Fig. 1.

Reaction testing and overview of experimental findings. The center graph shows the NO conversion for the ammonia selective catalytic reduction (NH₃-SCR) reaction testing results for the four Cu-exchanged zeolite materials under study, the traces correspond to the borders of the four schematics. The feed consists of 1000 ppm NO, 1000 ppm NH₃, 5% O₂, balanced by He. The data have been measured in steady-state mode (GHSV = 100,000 h⁻¹). The panels at the corners give a 2D schematic overview of the results of this study with regards to the distribution of Al and Cu in Cu-SSZ-13 and Cu-ZSM-5, which are distributed slightly heterogeneously in fresh Cu-SSZ-13 and Cu-ZSM-5. After the simulated 135,000 mile aging procedure the Cu in Cu-SSZ-13 is found to migrate somewhat, as the schematic shows, though the material still retains good catalytic activity. In Cu-ZSM-5, the simulated aging causes significant migration of Cu and Al into stoichiometric copper aluminate species. One of the significant reasons that Cu-ZSM-5 is more damaged is that both Cu and Al species are able to migrate through its larger rings, whereas the small rings in Cu-SSZ-13 prevent Al migration, limiting damage to the material