Surface and catalytic properties of a CuO/MgO system as influenced by Li2O-doping and exposure to γ-irradiation

The effects of Li2O-doping and gamma-irradiation of a CuO/MgO system on its surface and catalytic properties have been investigated. The extent of CuO loading was varied between 9 and 37 wt.% and the dopant concentration was changed between 0.4 and 2.35 wt.% Li2O. The doses of gamma-rays were ranged between 20 and 160 Mrad. Pure and variously doped solids were subjected to heat treatment at 400 degreesC. The results revealed that MgO dissolves CuO producing CuO-MgO solid solutions by heating the mixed solids at 400 degreesC. The maximum amount of CuO dissolved in MgO solid by heating at 400 degreesC attained 22.8 wt.%. The specific surface area of the system investigated decreased by increasing the amount of CuO present and by increasing the amount of dopant added. On the other hand, gamma-irradiation brought about an increase in the S-BET of the treated adsorbents. The catalytic activity in H2O2 decomposition of CuO/MgO system decreased by increasing the dose of gamma-irradiation. The exposure of the CuO/MgO sample (containing 28.3 wt.% CuO) precalcined at 400 degreesC to a dose of 160 Mrad resulted in a decrease of 54.5% in its catalytic activity expressed as reaction rate constant, per unit surface area for the reaction conducted at 30 degreesC (k(30 degreesC)(-)). The Li2O-doping of the same catalyst sample with 2.35 wt.% followed by calcination at 400 degreesC resulted in an increase of 130 and 94% in the values of k(20 degreesC)(-) and k(30 degreesC)(-), respectively. The doping process did not modify the activation energy of the catalyzed reaction but rather changed the concentration of the catalytic active constituents without changing their energetic nature. (C) 2002 Elsevier Science B.V. All rights reserved.