Three extraframework sits for cobalt in zeolites were proposed based on UV/visible (Vis) diffuse reflectance spectroscopy in mordenite. Experimental spectroscopic signatures of cobalt were reproduced before studying the methane SCR cycle over the catalysts. For a given cluster, the low-spin Co-O bonds were slightly shorter than the high-spin Co-O bonds. In all cases, the high-spin state was preferred by 20-40 kJ/mole depending on the cluster. The B-1,4 spectroscopic signatures agreed well with the experimental signature. Cobalt induced a deformation in the zeolite framework that shifts a framework IR mode to a lower frequency compared to the sodium form of the zeolite. The predicted B-1,4 high-spin UV/Vis spectrum also agreed with experiment, while the predicted low-spin spectrum did not. The spectroscopic signatures correlated to the Al substitution position rather than the extraframework site. Accurate knowledge of Co extraframework siting is the necessary first step towards understanding Co-zeolite SCR catalysts. This is an abstract of a paper presented at the 222nd ACS National Meting (Chicago, IL 8/26-30/2001).
|Original language||English (US)|
|Number of pages||6|
|Journal||ACS Division of Environmental Chemistry, Preprints|
|State||Published - Dec 1 2001|
ASJC Scopus subject areas
- Chemical Engineering(all)