Surface and catalytic properties of Cr2O3/MgO system doped with manganese and cobalt oxides

The effects of cobalt and manganese oxides-doping on surface and catalytic properties of Cr2O3/MgO system have been investigated. The dopant concentration was changed between 1 and 5 mol% cobalt and manganese oxides. Pure and variously doped solids were subjected to heat treatment at 400 and 700 degreesC. The techniques employed were X-ray diffraction (XRD), nitrogen adsorption at -196 degreesC, catalytic conversion of iso-propanol at 200-400 degreesC using flow technique and catalytic decomposition of H2O2 at 20-40 degreesC. The results revealed that the doping process of the system investigated followed by calcinations at 400 or 700 degreesC, enhanced the solid-solid interactions between catalyst constituents yielding (alpha-MgCrO4, beta-MgCrO4) and MgCr2O4, respectively. Furthermore, manganese and cobalt oxide-doping for Cr2O3/MgO system increased its catalytic activity much towards H2O2-decornposition. The increase was, however, more pronounced in the case of manganese-doping. Opposite results have been observed in the case of iso-propanol conversion, which proceeds via dehydrogenation and dehydration reaction. The S-BET of the investigated system was found to decrease by increasing the dopant concentration. The doping process did not modify the activation energy of the catalyzed reaction, but rather changed the concentration of the catalytically active constituents without changing their energetic nature. (C) 2004 Elsevier B.V. All rights reserved.