Deactivation by HCl of CeO₂–MoO₃/TiO₂ catalyst for selective catalytic reduction of NO with NH₃

Abstract

The effect of HCl on a CeO₂-MoO₃/TiO₂ catalyst for the selective catalytic reduction of NO with NH₃ was investigated with BET, XRD, NH₃-TPD, H₂-TPR, XPS and catalytic activity measurements. The results showed that HCl had an inhibiting effect on the activity of the CeO₂-MoO₃/TiO₂ catalyst. The deactivation by HCl of the CeO₂-MoO₃/TiO₂ catalyst could be attributed to pore blockage, weakened interaction among ceria, molybdenum and titania, reduction in surface acidity and degradation of redox ability. The Ce³⁺/Ce⁴⁺ redox cycle was damaged because unreactive Ce³⁺ in the form of CeCl₃ lost the ability to be converted to active Ce⁴⁺ in the SCR reaction. In addition, a decrease in the amount of chemisorbed oxygen and the concentrations of surface Ce and Mo was also responsible for the deactivation by HCl of the CeO₂-MoO₃/TiO₂ catalyst.