Reactive behaviors of iron-based shift catalyst promoted by ceria

The reductive behavior of iron-based shift catalyst promoted by cerium oxid e was investigated by temperature-programmed reduction (TPR). Two reduction peaks appeared, centered at 473 and 673 K in reduction gas mixtures. The p eaks illustrated that the reduced surface states were different, correspond ing the reductive temperatures. The optimum reductive temperature range is from 423 to 723 K for the catalyst. The results of temperature-programmed d esorption (TPD) and pulse reaction indicated that the mechanism of the wate r-gas shift reaction on the catalyst can be considered as a redox process. The reduced Fe-Ce-Cr-O can be oxidized by water and carbon dioxide at react ion temperatures(from 573 to 673 K). Water is decomposed to form hydrogen a nd adsorbed hydroxyl groups, and carbon monoxide reacts with hydroxyl group s to produce hydrogen and carbon dioxide simultaneously. FT-IR spectroscopy results showed that iron-based catalyst promoted by CeO2 is a structurally sensitive catalyst. It has excellent activity, selectivity, and stability under reaction conditions. Moreover, on the catalyst surface carbonate-like species were not found under reaction conditions, as established by IR spe ctra. (C) 2000 Elsevier Science S.A. All rights reserved.