W0294

In situ Reduction of Iron Oxides to Form Fe-metal Catalysts as Studied by High-energy, High-resolution Powder Diffraction. Richard Harlow, Michael Guise, William Holstein, Glover Jones, R. L. Harlow & Co., Inc., 7 Shull Dr., Newark, DE 19711 USA.

Fe-metal catalysts have been used for years in the Haber process for the production of ammonia from hydrogen and nitrogen. Originally made by reducing various iron ores with hydrogen, these catalysts are quite inexpensive and hence have found wider application as general reduction catalysts. Over the years, technologies for improving the activity of the Fe catalyst have been developed: doping of the iron oxide with other elements, co-feeding other gases with the hydrogen, pretreatment of the oxide by thermal annealing/melting, variations in the temperature and pressure of the reduction gases, etc. While it is possible to directly measure all of these effects on the activity of the Fe-catalyst, these measurements are very time consuming and expensive. Studies of the in situ reduction of various iron oxides (natural ores, by-product oxides, and commercial precursors) on the powder diffraction beamline of sector 5 (DND-CAT) at the APS were thus initiated. When early experiments suggested a correlation between activity and the breadth of the Fe(110) peak of the catalyst, the study was expanded into a general survey covering many aspects of Fe catalyst engineering. While using the example of Fe-metal catalyst, the more general theme of this talk will address the advantages of high-resolution powder diffraction studies using high-energy synchrotron radiation in which the positions, the intensities, and the peak breadths can all be measured simultaneously with a high degree of accuracy.