Deactivation mechanism of SO2 on Cu/SAPO-34 NH3-SCR catalysts: structure and active Cu2+

Abstract

The deactivation mechanism of Cu/SAPO-34 ammonia selective catalytic reduction catalysts (NH₃-SCR) by SO₂ poisoning has been systematically investigated using a range of analytical techniques in order to study the influence on both the zeolitic framework and the active Cu²⁺ ions. The different sulfate samples were obtained by SO₂ poisoning over Cu/SAPO-34 NH₃-SCR catalysts as a function of time and concentration in the feed. The obtained results reveal that the SO₂ poisoning could seriously decrease NO conversion during the whole temperature range (100–500 °C). The XRF results shows that there is almost no sulfur existing on the SAPO-34 support. The ex situ DRIFTS and BET results reveal that SO₂ poisoning has a less-pronounced effect on its framework structure. The TPR and EPR results demonstrate that SO₂ poisoning has a significant influence on the coordination environment and the content of the active isolated Cu²⁺ species. The kinetic results demonstrate that the SO₂ poisoning does not influence the apparent activation energy (E_a) of the NH₃-SCR reaction over Cu/SAPO-34 catalysts. The decline of the NH₃-SCR activity is due to the reduction of the number of isolated Cu²⁺ ions.