Abstract
In this study, density functional theory (DFT) calculations have been performed to investigate the adsorption mechanisms of toluene and water onto various cationic forms of Y zeolite (LiY, NaY, KY, CsY, CuY and AgY). Our computational investigation revealed that toluene is mainly adsorbed via π–interactions on alkalis exchanged Y zeolites, where the adsorbed toluene moiety interacts with a single cation for all cases with the exception of CsY, where two cations can simultaneously contribute to the adsorption of the toluene, hence leading to the highest interaction observed among the series. Furthermore, we find that the interaction energies of toluene increase while moving down in the alkaline series where interaction energies are 87.8, 105.5, 97.8, and 114.4 kJ/mol for LiY, NaY, KY and CsY, respectively. For zeolites based on transition metals (CuY and AgY), our calculations reveal a different adsorption mode where only one cation interacts with toluene through two carbon atoms of the aromatic ring with interaction energies of 147.0 and 131.5 kJ/mol for CuY and AgY, respectively. More importantly, we show that water presents no inhibitory effect on the adsorption of toluene, where interaction energies of this latter were 10 kJ/mol (LiY) to 47 kJ/mol (CsY) higher than those of water. Our results point out that LiY would be less efficient for the toluene/water separation while CuY, AgY and CsY would be the ideal candidates for this application.
Highlights
Volatile organic compounds (VOCs) are major air pollutants that are harmful to human health and to the environment [1,2,3,4]
The paper is organized as follows: we present and discuss the results obtained for the type and strength of interactions between toluene/water and FAU Y exchanged with Li+, Na+, K+, Cs+, Cu+ and Ag+ cations
Files of of most stable configuration calculated for toluene andon water on different cation-exmost stable configuration calculated for toluene and water different cation-exchanged changed faujasites areinavailable in supplementary faujasitesYare available supplementary materials. materials
Summary
Volatile organic compounds (VOCs) are major air pollutants that are harmful to human health and to the environment [1,2,3,4]. These pollutants affect air quality and have an impact on global warming [5,6,7,8]. The severity of the symptoms is often correlated with the concentration of toluene vapor. It has been shown that exposure to high concentrations of toluene (>45,000 mg/m3 ) for about 12 h can be fatal [19,20]
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