Yongheng Ren, Yang Chen, Hongwei Chen, Lu Zhang, Jiangfeng Yang, Qi Shi, Lin-Bing Sun, Jinping Li, Libo Li*
Chin. J. Struct. Chem., 2024, 43: 100394. DOI: 10.1016/j.cjsc.2024.100394
October 15, 2024
Zeolite; Carbon dioxide; Gas separation; Electrostatic potential; Kinetic diffusion
ABSTRACT
The identical molecular size and similar physical properties of carbon dioxide (CO2) and acetylene (C2H2) make their adsorptive separation extremely challenging to achieve with most adsorbents. Reports on the separation of CO2 and C2H2 mixtures by zeolites are even rarer with the mechanism of adsorptive separation requiring further exploration. In this paper, we report that ion modulation of zeolite 5A promotes the difference in kinetic diffusion of CO2 and C2H2, realizing the inverse separation of zeolite from selective adsorption of C2H2 to selective adsorption of CO2. Creating a compact pore space restricting the orientation of gas molecules enables charge recognition. The positive electrostatic potential at the pore openings was utilized to hinder the diffusion of C2H2 between the cages while ensuring the transfer of CO2, increasing their diffusion differences in the pore channels and leading to the CO2/C2H2 kinetic selectivity of 31.97. Grand canonical Monte Carlo (GCMC) simulation demonstrates that the CO2 distribution in K-5A-β is significantly higher than that of C2H2. Dynamic breakthrough experiments verified the excellent performance of the material in practical CO2/C2H2 separation, for CO2/C2H2 (50/50 and 1/99, v/v) mixtures can be separated in one step thus directly generating high purity C2H2 (>99.95%), which provides a promising thought for the zeolite-based separation of CO2 and C2H2.