Deactivation of CeO2-TiO2 catalyst by K2SO4 for NH3-SCR: An experimental and DFT study

Highlights: • The effect of SO₄²⁻ anion in K₂SO₄ on CT was studied by DFT calculations. • SO₄²⁻ promoted the surface reactions over CT. • K₂SO₄ showed inhibition on NH₃ adsorption but promotion on the formation of NO_x. • K₂SO₄ played an adverse role on the L-H and E-R mechanism on CT. K species in flue gas can lead to severe deactivation of SCR catalysts. In this study, the K₂SO₄ poisoning mechanism on the CeO₂-TiO₂ catalyst was investigated by experiments and DFT calculations. The presence of K₂SO₄ could result in the degradation of reducibility and surface acidity, and the decrease in Ce³⁺ and chemisorbed oxygen. DRIFTS results revealed that the NH₃ adsorption was inhibited and the NO_x adsorption was promoted. But only a few of newly formed NO_x were reactive. CeO₂-TiO₂ catalyst still followed L-H and E-R mechanisms despite K₂SO₄ doping, but both of them were suppressed. The experimental results were further confirmed by DFT calculations. In addition, the DFT calculation results showed that K⁺ could inhibit surface reactions of formation of oxygen vacancies, adsorption of NH₃ and chemisorbed oxygen, and hydrogenation. In comparison, SO₄²⁻ could promote these behaviors, especially the generation of oxygen vacancies. The simultaneous presence of K⁺ and SO₄²⁻ played an adverse role in the surface acidity and redox ability. The deactivation of CeO₂-TiO₂ catalyst caused by K₂SO₄ was verified by the calculation results of PDOS and Mulliken charges.