*3.1. Catalysts Preparation*

Ce-Al2O3 composite oxides (5 wt.% Ce) support was prepared by coprecipitation method, and the complete experimental procedure is detailed in references [8,44]. The catalysts were prepared by incipient wetness impregnation using Ni(NO3)2·6H2O and Co(NO3)2·6H2O as the precursors of Ni and Co, respectively. After impregnation and drying (120 ◦C, 3 h), the samples were calcined in air at 800 ◦C for 4 h. Finally, the mono-metallic Ni catalyst (Ni/Ce-Al2O3, 6 wt.% Ni), and Co-Ni bi-metallic catalysts {Co-Ni/Ce-Al2O3, 6 wt.% Ni, *x* wt.% Co (*x* = 3, 6, 9, 12, 15)} were made into columnar particles (length of 5 mm, diameter of 5 mm), and marked as NCA, C3-NCA, C6-NCA, C9-NCA, C12-NCA and C15-NCA, respectively.
