Promoter Effects on Nickel-Supported Magnesium Oxide Catalysts for the Carbon Dioxide Reforming of Methane

The nickel catalysts supported on bare MgO and its binary Mg-Al, Mg-La, and Mg-Fe metal oxides were prepared and used for carbon dioxide reforming of methane to syngas. The effects of Al, La, and Fe metal oxides on the structural properties, reducibility, and metal-support interaction of the Ni catalysts supported on MgO-based binary metal oxide were investigated. The X-ray powder diffraction (XRD), transmission electron microscopy (TEM), and hydrogen temperature-programmed reduction (H₂-TPR) analyses show that the nickel nanoparticles were highly dispersed on the supports. It is found that the Al ions can be well-incorporated into the MgO lattice to form uniform Mg-Al oxides, while isolated lanthanum oxides and iron oxides were observed in the Mg-La and Mg-Fe binary systems by TEM, respectively. Ni/Mg-Al metal oxide exhibits greatly improved catalytic activity, owing to the formation of a homogeneous Mg-Al oxide matrix with small particle sizes of Ni nanoparticles compared to bare Ni/MgO. Very low conversions for both CH₄ and CO₂ were obtained on Ni/Mg-La and Ni/Mg-Fe metal oxides, even at a high temperature of 800°C, as a result of the incomplete reduction of the nickel nanoparticles.