Process Evaluation of Fluorinated Ionic Liquids as F-Gas Absorbents

Abstract

The environmental impact of fluorinated gases (F-gases) necessitates the development of green technologies to mitigate them. Fluorinated ionic liquids (FIL/ILs) emerged as an alternative absorbent due to their unique and exceptional properties. In this work, a COSMO-based/ Aspen Plus methodology was used to evaluate the performance of FIL/ILs as absorbents in the process scale of two F-gases: 1,1,1,2-tetrafluoroethane (R-134a) and difluoromethane (R-32). Results of the absorption column in equilibrium mode revealed that the behavior of FIL/ILs is similar under the same conditions, reaching higher efficiencies in the case of absorbing R-134a at a high F-gas partial pressure. Rate-based calculations in packing column demonstrated a kinetic control with highly viscous FIL/ILs, revealing higher performance differences between FIL/IL absorbents. The regeneration stage was also evaluated in near-industrial conditions. Operating conditions of the absorption column were optimized with a column of height 10 m and diameter ranging from 1.1 to 1.2 m at 10 bar total pressure, reaching 90% F gas recovery with an L/G range of 6−10. Finally, preliminary economic analysis revealed operating costs to recover 90% of F-gas of 70 $/ton (R-134a) and 130 $/ton (R-32) with the FIL/IL that revealed the best behavior, 1-ethyl-3-methylimidazolium triflate.

Life Cycle Assessment of the Separation and Recycling of Fluorinated Gases Using Ionic Liquids in a Circular Economy Framework

“…The recovery of R-32 obtained, in a similar L/G ratio and pressure conditions, is in the same range as those published by other authors for diluted mixtures of R-32 in argon using similar FILs. 23 Sensibly lower values of the L/G ratio are obtained (5.77) compared to similar absorption separation processes involving imidazolium-based ionic liquids for the capture of CO 2 and tetrafluoroethylene (11.7–70.0). 36 , 41 The results corroborate the adequacy of the FIL selected and provide, for the first time, a technology process for the separation of the R-32 from a ternary mixture in an efficient-sustainable way.…”

“…Although the prediction worsens with the length of the alkyl chain and the pressure, these results have comparable accuracy to those published by other authors in similar studies where the solubility of gases in ILs was predicted with COSMO-RS. 23 , 41 , 42 …”

“…12 − 15 Given this fine-tuning capacity, fluorinated ionic liquids (FILs) and deep eutectic solvents 14 have been recently studied as absorbents for fluorinated compounds such as HFCs. 23 FILs are composed of fluorinated alkyl chains with a minimum of four carbon atoms in their chemical structure. The combination of fluorines and carbons, along with the typical ionic liquid cation–anion interactions, results in the formation of fluorinated, polar, and nonpolar nanosegregated areas within the same molecule, increasing their number of conformations and their capacity to absorb F-gases.…”

Fluorinated Ionic Liquids as Task-Specific Materials: An Overview of Current Research

“…Other study focused on evaluating the viability and costs of an absorption technology in near-industrial conditions for the capture of R-32 and R-134a (with HFC recoveries above 90%) from a dilute gas stream, using FILs or mere fluoro-containing ILs as absorbents. In this study a COSMO-based/Aspen Plus methodology was applied to evaluate the influence of ILs structure, HFC partial pressure, operating temperature, and FIL/IL mass flow on the recovery of HFCs [94].…”

Integration of Stable Ionic Liquid-Based Nanofluids into Polymer Membranes. Part II: Gas Separation Properties toward Fluorinated Greenhouse Gases

“…At present, there is a growing number of publications dealing with the separation of close-boiling point and azeotropic refrigerant gas mixtures. Most of them rely on the use of advanced materials, such as ionic liquids [9][10][11][12][13][14][15][16] or deep eutectic solvents [17], as selective absorbent species, and porous materials such as activated carbons [18], zeolites [19,20] or metal organic frameworks (MOFs) [21] as selective adsorbents. Moreover, regarding membrane technology, we have recently analyzed for the first time the potential of several poly(ether-b-amide) membranes, with trade name Pebax ® , to separate HFC/HFO mixtures [22], and reported an improved separation performance of composite Pebax ® 1657 ionic liquid polymer membranes (CILPMs) to selectively recover R32 from the mixture R410A [23].…”