The Role of SO3 Poisoning in CU/SSZ-13 NH3-SCR Catalysts

To reveal the role of SO3 poisoning in Cu/SSZ-13 NH3-SCR catalysts, fresh and sulfated Cu/SSZ-13 catalysts were prepared in the presence or absence of SO3 flux. The deactivation mechanism is probed by the changes of structural, copper species, and selective catalytic reduction (SCR) activity. The variations concentrate on the changes of copper species as the Chabazite (CHA) framework of Cu/SSZ-13 catalysts could keep intact at high ratios of SO3/SOx. The thermal gravimetric analyzer (TGA) results reveal that the copper sulfate formed during sulfation and the amounts of sulfate species increased with an increase in the SO3/SOx ratio. In contrast to the changing trend of copper sulfate, temperature program reduction (H2-TPR), and electron paramagnetic resonance (EPR) results manifest that, since the number of active copper ions declines with an increase of the SO3/SOx ratio, the active sites transform to these inactive species during sulfation. Due to the combination of NH3-SCR activity and the kinetic tests, it is shown that the decreased number of active sites is responsible for the declined SCR activity at low temperature. As Cu/SSZ-13 catalysts show excellent acid-resistance ability, our study reveals that the Cu/SSZ-13 catalyst is a good candidate for NOx elimination, especially when SO3 exists.