The influence of lithium on the hydrogen peroxide decomposition activity of manganese–alumina catalysts

Abstract

Addition of small quantities of Li 2O to Al 2O 3 was studied with respect to its influence on the catalytic decomposition of H 2O 2 over Mn/Al mixed oxide catalysts calcined at 400, 700 and 1000 °C for 6 h. The specific surface areas of pure and doped solids were determined by BET analysis of nitrogen adsorption isotherms. The catalytic activities and the values of S BET of pure and doped mixed oxides were found to decrease by increasing the amount of Li 2O present. The activation energy of sintering, Δ E, of various solids decreased considerably by increasing the amount of Li 2O added. The maximum decrease in Δ E due to the doping with 6 mol% Li 2O attained 50%. In other words, Li 2O doping facilitates the sinterability of the treated solids to an extent proportional to the amount of lithia present. This treatment did not modify the activation energy of the catalyzed reaction, i.e. doping of Mn/Al mixed oxides did not alter the mechanism of the catalytic reaction but changed the concentration of catalytically active sites taking part in the catalytic process without altering their energetic nature.