Steam-Stable Basic Immobilized Amine Sorbent Pellets for CO₂ Capture Under Practical Conditions

Pelletization of basic immobilized amine sorbent (BIAS) particles is required to improve their mechanical strength and facilitate their practical CO₂ capture application under fixed or dynamic reactor conditions. Herein, we utilized two methods to prepare amine-functionalized BIAS pellets. Method (ii-a) involved combining latex polychloroprene (PC)/polyamine solutions with fly ash (FA)/BIAS powder to form sorbent pellets. Alternatively, method (ii-b) entailed shaping and drying wet pastes of binder solution plus FA/SiO₂ powder into pellet supports. These supports were then functionalized with leach-resistant polyethylenimine MW = 800 (PEI₈₀₀)/N-N-diglycidyl-4-glycidyloxyaniline (tri-epoxide cross-linker, E3) or ethylenamine E100/E3 mixtures. All pellets were screened for CO₂ capture by thermogravimetric analysis (dry 14% CO₂/N₂, 55-75 °C), H₂O stability by accelerated water washing, and mechanical strength by crush and ball-mill attrition testing. The mechanism of superior method (ii-b) pellet formation was uncovered by N₂ physisorption measurements, diffuse reflectance infrared Fourier transform spectroscopy, and scanning electron microscopy. Extended fixed bed testing of optimum E3/PEI₈₀₀-0.13/1 pellets under practical conditions revealed complete CO₂ capture stability of 1.5 mmol CO₂/g after 48 h of continuous steam exposure (7.2% H₂O/He, 105 °C) and minimal 14.6% loss in capacity after 75 hours of combined CO₂ capture cycling and steam treating (48 h). This slight oxidative degradation could be alleviated by incorporating a K₂CO₃ antioxidant into the pellet formulation. Overall, the robust physiochemical properties of the polyamine/cross-linker method (ii-b) pellets confirm their suitability for pilot-scale testing.