Adsorption and Magnetic Properties of Samarium-Promoted Fe/MgAl₂O₄ Catalysts for the Hydrogenation of Carbon Monoxide

A study is performed of samarium-modified Fe-containing catalysts on aluminum–magnesium spinel (MgAl₂O₄) supports. Data on the adsorption and reduction properties of the catalysts, determined via in situ magnetometry and IR spectroscopy of adsorbed CO, are compared. The IR spectroscopy of adsorbed CO shows that the main Fe species which forms a bond with CO in unpromoted Fe/MgAl₂O₄ is Fe²⁺ cations on the surfaces of nucleation centers in both the oxide and the metal phase, while the contribution from complexes with Fe⁰ atoms is negligible. It is found that promotion with samarium in a ratio of Sm : Fe = 1 : 100 inside the catalyst contributes to the effective reduction of iron oxides. It is shown that the reduction of iron is greatest for the catalyst synthesized by depositing samarium on the surface of a Fe-containing catalyst.