Enhanced Activity of Ti-Modified V₂O₅/CeO₂ Catalyst for the Selective Catalytic Reduction of NO_<i>x</i> with NH₃

A novel V₂O₅/CeTiO_<i>x</i> catalyst showed excellent catalytic performance in the selective catalytic reduction (SCR) of NO_<i>x</i> with NH₃. The addition of Ti into V₂O₅/CeO₂ enhanced catalytic activity, N₂ selectivity, and resistance against SO₂ and H₂O. These catalysts were also characterized by N₂ adsorption, XRD, XPS, and H₂-TPR. The lower crystallinity, more reduced species, better dispersion of surface vanadium species, and more acid sites due to the modification of V₂O₅/CeO₂ with TiO₂ all improved the NH₃–SCR activity significantly. Based on <i>in situ</i> DRIFTS, it was concluded that the NH₃–SCR reaction over V₂O₅/CeTiO_<i>x</i> and V₂O₅/CeO₂ mainly followed the Eley–Rideal mechanism

Improvement of Nb Doping on SO₂ Resistance of VO_<i>x</i>/CeO₂ Catalyst for the Selective Catalytic Reduction of NO_<i>x</i> with NH₃

The influence of sulfation treatment on Nb–VO_<i>x</i>/CeO₂ and VO_<i>x</i>/CeO₂ catalysts for the selective catalytic reduction (SCR) of NO_<i>x</i> with NH₃ was fully investigated. The Nb–VO_<i>x</i>/CeO₂ catalyst showed higher catalytic activity and stronger resistance to SO₂ than VO_<i>x</i>/CeO₂. The formation of sulfates, small specific surface area, and reduction in the number of active sites were all responsible for the low catalytic activity over VO_<i>x</i>/CeO₂ after sulfation under SCR conditions. On the contrary, Nb–VO_<i>x</i>/CeO₂ adsorbed much more nitrate than sulfate when sulfated under SCR conditions and showed much higher NH₃-SCR activity than VO_<i>x</i>/CeO₂ after the same treatment. After sulfation by SO₂ + O₂ only, instead of sulfation under SCR conditions, both of the samples exhibited decreased NH₃-SCR activity, mainly due to the formation of sulfates and the blockage of the Langmuir–Hinshelwood reaction pathway

Significant Promotion Effect of Mo Additive on a Novel Ce–Zr Mixed Oxide Catalyst for the Selective Catalytic Reduction of NO_<i>x</i> with NH₃

A novel Mo-promoted Ce–Zr mixed oxide catalyst prepared by a homogeneous precipitation method was used for the selective catalytic reduction (SCR) of NO_<i>x</i> with NH₃. The optimal catalyst showed high NH₃-SCR activity, SO₂/H₂O durability, and thermal stability under test conditions. The addition of Mo inhibited growth of the CeO₂ particle size, improved the redox ability, and increased the amount of surface acidity, especially the Lewis acidity, all of which were favorable for the excellent NH₃-SCR performance. It is believed that the catalyst is promising for the removal of NO_<i>x</i> from diesel engine exhaust