Consideration of the Applicability of an Ionic Liquid–based Facilitated Transport Membrane to a DAC Process

Abstract

A facilitated transport membrane (FTM) is a functional membrane with high permeability and excellent permselectivity. An FTM containing a chemical compound with a CO₂–reactive amino group is a promising CO₂ separation membrane. Especially, the FTMs have a unique property that the CO₂ permeance increases with the decrease in the CO₂ partial pressure. Therefore, FTMs are an effective CO₂ separation membrane for direct CO₂ capture from the air with extremely low CO₂ concentration (Direct Air Capture: DAC). Among the FTMs for CO₂ separation, those containing an amino–functionalized ionic liquid as the CO2 carrier can permeate CO₂ faster than conventional FTMs even under low humidity conditions. In this paper, we investigate the applicability of a membrane module equipped with an amino acid ionic liquid–based FTM to a DAC process by conducting a process simulation. In the process simulation, we took into account the variation of the CO₂ permeability of the FTM along with the changes in the composition of the feed gas in the CO₂ separation membrane module.