Ion exchanged X zeolite for CO2 capture at 273 and 298 K

https://doi.org/10.3390/molecules26247520

“CO₂ adsorption isotherms obtained at 273 K and 298 K are presented in Figure 7A,B, respectively. The data values of CO₂ adsorption capacity are shown in Table 5. The CO₂ uptake increased in the order of Mg²⁺ < Ca²⁺ < K⁺ < Na⁺ < Li⁺. One should notice that the obtained results are positively correlated with the increased micro- and submicropore volume of these samples.”

“Figure 8 presents the correlations of CO₂ uptake vs. micropore or submicropore volumes at 273 K and 298 K. As the CO₂ uptake is negligible for non-porous materials, the linear equation has only one parameter, i.e., slope. In all cases, the R² parameter is above 0.9, which may indicate a high impact of the pore volume on the CO₂ uptake. One should notice that in case of submicropores, the slope has a higher value compared to impact. This indicates that submicropores are crucial for CO₂ sorption, which is supported by other studies [30,31,32].”

“The Li_0.61Na_0.39X form of zeolite indicated the CO₂ adsorption capacity of 5.94 mmol/g and 5.71 mmol/g at 273 K and 298 K, respectively. The other forms of ion-exchanged samples showed a decrease of CO₂ uptake compared with the sodium form. It is worth to notice that Li_0.61Na_0.39X and NaX samples indicated the rapid increase of CO₂ adsorption at a low equilibrium pressure. The same effect was observed for the potassium-exchanged form. Nevertheless, in case of the K_0.76Na_0.24X sample, this tendency declines at a higher pressure range. This is related to a reduction of the micropores fraction.