Abstract

Nanostructured manganese oxides were synthesized towards the catalytic decomposition of hydrogen peroxide. The effect of the type of precipitant (Na₂CO₃ and NH₄OH) over the particle size and crystallographic phase was determined. Also, the influence of particle size and crystal phase over the catalytic activity was established. Characterization of the obtained nanoparticles was performed through XRD analysis, BET surface area and TEM microscopy. Catalytic activity was followed through gasometry of the oxygen evolution [H₂O₂(l) → H₂O(l) + O₂ (g)] at 25°C. Na₂CO₃ (Mn-1) and NH₄OH (Mn-2) precipitants produced nanoparticles with average sizes of 5-10 nm and 20 nm, respectively. This result was attributed to higher pH stability of precipitant Na₂CO₃ during the synthesis process. XRD results revealed the presence of ß-MnO₂, Mn₅O₈ and Mn₃O₄ crystal phase mixture for Mn-1 and Mn₅O₈ for Mn-2 catalyst. Catalytic activity resulted in intrinsic rate constants (k_int = min^-1m^-2) of 5.2 and 2.3 for Mn-1 and Mn-2, respectively. The greater catalytic activity of Mn-2 catalyst was attributed to the presence of the Mn₅5O₈ phase.

Recommended Citation

Delgado Vigil, Manuel D.; Paraguay Delgado, Francisco; Collins Martínez, Virginia; and López Ortiz, Alejandro (2008) "Synthesis, Characterization and Kinetic Evaluation of Manganese Oxide Nanoparticles for the H₂O₂ Catalytic Decomposition," International Journal of Chemical Reactor Engineering: Vol. 6: A5.
Available at: http://www.bepress.com/ijcre/vol6/A5