Physical and chemical characterization of Cr-Y and Cr-X zeolites
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The physical and chemical properties of trivalent chromium supported in zeolites X and Y have been investigated by infrared, EPR, and diffuse reflectance spectroscopies. Nitric oxide was also used as a chemical probe and several chromium-nitrosyl complexes were characterized on the zeolite surface. Earlier investigators have reported that the dehydration of Y-type zeolites containing Cr(III) results in the reduction of a major fraction of the Cr to the divalent state. In contrast, we find no evidence for this reduction. The infrared and EPR parameters of chromium-nitrosyl complexes formed upon the addition of NO to dehydrated Cr-Y samples are explained on the basis of a Cr(III) precursor. In addition, Fenske-Hall molecular orbital calculations were performed for several models representing Cr-nitrosyl complexes in zeolitic coordination sites. These calculations support the assertion that Cr(III) is the predominant cation in Cr-Y samples. © 1980 American Chemical Society.
author list (cited authors)
Pearce, J. R., Sherwood, D. E., Hall, M. B., & Lunsford, J. H.