Modification of the Zeolite ZSM‑5 Adsorbent for CO Capture.

The rise in greenhouse gas emissions has significantly raised the average global temperature, intensifying the global warming crisis. Addressing this challenge requires substantial efforts from both academia and industry to deliver impactful mitigation solutions. Thus, the development of efficient materials and processes for mitigating greenhouse gases, particularly carbon dioxide (CO), is of great interest. In this study, various zeolite adsorbents were synthesized, including pristine NH-ZSM-5, the calcined form H-ZSM-5, and its cation-exchanged variants (Ba-ZSM-5, Mn-ZSM-5, Ni-ZSM-5, and Zn-ZSM-5), and their effectiveness in CO capture was tested at different temperatures. All of the adsorbent materials demonstrated decent CO capacity, with NH-ZSM-5 achieving the highest capacity of 1.45 mmol/g at 25 °C and 1 atm under pure CO tests. Although the cation-exchange process slightly reduces the CO capture capacity under dry conditions, it enhanced the CO capacity under humid conditions as compared to the pristine NH-ZSM-5 material and also improved CO/N selectivity by limiting N uptake. The capacity for CO adsorption declined with increasing temperature, indicating a physisorption-driven interaction mechanism. Additionally, the materials exhibited rapid adsorption kinetics best described by a pseudo-first-order kinetic model. The adsorbents also showed stable capacity over five adsorption-desorption cycles, indicative of the robustness of the material. Furthermore, unary CO and HO adsorption isotherms, coadsorption uptake of CO in the presence of humidity, and CO breakthrough experiments under humid conditions relevant to postcombustion CO capture scenario were also carried out. X-ray diffraction, Brunauer-Emmett-Teller (BET) surface area analysis, and scanning electron microscopy-energy dispersive X-ray spectroscopy techniques were employed to examine the physicochemical characteristics of the materials. Thus, the development of an efficient CO adsorbent with high uptake, rapid kinetics, high selectivity, and excellent thermal stability applying the realistic condition is of paramount importance for future CO capture applications.