Low-temperature formaldehyde oxidation over manganese oxide catalysts: Potassium mediated lattice oxygen mobility

Abstract

Manganese oxide catalysts with self-modulating K+ content and tunable concentration of lattice oxygen and Mn4+ were synthesized and investigated for HCHO oxidation. The preparation method affects the physicochemical properties and catalytic activity of the catalysts. Herein, the role of K+ in enhancing the lattice oxygen mobility of manganese oxide catalysts for enhanced formaldehyde (HCHO) is presented. The presence of K+ enhances the redox properties of Mn and promotes catalytic activity by enhancing the mobility of the lattice oxygen and sustaining the availability of surface active oxygen to sustain the reaction. Catalytic activity was observed to improve with increasing K+ content and the surface concentration of lattice oxygen and Mn4+. A drastic reduction in catalytic activity was observed in the acid-treated samples, with low K+ concentration. Characterization results indicate that the presence of K+ enhances activity and mobility of the lattice oxygen by the weakening the Mn-O bond in manganese oxide and promotes the redox properties of the catalyst. The absence of K+ impacted the mobility of the lattice oxygen and the ability of the catalyst to supplement the consumed oxygen species, resulting into reduced catalytic activity and deactivation in the room-temperature (30 °C) activity and stability test.