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

Abstract

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 NOx adsorption was promoted. But only a few of newly formed NOx 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.