(152b) Characterizing the Nanostructure of Metal Oxide Catalysts Using High Resolution Transmission Electron Microscopy | AIChE

(152b) Characterizing the Nanostructure of Metal Oxide Catalysts Using High Resolution Transmission Electron Microscopy

Authors 

Nair, H. - Presenter, Purdue University
Baertsch, C. D. - Presenter, Purdue University


High Resolution Transmission Electron Microscopy (HR-TEM) is capable of characterizing dynamic structural changes occurring on catalyst surfaces during reactions. Atomic spatial resolution in the presence of up to 4 Torr gas can be achieved using the FEI Titan 80 at Purdue. Atomic resolution images and elemental mapping has been successfully performed on monolayer thick samples of phosphomolybdic acid on C films. MacTempas was used to simulate the high-resolution images to interpret the arrangement and position of each atom in the image. Phosphomolybdic acid is known to be a selective and active catalyst for the oxidation of isobutane to methacrylic acid. However, its structure undergoes several changes during reaction resulting in both the formation of an active structure and its decomposition into an inactive bulk oxide form. The capabilities of the FEI Titan 80 at Purdue allow us to examine the atomic structure of phosphomolybdic acid and examine the structure changes associated with thermal and reactive decomposition of the catalyst. Similar HR-TEM techniques in conjunction with EELS (Electron Energy Loss Spectroscopy) have also been used to characterize the size and obtain an elemental map of supported metal oxide domains to establish a visual basis for structure-activity relations. Comparisons are made with bulk characterization techniques such as UV-vis Diffuse Reflectance Spectroscopy and Raman Spectroscopy.