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.