The effect of the incorporation of Fe and Mn into the tungsten zirconia catalyst is studied by means of DFT calculations for the first time.
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Medium size clusters, which are the most catalytically active species, are predicted to be more sinter resistant in the presence of the promoters.
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The overall Brønsted acidity is increased upon the incorporation of the Fe and Mn.
Abstract
Periodic DFT calculations are performed to unravel the effect of the incorporation of Fe and Mn into the tungstated zirconia catalyst, (WO3)x/ZrO2 (x = 1,3), in their electronic, geometric, and catalytic properties. Our results suggest that both Mn and Fe have a proclivity to occupy the same positions and thus both metals will compete for the same adsorption sites. The addition of Fe or Mn slightly destabilizes the WO3 monomer while stabilizes the (WO3)3 trimer. Hence, medium size clusters, which are the most catalytically active species, will be more sinter resistant in the presence of the promoters, leading to catalysts with longer lifetimes. The computed deprotonation energies evidence that the overall Brønstead acidity is increased upon the addition of the dopant atoms. It is proposed that the metals lead to a reduction of WZ and induce a local spin density imbalance.The function as redox initiators of these metals is confirmed.
Graphical abstract
The effect of the incorporation of Fe and Mn into the tungsten zirconia improves the stability and increases the overall Brønsted acidity of the catalyst.