Effects of Pore-Forming Additives on Adsorbent Loading in Structured Contactors for CO2 Capture

The global mean temperature continues to increase above pre-industrial levels due to human activities, and it will reach critical levels if carbon dioxide emissions continue at current rates. CO₂ capture technologies play a significant role in limiting the increase in global mean temperature by reducing both emissions and existing atmospheric CO₂. Some widely used CO₂ capture technologies include wet scrubbing systems, membrane separators, and solid adsorbents. Wet scrubbing, a commonly utilized industrial method, uses liquid absorbents to remove contaminants from a gas stream. Solid absorbents could be a better option for efficient CO₂ capture. In comparison to liquid absorbents, solid adsorbents have lower regeneration energy, lower capital costs, and more modularity. Adsorbents are typically implemented in structured contactors, which are highly porous polymeric structures. Compared to packed beds, structured contactors have a higher rate of mass transfer, lower pressure drop, easier and more efficient cooling/heating during adsorption/desorption cycles. A higher adsorbent loading is desirable for increasing the contactor CO₂ productivity and reducing energy requirements.

For structured contactors fabricated using phase inversion techniques, high porosity can be achieved by adding pore-forming agents. These additives are water-soluble polymers that are removed during quenching and post-processing steps, leaving behind open pores. However, it is unclear if and how these pore-forming additives affect the sorbent loading in the final fibers. Here, we study the effect of pore-forming additives on the loading of solid adsorbents in structured contactors by fabricating and characterizing fiber sorbents with varying loadings of the pore-forming agents. The sorbents studied are 13X and UiO-66, and the pore-forming agent is polyvinylpyrrolidone (PVP). Solutions with polymer, sorbent, and PVP were prepared with varying amounts of PVP. The solution was then extruded into fibers using phase inversion techniques. Typical fiber post-processing procedures were followed, including extensive solvent exchange steps. The fibers were then characterized using thermogravimetric analysis (TGA) to determine the fiber composition and final sorbent loading. Scanning electron microscopy (SEM) was used to qualitatively evaluate and compare the fiber porosity. Ultimately, these results provide guidelines on the amount of pore-forming additives that should be added to optimize sorbent loading and porosity, which will enhance the performance of structured contactors in CO₂ capture applications.