Mg-Ion-Promoted Resistance and Regeneration Ability of Cu/SSZ-13 Catalysts against Phosphorus Poisoning for Selective Catalytic Reduction of NOx

Abstract

The SSZ-13 zeolite-supported Cu (Cu/SSZ-13) is a commercial catalyst for ammonia selective catalytic reduction (NH₃–SCR), but it faces challenges such as phosphorus poisoning in practical applications. Despite extensive investigations into how phosphorus poisoning leads to the deactivation of Cu/SSZ-13, effective strategies for regenerating catalysts with high phosphorus loading poisoned under practical conditions remain underdeveloped. In this study, we propose that incorporating Mg ions into Cu/SSZ-13 zeolites can significantly enhance their resistance and regeneration ability against phosphorus poisoning. After hydrothermal aging at 650 °C, the NH₃–SCR activity of phosphorus-poisoned Cu/SSZ-13 catalysts with high phosphorus loading (0.6 mmol/g_cat) cannot be effectively restored; however, the addition of Mg enables nearly complete recovery of their activity. Combining advanced microscopy evidence with complementary spectroscopy results, we reveal that Mg ions occupy the Brønsted acid sites in the six-membered rings (6-MRs) of SSZ-13, which regulates the distribution of subsequently introduced Cu ions while enhancing the stability of Cu²⁺ and the framework Al of SSZ-13, inhibiting the aggregation of Cu species after phosphorus poisoning and thereby improving resistance. Furthermore, the preservation of the SSZ-13 framework also effectively facilitates the redispersion of Cu species after hydrothermal aging, significantly restoring NH₃–SCR performance.