Synergistic effect of freeze-drying and promoters on the catalytic performance of Ni/MgAl layered double hydroxide

Methane dry reforming is a potentially useful reaction but possesses some disadvantages such as catalyst deactivation by coking. Some new freeze-dried promoted-Ni/MgAl catalysts were used in this work for solving this drawback. The synergic effect of the freeze-drying method and incorporation of promoters was studied on physicochemical features of catalysts and catalytic performance. Field emission scanning electron microscopy images (FE-SEM) and high-resolution transmission electron microscopy (HR-TEM) revealed that the Sr-promoted Ni/MgAl catalyst had a scaffold structure with desirable pores in contact with feedstock gases. The temperature-programmed reduction (H₂-TPR) and temperature-programmed deposition (CO₂-TPD) techniques confirmed that the reduction behavior and basicity of the catalysts are affected by the type of promoter. In comparison to Y and Sr-promoted catalysts, the Sr-Ni/MgAl catalyst with the lower reduction temperatures, smaller Ni crystallite size, greater Ni dispersion, and higher basicity had the highest catalyst activity (72% CH₄ conversion) and stability after 20 h time on stream without any carbon deposition. The higher basic cites resulted in eliminating coke specimens from the catalyst surface.