A theoretical and experimental study of manganese oxides used as catalysts for VOCs emission reduction

The catalysts were prepared by two different methods: (1) oxidative decomposition of MnCO3 under flowing oxygen saturated with water and (2) oxidation of a MnSO4 dissolved in H2SO4. The solids were characterized by XRD, diffuse reflectance IR spectroscopy (DRIFTS), DRS-UV-vis and thermogravimetric analyses (TGA). The results showed that both solids belonged to the nsutite phase (γ-MnO2). Both catalysts showed similar catalytic activity in the complete oxidation of ethanol. The maximum activity of the catalysts was related to the structure of the catalysts (Mn4+ vacancies, presence of Mn3+ ions and OH groups). The catalyst obtained by decomposition of MnCO3 is the best catalyst because it is easier to prepare. The theoretical results revealed two possible adsorption-oxidation sites of C2H5OH on the nsutite phase; the OH groups formed from Mn4+ vacancies, where ethanol could be oxidized to CO2 and the terminal oxygen of the pyrolusite lattice, where ethanol could be partially oxidized to acetaldehyde, which it could be oxidized to CO2.