Evaluating the Performance of Micro-Encapsulated CO₂ Sorbents during CO₂ Absorption and Regeneration Cycling

We encapsulated six solvents with novel physical and chemical properties for CO₂ sorption within gas-permeable polymer shells, creating Micro-Encapsulated CO₂ Sorbents (MECS), to improve the CO₂ absorption kinetics and handling of the solvents for postcombustion CO₂ capture from flue gas. The solvents were sodium carbonate (Na₂CO₃) solution, uncatalyzed and with two different promoters, two ionic liquid (IL) solvents, and one CO₂-binding organic liquid (CO₂BOL). We subjected each of the six MECS to multiple CO₂ absorption and regeneration cycles and measured the working CO₂ absorption capacity as a function of time to identify promising candidate MECS for large-scale carbon capture. We discovered that the uncatalyzed Na₂CO₃ and Na₂CO₃-sarcosine MECS had lower CO₂ absorption rates relative to Na₂CO₃-cyclen MECS over 30 min of absorption, while the CO₂BOL Koechanol appeared to permeate through the capsule shell and is thus unsuitable. We rigorously tested the most promising three MECS (Na₂CO₃-cyclen, IL NDIL0309, and IL NDIL0230) by subjecting each of them to a series of 10 absorption/stripping cycles. The CO₂ absorption curves were highly reproducible for these three MECS across 10 cycles, demonstrating successful absorption/regeneration without degradation. As the CO₂ absorption rate is dynamic in time and the CO₂ loading per mass varies among the three most promising MECS, the process design parameters will ultimately dictate the selection of MECS solvent.