Nitrogen oxides and SO2 adsorption on Au/MOR catalyst: Adsorption sites, thermodynamic and vibrational frequencies. ONIOM study

Quantum chemical calculations were carried out to determine geometries, vibrational frequencies and adsorption energies of NO, NO2, N2O, and SO2 molecules on a gold-exchanged mordenite catalyst (Au/MOR). The results show that the adsorption energies are greater on [Au]+ than on [Au3]+ species. In general, the charge transferred from Au to the adsorbed molecules is higher for [Au3]+ than for [Au]+. It is shown for first time, that the SO2 adsorption is thermodynamically favored on the [Au]+ species, but not on [Au3]+ species. Therefore at low Au content, the Au/MOR catalyst could be able to adsorb SO2.

Graphical abstractFigure optionsDownload full-size imageDownload high-quality image (121 K)Download as PowerPoint slideHighlights► Al crystallography positions do not have influence on Au species properties. ► Thermodynamically, NO adsorption is stronger on [Au]+ than on aggregates [Au3]+. ► According DFT calculations, at low Au content, the catalyst is able to adsorb SO2.