Adsorption equilibria and kinetics of carbon monoxide on zeolite 5A, 13X, MOF-5, and MOF-177

Carbon monoxide adsorption equilibria and kinetics on zeolite 5A, 13X, MOF-5, and MOF-177 were measured volumetrically at (298, 237, and 194.5) K and carbon monoxide pressures up to 108 kPa. It was found that zeolite 5A had the highest adsorption capacity at ambient temperature (298 K) and ambient pressure (108 kPa), whereas MOF-177 was a better adsorbent at (194.5 and 237) K. Both the Langmuir and Freundlich isotherm models were used to correlate the adsorption isotherms. Diffusivities of carbon monoxide in these adsorbents were estimated from the adsorption uptake curves by a micropore diffusion model. The average carbon monoxide diffusivities at 298 K and carbon monoxide pressures below 108 kPa are 3.42·10^-11m²·s^-1, 1.40·10^-11 m²·s^-1, 1.72·10^-8 m²·s^-1, and 5.01 · 10^-9 m² · s^-1 for zeolite 5A, 13X, MOF-5, and MOF-177, respectively. The heat of adsorption of carbon monoxide at low coverage on zeolite 5A and 13X is below 70 kJ·mol^-1 and drops rapidly as the coverage increases, while the heat of adsorption of carbon monoxide in MOF-5 and MOF-177 is in the range of (16 to 22) kJ·mol^-1.