The structure of a pseudo-hexagonal iron carbide

Abstract

This paper describes an X-ray diffraction appraisal of an iron catalyst extracted after use in the Fischer-Tropsch process for the synthesis of hydrocarbons from carbon monoxide and hydrogen. The substance, in which the iron atoms form an approximately hexagonal dose-packed array, is monoclinic with cell dimensions a=b=2.794 /~, c=4.360 A and y=120.92 °. It is asmuned to be a carbide, with small amounts of associated oxygen. It is not possible, with X-ray powder diffrac-tion, to identify the structure completely, but on the basis of the formula Fe~C the possibilities are discussed.