Mp. Attfield et al., ON THE NATURE OF NONFRAMEWORK CATIONS IN A ZEOLITIC DENO(X) CATALYST - A SYNCHROTRON X-RAY-DIFFRACTION AND ESR STUDY OF CU-FERRIERITE, Journal of catalysis, 172(2), 1997, pp. 274-280
The location of extra-framework Cu2+ cations in the dehydrated copper
ion exchanged zeolite, ferrierite, has been determined from the analys
is of synchrotron X-ray powder diffraction data (Cu-0.023(Al0.065Si0.9
35)O-2; space group Immm, a = 18.8101(2) Angstrom, b = 14.0930(2) Angs
trom, c = 7.44527(7) Angstrom, V = 1973.67(6) Angstrom, Z = 36, R-wp =
9.89%, chi(2) = 1.12). One copper site was found towards the side of
the 8-ring window at the intersection of the 10- and 8-ring channels.
An electron spin resonance (ESR) spectroscopic study indicates the pre
sence of one Cu2+ species in the hydrated sample, which forms two Cu2 species upon evacuation to 200 degrees C, only one of which remains a
fter evacuation to 360 degrees C. This remaining Cu2+ species has nona
xial symmetry. The low coordination, but high accessibility of the cat
ion site provides a possible explanation for the high activity of ferr
ierite and its related pentasil family members for nitrogen oxide deco
mposition. (C) 1997 Academic Press.