Highly active manganese oxide catalysts for low-temperature oxidation of formaldehyde

Birnessite - type manganese oxides with very high surface areas (up to 154 m2/g) were successfully prepared using a microemulsion process. The morphology, surface area, pore size, and the surface reducibility of these materials were readily tailored via the synthesis temperature. The physiochemical properties of the manganese oxides were characterized by means of XRD, TEM, SEM, BET and H2-TPR techniques. These materials were also catalytically tested in HCHO oxidation, showing significantly high catalytic activity. It was found that the differences in catalytic performance of these materials were jointly attributed to the effects of the morphology, surface area and surface reducibility. The highly porous feature of the catalyst with nanospheres could allow HCHO molecules to easily diffuse onto catalytically active sites, which endows the nanospheres with high catalytic activity. The higher the surface area, the higher its catalytic activity. A higher surface reducibility offered a lower temperature of HCHO oxidation. The most active manganese catalyst (BSW-120) showed a 100% HCHO conversion at 100 °C.

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► Birnessite with very high surface area was prepared by a microemulsion process.
► Birnessite materials exhibit excellent catalytic activity for HCHO oxidation.
► The catalytic activity is highly dependent on their morphology and surface area.
► The catalyst prepared at 120 °C can completely oxidize HCHO into CO2 at 100 °C.