In situ ESR monitoring of CuH-ZSM-5 up to 500{degrees}C in flowing dry mixtures of NO (NO{sub 2}), C{sub 3}H{sub 6} (C{sub 2}H{sub 5}OH), and excess O{sub 2}
- Ford Motor Company, Dearborn, MI (United States)
A flow cell was used for ESR monitoring of the state of copper ions in Cu-ZSM-5 in situ at 20-500{degrees}C in a He stream containing C{sub 3}H{sub 6} (or C{sub 2}H{sub 5}OH), NO, and O{sub 2}. The gas mixtures approximate those in the selective catalytic reduction of NO{sub x}, save for the absence of steam. At room temperature, in propene flow, the formation of an oligomeric, carbonaceous material is accompanied by the reduction of a significant part of the Cu{sup 2+} cations. Heating of the sample at 200-300{degrees}C leads to quantitative reduction of the cupric ions. Ethanol is a less active reductant, and its sorption at 20-100{degrees}C results only in a coordination change of the Cu{sup 2+} by octahedral complex formation. The onset of the reduction of the Cu{sup 2+}ions in the [C{sub 2}H{sub 5}OH + He] flow is at {approximately}200{degrees}C. The equilibrium oxidation state of the copper in CuH-ZSM-5 depends on both the temperature and the composition of the gas mixture. At 500{degrees}C in the presence of propene or ethanol and in an excess of oxidant the condition prevailing during SCR, virtually all the copper remains in the Cu{sup 2+} state. At lower temperatures, in the 200-350{degrees}C range, in the same gas mixtures, a partial reduction of the Cu{sup 2+} ions takes place. High-temperature oxidation of the propene is accompanied by coke deposition on the outer surface of the zeolitic crystals. 25 refs., 9 figs.
- OSTI ID:
- 525929
- Journal Information:
- Journal of Catalysis, Vol. 152, Issue 1; Other Information: PBD: Mar 1995
- Country of Publication:
- United States
- Language:
- English
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