Hydrogen peroxide decomposition on various supported catalysts effect of stabilizers

The decomposition of hydrogen peroxide (H2O2) has been studied on various catalysts (platinum supported on silica; silver, iridium, platinum-tin or manganese oxides supported on alumina). The experiments were performed using two reactors: 1) a conventional constant pressure reactor for the determination of the volume increase vs time using diluted H2O2 Solutions; 2) a constant volume reactor to measure the pressure increase using more concentrated solutions. The first reactor leads to the determination of the kinetic order of the reaction, to the comparison of the activities of the different samples, and to the characterization of the influence of some stabilizers of H2O2 Solutions on the catalytic activity. Two kinetic orders were found, depending on the catalyst: a zero order and a first order. The shape of the catalysts samples is an important parameter, with powders always being more reactive than grains and pellets. The catalyst activities are sorted as follows: Pt-Sn/Al2O3 < Ir/Al2O3 < Pt/SiO2 < MnOx/Al2O3 < Ag/Al2O3. The presence of pyrophosphate stabilizer leads to a loss of activity mainly as a result of passivation in the case of MnOx-supported samples, whereas the presence of stannate increases slightly the activity of silver and displays no influence on manganese samples.