Direct Air Capture (DAC) Utilizing a Steam-based Vacuum Temperature Swing Adsorption (VTSA) Process with Honeycomb Structured Amine Sorbents

Direct Air Capture (DAC) using solid sorbents can benefit from structured honeycomb configuration which enables low pressure drop operation under large air throughput and is compatible with established large-scale manufacturing methods. This study investigates a steam-based vacuum temperature swing adsorption (VTSA) process employing polyethyleneimine (PEI)-like sorbents loaded onto extruded honeycomb substrates. Both reference cordierite substrates and developmental substrate materials were evaluated. Sorbent loading, amine chemistry, and substrate properties were varied to assess their influence on adsorption performance, cyclic stability, and resistance to oxidative degradation. VTSA cycling experiments were conducted under process-relevant conditions, including ambient air adsorption and steam-assisted regeneration under reduced pressure. Accelerated aging protocols were employed to evaluate sorbent stability over several 1000 cycles under realistic exposure conditions. Experimental results show that process-relevant performance metrics, particularly adsorption kinetics, thermal management, and cyclic stability, are more critical than equilibrium capacity alone. Sorbents supported on developmental substrate materials showed comparable or improved CO2 capture capacity and aging resistance compared to cordierite-based references, depending on amine formulation. Overall, steam-assisted VTSA with structured amine sorbents represents a promising and industrially relevant pathway for large-scale DAC deployment.