Wk. Jozwiak et Igd. Lana, INTERACTIONS BETWEEN THE CHROMIUM-OXIDE PHASE AND SUPPORT SURFACE - REDISPERSION OF ALPHA-CHROMIA ON SILICA, ALUMINA AND MAGNESIA, Journal of the Chemical Society. Faraday transactions, 93(15), 1997, pp. 2583-2589
Citations number
35
Categorie Soggetti
Chemistry Physical","Physics, Atomic, Molecular & Chemical
The appearance of alpha-Cr2O3 on the support surface of Cr/SiO2 cataly
st (ethene polymerization) suggests catalyst deactivation. This study
evaluates (using TPR and XRD) the possible redispersion of the crystal
line chromia on silica, alumina and magnesia during high-temperature o
xygen treatment. Both wet impregnation and dry physical mixing prepara
tions yielded active catalysts (Cr/SiO2) even when starting with alpha
-Cr2O3. A chromium redispersion mechanism on oxide support surface is
postulated. It involves the formation of mobile oxo species (CrO3) on
crystalline chromia surface, followed by their migration on the suppor
t through chromia/support interface contacts, and finally their anchor
age to suitable support adsorption sites resulting in stable monochrom
ate-like species. The redispersion effects strongly depend on the adso
rption capability of the support surface and the experimental conditio
ns (temperature, atmosphere and traces of water).