TOPOTACTIXITY OF THE HYDROGEN REDUCTION PROCESS IN FUSED IRON CATALYST

Microstructural characterization of highly porous fused iron catalyst in the reduced and partially reduced states has been performed using e lectron microscopy techniques. The microstructure consists of 30-50nm iron crystallites in a network of highly defected iron, forming an int erconnected porous structure. The size of the pores ranges from 10 to 20nm and they are aligned along a specific crystallographic direction of magnetite and/or iron. We found that the {111}Fe3O4 and the {O11}Fe planes are preferentially reduced and preferentially exposed, respect ively, during reduction. The magnetite-alpha-iron-pore channel chrysta llographic orientation relationship can be expressed as (<(1)over bar1 1>)Fe3O4 // (<(1)over bar10>)Fe // pore channel and (O(2) over bar2$)F e3O4 // (002)Fe perpendicular to pore channel. The former is known as the Nishiyama-Wassermann orientation relationship between face-centere d and body-centered cubic materials. It is suggested that the high act ivity of this catalyst is due to the presence of alkali atoms on top o f every other closely packed iron atom.