Carbonate-Promoted Drift of Alkali Cations in Small Pore Zeolites: Ab Initio Molecular Dynamics Study of CO2 in NaKA Zeolite

Ilya A Bryukhanov; Andrey A Rybakov; Alexander V Larin

doi:10.1021/acs.jpclett.9b00519

Carbonate-Promoted Drift of Alkali Cations in Small Pore Zeolites: Ab Initio Molecular Dynamics Study of CO₂ in NaKA Zeolite

J Phys Chem Lett. 2019 May 2;10(9):2191-2195. doi: 10.1021/acs.jpclett.9b00519. Epub 2019 Apr 19.

Authors

Ilya A Bryukhanov^{1

2}, Andrey A Rybakov³, Alexander V Larin³

Affiliations

¹ Institute of Mechanics , Lomonosov Moscow State University , Moscow 119192 , Russia.
² Mechanical Engineering Research Institute of the RAS , Moscow 119334 , Russia.
³ Department of Chemistry , Lomonosov Moscow State University , Moscow 119991 , Russia.

PMID: 30978026
DOI: 10.1021/acs.jpclett.9b00519

Abstract

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 CO₂ diffusion through 8R increases. For the first time, correlations between cationic and HCO₃^-/CO₃^2- positions are demonstrated in favor of their significant interaction leading to the cationic drift from 8R windows. This phenomenon explains a nonzero CO₂ 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.