Washcoated zeolite structured adsorbents for CO2 capture and recovery by rotary adsorption

Abstract

Adsorption has long been recognized as a vital and extensively utilized technology for CO2 capture, for which developing a cost-effective process is a long-sought goal. The structured adsorbent with faster heat and mass transfer, present new opportunities for advancing rotary adsorption process, however, lacks comprehensive evaluation and discussion on CO₂ sorption. In this study, structured adsorbents were prepared by washcoating commercial NaY and 13X zeolites onto a fiberglass honeycomb support. A series of characterizations and breakthrough test demonstrated the advantages of structured adsorbents over conventional pellets. NaY zeolite emerged as the thermodynamically and kinetically preferred CO₂ adsorbent, exhibiting an equilibrium adsorption capacity of 5.972 mmol·g^-1 and an internal mass transfer coefficient of 5.12 × 10^–3 s^-1 (15 % CO₂, 298 K, 1 bar). These values are 18.3 % and 164 % higher than those of its pellet counterpart and 12.3 % and 36.9 % higher than those of the 13X honeycomb. NaY's great adaptability across various applications was indicated by its breakthrough capacities at different temperatures and CO₂ feed concentrations, as well as the minimal influence of feed gas flow rate on CO₂ adsorption equilibrium and kinetics. By employing a recirculating thermal desorption strategy, CO₂ can be enriched from 5 % to 61 %, 15 % to 79 %, and 55 % to 92 %, achieving a 90 % recovery under mild desorption conditions. A two-stage rotary adsorption process for low-concentration CO₂ capture was proposed, enabling CO₂ enriched from 5 % to 55 % in the first stage, and further to 90 % in the second stage. This work introduces a promising approaches for low-cost industrial carbon capture and even direct air carbon capture.