Investigation of adsorbate reactivity during NO decomposition over different levels of copper ion-exchanged ZSM-5 using in situ IR technique
- Univ. of Akron, OH (United States). Dept. of Chemical Engineering
In situ infrared (IR) and mass spectroscopy (MS) coupled with temperature-programmed reaction (TPR), isotopic temperature-programmed desorption (TPD), step transient, and pulse transient techniques have been used to study the dynamic behavior of adsorbed species in the NO decomposition reaction on over- and underexchanged Cu-ZSM-5. Overexchanged Cu-ZSM-5 showed higher NO decomposition activity and produced more Cu{sup +} sites at lower temperatures than the underexchanged sample during the TPR study. Furthermore, overexchanged Cu-ZSM-5 allows rapid equilibrium between gaseous NO and Cu{sup +}(NO)/Cu{sup 2+}(NO{sub 3}{sup {minus}}) during NO decomposition. N{sub 2} formation accompanied by the presence of Cu{sup +}(NO) suggests that Cu{sup +} initiates the NO decomposition process. However, no direct correlation between Cu{sup +}(NO)/Cu{sup +}(NO){sub 2} intensity and N{sub 2} formation was observed. Adsorbed oxygen from dissociated NO changes the oxidation state of Cu{sup +} ion, causing the formation of Cu{sup 2+}(NO{sub 3}{sup {minus}}). While Cu{sup 2+}(NO{sub 3}{sup {minus}}) decomposes to N{sub 2}, N{sub 2}O, NO{sub 2}, and O{sub 2} during TPD, it is only partially responsible for the formation of O{sub 2} during NO decomposition. Isotopic study shows that adsorbed oxygen on Cu-ZSM-5 desorbs during the pulse NO reaction. These results demonstrate the presence of two pathways for O{sub 2} formation: oxygen produced from the decomposition of Cu{sup 2+}(NO{sub 3}{sup {minus}}) and oxygen from the desorption of adsorbed oxygen on Cu-ZSM-5.
- OSTI ID:
- 682115
- Journal Information:
- Journal of Physical Chemistry B: Materials, Surfaces, Interfaces, amp Biophysical, Vol. 103, Issue 28; Other Information: PBD: 15 Jul 1999
- Country of Publication:
- United States
- Language:
- English
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