Reduction behaviors and catalytic properties for methanol steam reforming of Cu-based spinel compounds CuX₂O₄ (X=Fe, Mn, Al, La)

In this study, various Cu-based spinel compounds, i.e., CuFe ₂O₄, CuMn₂O₄, CuAl₂O ₄ and CuLa₂O₄, were fabricated by a solid-state reaction method. Reduction behaviors and morphological changes of these materials have been characterized by H₂ temperature-programmed reduction (H₂-TPR), X-ray diffraction (XRD), Scanning electron microscopy (SEM), and transmission electron microscopy (TEM). Moreover, the catalytic properties for steam reforming of methanol (SRM) of these Cu-based spinel compounds were investigated. H₂-TPR results indicated that the reducibility of Cu-based spinel compounds was strongly dependent on the B-site component while the CuFe₂O₄ catalyst revealed the lowest reduction temperature (190 C), followed respectively by CuAl₂O ₄ (267 C), CuMn₂O₄ (270 C), and CuLa ₂O₄ (326 C). The reduced CuAl₂O₄ catalyst demonstrated the best performance in terms of catalytic activity. Based on the SEM and XRD results, pulverization of the CuAl₂O₄ particles due to gas evolution and a high concentration of nanosized Cu particles (≈50.9 nm) precipitated on the surfaces of the Al₂O ₃ support were observed after reduction at 360 C in H₂. The BET surface area of the CuAl₂O₄ catalyst escalated from 5.5 to 13.2 m²/g. Reduction of Cu-based spinel ferrites appear to be a potential synthesis route for preparing a catalyst with high catalytic activity and thermal stability. The catalytic performance of these copper-oxide composites was superior to those of conventional copper catalysts.