Disparate Essences of Residual, Ion-Exchanged, and Impregnated Na Ions on Topology Structure for Cu/SSZ-13 NH3 Selective Catalytic Reduction Catalysts

To investigate the nature of sodium via different introduction methods, a series of SSZ-13 supports and Cu/SSZ-13 catalysts were prepared via synthetic residual (R), ion-exchange (IE), and impregnation (IP) methods and hydrothermally treated. Fresh R-Na and IE-Na supports and catalysts show the same long-term structural properties. Cu species analyses show more Cu(OH)(+)-Z species dispersing in the cages of IE-Na-Cu/SSZ-13 compared with that in R-Na-Cu/SSZ-13, and as a result, more mesopore generation was observed after harsh hydrothermal aging at 800 degrees C. Using NMR methods and DFT calculations, R-Na and IE-Na ions were found to protect Al-O-Si bonds from water attack during aging, while IP-Na ions caused desilicication and formed the H2Si2O5 phase and Al(OSi)(1)(OH)(3) configuration. Consequently, our study reveals that a small number of R-Na ions should remain and this will benefit the long-term stability of Cu/SSZ-13 catalysts, especially when a diesel particle filter is applied upstream for selective catalytic reduction.