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SO2-Derived Enhanced Stability of Ag-Alumina Catalysts for the Selective Catalytic Reduction of NOx with Methane

Xiaoyan She1, Maria Flytzani-Stephanopoulos2, Chongmin Wang1, Yong Wang1, and Charles H. F. Peden1. (1) Institute for Interfacial Catalysis, Pacific Northwest National Laboratory, PO Box 999, MSIN: K8-87, Richland, WA 99352, (2) Chemical and Biological Engineering, Tufts University, 4 Colby Street, Medford, MA 02155

Silver/alumina is one of the most promising DeNOx catalysts, and has been evaluated for the selective catalytic reduction (SCR) of NOx by both hydrocarbons and oxygenates [1-3]. The importance of silver structure has been identified in the early literature. Thus, well dispersed silver, but not silver particles are associated with the active sites for the SCR reaction. Loss of activity by sulfur dioxide has been reported for some reductants, but not for others. We have recently reported that silver-alumina catalysts used for the SCR of NOx by methane, CH4-SCR, are very promising for flue-gas treatment in the presence of high concentrations of SO2 (~1000ppm)[4], as long as the temperature was kept > 600 oC, hence this type catalyst may be used as an alternative to high-temperature NH3-SCR catalysts, and for treatment of gas turbine exhaust gases. Further, an extraordinary stabilizing effect of SO2 on the above catalytic system was identified for the first time in our work. Here, the enhanced structural stability and activity of silver-alumina catalysts imparted by the presence of SO2 was investigated by catalytic activity measurements and detailed characterization of fresh and aged catalysts with TPO, TEM, XPS, and XRD analyses.

References

1. T. Miyadera, Appl. Catal. B 2 (1993) 199.

2. R. Burch, J.P. Breen, F.C. Meunier, Appl. Catal. B 39 (2002) 283.

3. X. She, M. Flytzani-Stephanopoulos, J. Catal. 237 (2006) 79.

4. X. She, M. Flytzani-Stephanopoulos, Catal. Today, 127 (2007) 207.