(703e) Amine-Impregnated Al2O3 Materials for the Direct Air Capture of CO2 Under Sub-Ambient Conditions
AIChE Annual Meeting
Friday, November 18, 2022 - 9:04am to 9:20am
CO2 adsorption capacities at 25 oC and 400 ppm were highest for TEPA impregnated alumina samples (2.1 mmol/g), and moderate for PEI-alumina (0.9 mmol/g). The CO2 capacities for both PEI-, and TEPA-alumina samples decreased at -20 oC (0.45 mmol/g, and 1.1 mmol/g, respectively). The loss of CO2 uptake at low temperatures was primarily due to the freezing of the chains and their subsequent lower mobility that limits the diffusion of CO2. TEPA impregnated alumina samples showed a promising working capacity of 0.8 mmol/g after 8 cycles of adsorption-desorption (adsorption at -20 oC and desorption conducted at 60 oC). For both PEI and TEPA samples, the CO2 was strongly adsorbed at both 25 °C and -20 °C. Introducing moisture (70% RH at -20 °C) improved the CO2 capacity of PEI impregnated alumina to ~0.8 mmol/g. Reducing the amine content from 40% to 20% decreased the CO2 capacities at 25 °C as expected (0.6 mmol/g for PEI and 1.6 mmol/g for TEPA). While the CO2 capacities at -20 °C decreased for both samples (0.43 mmol/g for PEI and 1.1 mmol/g for TEPA), these values are equal to those observed at -20 oC for the 40% amine samples, indicating that there is better amine utilization at slightly lower loadings due to better diffusion of CO2 along the pores, which may arise due to greater volume available for CO2 diffusion at low temperatures. These results indicate that alumina impregnated with amines are a potentially promising class of materials for direct air capture at sub-ambient conditions, opening up a variety of opportunities to optimize these materials for the scalable deployment of DAC plants at different environmental conditions.