METASTABLE STRUCTURE OF FE3O4 FOR WATER-G AS SHIFT CATALYST

Different oxygen parameters of Fe3O4 which were reduced from alpha - F e2O3 and gamma - Fe2O3 with water - gas at 400 degrees C were observed by means of X - ray powder diffraction Rietveld structure refinement. Using bond - valence calculation method, the electrovalences of tetra hedra site A and octahedra site B of Fe3O4 reducing from gamma - Fe2O3 are obviously different from that reducing from alpha - Fe2O3, but th ey can change into the normal ones after being aged at 600 degrees C i n reducing atmosphere. There are also different in Mossbauer spectra o f two types of Fe3O4. The first peak of Mossbauer spectrum of Fe3O4 re ducing from alpha - Fe2O3 occurs splitting. The electrovalence changin g directions of Fe deduced from the changes of isomer shift of A site and B site are the same as that bond - valence calculating method. A m etastable Fe3O4 was obtained from gamma - Fe2O3, having different elec trovalence from normal Fe3O4 and having correlating with low-temperatu re catalytic activity of water - gas shift reaction.