(278f) A Facilitated Transport Membrane Composed of Restricted Ionic Liquid in Graphene Oxide/Single Walled Carbon Nanotube Framework for Efficient Carbon Capture

Carbon Dioxide (CO₂) emissions is the primary contributor to global warming. A significant fraction of this contribution comes from power plants. Membrane processes may offer a promising solution for low cost, robust and energy efficient CO₂ capture from these plants. Facilitated transport membranes, although showing strong capability for CO₂ capture at low concentrations and under humid conditions, suffer from the loss of facilitators, such as amines, leading to decline in performance over long term operation. Ionic liquids (ILs) are chemically and thermally stable as well as have low vapor pressure, which is ideal to prevent aforementioned losses. However, mechanical stability of supported IL membranes, especially under pressure drop conditions, is a concern. Moreover, amino acid ILs were rarely studied as an efficient CO₂ facilitator. In this work, we report the use of an amino acid IL, 1-ethyl-3-methylimidazolium glycinate ([EMIM] [GLY]), as the facilitator for CO₂ capture. In order to selectively load and confine [EMIM] [GLY] in a thin selective layer, we fabricated a Single Walled Carbon Nanotubes (SWCNT) intercalated Graphene Oxide (GO) layer (thickness:~200 nm; pore size: ~10 nm). The distribution of Ionic liquid in the GO/SWCNT framework is expected to be critical for the formation of a thin selective layer. To understand and optimize this, the ratio of GO to SWCNT was varied in an attempt to adjust the interaction between the framework and [EMIM] [GLY]. The negatively charged GO (because of hydroxyl, carboxyl and epoxy groups) acts as anchoring sites for [EMIM] [GLY] molecules (due to electrostatic interaction between anions on GO and cations of ionic liquid), while the interconnected GO/SWCNT network provides numerous nanochannels for unrestricted gas transport. The influence of membrane thickness, temperature, pressure and humidity on performance of the [EMIM] [GLY] restricted in GO/SWCNT framework was evaluated. The optimized membrane showed a CO₂ permeance of >1,500 GPU and CO₂/N₂ selectivity >300 for simulated flue gas.