Reactivity and Durability of Metal Oxide Nano-array based Oxidation Catalysts

Pu-Xian  Gao, University of Connecticut

Reactivity and stability are contradictory attributes in emission control auto-catalysts, which usually work under elevated temperature conditions to allow good enough catalyst reactivity, but usually compromise their physical and chemical stability and thus reduce their lifetime. As such, a catalyst regeneration or replacement process is generally needed over certain operation time spans. Recently, a series of metal oxide nanostructure arrays (nano-arrays) (e.g., CeO2, Co3O4, (La, Sr)(Co, Mn, Fe)O3, MnO2, TiO2, ZnO, etc.), with or without catalytically active metal decoration, have been successful integrated onto monolithic honeycomb substrates with well-defined size, shape, orientation, thickness, and chemical compositions, forming a new type of monolithic catalysts. These nano-array-based catalysts have displayed good durability and catalytic performance toward various gas phase catalytic reactions, while showing good potential of reducing the material (noble metal and metal oxides) usage. Here we comparably look into the reactivity and durability of both noble metal-containing and noble metal-free nano-array catalysts for oxidation of various hydrocarbons and CO. As unique supports, the nano-array ‘forest-like’ structure configuration proves to improve the dispersion and immobilization of metal nanocatalysts under various aging and reactive conditions, besides the lower pressure drop and improved adherence to the monolith substrates over washcoated catalysts. On the other hand, electronic interactions between metals and nano-array support are found to be adjustable toward favoring catalytic oxidation while improving the catalyst robustness. Furthermore, chemical leaching treatment in these metal oxide based catalysts could help tune their chemical and structural characteristics, boosting low temperature oxidation reactivity while maintaining robustness.

 

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