Issue 9, 2023

A systematic DFT screening of cationic faujasite-type zeolites for the adsorption of NO, NO2 and H2O

Abstract

The limitation of NO and NO2 (NOx) emissions out of exhaust gases released from diesel engines in confined environments requires efficient adsorbents. Since NOx species are present in trace amounts (50–1000 ppm) in exhaust gases, and always co-exist with a large content of H2O (2–12 wt%), adsorbents need to be highly selective to trap NOx over H2O. To this end, periodic density functional theory (DFT) calculations in combination with dispersion corrections have been used for a systematic screening of monovalent and divalent cation-exchanged faujasite zeolites. The present work investigates the effect of the cation nature and Si/Al ratios (1.4; 2.43; 23; 47), on the adsorption selectivity of faujasite towards NO and NO2 against H2O. Alkali and alkali-earth metals Li(I), Na(I), K(I), Rb(I), Cs(I) and Ca(II), Ba(II), as well as monovalent and divalent transition metals Cu(I), Ag(I), and Zn(II), Pt(II), Pd(II), Cu(II), Fe(II), Co(II), Ni(II) embedded in faujasites, have been explored for their ability to capture NO and NO2. Bond activation of adsorbed gases has also been checked for the most promising materials to assess the tendency of these gases to further react with the adsorption site. Bader charges and charge density difference calculations were carried out for the most effective faujasite structures to assess the bond formation between materials and adsorbed gases. Much weaker interaction energies were predicted for Y vs. X faujasites, which is in favour of the material's regeneration. Cu(I) and Fe (II) based Y zeolites (Si/Al = 2.43) were identified as the most attractive candidates. Nevertheless, iron strongly activated the bonds of NO2 upon adsorption raising doubts about its implementation with faujasite. This is the first time that such a large screening of cationic zeolites has been performed for a separation topic using DFT calculations. In the specific case of NOx/H2O separation, the present work helped to exclude most of the zeolites explored from future theoretical or experimental investigations, highlighting the potential of Cu(I)Y and the promising selectivity that Fe(II) can bestow on a zeolite.

Graphical abstract: A systematic DFT screening of cationic faujasite-type zeolites for the adsorption of NO, NO2 and H2O

Supplementary files

Article information

Article type
Paper
Submitted
22 Mar 2023
Accepted
12 May 2023
First published
12 May 2023
This article is Open Access
Creative Commons BY-NC license

Mol. Syst. Des. Eng., 2023,8, 1165-1181

A systematic DFT screening of cationic faujasite-type zeolites for the adsorption of NO, NO2 and H2O

I. Karamanis, A. Daouli, H. Monnier, M. Dziurla, G. Maurin and M. Badawi, Mol. Syst. Des. Eng., 2023, 8, 1165 DOI: 10.1039/D3ME00044C

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