Hierarchical Fe-modified MgAl2O4 as a Ni-catalyst support for methane dry reforming

Abstract

MgAl₂O₄ and its Fe-modified analogue (MgFe_xAl_2−xO₄) were synthesized as supports with a nanostructure by a hydrothermal process, and employed as supports for Ni catalysts in methane dry reforming (DRM). All prepared supports had a hierarchical architecture displaying clusters of nanosheets. Fe-modified MgAl₂O₄ was characterized by X-ray diffraction (XRD), N₂ adsorption–desorption, scanning electron microscopy (SEM), high-resolution transmission electron microscopy (HRTEM), and temperature-programmed desorption (TPD). The activity and stability of the catalysts with a hierarchical support were tested in DRM at 750 °C, 111.3 kPa, and a CH₄ : CO₂ ratio of 1. The Ni/MgAl₂O₄ sample with a 0.5 Mg : Al molar ratio showed higher activity than Ni on common MgAl₂O₄ due to the larger surface area and stronger metal interaction with the hierarchical support. Besides, a series of Ni/MgFe_xAl_2−xO₄ catalysts with an Fe/Ni ratio between 0 and 0.5 was synthesized and reduced, yielding a supported Ni–Fe alloy. The structure evolution of the Ni/MgFe_xAl_2−xO₄ catalyst during H₂ temperature-programmed reduction (H₂-TPR), CO₂ temperature-programmed oxidation (CO₂-TPO), and dry reforming was investigated by in situ XRD. For Fe/Ni ≤ 0.05, a Ni–Fe surface alloy is obtained with high catalyst activity, efficient control of carbon deposition and superior regeneration ability. Ni supported on hierarchical Fe-modified MgAl₂O₄ proves to be a promising and effective catalyst for methane dry reforming.