Carbon monoxide adsorption in ZIF-8- Kinetics and equilibrium

Abstract

We present the results of a study of the kinetics and equilibrium characteristics of CO sorption in ZIF-8. We measured adsorption isotherms at five temperatures between 72.67 and 104.58 K; all the isotherms exhibit three sub-steps below saturation. We have studied the evolution of the adsorption kinetics of this system by monitoring the equilibration times as a function of sorbent loading. We find that there is a very large, sharp maximum, in the equilibration times in the region corresponding to the highest loading sub-step in the sorption data; and we find a much smaller local maximum for loadings corresponding to the intermediate-loading sub-step. We have determined the isosteric heat of adsorption for CO in ZIF-8 and its dependence on sorbent-loading. We find a sharp isosteric heat of adsorption peak at values of the sorbent-loading corresponding to the highest loading isotherm sub-step. We discuss a possible explanation for the combined results of kinetic and isosteric results for this system. We have also studied the temperature evolution of the characteristics of the sub-steps present in the isotherms. We find that, as was the case for other systems in ZIF-8, the relative pressures at which the two higher-loading isotherm sub-steps occur move increasingly closer to the saturated vapor pressure as the isotherm temperatures increase.

Publication
Microporous and Mesoporous Materials
Dinuka H. Gallaba
Dinuka H. Gallaba
Visiting Assistant Professor of Physics

My research interests include gas adsorption, energy storage and sensor applications of Metal Organic Frameworks and Transition Metal Dichalcogenide.

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