Anti-coking freeze-dried NiMgAl catalysts for dry and steam reforming of methane
Finding supported nickel catalysts with high activity and stability is yet a challenging aim for industrial applications. In this work, we synthesized a surface defect-promoted Ni catalyst supported on Mg/Al hydrotalcite via a freeze-dried method instead of calcination. This approach leads to the increase in oxygen vacancies, which is attributed to the high dispersion of active sites after adding samarium. X-ray diffraction (XRD) measurements demonstrate a homogeneous layered double hydroxide (LDH) structure without the formation of any oxides. High-resolution transmission electron microscopy (HR-TEM) and field emission scanning electron microscopy images (FE-SEM) illustrated that the samarium-promoted NiMgAl catalyst possesses a scaffold structure with surface defects and oxygen vacancies compared to the unpromoted NiMgAl catalyst which confirmed by X-ray photoelectron spectroscopy (XPS). Moreover, the impact of the samarium incorporation on the physicochemical features of NiMgAl catalysts was investigated for catalytic activity in dry and steam reforming of methane at 700 °C. NiMgAl-Sm catalyst showed the highest conversion of CH4 (72%) and stability without any carbon formation during 20 h of time on stream in dry reforming process. because the strong metal–support interaction inhibits the sintering of nanocatalysts at 700 °C and the scaffold structure increases the mass transportation of feedstock and products.