Vapour phase H2O2 decomposition on Mn based monolithic catalysts synthesized by innovative procedures

Manganese oxide catalysts supported on monolithic yttria stabilized zirconia honeycombs were studied for H2O2 decomposition in view of space propulsion applications. The materials were prepared by impregnation (IM), precipitation (PR) and sol–gel (SG) methods and characterized by N2 adsorption, SEM and H2 temperature programmed reduction (TPR). The catalytic activity for H2O2 decomposition was studied under vapour phase conditions. The tests were carried out in a flow apparatus at T = 200 ◦C, gas hourly space velocity (GHSV) = 2.00 and 2.67 s−1, H2O2 concentrations of 11.3 mol%. The redox properties of the catalysts were markedly influenced by the preparation method. In the SG catalyst, a large fraction of Mn was not reducible in the TPR tests differently from the PR and IM materials. Despite this effect, the SG catalyst showed an activity comparable or higher than that of PR and IM, due to a more effective dispersion of Mn species. A too strong effect of space velocity on H2O2 conversion was attributed to an autocatalytic effect. A radical mechanism was hypothesized: it was assumed that a reaction between O2 and Mn species produced radicals that promoted the overall reaction.