A quantitative diffuse reflectance spectroscopy study of supported chromium catalysts

The diffuse reflectance spectra of chromium supported on alumina, on silica, and on silica-alumina have been investigated after calcination, CO reduction, and recalcination. A method for quantifying the Cr 6+ , Cr 3+ , and Cr 2+ concentrations was developed. After calcination at 550 o C, the chromate:dichromate ratio is ∞, 0.56, and 2. 18 on respectively alumina, silica, and silica-alumina. Reduction results in the formation of three new species: octahedral Cr 3+ , octahedral Cr 2+ , and pseudotetrahedral Cr 2+