Surface and catalytic properties of Fe2O3-Cr2O3/Al2O3 solids as being influenced by Li2O and K2O-doping

The effects of Li2O (0.15-0.60 wt.%) and K-2 (0.45-1.80 wt%)-doping on surface and catalytic properties of Fe2O3-Cr2O3/Al2O3 solids were studied using nitrogen adsorption at - 196 degreesC and oxidation of CO by O-2 at 225-300 degreesC. The results showed that Li2O (0.6%) and K2O (1.8%) doping followed by precalcination at 700 degreesC resulted in an important increase in the BET- surface areas (about one-fold) of the treated solids. The precalcination of variously doped solids at 400 degreesC exerted no significant change in the specific surface areas of the hoped adsorbents. The catalytic activity increased by increasing the amount of Li2O added to the solids preheated at 400 and 700 degreesC. On the other hand, K2O-doping conducted at 400 degreesC, which resulted in a considerable increase in the catalytic activity of the treated solids, much decreased their catalytic activity upon precalcination at 700 degreesC. The doping process did not modify the mechanism of catalytic oxidation of CO by O-2, but changed the concentration of catalytically-active component (surface Fe2O3 crystallites) without modifying their energetic nature. (C) 2001 Elsevier Science B.V. All rights reserved.