A molecular mechanism for Fischer-Tropsch catalysis

The catalysts Co(HCN)(2)-Fe(HCN)(2)-Co(HCN)(2) and [Fe(HCN)(2)](3) were designed, produced and proven for Fischer-Tropsch conversion of synthesis gas to liquid, and waxy aliphatic hydrocarbons, respectively. Hydrocarbons formed upon exposure of the catalysts to synthesis gas at room temperature and above. Hydrogen cyanide, released from the catalysts, was shown by direct MS measurements to be converted initially to nitriles. Thus, hydrogen cyanide became an in situ model compound illuminating a C-1 molecular insertion mechanism. This mechanism accounted for all products. FTIR and GC-MS measurements indicated the type and distribution of liquid hydrocarbons produced. Linear hydrocarbons formed from CO/H-2 while branched hydrocarbons formed from a mixture of acetylene plus CO/H-2 demonstrating the initial C-1 species associated with the catalyst, whether it was CO, HCN or one carbon of acetylene, acted as both tether and terminus in the step-wise chain growth mechanism. (C) 2001 Elsevier Science B.V. All rights reserved.