An improved CO2 adsorption efficiency for the zeolites impregnated with the amino group: A molecular simulation approach

The molecular dynamic and Grand Canonical Monte Carlo simulation study were conducted to investigate the adsorption and diffusion behaviors of mixture of CO2 and N2. Pure silicalite structures of zeolites TON, AFI, and LTL were selected as the host materials to be evaluated in this study. The effect of surface modification of TON, realized by impregnating the amino functional group on TON surface, on the adsorption and the diffusion were analyzed and compared with the normal TON structure. The results show that, in the adsorption behaviors, the modified TON adsorbs more CO2 than the normal TON structure, however, at high pressure regions, CO2 uptake is lower than the normal TON due to reductions of pore volume. As well as the adsorption isotherm, CO2/N2 adsorption selectivity was also calculated, and it suggested that although the modified TON has low adsorption capacity of CO2, it has a high adsorption selectivity of CO2 over N2 comparable with other sorbents. In the diffusion behaviors, the mixture in the modified TON has a lower diffusivity than the mixture in the normal TON due to additional attractive interaction between the amino group and mixture. In addition, because of the small pore size of the selected zeolite structures, the single file mobilities as well as the self-diffusion coefficients were employed to describe the observed diffusion behaviors. Afterward, parametric studies for effects of the different pore length and zeolite structures on the diffusion of the mixture were carried out.