Carburizing phase transformations

Iron catalysts used in Fischer-Tropsch synthesis are very sensitive to conditions of their preparation and pretreatment. Metallic iron exhibits very low activity. Under Fischer-Tropsch reaction conditions, however, it is slowly transformed into an active catalyst. For example, iron used in medium-pressure synthesis required an activation process of several weeks at atmospheric pressure to obtain optimum activity and stability.188 During this activation period, called carburization, phase... 

In the synthesis of carbides or nitrides, the reduction and the associated carburization or nitridation follow the same general pattern. As expected, different metal oxides form different solid intermediate phases at different transformation temperatures. 

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