The effect of acid/alkali treatment on the catalytic combustion activity of manganese oxide octahedral molecular sieves

Abstract

Manganese oxide octahedral molecular sieves (OMS-2) are a type of widely applied catalyst for its excellent catalytic properties and competitive price. We use CH₃COOH and KOH to modify the microstructure, the concentration of K⁺, the acidity, the redox properties and the oxygen vacancies of the OMS-2 materials. The acid-treated OMS-2 displays superior catalytic combustion activities in dimethyl ether combustion (T₁₀ of 170 °C and T₉₀ of 230 °C, E_a of 64.7 kJ mol⁻¹) and toluene combustion (T₁₀ of 170 °C and T₉₀ of 194 °C, E_a of 62.4 kJ mol⁻¹), whereas the alkali treatment imposes a negative effect on the catalytic activity. The superior activity of the acid-treated OMS-2 can be ascribed to the richer surface oxygen, higher oxygen mobility and redox properties, and stronger acidic sites of the catalyst.