Catalytic Oxidation of Formaldehyde over Manganese-Based Catalysts and the Influence of Synergistic Effect

Formaldehyde is one of the major indoor pollutants and has threatened the human health seriously. The treatment of formaldehyde has attracted broad attention. Catalytic oxidation is one of the most effective and environment-friendly technology. Presently, the catalytic deep oxidation of formaldehyde over manganese-based catalysts has become the research hotspot owing to the structure flexibility and good oxidation ability of manganese oxides (MnOx). The review mainly summarizes the recent progress in formaldehyde oxidation over manganese-based catalysts from four perspectives: pure MnOx catalysts, manganese-based composite oxides, MnOx immobilization on porous material and MnOx supported noble-metal catalysts. Catalytic mechanisms are elaborated based on Mars-van Krevelen mechanism. Specified surface oxygen species and active sites in variety of catalysts produce corresponding intermediates during the catalytic oxidation of formaldehyde and consequently induce different reaction pathways. The influence of synergistic catalytic effect is emphatically discussed between catalyst components. The synergistic effect of manganese-based catalysts is achieved through one component activation by the other between two catalytic components for enhanced activity, or successional catalytic functioning of two components in catalytic reactions probably involving multi-step for enhanced activity and/or selectivity. Finally, the challenges and outlook are featured based on such catalysts in the application of HCHO removal.