The reduction rate of wustite with hydrogen at 1133 to 1233 K and for hydrogen pressures between 1.6 and 5 mbar has been measured gravimetrically upon varying the separation between tablets made of wustite and iron or nickel. The reduction rate of wustite is increased by a factor 2.4 prior to precipitation of iron on wustite when the wustite-metal distance is changed from 2 mm to 0.35 at Hz pressures of 1.6 mbar and 2.3 mbar respectively. It has thus been demonstrated for the first time, that the catalytic effect of the metal phase on wustite reduction also exists when metal and wustite are separated. To describe this catalytic effect mathematical relations have been derived on the basis of a reaction model. These relations are in good accord with the results of the measurements. From recently published experimental findings, it may be concluded that, as a result of heterogeneous reactions, translationally 'hot' Hz molecules are desorbed from the metal surface. These induce a rapid reaction at wustite unless they have been deactivated by molecular collisions within the bulk gas between the tablets. EinfluB des Metall-Wustit-Abstandes auf die Reduktion von Wustit mit Wasserstoff. Die Geschwindigkeit der Reduktion von Wustit mit Wasserstoff wurde bei Variation des Abstandes zwischen Tabletten aus WGstit und Eisen oder Nickel bei WasserstoffdrGcken von 1,6 bis 5 mbar und Temperaturen von 1133 bis 1233 K gravimetrisch gemessen. Bei Anderung des WGstit-Metallabstandes von 2 auf 0,35 mm wird die Reduktionsgeschwindigkeit des Wustits bei Hz-Drucken von 1,6 und 2,3 mbar vor Ausscheidung der arteigenen Eisenphase um den Faktor 2,4 erh6ht. Damit wurde erstmalig gezeigt, daB der katalytische EinfluB der Metallphase auf die Wustitreduktion auch bei raumlicher Trennung des Metalls von Wustit vorhanden ist. Zur Beschreibung dieses katalytischen Effektes wurden auf der Basis eines Reaktionsmodells Beziehungen abgeleitet, die mit den Messungen gut Gbereinstimmen. Bisherige experimentelle Befunde lassen den Schlufs zu, daB von der Metalloberflache als Foige von Heterogenreaktionen translatorisch .heifse' Hz-MolekGle desorbiert werden, die an Wustit eine schnelle Reduktion bewirken, sofern sie nicht durch Moiekularst6Be im Gasraum desaktiviert werden.The accelerating effect of iron and other metals on the reduction of iron oxides, in particular of wustite, has been investigated systematically by Morawietz and Schafer')'), by Neuschiitz and Towhidi 3 )4), and by Pluschkell and Yoshikoshi'). It was shown that accelerated reduction takes place not only after formation of the iron phase on wustite but from the very beginning if the oxide to be reduced is in contact with metals such as Fe, Ni, Co and Cu.In an effort to explain this effect, Morawietz and Schafer') discussed the nuclei-forming role played by metallic phases. However, Neuschiitz and Towhidi') showed in addition, that the degradation of oxygen from wustite within the latter's range of homogeneity, is accelerated through contact with nickel powder.Pluschkell and Yoshikoshi ...
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