chain packing by architectural designs using highly rigid and contorted spirobisindane-, triptycene-, ethanoanthracene-, and Tröger's base-building blocks. [13,[16][17][18][19][20][21] To date, technical challenges associated with fabricating defect-free, inexpensive, thin-film composite membranes as well as the inability to achieve low-molecular-weight cutoffs (MWCOs) have severely limited the industrial use of PIM-based and similar membrane materials. For example, Cook et al. demonstrated successful Polymeric membranes with increasingly high permselective performances are gaining a significant role in lowering the energy burden and improving the environmental sustainability of complex chemical separations. However, the commercial deployment of newly designed materials with promising intrinsic properties for fluid separations has been stalled by challenges associated with fabrication and scale up of low-cost, high-performance, defect-free thin-film composite (TFC) membranes. Here, a facile method to fabricate next-generation TFC membranes using a bridged-bicyclic triptycene tetra-acyl chloride (Trip) building block with a large fraction of finely tuned structural submicroporosity (por...

A novel trimethyl-substituted carboxyl-containing polyimide was synthesized by a one-pot high temperature polycondensation reaction of 4,4'-(hexafluoroisopropylidene)diphthalic anhydride (6FDA) and 3,5-diamino-2,4,6-trimethylbenzoic acid (TrMCA). The polyimide (6FDA-TrMCA) displayed Brunauer-Emmett-Teller (BET) surface area of 260 m 2 g-1 demonstrating intrinsic microporosity in contrast to the related low-free volume COOH-functionalized polyimide 6FDA-DABA. Compared to the non-functionalized 6FDA polyimide analog made from 2,4,6-trimethyl-m-phenylenediamine (TrMPD)also known as 6FDA-DAM-carboxyl functionalization in 6FDA-TrMCA resulted in reduced surface area, lower fractional free volume, and tighter average chain spacing. Gas permeabilities of 6FDA-TrMCA were typical of functionalized polyimides of intrinsic microporosity (PIM-PIs). For example, at 2 atm and 35 °C, 6FDA-TrMCA showed pure-gas H 2 and CO 2 permeability of 193 and 144 barrer coupled with H 2 /CH 4 and CO 2 /CH 4 selectivity of 61 and 45, respectively. Notably, in mixed-gas permeation tests with an equimolar CO 2-CH 4 mixture at 12 atm CO 2 partial pressure, 6FDA-TrMCA demonstrated performance located on the 2018 mixed-gas upper bound with a CO 2 permeability of ~ 98 barrer and CO 2 /CH 4 permselectivity of 38. As the first reported COOH-functionalized PIM-PI homopolymer, 6FDA-TrMCA revealed excellent resistance against CO 2-induced plasticization at least up to a CO 2 partial pressure of 15 atm covering the range of typical wellhead CO 2 partial pressures (5-10 atm).