Cu-65 NMR spectroscopy of Cu-exchanged ZSM-5 catalysts

Cu-65 NMR and Cu-65-Al-27 spin-echo, double-resonance (SEDOR) measurements from Cu-exchanged ZSM-5 catalysts are reported. The presence of Cu+ cations in CuZSM-5 was detected directly by Cu-65 NMR; upon heating, we observed the autoreduction of Cu2+ to Cu+. It was found that the Cu+ cations can be reduced further to Cu-0 by exposure to carbon monoxide at high temperatures. The internuclear distance between the two quadrupolar nuclei Cu (spin-3/2) and Al (spin-5/2) was determined to be 0.23 +/- 0.02 nm, in good agreement with the value of 0.24 nm obtained from density functional theory calculations.