Accelerating Decarbonization via Tailored Zeolitic Monoliths: Insights into the Interfacial Physics of the Carbon Dioxide Adsorption Process

Conventional packed bed carbon dioxide capture systems with randomly positioned solid sorbent beads suffer from wall channeling, early breakthroughs, excessive pressure drop penalties, and poor contact-limited thermal transport characteristics. Advanced 3D printing techniques enable monolithic lattice topologies made of sorbent that can be tailored to minimize the shortcomings of conventional packed bed systems. The full potential of the design freedom enabled by sorbent 3D printing can only be realized through a detailed understanding of the interfacial adsorption physics within sorbent lattice monoliths at the level of individual struts. In particular, the optimal topology of a 3D-printed monolithic sorbent bed is a complex function of sorbent length scale, permeability, and flow characteristics. A sorbent monolithic bed made of small-diameter struts offers a high sorbent-air interfacial-area-to-volume ratio augmenting the carbon capture adsorption rate but a low carbon uptake capacity. This implies a trade-off between carbon dioxide uptake rate and capacity, determined by whether the adsorption process is limited by reaction kinetics or diffusion. Results show that the carbon adsorption process of zeolitic struts is limited by reaction kinetics at high zeolite permeability values of 1.1 × 10^-4-10^-8 m² while diffusion-limited at a zeolite permeability of 1.1 × 10^-12 m². Additionally, when the zeolite strut diameter decreases from 6 mm to 1 mm, the gravimetric CO₂ uptake rate increases 10-fold, while the equilibrium volumetric uptake capacity decreases by 48%. The insights obtained from this study accelerate the development of next-generation 3D-printed carbon dioxide capture systems for industrial decarbonization and space life support applications.