In situ UV-Vis diffuse reflectance spectroscopy - on line activity measurements of supported chromium oxide catalysts: relating isobutane dehydrogenation activity with Cr-speciation via experimental design
Bm. Weckhuysen et al., In situ UV-Vis diffuse reflectance spectroscopy - on line activity measurements of supported chromium oxide catalysts: relating isobutane dehydrogenation activity with Cr-speciation via experimental design, J MOL CAT A, 151(1-2), 2000, pp. 115-131
The dehydrogenation of isobutane over supported chromium oxide catalysts wa
s studied by a combination of in situ UV-Vis diffuse reflectance spectrosco
py and on line GC analysis. A well-defined set of experiments, based on an
experimental design, was carried out to develop mathematical models, which
quantitatively relate Cr-speciation and dehydrogenation activity with react
ion temperature and time, support composition, gas composition and Cr loadi
ng. It will be shown that: (1) the dehydrogenation activity is proportional
with the amount of in situ measured surface Cr2+/3+, and maximum for a 7.5
wt.% Cr/Al2O3 catalyst operating at 500 degrees C in 2% isobutane in N-2;
and (2) Cr3+-sites are more active in alkane dehydrogenation than Cr2+-site
s. This paper is the first example of the use of experimental design for de
riving structure-activity relationships in the field of heterogeneous catal
ysis. (C) 2000 Elsevier Science B.V. All rights reserved.