Sphere-Shaped Mn₃O₄ Catalyst with Remarkable Low-Temperature Activity for Methyl-Ethyl-Ketone Combustion

Mn₃O₄, FeMnO_x, and FeO_x catalysts synthesized via a solvothermal method were employed for catalytic oxidation of methyl-ethyl-ketone (MEK) at low temperature. Mn₃O₄ with sphere-like morphology exhibited the highest activity for MEK oxidation, over which MEK was completely oxidized to CO₂ at 200 °C, and this result can be comparable to typical noble metal loaded catalysts. The activation energy of MEK over Mn₃O₄ (30.8 kJ/mol) was much lower than that of FeMnO_x (41.5 kJ/mol) and FeO_x (47.8 kJ/mol). The dominant planes, surface manganese species ratio, surface-absorbed oxygen, and redox capability played important roles in the catalytic activities of catalysts, while no significant correlation was found between specific surface area and MEK removal efficiency. Mn₃O₄ showed the highest activity, accounting for abundant oxygen vacancies, low content of surface Mn⁴⁺ and strong reducibility. The oxidation of MEK to CO₂ via an intermediate of diacetyl is a reaction pathway on Mn₃O₄ catalyst. Due to high efficiency and low cost, sphere-shaped Mn₃O₄ is a promising catalyst for VOCs abatement.