The effect of Cl- on CeO2-WO3/TiO2 catalyst for selective catalytic reduction of NO with NH3

Abstract

The 30CeO₂-4WO₃/TiO₂ catalyst was prepared utilizing cost-effective cerium chloride instead of the traditional cerium nitrate as the cerium source in this paper. The structure, physical and chemical properties, catalytic performance were characterized. The catalytic performance and N₂ selectivity of the 30CeO₂-4WO₃/TiO₂ catalyst significantly deteriorate with increased the content of Cl^-. Specifically, denitration efficiency of 30CeO₂-4WO₃/TiO₂-0.007 % exceeding 80 % and 90 % were 225 ∼ 520 °C and 241 ∼ 504 °C, respectively, whereas the maximum denitration efficiency of the 30CeO₂-4WO₃/TiO₂-0.161 % sample was only 79.83 %. The effect mechanism of Cl^- on catalytic performance was discussed. (1) XRD and BET results show that Cl^- can cause the expansion of the lattice of TiO₂ and CeO₂, thereby increasing its crystallinity and decreasing the specific surface area. (2) Cl^- interacts with NH₄⁺ to form NH₄Cl, which subsequently reacts with CeO₂ to produce CeOCl, leading to the obstruction of the catalyst’s micropores. (3) XPS, NH₃-TPD, and H₂-TPR analyses reveal that Cl^- would occupy the oxygen vacancies, impeding oxygen migration and diminishing active surface centers. (4) In-situ DRIFTs analysis demonstrates that elevated Cl^- concentrations diminish NH₃ adsorption capacity and facilitate nitrate species formation. The accumulation of nitrates was a primary cause of the decline in catalyst activity.