Measurement of CO2 Diffusivity in Phase-Changing Aminosilicone CO2 Capture Solvent

The mass transfer performance of a phase-changing aminosilicone CO2 post-combustion capture absorbent has been characterized. The aminosilicone, 1,3-bis(3-aminopropyl)-1,1,3,3-tetramethyldisiloxane (GAP-0), rapidly transforms from a low-viscosity liquid into a friable solid upon exposure to gaseous CO2. Mass transfer performance of this absorbent was studied to inform design and scaleup of a CO2 capture process. The long-term mass transfer rate of CO2 gas through a solid GAP-0 carbamate salt layer into a quiescent pool of liquid GAP-0 was characterized using pressurized thermogravimetric analysis. This experiment led to an estimate of the CO2 permeability of the carbamate salt solid of 1.46 × 10–9 mol of CO2 m–1 s–1 atm–1. Given literature-reported values of CO2 solubility in silicone polymers, the CO2 diffusivity through GAP-0 carbamate salt was inferred to be approximately 4.39 × 10–11 m2/s. In parallel, the CO2 absorption rate into a spray of GAP-0 droplets was studied in a laboratory spray reactor. Wh...