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

Birnessite - type manganese oxides with very high surface areas (up to 154 m(2)/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 H-2-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 degrees C. (c) 2011 Elsevier Inc. All rights reserved.