Direct application of Na-containing SSZ-13 for the synthesis of Cu-SSZ-13 as NH₃-SCR catalyst

The Na containing SSZ-13 is usually used for the synthesis of Cu-SSZ-13 after being converted to proton or ammonium form of SSZ-13 by washing with high-concentration NH₄NO₃/NH₄Cl solution (1.0 mol/L) for several times, followed by washing with numerous DI water. In this work, we developed a liquid ion exchange (IE) method for the synthesis of Cu-SSZ-13 directly using SSZ-13 that contains 0.88 wt.% Na. The Na can be replaced by Cu ions in the Cu nitrate solution, leading to the facilitation in the rate of ion exchange of Cu compared with the H-SSZ-13. When the Cu was introduced to SSZ-13 by novel impregnation (NIM) method, since the Na will compete with the Cu for the ion exchange sites of SSZ-13, most of the Na needs be simply removed by washing with dilute NH₄Cl (0.01 mol/L). Interestingly, the residual Na not only acts as Al protectors but also promotes the formation of [Cu(OH)]⁺-Z which possesses higher low-temperature activity. The proper amount of Na exists in SSZ-13 is beneficial for the synthesis of Cu-SSZ-13 with excellent hydrothermal stability and deNO_x activity simultaneously no matter IE or impregnation method was used. Thus, we propose that the Na containing SSZ-13 is more competitive than H-SSZ-13 which is usually employed in scientific research and industrial manufacture.