(410c) Role of Zn On Structure and Catalytic Activity of MnO2 Catalysts

Cryptomelane is a manganese oxide octahedral microporous material, with manganese mainly in the Mn⁺⁴ and Mn⁺³oxidation states.  Potassium ions are typically located in one-dimensional tunnel strcutures that are characteristic of cryptomelane. In this study, the effects of Zn-dopant concentration and synthesis method on structure and catalytic activity of Zn-doped cryptomelane have been investigated. 

Zn-doped cryptomelane catalysts have been prepared by three methods: 1) a refluxing method, , 2) a sol-gel method, and 3) a flame aerosol method.  Of these three methods, the refluxing method is most commonly used to synthesize cryptomelane in a laboratory, and the flame aerosol method is a novel method for synthesizing cryptomelane.  Each method results in Zn-doped cryptomelane catalysts with differing surface and structural characteristics, and hence, catalytic activity. 

The effects of Zn dopant concentration and synthesis method on structural  properties and catalytic activity for VOC oxidation were investigated.  The catalysts were characterized for crystallinity, morphology, surface area and pore size distribution, and composition using X-ray diffraction, scanning electron microscopy, transmission electron microscopy, energy dispersive spectroscopy, and BET surface area analysis. The oxidation of ethanol vapor and toluene were used as measures of catalytic activity of these catalysts.