One-step ion-exchange from Na-SSZ-13 to Cu-SSZ-13 for NH3-SCR by adjusting the pH value of Cu-exchange solution: The effect of H+ ions on activity and hydrothermal stability

Abstract A one-step ion-exchange method is developed to prepare high-performance Cu-SSZ-13 from Na-SSZ-13, by adjusting pH values of Cu salt solution during Cu-exchange. The H+ concentration has a significant influence on the Cu loading and distribution. In the absence of H+, the Cu2+ can only exchange the Na+ in 8 member rings (8-MR) as Cu(OH)+, due to the steric hindrance of Na+ ions located in 6 member rings (6-MR). When H+ is present, it is found to compete with Cu2+ to exchange the Na+ and to occupy the exchange sites in Na-SSZ-13. The Cu2+ ions take a priority over H+ to occupy the neighboring Al sites in 6-MR, while H+ takes precedence over Cu2+ to occupy ion-exchange sites in 8-MR, causing that Cu2+ coordinated to 6-MR is dominant in Cu-SSZ-13 via one-step method. The H+ concentration affects the overall catalytic activity and hydrothermal stability by controlling the Cu2+ loading and distribution.