Carbonate-Promoted Drift of Alkali Cations in Small Pore Zeolites: Ab Initio Molecular Dynamics Study of CO 2 in NaKA Zeolite

• Published in: The journal of physical chemistry letters Vol. 10; no. 9; pp. 2191 - 2195
• Main Authors: Bryukhanov, Ilya A, Rybakov, Andrey A, Larin, Alexander V
• Format: Journal Article
• Language: English
• Published: United States 02-05-2019
• ISSN: 1948-7185; 1948-7185
• DOI: 10.1021/acs.jpclett.9b00519

An effect of deblocking of small size (8R, D8R) pores in zeolites due to cation drift is analyzed by using ab initio molecular dynamics (AIMD) at the PBE-D2/PAW level. The effect of carbonate and hydrocarbonate species on the carbon dioxide uptake in NaKA zeolite is demonstrated. It is shown that a hydrocarbonate or carbonate anion can form strong complexes with K
cation and withdraw it from the 8R window, so that the probability of CO
diffusion through 8R increases. For the first time, correlations between cationic and HCO
/CO
positions are demonstrated in favor of their significant interaction leading to the cationic drift from 8R windows. This phenomenon explains a nonzero CO
adsorption in narrow pore zeolites upon high Na/K exchange. In a gas mixture, such deblocking effect reduces the separation factor because of the possible passage of both components through the plane of partly open 8R windows.