Applying TEM, XRD analysis, XPS, TPR/TPO cycles evidence is presented to support the presence of two distinctly different copper species on reduced copper on silica catalysts (2.1‐9.5 wt.% Cu) which are prepared by the ion‐exchange method.

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Isotopic labeling studies of the reaction between l5NO and 14NH3 have been performed over a range of vanadiatitania-based SCR catalysts (pure VtO5 and catalysts containing 1.4-23.2 wt % V205) for the extended temperature range of 200-500 OC. For temperatures less than 350 O C , I4Nl5N is always the major product. At higher temperatures, however, product distributions are very sensitive to vanadia content; ammonia oxidation to 14NO is particularly dominant for pure VZOS and, at 500 OC, accounts for more than 70% of the nitrogen-containing products. Pure VZOS also produces significantly more 14N'SN0, and at much lower temperatures, than that observed for a 1.4 wt % Vz05/Ti02 catalyst. On the basis of these results it is clear that ammonia oxidation to I4NO is the major reason for the observed decrease in the N O conversion over vanadia-based catalysts at temperatures greater than 400 OC. Ammonia oxidation to nitrogen and nitrous oxide is less significant; I4NzO and 14N2 each comprise less than 10% of the total products for both the pure and supported vanadia catalysts. Addition of 1.6% water decreases the amount of nitrous oxide (largely I4N15NO) produced over the supported catalyst at 450 OC by over 90%. A simultaneous increase in the amount of l4NISN is also observed. The presence of water also suppresses the 14NH3 oxidation to 14N2, I4N2O, and 14N0, even at 500 OC. By contrast, for pure VzO5 at 500 OC, water has a relatively minor effect on the product distribution, and the major product remains 14N0. In general, high temperatures, dry feed gas conditions, and high vanadia contents favor both the production of l4N'5NO relative to l4NIsN and the ammonia oxidation reaction producing 14N0. Results from this and previous studies suggest that there is a relationship between NzO formation and NH3 oxidation capability.