Effects of iron-oxygen precursor phase on carbon-carbon bond scission in naphthylbibenzylmethane

Eleven iron-oxygen compounds prepared using standard laboratory syntheses were tested as precursors for carbon-carbon bond scission catalysts with the coal model compound naphthyl-bibenzylmethane in the presence of elemental sulfur and a hydrogen-donating solvent. The structure of the iron-oxygen catalyst precursor was found to be the most significant factor determining the reactivity of the catalyst produced. The reactivity of the iron-oxygen compounds showed little apparent correlation with surface area, iron content, or water content. The iron-containing single-phase materials with the best catalytic activity at 400 °C were determined to be ferric oxyhydroxysulfate (Fe₈O₈(OH)₈SO₄), six-line ferrihydrite, goethite (α-FeOOH), and akaganeite (β-FeOOH). The worst iron-oxygen compounds were found to be wustite (FeO), two-line ferrihydrite, magnetite (Fe₃O₄), and maghemite (γ-Fe₂O₃). The general order of reactivity of the iron-oxygen compounds toward carbon-carbon bond scission was found to be proto-oxyhydroxides>oxyhydroxides>oxides. All of the iron-oxygen compounds tested were at least as active as metallic iron (α-Fe). All of the active catalyst precursors produced similar distributions of organic reaction products from the model compound. The best catalyst precursor tested was ferric oxyhydroxysulfate, which formed a catalyst which selectively cleaved carbon-carbon bonds at the α-naphthyl-methylene (`a') and the β-naphthyl-methylene (`b') positions with a model compound consumption of greater than 90% under the test conditions. The ferric oxyhydroxysulfate was found to contain a relatively large amount of water and small amount of iron, 18% and 43%, respectively, by weight.