Efficient regeneration of Cu-SSZ-13 NH3-SCR catalysts deactivated by Na, P and (Na plus P) poisoning

The deactivation of Cu-SSZ-13 zeolite SCR catalysts poisoned by mineral impurities (Na, P and Na+P) from biodiesel remains a significant challenge but lacks corresponding regeneration strategies. Herein, optimized regeneration approaches were exploited for the target poisoned catalysts, leading to a remarkable recovery of SCR activity. Comprehensive characterization experiments and theoretical calculations were conducted. The Na poisoning species and unwanted CuOx were effectively removed by sulfuric acid (H2SO4) aqueous solution, leading to the recovery of Br & Oslash;nsted acid sites and the re-exposure of active Cu2+ sites, although sacrificing a small amount of Cu2+ sites. P poisoning species mainly decreased the accessibility of porosity and weakened the redox ability of active Cu2+ sites due to the strong interaction of Cu-P species; The combination of washing with hot water and high-temperature hydrothermal aging treatment (HAT) contributed to good recovery of the Ppoisoned catalysts owing to the dissolution of a portion of P species in hot water and the partial decomposition of Cu-P species, with the release of active Cu2+ sites. Both Na and P poisoning effects were observed after equimolar Na+P co-addition. Considering that the deactivation trend for Na+P poisoning was closer to that observed with P poisoning, it was demonstrated that the P poisoning species were preferentially removed by hot water and Na species were subsequently eliminated by H2SO4 aqueous solution, with consequent HAT, the SCR activity was further restored. The current study provides efficient regeneration strategies to extend the service life of the CuSSZ-13 catalyst in practical applications.