(304b) Experimental Characterization of Sorbents for Direct Air Capture of Carbon Dioxide

Direct air capture (DAC) technology is an unprecedented and important solution to climate change. Even if we reduced CO₂ emissions to zero in a relatively short period of time, we will still need to remove 1,000 gigatons of CO₂ from the atmosphere by the end of the century to prevent the planet from warming above 1.5 ËšC¹. Temperature, pressure, and moisture swing DAC processes are amenable to a range of advanced sorbents which promote efficient CO₂ sorption and regeneration^2,3. The development, selection, and application of appropriate sorbents require a full understanding of essential characteristics during both sorption and desorption: 1) reaction kinetics; 2) mass transfer; 3) heat transfer; 4) equilibrium capacity; 5) cyclability (lifetime). The definition of these characteristics enables the development, design and scale-up of system processes and equipment to attain technical and economic feasibility⁴. There are numerous candidate materials with potential for DAC, each can be used in a variety of process cycles or regional climates. We have developed a systematic approach to evaluate sorbents from the milligram to tonne scale considering the important parameters mentioned above. Our systems comprise 1) a closed system (150 mL total volume) for fast screening of sorbents in the 1-10 mg scale; 2) an open flow system to test 0.1-1 g scale; 3) a wind tunnel system to test 1-100 g scale under representative air flow velocities and with appropriate form factor; 4) a bench scale reactor to test 0.1-2 kg scale; 5) and finally, our mechanical tree prototype which will be able to test at the 0.1-1 tonne scale. We will describe those systems and provided relevant results for representative sorbents which demonstrate favorable rate and capacity characteristics.

References:

1. Intergovernmental Panel on Climate Change (IPCC). Special Report Global Warming of 1.5 C°, Available at: <www.ipcc.ch>
2. Tao Wang; Klaus S. Lackner; and Allen B. Wright. Moisture-swing sorption for carbon dioxide capture from ambient air: a thermodynamic analysis. Phys. Chem. Chem. Phys., 2013, 15, 504.
3. Xiaoyang Shi; Hang Xiao; Habib Azarabadi; Juzheng Song; Xiaolong Wu; Xi Chen; and Klaus S. Lackner. Sorbents for the Direct Capture of CO₂ from Ambient Air. Chem. Int. Ed. 2020, 59,6984 –7006
4. Habib Azarabadi; Klaus S. Lackner. A sorbent-focused techno-economic analysis of direct air capture. Applied Energy 250 (2019) 959–975.