Effect of surface species and structure on the performance of CeO2 and SO42− doped MCM-41 catalyst toward NH3-SCR

Abstract

The present work elucidated the effects of structures and surface species on the activity of CeO₂ and SO₄²⁻ doped MCM-41 catalysts toward NO reduction by NH₃. The results indicated that the sulfated species were generated over Cat-A (Ce(NO₃)₃·6H₂O and H₂SO₄ simultaneously doped on MCM-41) and Cat-B (Ce(NO₃)₃·6H₂O first immersed to MCM-41 and followed by impregnation of H₂SO₄) except for Cat-C (H₂SO₄ first doped onto MCM-41 and followed by Ce(NO₃)₃·6H₂O). The sulfate ion contributed to the formation of Ce³⁺ concentration, oxygen vacancies, and surface acidity, resulting in improvement of SCR activity. However, the positive influence on SCR activity was overwhelmed by the decomposition of sulfated species. The apparent activation energy of Cat-A (60 kJ mol⁻¹) was much lower compared with that of Cat-B and Cat-C (71 and 78 kJ mol⁻¹, respectively). Pore structures and surface species were responsible for the SCR activity over the CeO₂ and SO₄²⁻ doped MCM-41 catalysts. The best catalytic activity was obtained over Cat-A, followed by Cat-B, and Cat-C exhibited the least catalytic activity.