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CO2 adsorption on a yellow tuff has been studied, by performing dynamic breakthrough experiments in fixed bed, focusing on the thermodynamics and kinetics of the process. The effect of both temperature (25 - 150 °C) and CO2 partial pressure (0.01 - 0.20 atm) has been assessed. The CO2 adsorption isotherms in the low pressure region typical of combustion flue gases are more accurately described by the Freundlich equation than by the Langmuir one, thus indicating a multilayer and heterogeneous surface binding. The obtained values of the main thermodynamic parameters suggested that the adsorption process is spontaneous, exothermic and physical in nature. The pseudo-first order kinetic model better fitted the experimental data at all the investigated adsorption temperatures than the pseudo-second order does. Based on the thermodynamic properties, some insights into the process strategy for post-combustion capture (i.e. pressure vs vacuum swing) are derived.

Even though the performances of CO2 adsorbent materials for temperature swing adsorption (TSA) are typically assessed based on the equilibrium adsorption capacity, the actual feasibility of a sorbent in real applications cannot be reliably inferred from only this parameter. Indeed, more than the maximum CO2 uptake achievable at equilibrium, it is necessary to know the actual amount of CO2 that can be captured in a full adsorption/desorption cycle, namely the difference between the amount of CO2 adsorbed under adsorption and desorption conditions, which is defined as the CO2 working capacity. In this work, dynamic breakthrough and regeneration tests have been performed using a commercial activated carbon in a lab-scale TSA sound-assisted fluidized bed apparatus in order to experimentally evaluate the CO2 working capacity. In particular, the effect of adsorption/desorption temperatures (18 - 150 °C) and CO2 partial pressure (0.05 - 0.20 atm) has been evaluated.

The aim of the present work is to compare the adsorption performances of different materials (two activated carbons, four zeolites and a metal organic framework) under sound-assisted fluidization conditions (140 dB-80 Hz) in order to maximize the gas-solid contact efficiency and, in turn, minimize the limitations to the intrinsic adsorption capacity of the sorbents. All the tests were performed at ambient temperature and pressure with values of CO2 concentration typical of flue gases (5-10 vol.%). The different behaviors exhibited by the materials were explained on the basis of their textural properties. In particular, the microporosity falling in the range of 8.3-12 Å strongly affects the CO2 adsorption performances under the investigated operating conditions.