Mp. Attfield et al., ON THE NATURE OF NONFRAMEWORK CATIONS IN A ZEOLITIC DENO(X) CATALYST - CU-MORDENITE, Journal of catalysis, 170(2), 1997, pp. 227-235
The locations of extra-framework Cu2+ cations in hydrated copper ion-e
xchanged mordenite (formula Cu1.384T48O2 . 28H(2)O, space group Cmcm,
a=18.1659(4) Angstrom, b=20.375(1) Angstrom, c=7.495(1) Angstrom, V=27
74.4(4) Angstrom(3), Z=1, R=5.13%) and its partially dehydrated analog
(formula Cu1.468T48O2 . 4.04H(2)O, space group Cmcm, a=18.0546(7) Ang
strom, b=20.298(2) Angstrom, c=7.4772(3) Angstrom, V=2740.2(3) Angstro
m(3), Z=1, R=3.90%) have been determined from the analysis of room-tem
perature single-crystal X-ray data. Two copper sites were found in the
hydrated sample: one in the elliptical 8-ring and the other in the ce
nter of the main 12-ring channel. Upon dehydration three copper sites
were determined; one in the elliptical 8-ring, one above the 6-ring in
the main channel and the last in the circular 8-ring that leads into
the main channel. The low coordination, but high accessibility, of the
latter two cation sites in the partially dehydrated sample provides a
possible explanation for the high activity of mordenite and its relat
ed pentasil family members for nitrogen oxide composition. (C) 1997 Ac
ademic Press.