X-ray diffraction and electron magnetic resonance studies of M/Fe/Al2O3 (M=Ni, Mo and Pd) catalysts for CH4 to H2 conversion

Efficient production of hydrogen (H2) from methane (CH4) at 700 °C has been recently demonstrated using the reduced catalysts 0.5% M/4.5% Fe/Al2O3 (M=Ni, Mo, Pd). In this work, X-ray diffraction (XRD) at 300 K and electron magnetic resonance (EMR) spectroscopy at 5 and 300 K were used to determine the nature of the different phases present in these materials before and after the reaction with CH4 at 700 °C to produce H2. It is observed that before the reaction, catalysts reduced at 700 °C contain γ-Al2O3, elemental Fe, iron oxides and Fe3+ substituting for Al3+ in Al2O3, and that the presence of Ni, Mo and Pd promotes the reduction of iron oxides to Fe. In the post reaction catalysts, the amount of Fe is considerably lowered and the presence of Fe3C and graphitic nanotubes is observed. However, there are no significant changes in the concentrations of Fe3+/Al2O3 and the iron oxides. The materials aspects of these results for the production of H2 from CH4 at 700 °C are discussed.