(552d) Investigation of Moisture Swing Adsorption Processes with Dynamic Breakthrough Experiments

Most sorbent systems for direct air CO₂ capture (DAC) to date are developed based on amine materials because of the strong interactions between amine moieties and CO₂ molecules even at ultra-dilute CO₂ concentrations. However, these highly selective interactions typically come with costs of intensive energy consumption for sorbent regeneration. In addition, the long-term operation stability is significantly constrained by degradation propensity of amine materials due to oxidation at elevated regeneration temperature.

Recently, a class of ionic sorbents have been employed for DAC application based on moisture swing adsorption (MSA) processes. These sorbents absorb CO₂ at low humidity conditions and release CO₂, without applying heat for regeneration, when humidity is high. Previous studies in this field primarily evaluate the DAC performance of MSA sorbents in closed environment. In this study, a commercially available material’s DAC performance based on MSA processes was systematically investigated using dynamic breakthrough experiments. The coadsorption CO₂ uptake capacities as a function of feeding gas relative humidity (RH) were measured, and a CO₂ working capacity, defined as the difference of CO₂ coadsorption capacities at adsorption (low RH) and desorption (high RH) conditions was determined. Other material properties were investigated as well to provide design guidelines for the development of next-generation MSA sorbents.