Adsorption structures of heterocyclic nitrogen compounds over Cu(I)Y zeolite: A first principle study on mechanism of the denitrogenation and the effect of nitrogen compounds on adsorptive desulfurization

The adsorption configurations of quinoline, acridine, indole and carbazole over Cu(I)Y zeolite were studied by the density functional theory (DFT) method. The η2 adsorption mode has been found to be energetically preferred for neutral nitrogen compounds, i.e. indole and carbazole; while for basic ones, quinoline and acridine, the η1N adsorption mode is the most preferential one, implying that in the competitive adsorption aromatics show a strong preference over neutral nitrogen compounds than over basic ones. The adsorption energies of the adsorbate over Cu(I)Y zeolite decrease as follows: basic heterocyclic nitrogen compounds > neutral heterocyclic nitrogen compounds > thiophenic compounds, suggesting that deep denitrogenation and desulfurization could be carried out simultaneously over Cu(I)Y zeolite under ambient temperature, while for Cu(I)Y zeolite the adsorption of nitrogen compounds is preferable to that of sulfur compounds, and good selectivity will be shown for the basic nitrogen compounds during denitrogenation. Meanwhile, when the adsorbent is used for selective deep desulfurization, the presence of nitrogen compounds can greatly retard sulfur removal.

Graphical abstractThe adsorption configurations of quinoline, acridine, indole and carbazole over Cu(I)Y zeolite were studied by the density functional theory (DFT) method. The η2 adsorption mode has been found to be energetically preferred for neutral nitrogen compounds, while for basic ones the η1N adsorption mode is the most preferential one, implying that in the competitive adsorption aromatics show a strong preference over neutral nitrogen compounds than over basic ones. The adsorption energies of the adsorbate over Cu(I)Y zeolite decrease as follows: basic heterocyclic nitrogen compounds > neutral heterocyclic nitrogen compounds > thiophenic compounds, suggesting that deep denitrogenation and desulfurization could be carried out simultaneously over Cu(I)Y zeolite under ambient temperature, while Cu(I)Y zeolite is a preferable adsorbent for nitrogen compounds rather than for sulfur compounds.Figure optionsDownload full-size imageDownload as PowerPoint slide