Ideal CO₂/Light Gas Separation Performance of Poly(vinylimidazolium) Membranes and Poly(vinylimidazolium)-Ionic Liquid Composite Films

Abstract

Six vinyl-based, imidazolium room-temperature ionic liquid (RTIL) monomers were synthesized and photopolymerized to form dense poly(RTIL) membranes. The effect of polymer backbone (i.e., poly(ethylene), poly(styrene), and poly(acrylate)) and functional cationic substituent (e.g., alkyl, fluoroalkyl, oligo(ethylene glycol), and disiloxane) on ideal CO2/N2 and CO2/CH4 membrane separation performance was investigated. The vinyl-based poly(RTIL)s were found to be generally less CO2-selective compared to analogous styrene- and acrylate-based poly(RTIL)s. The CO2 permeability of n-hexyl- (69 barrers) and disiloxane- (130 barrers) substituted vinyl-based poly(RTIL)s were found to be exceptionally larger than that of previously studied styrene and acrylate poly(RTIL)s. The CO2 selectivity of oligo(ethylene glycol)-functionalized vinyl poly(RTIL)s was enhanced, and the CO2 permeability was reduced when compared to the n-hexyl-substituted vinyl-based poly(RTIL). Nominal improvement in CO2/CH4 selectivity was observed upon fluorination of the n-hexyl vinyl-based poly(RTIL), with no observed change in CO2 permeability. However, rather dramatic improvements in both CO2 permeability and selectivity were observed upon blending 20 mol % RTIL (emim Tf2N) into the n-hexyl- and disiloxane-functionalized vinyl poly(RTIL)s to form solid–liquid composite films.

Phosphonium-based poly(Ionic liquid) membranes: The effect of cation alkyl chain length on light gas separation properties and Ionic conductivity

“…Indeed, to our knowledge the permeability of 186 barrers measured for the poly([P 888VB ][Tf 2 N]) membrane is the highest reported for a neat PIL membrane, surpassing even siloxane-functionalized imidazolium PILs(Figure 4) (max. 130 barrers) while maintaining comparable CO 2 /N 2 selectivity (15 vs. 14) 22. The higher CO 2 permeability of poly([P 888VB ][Tf 2 N]) can be explained by comparing the gas diffusivities for CO 2 and CH 4 in each material (…”

Study on Gas Permeation and CO2 Separation through Ionic Liquid-Based Membranes with Siloxane-Functionalized Cations

“…In contrast, Bara et al 24 exhibited the greatest gas permeabilities, but presented the lowest selectivities. 24 Later, Carlisle et al 25 The disiloxane-functionalized vinylimidazolium PIL showed the highest CO 2 permeability but low CO 2 /N 2 and CO 2 /CH 4 selectivities. 25 Furthermore, polydimethylsiloxane (PDMS) has been commonly used for several gas separation applications not only due its chemical and thermal stabilities and low price, but also because of its high permeability to a wide range of gas species, justified by its chain flexibility and large free volume.…”

“…24 Later, Carlisle et al 25 The disiloxane-functionalized vinylimidazolium PIL showed the highest CO 2 permeability but low CO 2 /N 2 and CO 2 /CH 4 selectivities. 25 Furthermore, polydimethylsiloxane (PDMS) has been commonly used for several gas separation applications not only due its chemical and thermal stabilities and low price, but also because of its high permeability to a wide range of gas species, justified by its chain flexibility and large free volume. [26][27][28][29] In the present work, the gas permeation properties and CO 2 The highest relative standard uncertainty registered for the dynamic viscosity and density measurements was 0.03 and 2·10 −4 , respectively.…”

Novel pyrrolidinium-based polymeric ionic liquids with cyano counter-anions: High performance membrane materials for post-combustion CO2 separation

“…The lack of diversity in what concerns the different chemical structures of cations and anions is another key issue, since the majority of the efforts to use PIL-IL membranes for CO 2 separation used imidazolium moieties as pendant groups of the polycation backbone and the bis(trifluoromethylsulfonyl)imide ([NTf 2 ] À ) as counter-anion [57][58][59][60][62][63][64][65].…”