The synthesis and characterization of iron colloid catalysts in inverse micelle solutions

We have studied the synthesis and characterization of Fe based nanometer sized clusters formed in inverse micelle solutions. Inverse micelles provide a colloidal sized reaction template in an oleic solvent. Metal salts are solubilized within the interior of inverse micelles, and the addition of a reducing agent initiates nucleation and growth to produce the clusters, Surfactant acts to stabilize the particles. TEM shows that the average particle size is less than 3 nm in diameter. The reduction reaction of iron salts with LiBH4 in inverse micelle solutions results in the formation of FeB, Fe2+BOx (i.e. pyroborate), and alpha-Fe as determined by Mossbauer spectroscopy, electron diffraction, and X ray photoelectron spectroscopy (XPS). Oxidation after exposure to air leads to the conversion of the FeB to alpha-Fe then to an undetermined Fe2+ phase and then finally to Fe3O4. Iron based metals are of interest as active, selective catalysts for a number of hydrogenation reactions including methanation and Fischer-Tropsch synthesis, We report catalytic results of iron clusters in the hydrogenolysis of naphthyl bibenzyl methane (NBM), a model reaction for coal liquefaction, The role of surfactant in the reaction mechanism is determined. (C) 1997 Elsevier Science B.V.