Identification of the arsenic resistance on MoO₃ doped CeO₂/TiO₂ catalyst for selective catalytic reduction of NOx with ammonia

Arsenic resistance on MoO₃ doped CeO₂/TiO₂ catalysts for selective catalytic reduction of NO_x with NH₃ (NH₃-SCR) is investigated. It is found that the activity loss of CeO₂-MoO₃/TiO₂ caused by As oxide is obvious less than that of CeO₂/TiO₂ catalysts. The fresh and poisoned catalysts are compared and analyzed using XRD, Raman, XPS, H₂-TPR and in situ DRIFTS. The results manifest that the introduction of arsenic oxide to CeO₂/TiO₂ catalyst not only weakens BET surface area, surface acid sites and adsorbed NO_x species, but also destroy the redox circle of Ce⁴⁺ to Ce³⁺ because of interaction between Ce and As. When MoO₃ is added into CeO₂/TiO₂ system, the main SCR reaction path are found to be changed from the reaction between coordinated NH₃ and ad-NO_x species to that between an amide and gaseous NO. Additionally, for CeO₂-MoO₃/TiO₂ catalyst, As toxic effect on active sites CeO₂ can be released because of stronger As-Mo interaction. Moreover, not only are the reactable Brønsted and Lewis acid sites partly restored, but the cycle of Ce⁴⁺ to Ce³⁺ can also be free to some extent.