Small metal particles Mossbauer spectroscopy

Fe/Ir catalysts on silica and alumina Fe and Ir Mossbauer spectroscopy silica- and alumina-supported Fe-Ir catalysts formed by calcination in air contain mixtures of small particles of Fe(III) oxide and Ir(IV) oxide. IrOz is reduced in hydrogen to metallic Ir. a-Fe203 on SiOz is reduced in hydrogen to an Fe-Ir alloy, whilst supported on alumina stabilizes in hydrogen as Fe(II). Possible use for methanol formation is discussed... 

The explanation of endotactic heterostructures in molecular dispersion for the X-ray anomalies of ammonia iron was proved by H. Topsoe by Mossbauer spectroscopy. The Mossbauer data imply the presence of small amounts of non-metal iron components which are present, however, as large particles of structural promoter oxides. They are located in grain boundaries and at the outer surface of the catalyst. This location also explains the SIMS data on Fe-Al-O fragments which were intended to support the hypothesis of endotactic heterostructures.The EXAFS data ° ° provide clear evidence for the identical average local coordination of iron in ammonia iron and normal iron. 

Another route to trapping small Fe and Co particles within the supercages of faujasite zeolites is the metal vapor solution condensation ( metal atom solvate ) method, used by Nazar and Ozin 148). When characterized by Fe Mossbauer and ferromagnetic resonance spectroscopies, Fe particles in the size range of 5-12 A are located in the zeolite supercage and its 12-member ring entrance. In using these Fe -NaY or Co -NaY catalysts for... 

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