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

Abstract

In this study, various Cu-based spinel compounds, i.e., CuFe2O4, CuMn2O4, CuAl2O4 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 CuAl2O4 (267°C), CuMn2O4 (270°C), and CuLa2O4 (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 (≈50.9nm) precipitated on the surfaces of the Al2O3 support were observed after reduction at 360°C in H2. The BET surface area of the CuAl2O4 catalyst escalated from 5.5 to 13.2m2/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.