AN OBSERVATION OF HOMOGENEOUS AND HETEROGENEOUS CATALYSIS PROCESSES IN THE DECOMPOSITION OF H2O2 OVER MNO2 AND MN(OH)2

The kinetics of peroxide decomposition by manganese dioxide (MnO2) and manganese hydroxide (Mn(OH)2) have been studied in alkaline solutions. The activity for peroxide decomposition on Mn(OH)2 was generally higher than MnO2 and the kinetics for the decomposition of H2O2 were first-order in the case of MnO2 catalysts, but 1.3-order for Mn(OH)2 catalysts. It is suggested that H2O2 is mainly homogeneously decomposed by Mn2+ ions (in the form of HMnO2 ions in concentrated alkaline solutions) dissolved in the solution in the case of Mn(OH)2. Compared with the results reported for the decomposition of H2O2 in the presence of 1 ppm Co-2 ions, it is concluded that the kinetics of the homogeneous decomposition of H2O2 are directly influenced by the concentration of the active species in the solution. © 1991.