Iron Nitrides as Fischer-Tropsch Catalysts

Publisher Summary This chapter discusses the composition, structure, and methods of preparation of nitrides, carbides, and carbonitrides of iron; their reactions with hydrogen, carbon monoxide, and synthesis gas, and describe the use of iron nitrides as Fischer–Tropsch catalysts. Nitrides, carbides, and borides of iron are thermodynamically unstable, nonionic, interstitial compounds in which the interstitial atoms apparently occupy interstices between iron atoms. These compounds have metallic properties, such as appearance, electrical conductivity, and magnetic behavior that are not drastically different from those of iron. The selectivity of nitrided iron catalysts differs significantly from that of reduced, carbided, or inducted catalysts, the nitrides producing a product of lower average molecular weight containing high yields of oxygenated organic molecules. The high mechanical stability of nitrides suggest their application to synthesis in commercial-type reactors wherever the product distribution of the nitrided catalysts is acceptable. These data suggest that nitriding is advantageous even for operation at temperatures at which the nitrides are relatively unstable.