One-pot synthesis of hierarchical MnCu-SSZ-13 catalyst with excellent NH3-SCR activity at low temperatures

Abstract

Cu-SSZ-13 catalyst with small pore structure has been considered as one of the most efficient catalysts in controlling NOx emissions from the diesel vehicles. But the low NOx conversion in the temperature range of < 200 °C seriously limits its wide applications in many situations. In this study, in order to improve the NH3-SCR performance at low temperatures, MnCu-SSZ-13-OP and Cu-SSZ-13-OP catalysts were successfully prepared by one-pot method. Experimental results indicated that the Mn and Cu co-doped catalyst had excellent SCR activity with 68% of NOx conversion at 150 °C compared to the Cu-SSZ-13-OP catalyst with NOx conversion of 31%. Meanwhile, the MnCu-SSZ-13-OP catalyst exhibited higher low-temperature activity than Cu-SSZ-13-OP catalyst (71% vs 51% NOx conversion at 200 °C) even after hydrothermal treatment, which should be attributed to the highly dispersed Mn species and its unique NO adsorption properties. Particularly, the hierarchical pores structure of MnCu-SSZ-13 played key roles for the distribution of active sites and gas diffusion. The in situ XRD results also found that the addition of TEPA and a small amount of Mn species during the synthesis process had no obvious influence on the thermal stability of the zeolite catalysts. This study also provides a new guidance to the design and simple synthesis of the catalyst based on SSZ-13zeolite with high-performance for the removal of NOx at a broad temperature window.