Structural transformation of Pd-α-Fe2O3 and Pd-γ-Fe2O3 catalysts and application in the CO oxidation reaction
Abstract
Pd-α-Fe2O3 and Pd-γ-Fe2O3 catalysts were acquired by treating Pd–Fe catalysts with redox pretreatment. These catalysts were characterized by various techniques and applied in the CO oxidation reaction. Characterization reveals that the Pd-α-Fe2O3 catalyst is obtained after calcination in air at 400 °C. The following reduction at lower temperature forms the Pd-γ-Fe2O3 catalyst. In the case of larger Pd (or PdO) and Fe2O3 nanoparticles, the Pd-γ-Fe2O3 catalyst is highly active for low temperature CO oxidation compared with the Pd-α-Fe2O3 catalyst, which may originate from the high oxygen storage properties of γ-Fe2O3 and stronger interaction between Pd and γ-Fe2O3. Higher reduction temperature results in much larger particle sizes and decreased activity. Stability tests also indicate that the highly active Pd-γ-Fe2O3 catalyst could transform to Pd-α-Fe2O3 in reactive atmosphere, leading to catalyst deactivation. Re-reduction treatment of the inactivated catalyst results in reproduction of the activity.