ISSN:
1572-879X
Keywords:
TPR
;
FT-IR
;
XPS
;
copper location
;
Y zeolite
;
ionic exchange
;
impregnation
Source:
Springer Online Journal Archives 1860-2000
Topics:
Chemistry and Pharmacology
Notes:
Abstract The location of transition ions in copper- and copper-zinc-loaded Y type zeolites prepared by different procedures has been studied by temperature-programmed reduction, infrared spectroscopy of CO adsorbed on pretreated samples and X-ray photoelectron spectroscopy. Samples outgassed at 673 K showed Cu+ species due likely to reduction of Cu2+ ions under vacuum. Over exchanged CuY zeolites copper species in exchange sites were detected, while an impregnated sample exhibited bands of CO adsorbed on both Cu2+ and Cu+ ions developed at the surface of CuO crystals, and small proportions of Cu+ ions located in accessible exchange sites SII and SnII. Similar findings were observed in Zn- and Cu-exchanged zeolites although the relative proportion of Cu in SI positions was decreased due to competition between Cu2+ and Zn2+ ions. Samples reduced in hydrogen at 523 K showed the appearance of Cu0 species in impregnated samples, whereas Cu+ dominated in the exchanged counterparts. Reduction at 598 K led to substantial changes in Cu-exchanged samples in water. The proportion of Cu+ species decreased by reduction to Cu0 and simultaneously migration to Cu+ to SII sites occurred. While Cu2+ or Cu+ were found on outgassed samples, only Cu0 and intrazeolite Cu+ were observed after H2-reduction at 623 K. Changes in copper exposure as a function of sample pretreatments were also revealed by X-ray photoelectron spectroscopy.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF00811713
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