Measurement and Prediction of the Heat of Adsorption and Equilibrium Concentration of CO₂ on Zeolite 13X

Abstract

Adsorption isotherms are reported for pure carbon dioxide on zeolite 13X (also called zeolite NaX) pellets over a temperature range of 0 to 200 °C and a pressure range of 0.001 to 100 kPa. These pure-component equilibria are fit with Langmuir, Toth, two-site Langmuir, and three-site Langmuir models, both with and without temperature dependence being included in the saturation capacity. The agreement between fitted and measured isotherms is shown to increase with increasing number of available fitting parameters in the model, with the constant-saturation, twosite Langmuir isotherm providing the best balance between agreement with the measurements and model complexity. The isosteric heats of adsorption are measured across a temperature range from 10 to 200 °C using differential scanning calorimetry. The measured heats of adsorption decrease with increasing CO 2 loading but show little variation with temperature. The measurements are shown to agree with predicted heats of adsorption derived from the fitted Langmuir and Toth isotherms (via the Clausius−Clapeyron equation); the heats of adsorption predicted using the more complex multisite Langmuir models suffer from nonphysical artifacts.

Theoretical studies on carbon dioxide adsorption in cation-exchanged molecular sieves

“…The calculated adsorption energy of CO 2 adsorbed on NaY and NaZSM-5 were about À9.56 kcal mol À1 in our work, which was consistent with the experimental data (À7.05 to À10.28 kcal mol À1 ) obtained by calorimetry measurements. 7,35,36 Our calculation indicates that it is hard for Cu + to adsorb CO 2 , and is also in line with the experimental adsorption isothermal studies. 37,38 All of these can demonstrate that the models, functionals and basis set adopted here are reasonable and suitable.…”

Rotary Adsorption: Selective Recycling of CO2 in Combined Cycle Gas Turbine Power Plants

“…31, where (−ΔH ads ) is the enthalpy of adsorption and K L0 is the pre-exponential factor. The single-site Langmuir isotherm describes monolayer adsorption on homogeneous flat surfaces and assumes that ideal gas conditions under isothermal conditions apply; adsorbed molecules are held at definite, localized sites each of which can accommodate one molecule; the adsorption energy is constant over all sites; and there is not interaction between neighboring adsorbate molecules (Son et al, 2018). Further work will consider isotherms that account for surface heterogeneity or multiple homogenous but energetically different sites to accommodate one molecule, e.g., Toth model and multisite Langmuir model, respectively.…”

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“…3 for the experiment. The temperature dependence of the adsorption isotherm was evaluated using the multi-site Langmuir model [12][13][14] (Eq. ( 14)) that can represent multiple adsorption sites.…”