Characterization of Cu-exchanged SSZ-13: a comparative FTIR, UV-Vis, and EPR study with Cu-ZSM-5 and Cu-beta with similar Si/Al and Cu/Al ratios

Cu-SSZ-13 has been characterized by different spectroscopic techniques and compared with Cu-ZSM-5 and Cu-beta with similar Si/Al and Cu/Al ratios and prepared by the same ion exchange procedure. On vacuum activated samples, low temperature FTIR spectroscopy allowed us to appreciate a high concentration of reduced copper centres, i.e. isolated Cu+ ions located in different environments, able to form Cu+(N-2), Cu+(CO)(n) (n = 1, 2, 3), and Cu+(NO)(n) (n = 1, 2) upon interaction with N-2, CO and NO probe molecules, respectively. Low temperature FTIR, DRUV-Vis and EPR analysis on O-2 activated samples revealed the presence of different Cu2+ species. New data and discussion are devoted to (i) [Cu-OH](+) species likely balanced by one framework Al atom; (ii) mono(mu-oxo)dicopper [Cu-2(mu-O)](2+) dimers observed in Cu-ZSM-5 and Cu-beta, but not in Cu-SSZ-13. UV-Vis-NIR spectra of O-2 activated samples reveal an intense and finely structured d-d quadruplet, unique to Cu-SSZ-13, which is persistent under SCR conditions. This differs from the 22 700 cm(-1) band of the mono(mu-oxo)dicopper species of the O-2 activated Cu-ZSM-5, which disappears under SCR conditions. The EPR signal intensity sets Cu-beta apart from the others.